PL193700B1 - Biodegradable shape memory polymers, and their use - Google Patents

Abstract

A degradable shape memory polymer composition, characterized in that it comprises at least one hard segment having a Ttrans transition temperature in the range of -40 to 270°C, and at least one soft segment bonded to at least one hard segment having a Ttrans transition temperature at least 10°C lower than the Ttrans transition temperature of the hard segment(s), and furthermore at least one of the hard or soft segments has a degradable region, or at least one pair of hard and soft segments has a degradable bond. 1 for the production of technical, pharmaceutical, biomedical, cosmetic and care articles and devices, such as capsules, surgical threads, orthodontic materials, splints, rods, screws, nails and plates used in bone surgery, scaffolds for tissue engineering, films, drainage tubes, catheters, prostheses, transplants and implants, contact lenses, pumps and meshes, devices for dispensing light, thermal indicators and sensors, diapers, sanitary napkins and packaging, contrast agents used, among others, in tomographic, magnetic resonance and X-ray examinations.

Description

Description of the invention

Subject of the invention

The invention relates to a degradable shape memory polymer composition. Furthermore, the invention relates to the use of the degradable shape memory polymer composition, particularly for the production of technical, pharmaceutical, biomedical, cosmetic, and personal care products and devices.

State of the art

Shape memory is the ability of a material to retain its original shape after mechanical deformation, which is a unidirectional effect, or after thermal deformation due to cooling and heating, which is a bidirectional effect. This phenomenon is based on a structural phase transition.

The first known materials characterized by these properties were shape-memory metal alloys (SMAs), including TiNi (Nitinol), CuZnAl, and FeNiAl alloys. The structural phase transformation of these materials is referred to as the martensitic transformation. These materials are used in a variety of applications, including vascular dilatation tubes, medical guide tubes, orthodontic wires, vibration dampers, pipe connectors, electrical connectors, thermostats, actuators, spectacle frames, and bra wires. However, the use of these alloys is limited, particularly due to their high cost.

However, shape memory polymers (SMPs) are increasingly being used to replace or complement SMAs, in part because these polymers are lighter, have significantly higher shape recovery, are easy to handle, and are more economical to use. In the literature, SMPs are generally characterized as phase-segregated, linear copolymers having a hard segment and a soft segment. The hard segment is typically crystalline with a defined melting point, and the soft segment is typically amorphous with a defined glass transition temperature. However, in some embodiments, the hard segment is amorphous and has a glass transition temperature rather than a melting point. In other embodiments, the soft segment is crystalline and has a melting point rather than a glass transition temperature. The melting temperature or glass transition temperature of the soft segment is significantly lower than the melting temperature or glass transition temperature of the hard segment.

When the SMP is heated above the melting point or glass transition temperature of the hard segment, the material can be shaped. This (original) shape can be stored by cooling the SMP below the melting point or glass transition temperature of the hard segment. When the shaped SMP is cooled below the melting point or glass transition temperature of the soft segment, during which the shape is deformed, a (temporary) shape is established. The original shape is recovered by heating the material above the melting point or glass transition temperature of the soft segment but below the melting point or glass transition temperature of the hard segment. In another method for establishing a temporary shape, the material is deformed at a temperature below the melting point or glass transition temperature of the soft segment, resulting in stress and strain absorbed by the soft segment. When a material is heated above the melting point or glass transition temperature of the soft segment but below the melting point (or glass transition temperature) of the hard segment, the stresses and strains are relieved and the material returns to its original shape. The recovery of the original shape, which is induced by an increase in temperature, is called the thermal shape memory effect. Properties that describe the shape memory capabilities of a material are the shape recovery of the original shape and the shape setting of a temporary shape.

Several physical properties of SMPs other than shape memory are significantly altered in response to external changes in temperature and stress, particularly at the melting point or glass transition temperature of the soft segment. These properties include elastic modulus, hardness, compliance, vapor permeability, damping, refractive index, and dielectric constant. The elastic modulus (the ratio of stress to the corresponding strain) of SMPs can change by a factor of up to 200 when heated above the melting point or glass transition temperature of the soft segment. The hardness of the material also changes dramatically when the soft segment is at or above the melting point or glass transition temperature. When the material is heated to a temperature above the melting point or glass transition temperature of the soft segment, the damping capacity can be up to five times greater.

PL 193 700 B1 higher than a conventional rubber product. The material can easily regain its original molded shape after numerous thermal cycles and can be heated above the melting point of the hard segment and have its shape changed, and upon cooling, have its new original shape established.

Conventional shape memory polymers are essentially segmented polyurethanes and have hard segments containing aromatic specific portions. For example, U.S. Patent No. 5,145,935 to Hayashi discloses a shape memory article formed from a polyurethane elastomer polymerized from a difunctional diisocyanate, a difunctional polyol, and a difunctional chain extender.

Examples of polymers used to prepare the hard and soft segments of known SMPs include various polyethers, polyacrylates, polyamides, polysiloxanes, polyurethanes, polyether amides, polyurethane/ureas, polyether esters, and urethane/butadiene copolymers. See, for example, U.S. Patent No. 5,506,300 to Ward et al.; U.S. Patent No. 5,145,935 to Hayashi; U.S. Patent No. 5,665,822 to Bitler et al.; and Gorden, "Applications of Shape Memory Polyurethanes," Proceedings of the First International Conference on Shape Memory and Superelastic Technologies, SMST International Committee, pp. 115-19 (1994).

Although these polymers have been proposed for a number of applications, their medical applications have been limited to devices that are not implanted or left in the body. It is desirable to have shape memory polymers that are biodegradable. Many applications for biodegradable shape memory polymers are obvious, for example, in diapers and sanitary napkins, medical surgical liners, or in food packaging or other materials where disposal measures are indicated. It is not obvious from the characteristics of known commercially available polyurethane materials that biodegradable materials can be incorporated into a shape memory polymer and still retain the structural and other physicochemical properties characteristic of shape memory polymers and their applications. Furthermore, components of known polyurethane shape memory polymers contain aromatic groups, which would be expected to be biocompatible.

Taking the above into account, the aim of the invention was to develop and introduce biodegradable shape memory polymers into use.

Yet another goal was to obtain a qualitatively new type of shape memory polymers with different, more useful physicochemical and structural properties compared to the current state of the art.

The essence of the invention

The essence of the first invention is that the polymer composition comprises at least one hard segment having a transition temperature Ttrans in the range from -40 to 270°C, and at least one soft segment bonded to at least one hard segment having a transition temperature Ttrans at least 10°C lower than the transition temperature Ttrans of the hard segment(s), and furthermore at least one of the hard or soft segments has a degradable region, or at least one pair of hard and soft segments has a degradable bond.

It is advantageous when the composition contains shape memory polymers that are subject to the action of external stimuli, especially temperature or light.

It is also advantageous when the transformation temperature Ttrans of the hard segment is in the range from 30 to 150°C, preferably up to 100°C.

Furthermore, it is advantageous when the transition temperature Ttrans of the soft segment(s) is at least 20°C lower than the transition temperature Ttrans of the hard segment(s).

It is also advantageous when at least one of the hard and soft segments is a thermoplastic polymer.

Furthermore, it is advantageous when cyclic parts occur in the hard segment.

It is also advantageous if the weight ratio of the hard and soft segments is in the range of from about 5:95 to 95:5, preferably from 20:80 to 80:20.

