CA2411443A1 - Method to produce graphite/polymer composites - Google Patents

Abstract

Graphite/polymer hybrid composites with tailored structure were prepared using a novel synthesis method based on stable free radical polymerization combined with polymerization compounding. Highly filled and well-dispersed filler/polymer composites have been developed using this method. Grafting polymers onto carbon fillers was carried out in bulk polymerization, in solution and in colloidal dispersion. This method allows control of the percentage of grafted polymers, the architecture of grafted polymers, the length of chains, and the polydispersity index. The organic fillers may be graphite, carbon black and the like in the form of flakes, fibers, colloidal suspensions, films or powders. The synthesis process performed by this method gave grafting percentages of polymers and copolymers ranging from 12 to 88 wt %. Graphite/Polymer