Furthermore, it is advantageous if the shape memory polymer belongs to the group consisting of grafted, linear and dendritic polymers.

It is also significantly advantageous when the degradable region of the polymer belongs to the group consisting of polyhydroxy acids, ether polyesters, polyorthoesters, polyamino acids

PL 193 700 B1 s, synthetic polyamino acids, polyanhydrides, polycarbonates, polyhydroxyalkanoates, and polyphenolic acid caprolactones).

It is advantageous for the polymer to contain a biodegradable bond that belongs to the group consisting of ester, carbonate, amide, anhydride and orthoester subgroups.

It is also advantageous when the composition contains a completely biodegradable polymer.

It is significantly preferred that the composition comprises a degradable thermosetting polymer which in turn comprises a crystallizable soft segment having a cross-linked covalent structure having a melting temperature Tm in the range of from 250°C to (-)40°C, preferably from 200°C to 0°C, or a soft segment having a cross-linked covalent structure having a transition temperature Ttrans in the range of from 250°C to (-)60°C, preferably from 200°C to 0°C.

It is also advantageous when the composition contains at least two segments:

a) the first segment, whose transformation temperature Ttrans is in the range from -40 to 270°C,

b) a second segment that is bonded to at least one first segment and that comprises an ionic interaction of sufficient strength for the second segment to be capable of forming a physical cross-link other than at the melting or glass transition temperature, wherein at least one of the segments has a biodegradable region or at least one of the first segments is bonded to at least one of the second segments via a biodegradable bond.

Furthermore, it is advantageous when the ionic interaction consists of polyelectrolytic segments, or polyelectrolytic segments and ions, or polyanionic and polycationic segments, or supramolecular effects based on highly organized hydrogen bonds.

It is also advantageous when the polymer is characterized by a reverse temperature effect, wherein the shape recovery of the composition occurs upon cooling below the shape recovery temperature.

It is further preferred that the composition comprises polymer compositions comprising two-, three- or four-block copolymers and one homo- or copolymer.

It is significantly advantageous when the composition comprises a polymer composition belonging to the group consisting of physical polymer mixtures, polymer compositions containing hard segments with different Ttrans transition temperatures and soft segments with the same Ttrans transition temperature, multiblock copolymer compositions in which at least one of the segments of the first copolymer is miscible with at least one of the segments of the second copolymer, and compositions of at least one multiblock copolymer and at least one homo- or copolymer.

It is also advantageous when the composition contains a coating that changes the degradation of the shape memory polymer.

The essence of the second invention is the use of the polymer composition according to the invention for the production of technical, pharmaceutical, biomedical, cosmetic and care articles and devices, such as capsules, surgical threads, orthodontic materials, splints, rods, screws, nails and plates used in bone surgery, scaffolds for tissue engineering, films, drainage tubes, catheters, prostheses, transplants and implants, contact lenses, pumps and meshes, light dispensing devices, thermal indicators and sensors, diapers, sanitary napkins and packaging, contrast agents used, among others, in tomographic, resonance and X-ray examinations.

The biocompatible polymer compositions described above comprise one or more hard segments and one or more soft segments, wherein at least one polymer contained therein or at least one segment bond therein is biodegradable.

Shape memory polymers, on the other hand, contain at least one physical cross-link (physical interaction of the hard segment) or contain a covalent cross-link in place of the hard segment. These polymers can also be interpenetrating networks, in whole or in part.

In addition to changes from solid to liquid state (melting or glass transition temperature), hard and soft segments may undergo solid-to-solid transitions, ionic interactions involving polyelectrolytic segments, or supramolecular phenomena based on highly organized hydrogen bonds.

Polymer products can be obtained from shape memory polymer compositions, for example, by injection molding, blow molding, extrusion, and laser removal. To prepare a shape memory article, the product can be molded at a temperature below the Ttrans

PL 193 700 B1 hard segment and cooled to a temperature below the Ttrans of the soft segment. The original shape can be restored by heating the object above the Ttrans of the soft segment and below the Ttrans of the hard segment.

Thermosetting polymers can be prepared by pre-shaping the macromonomer, for example by extrusion, and fixing the initial shape at a temperature above the T trans of the thermosetting polymer, for example by photocuring the active groups on the macromonomer.

Examples

The invention will be presented on the basis of exemplary embodiments shown in the drawing, in which:

Fig. 1 is an illustration of the one-way shape memory effect;

Fig. 2 is an illustration of the bidirectional (thermal) shape memory effect;

Fig. 3 is an illustration of the combination of the respective classes of thermoplastic materials;

Fig. 4 is a reaction sequence diagram for the synthesis of a preferred motocrosslink;

Fig. 5 is an illustration of the photoinduced shape memory effect.

Fig. 6 is an illustration of the mechanism of the thermal shape memory effect for a multi-block copolymer.

Fig. 7 is a graph showing stress versus elongation for a multi-block copolymer shape memory polymer.

Fig. 8 is a graph showing the melting point of diols, dimethacrylates, and poly(phenylene-caprolactone) thermosets as a function of the molar mass M _{n of} the macromonomers.

Detailed description of the invention

Biodegradable shape memory polymer compositions, articles manufactured therefrom, and methods of preparing and using them are described.

Definitions

As used herein, the term "biodegradable" refers to materials that are biologically resorbed and/or degraded and/or broken down by mechanical degradation upon interaction with the physiological environment into components that are metabolized or excreted, over a period of time ranging from minutes to three years, preferably less than one year, while maintaining the necessary structural integrity. As used herein with respect to polymers, the term "degrade" refers to the cleavage of a polymer chain such that the molecular weight remains approximately constant at the oligomer level and the polymer particles remaining after degradation. The term "completely degrade" refers to the cleavage of a polymer at the molecular level such that substantially complete mass loss occurs. The term "degrade," as used herein, includes "complete degradation," unless otherwise indicated.

A polymer is a shape memory polymer if the original shape of the polymer is recovered by heating it above the shape recovery temperature (defined as the Ttrans of the soft segment) even if the originally formed shape of the polymer is mechanically destroyed at a temperature lower than the shape recovery temperature, or if the memorized shape is recovered by applying another stimulus.

As used herein, the term "segment" refers to a block or sequence of polymer forming part of a shape memory polymer.

As used herein, the terms hard segment and soft segment are relative terms, referring to the Ttrans of the segments. The hard segment(s) have a higher Ttrans than the soft segment(s).

The shape memory polymers may comprise at least one hard segment and at least one soft segment, or may comprise at least one type of soft segment, wherein one type of soft segment is cross-linked, without the presence of a hard segment.

The hard segments may be oligomers or linear polymers and may be cyclic compounds such as crown ethers, cyclic di-, tri- or oligopeptides and cyclic oligo(esteramides).

The physical interactions between hard segments can be based on charge transfer complexes, hydrogen bonds, or other interactions, as some segments have melting points higher than the degradation temperature. In these cases, there is no melting point or glass transition temperature for the segment. A nonthermal mechanism, such as a solvent, is required to change the segment bonding.

The weight ratio of hard segment:soft segments is between about 5:95 and 95:5, preferably between 20:80 and 80:20.

PL 193 700 B1

Shape memory polymer compositions

Thermoplastic shape memory materials are shaped/molded to the desired shape above the T trans of the hard segment(s) and cooled to a temperature below the shape recovery temperature, where the polymer can undergo mechanical deformation and strains are generated in the polymer. Deformed polymers can be recovered to their original shape by heating them to a temperature above their shape recovery temperature. Above this temperature, the strains in the polymer are relaxed, allowing the polymer to return to its original shape. In contrast, thermoset shape memory materials are shaped/molded to the desired shape before the macromonomers used to create the thermoset polymers polymerize. The macromonomers are polymerized after the shape has established.

The polymer compositions are preferably compressible by at least one percent or expandable by at least five percent of their original thickness at a temperature below the shape recovery temperature, wherein the deformation is established by the application of a stimulus such as heat, light, ultrasound, magnetic fields, or electric fields. In certain embodiments, the materials exhibit a recovery ratio of 98% (see Experimental Examples).

When a significant stress is applied, resulting in forced mechanical deformation at a temperature below the shape recovery temperature, the strain is retained in the soft segments or amorphous regions, and a large change in shape is maintained even after partial stress release by the polymer's elasticity. If the molecular chain configuration is disturbed by the influence of regulated molecular chain ordering at a temperature below the glass transition temperature, it is assumed that the molecular chains re-arrange themselves by increasing the bulk size and reducing the free volume content. The original shape is recovered by shrinking the hard segment clusters by increasing the temperature under strict control of the chain conformations, and the polymer shape is restored to the stored shape.

In addition to changes from the solid to the liquid state (melting point or glass transition temperature), the hard and soft segments can undergo solid-to-solid transitions and may be subject to ionic interactions involving polyelectrolytic segments or supramolecular effects based on highly organized hydrogen bonds. SMPs can undergo solid-to-solid transitions (e.g., a change in morphology). Solid-to-solid transitions are well known to those skilled in the art, for example, as in poly(styrene-block-butadiene).

Various changes can occur in the structure of an object formed using shape memory polymers. If the objects are three-dimensional, the shape changes may be two-dimensional. If the objects are essentially two-dimensional, such as fibers, then the shape changes will be one-dimensional, such as along the length. The thermal and electrical conductivity of materials can also change in response to changes in temperature.

The moisture permeability of the composition can be altered, particularly when the polymer is formed into a thin film (i.e., less than about 10 μm). Certain polymer compositions, in their original shape, have sufficient permeability such that water vapor molecules can be transmitted through the polymer film, while water molecules are not large enough to penetrate the polymer film. The resulting materials have low moisture permeability at temperatures below room temperature and high moisture permeability at temperatures above room temperature.

Stimuli other than temperature may be used to induce shape changes. As described below with respect to certain embodiments, shape changes may be induced by exposure to light or an agent such as an ion that alters interpolymer bonds.

I. Polymer segments

The segments are preferably oligomers. As used herein, the term "oligomer" refers to a linear chain molecule having a molecular weight of up to 15,000 Daltons.

The polymers are selected based on the desired glass transition temperature(s) (if the at least one segment is amorphous) or melting point(s) (if the at least one segment is crystalline), which in turn is based on the desired applications, taking into account the environment of use. Preferably, the number average molecular weight of the polymer segment is greater than 400 and preferably is in the range between 500 and 15,000.

PL 193 700 B1

The transition temperature at which the polymer suddenly becomes soft and deforms can be controlled by changing the monomer composition and type of monomer, which allows the shape memory effect to be adjusted at the desired temperature.

The thermal properties of polymers can be detected, for example, by dynamic mechanical thermoanalysis or differential scanning calorimetry (DSC) studies. In addition, the melting point can be determined using standard melting point apparatus.

1. Thermosetting or thermoplastic polymers

Polymers may be either thermosetting polymers or thermoplastic polymers, although thermoplastic polymers may be preferred due to their ease of forming.

Preferably, the degree of crystallinity of the polymer or polymer block(s) is between 3 and 80%, more preferably between 3 and 60%. When the degree of crystallinity is greater than 80% while all the soft segments are amorphous, the resulting polymer composition has unsatisfactory shape memory characteristics.

The tensile strength of polymers below Ttrans is typically between 50 Mpa and 2 Gpa (gigapascals), while the tensile strength of polymers above Ttrans is typically between 1 and 500 Mpa. Preferably, the ratio of the elastic moduli above and below Ttrans is 20 or greater. The higher this ratio, the better the shape memory of the resulting polymer composition.

The polymer segments may be natural or synthetic, although synthetic polymers are preferred. The polymer segments may be biodegradable or non-biodegradable. Although the resulting SMP composition is biodegradable, biocompatible polymers are particularly preferred for medical applications. Generally, these materials degrade by hydrolysis, by exposure to water or enzymes under physiological conditions, by surface erosion, by bulk erosion, or a combination thereof. Non-biodegradable polymers used for medical applications preferably do not contain aromatic groups other than those present in naturally occurring amino acids.

Representative natural polymer segments or polymers include proteins such as zein, modified zein, casein, gelatin, gluten, serum albumin, and collagen, and polysaccharides such as alginate, celluloses, dextrans, pullulan, and polyhyaluronic acid, as well as chitin, poly(3-hydroxyalkanoates), especially poly(ε-hydroxybutyrate), poly(3-hydroxyoctanoate), and poly(3-hydroxy fatty acids).

Representative natural biodegradable polymer segments or polymers include polysaccharides such as alginate, dextran, cellulose, collagen, and chemical derivatives thereof (substitutions, additions of chemical groups, for example, alkyl, alkylene, hydroxylations, oxidations, and other modifications routinely performed by those skilled in the art), and proteins such as albumin, zein, copolymers, and compositions thereof, alone or in combination with synthetic polymers.

Representative synthetic polymer blocks include polyphosphazenes, polyvinyl alcohols, polyamides, polyester amides, polyamino acid(s), synthetic polyamino acid(s), polyanhydrides, polycarbonates, polyacrylates, polyalkylenes, polyacrylamides, polyalkylene glycols, polyalkylene oxides, polyalkylene terephthalates, polyorthoesters, polyvinyl ethers, polyvinyl esters, polyvinyl halides, polyvinylpyrrolidone, polyesters, polylactides, polyglycolides, polysiloxanes, polyurethanes, and copolymers thereof.

Examples of suitable polyacrylates include poly(methyl methacrylate), poly(ethyl methacrylate), poly(butyl methacrylate), poly(isobutyl methacrylate), poly(hexyl methacrylate), poly(isodecyl methacrylate), poly(lauryl methacrylate), poly(phenyl methacrylate), poly(methyl acrylate), poly(isopropyl acrylate), poly(isobutyl acrylate), poly(octadecyl acrylate).

Synthetically modified natural polymers include cellulose derivatives such as alkyl celluloses, hydroxyalkyl celluloses, cellulose ethers, cellulose esters, nitrocelluloses, and chitosan. Examples of suitable cellulose derivatives include methyl cellulose, ethyl cellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose, hydroxybutyl methyl cellulose, cellulose acetate, cellulose propionate, cellulose acetate butyrate, cellulose acetate phthalate, carboxymethyl cellulose, cellulose triacetate, and sodium cellulose sulfate. They are collectively referred to herein as "celluloses."

Representative synthetic degradable polymer segments include polyhydroxy acids such as polylactides, polyglycolides, and copolymers thereof; poly(ethylene terephthalate); poly(hydroxybutyric acid); poly(hydroxyvaleric acid); poly[lactide-co-fe-caprolactone]; poly[glycolide-(e-caprolactone)]; polycarbonates, poly(pseudoamino acids); poly(amino acids); poly(hydroxyalkanoates); polyanhydrides; polyorthoesters, and blends and copolymers thereof.

PL 193 700 B1

Examples of non-biodegradable synthetic polymer segments include ethylene vinyl acetate, poly(meth)acrylic acid, polyamides, polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyvinylphenol, and copolymers and mixtures thereof.

Rapidly bioerodible polymers such as poly(lactide-co-glycolide), polyanhydrides, and polyorthoesters, which have carboxyl groups exposed to the outer surface when the smooth polymer surface erodes, can also be used. Furthermore, polymers containing labile bonds, such as polyanhydrides and polyesters, are well known for their hydrolytic reactivity. Their hydrolytic degradation rates can be substantially altered by simple changes in the polymer backbone and their sequence structure.

Various polymers, such as polyacetylene and polypyrrole, are conductive polymers. These materials are particularly favored for applications where electrical conductivity is important. Examples of these applications include tissue engineering and biomedical applications where cell growth is to be stimulated. These materials may find particular utility in the field of computer science because they can absorb heat without increasing temperature better than SMA. Conductive shape memory polymers are useful in tissue engineering for stimulating tissue growth, such as neural tissue.

2. Hydrogels

The polymer may be in the form of a hydrogel (typically absorbing up to about 90% by weight of water) and may optionally be ionically cross-linked with polyvalent ions or polymers. The ionic cross-link between the soft segments may be used to maintain the structure, which, when deformed, can be reformed by breaking the ionic cross-links between the soft segments. The polymer may also be in the form of a gel in solvents other than water or aqueous solutions. In these polymers, the temporary shape may be established by hydrophilic interactions between the soft segments.

Hydrogels can be formed from polyethylene glycol, polyethylene oxide, polyvinyl alcohol, polyvinyl pyrrolidone, polyacrylates, polyethylene terephthalate, polyvinyl acetate, and their copolymers and blends. Some polymer segments, such as acrylic acid, become elastomeric only when the polymer is hydrated and hydrogels are formed. Other polymer segments, such as methacrylic acid, are crystalline and capable of melting even when the polymers are not hydrated. Any polymer block can be used, depending on the desired application and conditions of use.

For example, shape memory is observed in acrylic acid copolymers only in the hydrogel state, because the acrylic acid units are essentially hydrated and behave like a soft elastomer with a very low glass transition temperature. Dry polymers are not shape memory polymers. When dry, the acrylic acid units behave like a hard plastic even above the glass transition temperature and exhibit no abrupt change in mechanical properties upon heating. In contrast, copolymers containing methyl acetate polymer segments as soft segments exhibit shape memory properties even when dry.

3. Polymers capable of forming a gel at elevated temperatures.

Certain polymers, such as poly(ethylene oxide-co-propylene oxide) (PLURONICS™), are water-soluble at temperatures below body temperature and become hydrogels at temperatures above body temperature. Incorporating these polymers as segments into shape memory polymers provides shape memory polymers with the ability to respond to temperature changes in a manner opposite to typical shape memory polymers. These materials recover their shape when cooled below their shape recovery temperature rather than when heated above their shape recovery temperature. This effect is called the reverse thermal shape memory effect. Shape memory polymer compositions incorporating these polymer segments are useful in various biomedical applications where the polymer can be inserted as a liquid and cooled to recover the intended shape in situ. The reverse thermal shape memory effect can be achieved by incorporating two different segments into the polymer that are miscible at temperatures lower than Tmisc (Tmixing) but immiscible at higher temperatures. Phase separation at higher temperatures stabilizes the temporary shape.

Polymers can be obtained from commercial sources such as Sigma Chemical Co., St. Louis, MO.; Polysciences, Warrenton, PA; Aldrich Chemical Co., Milwaukee, WI; Fluka, Ronkonkoma, NY; and BioRad, Richmond, CA. Alternatively, polymers can be synthesized from monomers obtained from commercial sources using standard techniques.

PL 193 700 B1

II. Assembly of polymer segments

The shape memory polymer comprises one or more hard segments and one or more soft segments, wherein at least one of the segments is biodegradable or at least one of the segments is linked to another segment via a biodegradable linkage. Representative biodegradable linkages include ester-, amide-, anhydride-, carbonate-, or orthoester linkages.

1. Polymer structures.

The shape memory effect is based on the morphology of the polymer. In thermoplastic elastomers, the original shape of the object is established by physical cross-links caused by the hard segment. In thermosetting polymers, the soft segments are covalently cross-linked instead of having hard segments. The original shape is established by the cross-linking process.

Unlike existing segmented polyurethane SMPs in the art, the segments of the compositions described herein need not be linear. The segments may be partially grafted or attached at dendritic side groups.

A. Thermoplastic and thermoelastic polymers

The polymers may be in the form of linear diblock, triblock, tetrablock, or multiblock polymers, branched or grafted polymers, thermoplastic elastomers that contain dendritic structures, and blends thereof. Figure 3 illustrates certain combinations of suitable classes of thermoplastic materials forming hard and soft segments. The thermoplastic shape memory polymer composition may also be a blend of one or more homopolymer or copolymer with one or more diblock, triblock, tetrablock, or multiblock copolymers, branched or grafted polymers. These types of polymers are well known to those skilled in the art.

As used herein, the term "degradable thermosetting material" refers to (i) thermosetting SMPs that contain cleavable bonds and (ii) thermosetting materials containing more than one soft segment, wherein at least one soft segment is degradable or different soft segments are connected by cleavable bonds. There are four different types of thermosetting polymers that have shape memory capability. These include polymer networks, semi-interpenetrating networks, interpenetrating networks, and mixed interpenetrating networks.

i. Polymer networks

A polymer network is prepared by covalently cross-linking macromonomers, i.e., polymers containing polymerizable end groups such as carbon-carbon double bonds. The polymerization process can be induced by the use of light- or heat-sensitive initiators or by curing with ultraviolet light without an initiator. Shape-memory polymer networks are prepared by cross-linking one or more soft segments that respond to one or more thermal transitions.

In an embodiment preferred for medical applications, cross-linking is accomplished using photocrosslinking and does not require any chemical initiator. Photocrosslinking advantageously eliminates the need for initiator molecules, which can be toxic. Fig. 4 is a reaction sequence diagram for the synthesis of the preferred photocrosslinker, which produces an overall reaction yield of approximately 65%.

ii. Interpenetrating networks

Interpenetrating networks ("IPNs") are defined as networks where two components are cross-linked but not interconnected. The primary shape is determined by the network with the highest cross-link density and the highest mechanical strength. The material has at least two Ttrans corresponding to different soft segments of the two networks.

iii. Mixed networks that interpenetrate each other

A mixed IPN comprises at least one physically cross-linked polymer network (thermoplastic polymer) and at least one covalently cross-linked polymer network (thermoset polymer), which cannot be separated by any physical means. The primary shape is established by the covalently cross-linked network. The temporary shapes correspond to the T trans of the soft segments and the T trans of the hard segment of the thermoplastic elastomer component.

A particularly preferred mixed interpenetrating network is prepared by polymerizing a reactive macromonomer in the presence of a thermoplastic polymer, for example,

PL 193 700 B1 by photopolymerization of carbon-carbon double bonds. In this embodiment, the weight ratio of thermosetting polymer to thermoplastic polymer is preferably between 5:95 and 95:5, more preferably between 20:80 and 80:20.

iv. Semi-interpenetrating networks

Semi-interpenetrating networks ("semi-IPNs") are defined as two independent components, where one component is a cross-linked polymer (polymer network) and the other component is a non-cross-linked polymer (homopolymer or copolymer), wherein the components cannot be separated by physical means. The semi-interpenetrating network has at least one thermal transition corresponding to the soft segment(s) and the homo- or copolymer components. The cross-linked polymer preferably constitutes between about 10 and 90% by weight of the semi-interpenetrating network composition.

v. Polymer kits

In a preferred embodiment, the shape memory polymer compositions described herein are formed from a biodegradable polymer composition. As used herein, a "biodegradable polymer composition" is a composition having at least one biodegradable polymer.

Shape memory polymers can exist as physical mixtures of thermoplastic polymers. In one embodiment, the shape memory polymer composition can be prepared by the interaction or blending of two thermoplastic polymers. The polymers can be semi-crystalline homopolymers, semi-crystalline copolymers, thermoplastic elastomers with linear chains, thermoplastic elastomers with side chains or any type of dendritic structural elements, and branched copolymers, and can be blended in any combination thereof.

For example, a multiblock copolymer with a hard segment with a relatively high T trans and a soft segment with a relatively low T trans can be mixed or combined with a second multiblock copolymer with a hard segment with a relatively low T trans and the same soft segment as in the first multiblock copolymer. The soft segments in both multiblock copolymers are identical, so the polymers are miscible with each other when the soft segments are melted. There are three transition temperatures in the resulting composition: that of the first hard segment, that of the second hard segment, and that of the soft segment. Accordingly, these materials are capable of memorizing two different shapes. The mechanical properties of these polymers can be adjusted by changing the weight ratio of the two polymers.

Other types of sets of at least two multiblock copolymers can be prepared, in which at least one segment is mixed with at least one segment from another multiblock copolymer. If two different segments are miscible and together form a single domain, then the thermal transition of that domain depends on the weight fraction of the two segments. The maximum number of memorized shapes results from the number of thermal transitions of the set.

Shape memory polymers can have better shape retention than the components themselves. Shape memory polymers are composed of at least one multiblock copolymer and at least one homo- or copolymer. In principle, di-, tri-, or tetrablock copolymers can be used instead of the multiblock copolymer.

Shape memory polymers are highly useful in industrial applications because a wide range of mechanical, thermal, and shape memory properties can be obtained from just two or three basic polymers by combining them in different weight ratios. A twin-screw extruder is an example of standard process equipment that can be used for compounding and processing the polymers.

III. Methods of performing SMP

The polymers described above are either commercially available or can be synthesized using methods known to those skilled in the art. Examples 1 and 2 below present experimental procedures for preparing SMPs.

IV. Methods of shaping SMP compositions

These compositions may be formed into a first shape under appropriate conditions, for example, at a temperature above the T trans of the hard segments and cooled below the T trans of the soft segment(s). Standard techniques include extrusion and injection molding. Optionally, the article may be remolded into a second shape. Under the influence of heat or another appropriate set of factors, the article returns to its original shape.

PL 193 700 B1

Thermosetting polymers can be prepared by extruding prepolymerized material (macromonomers) and setting the original shape at a temperature above the T trans of the thermosetting polymer, for example by photocuring reactive groups on the monomer.

The temporary shape is established by cooling the material below Ttrans after the material has been deformed.

Fig. illustrates the photo-induced shape memory effect.

Cross-linking can also be performed in a solution of the macromonomers, with the solvent being removed from the formed gel in a subsequent operation.

Compositions made from thermoplastic polymers can be blown, extruded into sheets, or shaped by injection molding, for example, to form fibers. These compositions can also be shaped by other methods known to those skilled in the art to shape solid objects, for example, laser abatement, micromachining, machining, hot wire, and CAD/CAM (computer-aided design/manufacturing) processes. These processes are preferred for shaping thermoset polymers.

V. Therapeutic, prophylactic and diagnostic applications

Any of a variety of therapeutic, prophylactic and diagnostic agents may be incorporated into the polymer compositions, which can locally or systemically deliver the incorporated agents upon administration to a patient.

Examples include synthetic inorganic and organic compounds or molecules, proteins and peptides, polysaccharides and other sugars, lipids, and nucleic acid molecules having therapeutic, prophylactic, and diagnostic activities.

Nucleic acid molecules include genes, plasma DNA, bare DNA, antisensory molecules that bind to complementary DNA to inhibit transcription, ribozymes, and ribozyme guidance sequences. Due to their diverse biological activities, they include vasoactive agents, neuroactive agents, hormones, growth factors, cytokines, anesthetics, steroids, anticoagulants, anti-inflammatory agents, immunomodulators, cytotoxic agents, prophylactic agents, antibiotics, antivirals, antisensory agents, antigens, and antibodies. In some cases, proteins may be antibodies or antigens that would otherwise require injection to elicit a response.

Proteins are defined as consisting of 100 or more amino acid residues; peptides are residues of fewer than 100 amino acids. Unless otherwise specified, the term protein refers to both proteins and peptides. Polysaccharides, such as heparin, may also be administered. Compounds with a wide range of molecular weights, for example, between 10 and 500,000 grams per mole, may be encapsulated.

Commercially available imaging agents may also be mentioned that can be used in positron emission tomography (PET), computer-assisted tomography (CAT), single-photon emission computerized tomography, X-ray, fluoroscopy, magnetic resonance imaging (MRI), and ultrasound imaging.

VI. Articles, Devices and Coatings

SMP compositions can also be used in biomedical and other applications.

1. Articles and devices for medical applications

Examples of such applications include sutures, orthodontic materials, bone screws, nails, plates, catheters, tubes, films, patency tubes, orthopedic braces, splints, cast preparation tape, tissue engineering scaffolds, contact lenses, drug delivery devices, implants, and thermal indicators.

SMP compositions are preferably made from biocompatible polymers and, for most applications, biodegradable polymers, where the rate of degradation can be controlled depending on the type of composition and polymer crosslinking. Biodegradable polymer implants eliminate the need for implant recovery and can be used concurrently to deliver therapeutic agents.

These materials can be used in many applications requiring load-bearing capacity and controlled degradation.

Polymer compositions can also be molded into the shape of an implant to be implanted inside the body to perform a mechanical function. Examples of such implants include rods, pins, screws, plates, and anatomical shapes.

PL 193 700 B1

A particularly recommended use of the composition is the preparation of sutures that are stiff enough to ensure easy insertion, but after reaching body temperature they soften and create a second shape that is more comfortable for the patient during further treatment.

Another beneficial application is for catheters, which should be stiff below body temperature for easier insertion and soften when warmed to body temperature, providing adequate patient comfort.

The polymer compositions may also be combined with fillers, reinforcing materials, radioimaging materials, excipients, or other materials as needed for the particular implant application. Examples of fillers include calcium sodium metaphosphate, which is described in U.S. Patent No. 5,108,755. Those skilled in the art can readily determine the appropriate amount of these materials to include in the composition.

Articles may incorporate various therapeutic and/or diagnostic measures as described above.

2. Non-medical applications

There are numerous applications for shape memory polymer compositions other than biomedical applications.

Examples of non-medical applications for biodegradable polymers include items for which disposal is a concern, such as disposable diapers and sanitary napkins, and packaging materials.

3. Coatings with controlled degradation

Shape memory polymers can be designed to have variable degradation rates. For example, in one embodiment, a hydrolytically degradable polymer can be selectively protected by applying a hydrophobic SMP coating to temporarily prevent water from reaching the hydrolytically cleavable bonds in the polymer mass. The protective feature of the coating can then be modified as desired by applying an external stimulus such that the diffusion properties of the coating are altered, allowing water and other aqueous solutions to penetrate the coating and initiate the degradation process. If the hydrolysis rate is relatively high compared to the water diffusion rate, then the rate of water diffusion through the coating determines the degradation rate. In another embodiment, a hydrophobic coating composed of densely cross-linked soft segments can be used as a diffusion barrier for water or aqueous solutions. The soft segments should be at least partially cross-linked by bonds that can be cleaved by the application of a stimulus. The rate of water diffusion can be increased by lowering the cross-link density.

VII. Methods of use

Certain manufactured articles are designed to maintain their intended shape unless they function in a manner inconsistent with their normal use. For example, a car bumper will maintain its intended shape unless impacted. These manufactured articles are intended to be used in their intended shape and repaired, for example, by applying heat, if damaged.

Other manufactured articles are designed for use in such a way that a first shape is intended for initial use and a second shape is intended for subsequent use. Examples of these articles include biomedical devices that can form a second shape upon reaching body temperature or upon the application of an external stimulus that heats the device above body temperature.

Still other manufactured articles are designed to be used such that their shape changes in response to or adjusts according to changes in temperature, such as thermal sensors in medical devices.

The present invention will be better understood by the following non-limiting examples.

Example 1: Copolyesterurethane shape memory polymers

A group of biocompatible and biodegradable multiblock copolymers exhibiting a thermal shape memory effect were synthesized. These polymers were composed of a crystallizable hard segment (Tm) and a soft segment with a thermal transition temperature Ttrans between room temperature and body temperature. Unlike prior art segmented polyurethanes, the hard segment was an oligoester or oligoetherester and did not contain an aromatic component.

PL 193 700 B1

The mechanism of temporary shape programming and permanent shape recovery of the multiblock copolymer is shown in Fig. 6. The permanent shape of the materials was set by melting the polymer and cooling above Ttrans (Fig. 6, top). The polymer was then formed into its temporary shape (Fig. 6, right), which was set by cooling below Ttrans (Fig. 6, bottom).

lower). After unloading, the solid shape was recovered by heating above Ttrans.

Synthesis of telechelics, oligomers with functional groups at both ends

The telechelic macrodiol was synthesized by ring-opening polymerization of cyclic monomers with di(n-butyl)tin oxide as a transesterification catalyst in a N2 atmosphere.

The hard segment α,β-dihydroxy[oligo(ethylene glycol glycolate)ethylene oligo(ethylene glycol glycolate)]-(PDS1200 and PDS1300) was prepared as follows. The p-dioxane-2-one monomer was obtained by distillation (thermal depolymerization) of the oligomer before use. 57 g (0.63 mol) of the monomer, 0.673 g (10.9 mmol) of ethylene glycol, and 0.192 g (0.773 mmol) of di(n-butyl)tin oxide were heated to 80°C for 24 h. The end of the reaction (equilibrium) was determined by GPC. The product was dissolved in hot 1,2-dichloroethane and hot filtered through a Buechner funnel packed with silica gel.

The product was obtained by precipitation in hexanes and dried in vacuum for 6 h.

Soft segment

i. Crystalline

Poly(propylene-caprolactone)diols with various _Mn are commercially available, for example, from Aldrich and Polisciences. Here, PCL-2000 was used.

ii. Amorphous α,β-O-dihydroxy[oligo(L-lactane-co-glycolate)ethylene oligo(L-lactane-co-glycolate)-(abbreviation: PLGA2000-15) was prepared as follows. In a 1000 ml two-necked round-bottom flask, 300 g (2.08 mol) L,L-dilactide, 45 g (0.34 mol) diglycolide, and 4.94 g (0.80 mol) ethylene glycol were heated to melt at 40°C and stirred. 0.614 g (2.5 mmol) tin di(n-butyl)oxide was added. After 7 h, the reaction reached equilibrium as determined by GPC. The reaction mixture was dissolved in 1,2-dichloroethane and purified on a silica gel column. The product was obtained by precipitation in hexanes and dried in vacuum for 6 h.

Properties of telechelics

The molecular weight Mn and thermal properties of the macrodiols were determined as shown in Table 1 below.

T a b l e 1:

Molecular mass and thermal properties of macrodiols

Label Mn GPC [g-mol ^-1 ] MnVPO [g-mol ^-1 ] Tm [°C] ΔΗ [Jg ^-1 ] 1 about ΔCp [Jg ^-1 ] PCL2000 1980 1690 43 73.5 <-40 - PDS1300 1540 1340 97 74.5 <-20 - PDS1200 2880 1230 95 75.0 <-20 - PLGA2000 2020 1960 - - 29.0 0.62

Synthesis of thermoplastic elastomers (multiblock copolymer)

In a 100-ml two-necked round-bottomed flask connected to a Soxhlet extractor packed with 0.4-nm molecular sieves, two different macrodiols (one hard segment and one soft segment), as described in Table 2 below, were dissolved in 80 ml of 1,2-dichloroethane. The mixture was recirculated to dryness by azeotropic extraction from the solvent. Freshly distilled trimethylhexane-1,6-diisocyanate was added by syringe, and the reaction mixture was heated to 80°C for at least 10 days. At regular intervals, samples of the mixture were taken to determine the molecular weight of the polymer by GPC. At the end of the reaction, the product was obtained by precipitation of the polymer in hexanes and purified by redissolving it in 1,2-dichloroethane and precipitating it in hexanes.

Multiblock copolymers were prepared from the following two types of polymers.

PL 193 700 B1 (i) PDC polymers contain polyphenylene-caprolactone.) T _trans for the soft segment is the melting point.

(ii) PDL polymers contain α, ff>-dihydroxy[oligo(L,-lactane-co-glycolate)ethylene oligo(L-lactane-co-glycolate). Ttrans for the soft segment is the glass transition temperature.

T a b l e 2:

Synthesis of multiblock copolymers

Polymer 1. Diol m [g] n [mmol] 2. Diol m [g] n [mmol] TMDI [mmol] time [days] PDC22 PDS1200 3.0245 2,653 PCL2k 6.0485 3,024 5,738 10 PDL23 PDS1200 2.2787 2,000 PLGA2k 6.1443 3,070 5,163 10 PDC27 PDS1300 2.5859 1,724 PCL2k 5.3611 2,681 4,368 14 PDC40 PDS1300 3.6502 2,433 PCL2k 3.9147 1,957 4,510 13 PDC37 PDS1300 3.2906 2,194 PCL2k 4.8619 2,431 4,500 16 PDL30 PDS1300 3.7115 2,474 PLGA2k 4.0205 2,011 4,480 16

Properties of thermoplastic elastomers

The physical, mechanical and degradation properties determined for the compositions are given in Tables 3-9 below.

The hydrolytic degradation behavior of the new materials was studied in a pH 7 buffer solution at 37°C. It was shown that the polymers are completely degradable and their degradation rate can be controlled by the concentration of easily hydrolyzable ester bonds. The values of relative mass loss mr = m(t0)/m(t) in % at 37°C, and the relative molecular mass loss Mr = Mw(t)/M(t0) in % at 37°C.

The toxicity of two different multiblock copolymers was tested using the chicken egg test. It was shown that blood vessels developed regularly and were not affected by the polymer samples.

T a b l e 3:

Composition of copolyester urethanes determined by ¹ H-NMR spectroscopy at 400 MHz

Label Hard segment Mass content [%]* Soft segment Mass content [%]* PDL23 PDS 23.0 PLGA 54.2 PDL30 PDS 30.0 PLGA 52.1 PDC22 PDS 22.0 PCL 64.5 PDC27 PDS 27.0 PCL 61.1 PDC37 PDS 31.1 PCL 55.4 PDC40 PDS 40.4 PCL 46.2

* There is a difference in urethane content of up to 100%

PL 193 700 B1

T a b l e 4:

Molecular mass Mm of urethane copolyester films determined by multidetector-GPC

Label Polymer film Mw(LS) [g-mol ^-1 ] Mw(Visc) [g-mol ^-1 ] dn/dc [g-mol ^-1 ] PDL23 161,500 149,000 0.065 PDL30 79,100 83,600 0.057 PDC22 119,900 78,500 0.078 PDC27 72,700 61,100 0.080 PDC31 110,600 108,600 0.065 PDC40 93,200 86,300 0.084

T a b l e 5:

Transition temperatures Tm and Tg, melting enthalpies \H _TI and change in heat capacity Δcp of the polymer film from DSC

Measurements (values given from the second heating process) Label Έ o i— ΔHm1 [Jg ^-1 ] Tg [°C] ΔCp [Jg ^-1 ] Tim ² [ ^o C] \Hm2 [Jg ^-1 ] PDL23 - - 34.5 0.38 - - PDL30 - - 33.5 0.25 85.0 8.5 PDC22 35.0 26.0 - - - - PDC27 37.0 25.0 - - 75.5 3.5 PDC31 36.5 28.5 - - 76.5 5.5 PDC40 35.0 7.0 - - 77.5 7.0

T a b l e 6:

Mechanical properties of polymer films at 50°C from tensile tests

Code E-modulus [Mpa] Or [%] σρ [Mpa] smax [%] cmax [Mpa] PDL27 1.5 1,350 2.1 1,300 2.3 PDC31 1.5 1,400 4.9 1,300 5.4 PDC40 4.0 1,250 5.8 1,300 5.9 PDL30 2.0 1,400 2.1 1,250 2.3

T able 7: Degradability of PDL22

Degradation time [days] Mr(viscometry) [%] Mr(light scattering) [%] 14 81.3 85.7 21 67.1 74.6 29 62.9 65.6 42 43.6 47.7 56 54.4 41.9

PL 193 700 B1

Table 8: Degradability of PDL23

Degradation time [days] Mr(viscometry) [%] Mr(light scattering) 14 61.1 87.3 21 40.7 76.7 29 32.8 62.2 42 17.4 46.7 56 16.9 18.7

Table 9: Relative mass loss

PDC22 PDL23 Degradation time [days] m _r [%] m _r [%] 14 99.2 98.1 21 99.3 97.5 29 98.6 97.2 42 98.3 96.9 56 97.3 93.3

Shape memory properties

Figure 7 shows the results of tensile tests performed on multiblock copolymers as a function of thermolytic cycles. The average rate of shape fixation of the thermocycled polymers and the dependence of the strain recovery rate as a function of the number of cycles are shown below in Tables 10 and 11, respectively. The polymers have high shape fixation and equilibrium was reached after only two cycles.

T a b l e 10:

Average shape-fixing speed Rf

Label Rf [%] PDC27 97.9 PDC40 96.2 PDL30 97.7

T a b l e 11:

Dependence of the number of cycles on the strain removal rate Rr

PDC27 PDC40 PDL23 Number of cycles Rr [%] Rr [%1] Rr [%] 2 77.3 73.7 93.8 3 93.2 96.3 98.8 4 98.5 98.7 98.9 5 98.5 98.7 98.8

Example 2: Degradable shape memory thermoset with a crystallizable soft segment

A range of poly(poly ...

PL 193 700 B1

Macromonomer synthesis

Poly(phenyl)caprolactone)dimethacrylates (PCLDMA) were prepared as follows. To a solution of poly(phenyl)caprolactone)diol with M _n = 2'000mol ^-1 (20.0 g, 10 mmol) and triethylamine (5.3 ml, 38 mmol) in 200 ml of dry THF, methacryloyl chloride (3.7 ml, 38 mmol) was added dropwise at 0°C. The solution was stirred at 0°C for 3 days and the precipitated salt was filtered off. After concentrating the mixture at room temperature under reduced pressure, 200 ml of ethyl acetate was added and the solution was again filtered and precipitated into a tenfold excess of a mixture of hexanes, diethyl ether, and methanol (18:1:1). The colorless precipitate was collected, dissolved in 200 ml of dichloroethane, reprecipitated and dried carefully at room temperature under reduced pressure.

Synthesis of thermosetting materials

The macromonomer (or monomer mixture) was heated to 10°C above its melting point (Tm) and placed in a mold formed by two glass plates (25 mm x 75 mm) and a 0.60 mm thick Teflon spacer. To achieve good homogeneity, the mold was kept at Tm for a further hour. Photocuring was performed on the heated plate at Tm for 15 min. The distance between the heating lamp head and the sample was 5.0 cm. After cooling to room temperature, the sample was extracted and swollen with a 100-fold excess of dichloromethane overnight and washed thoroughly. Finally, the sample was dried at room temperature under vacuum.

Properties of macromonomers and thermosetting materials

Table 12 below lists the poly(phenylene-caprolactone)dimethacrylates that were prepared, as well as the corresponding degree of acrylation (Da) (%). The number following PCLDMA is the molecular weight Mn of the poly(phenylene-caprolactone)diol used in the synthesis as determined using ¹² H-NMR and GPC, rounded to the nearest 500.

T a b l e 12:

Poly(s-caprolactone)diol and degree of acrylation

Name Da [%] PCLDMA1500 87 PCLDMA2000 92 PCLDMA3500 96 PCLDMA4500 87 PCLDMA6500 93 PCLDMA7000 85 PCLDMA10000 86

Figure 8 shows the melting temperature (Tm) of diols, dimethacrylates, and poly(phenylene)caprolactone thermosets as a function of the molar mass _{Mn of} the macromonomers. In the graph, macrodiols are represented by ----; macromonomers by......, and thermosets by -▲The tensile properties of poly(phenylene)caprolactone thermosets C1 to C7 at room temperature are shown below in Table 13, where E is the elastic modulus (Young's modulus), ε, _; is the elongation, and σ, is the stress at yield, a _max is the maximum stress, _επ3χ is the elongation at _σπ3χ , _εκ is the elongation at break, and _σβ is the stress at break. Table 14 below shows the tensile properties of the same poly(polyphenyl)caprolactone thermosets at 70°C.

PL 193 700 B1

T a b l e 13:

Tensile properties of thermosetting materials at room temperature

Name E [MPa] εs [%] σs [MPa] ^ax ^[ % ^] G'max [MPa] εR [%] σ _R [MPa] Cl 2.4+0.6 - - 16.1±2.0 0.4±0.1 16.1 ±2.3 0.38+0.02 C2 35±3 - - 20.6±0.3 4.7±0.1 20.6+0.3 4.7+0.1 C3 38±1 48±1 11.2±0.1 180+20 12.1±1.2 190±20 11.7±1.6 C4 58±4 54±1 12.2±0.1 247±4 13.6+1.9 248±13 15.5±2.7 C5 7211 56±2 15.5±0.2 275±10 15.6+1.7 276±6 15.0±1.0 C6 71±3 43±2 14.2+0.1 296±14 15.5±0.2 305±8 13.8±2.7 C7 71±2 42±5 13.6±0.2 290±30 16.2±0.5 290±30 15.7±0.9

T a b l e 14:

Tensile properties of thermosetting materials at 70°C

Name E [MPa] G'max [MPa] εR [%] Cl 1.84+0.03 0.40±0.08 24±6 C2 2.20±0.12 0.38±0.05 18±2 C3 6.01+0.12 2.05±0.21 43±9 C4 2.30±0.16 0.96±0.01 61±3 C5 1.25±0.08 0.97±0.15 114±13 C6 1.91±0.11 1.18±0.06 105±11 C7 0.70±0.09 0.79±0.10 210±7

Shape memory properties

Thermosetting materials were determined to have the thermomechanical properties shown in Table 15. The average molecular weight (Mn) refers to the macromonomer. The lower limiting temperature, T1, is 0°C, and the upper limiting temperature, Th, is 70°C. The extension of the temporary shape is 50%. Rr(2) is the strain recovery rate of the second cycle, Rr,tot is the total strain recovery rate after 2 cycles, and Rf is the average strain fixation rate.

T a b l e 15:

Thermomechanical properties of thermosetting materials

Name Mn [g-mol ^-1 ] Rr(2) [%] Rr,tot [%] Rf [%] C4 4,500 93.3 93.0 93.9+0.2 C5 6,500 96.3 94.5 93.9±0.2 C6 7,000 93.8 92.1 92.5±0.1 C7 10,000 98.6 96.8 86.3±0.5

Patent claims

Claims (19)

Patent claims A degradable shape memory polymer composition comprising at least one hard segment, the transformation temperature of which Ttrans is in the range of -40 to 270 ° C, and at least one associated with the at least one hard segment, The soft segment, the transformation temperature of which Ttrans is at least 10 ° C lower than the transformation temperature Ttrans of the hard segment (s), and at least one of the hard or soft segments has a degradable region, or at least one pair of hard and soft segments has a degradable bond. 2. A degradable composition according to Claim 1; The composition of claim 1, wherein the shape memory polymers are affected by external stimuli, especially temperature or light. 3. A degradable composition according to Claim 1; The method of claim 1 or 2, characterized in that the transformation temperature Ttrans of the hard segment is in the range from 30 to 150 ° C, preferably up to 100 ° C. 4. A degradable composition according to Claim 1; The process of claim 1 or 2, characterized in that the transformation temperature Ttrans of the soft segment (s) is at least 20 ° C lower than the transformation temperature Ttrans of the hard segment (s). 5. A degradable composition according to Claim 5; The method of claim 1 or 2, characterized in that at least one of the hard and soft segments is a thermoplastic polymer. 6. A degradable composition according to Claim 6; The method of claim 1 or 2, characterized in that cyclic portions are present in the hard segment. 7. A degradable composition according to Claim 7; The method of claim 1 or 2, characterized in that the weight ratio of the hard and soft segments is in the range from about 5: 95 to 95: 5, preferably from 20: 80 to 80:20. 8. A degradable composition according to Claim 8; The shape-memory polymer as claimed in claim 1 or 2, wherein the shape memory polymer belongs to the group consisting of graft, linear and dendritic polymers. 9. A degradable composition according to Claim 9; The method of claim 1 or 2, wherein the degradable region of the polymer belongs to the group consisting of polyhydric acids, polyester ether, polyorthoesters, polyamino acids, synthetic polyamino acids, polyanhydrides, polycarbonates, polyhydroxyalkanes, and polyphaprolactones). 10. A degradable composition according to Claim 10; The method of claim 1 or 2, wherein the polymer comprises a biodegradable bond that belongs to the group consisting of ester, carbonate, amide, anhydride and orthoester subgroups. 11. A degradable composition according to Claim 11; The composition of claim 1 or 2, characterized in that the polymer is completely biodegradable. 12. A degradable composition according to Claim 1; The method of claim 1 or 2, characterized in that it comprises a degradable thermosetting polymer which in turn comprises a crystallizing soft segment with a cross-linked covalent structure having a melting point Tm in the range of 250 ° C to (-) 40 ° C, preferably of 200 ° C. ° C to 0 ° C, or a soft segment, cross-linked covalent structure, having a transition temperature Ttrans ranging from 250 ° C to (-) 60 ° C, preferably from 200 ° C to 0 ° C. 13. A degradable composition according to Claim 1; 3. The method of claim 1 or 2, characterized in that it comprises at least two segments: a) the first segment, the transformation temperature of which Ttrans is in the range from -40 to 270 ° C, b) a second segment which is associated with at least one first segment and which is an ionic interaction of sufficient strength that the second segment is capable of forming a physical cross-link other than at the melting or glass transition temperature, at least one of the segments having a melting point. the biodegradable region or at least one of the first segments is bound to at least one of the second segments through a biodegradable bond. 14. A degradable composition according to Claim 14; The method of claim 13, wherein the ionic interaction is polyelectrolyte segments, or polyelectrolyte segments and ions, or polyanionic and polycationic segments, or supramolecular effects based on highly organized hydrogen bonds. 15. A degradable composition according to Claim 15; The polymer of claim 1 or 2, wherein the polymer has an inverted temperature effect, wherein the composition is recovered in shape upon cooling below the shape recovery temperature. 16. A degradable composition according to Claim 16; 2. A composition according to claim 1 or 2, characterized in that it comprises polymer compositions containing two-, three- or four-block copolymers and one homo- or copolymer. PL 193 700 B1 17. A degradable composition according to Claim 17; A polymer composition according to claim 1 or 2, characterized in that it contains a polymer set belonging to the group consisting of physical polymer mixtures, polymer sets containing hard segments with different transformation temperatures Ttrans and soft segments with the same transformation temperature Ttrans, sets of multi-block copolymers in which at least one of The segments of the first copolymer are miscible with at least one of the segments of the second copolymer, and sets of at least one multi-block copolymer and at least one homo- or copolymer. 18. A degradable composition according to Claim 18; The shape of any of the preceding claims, wherein the coating comprises a degradation modifying coating of the shape memory polymer. 19. The use of a degradable shape memory polymer composition as in Claim 1 for the production of technical, pharmaceutical, biomedical, cosmetic and care articles and devices, such as, for example, capsules, sutures, orthodontic materials, splints, rods, screws, nails and plates used in bone surgery, tissue engineering scaffolds, films, tubes patencyers, catheters, prostheses, transplants and implants, contact lenses, pumps and nets, light metering devices and thermal sensors, diapers, sanitary napkins and packaging, contrast agents, used, inter alia, in tomographic, resonance and x-ray examinations.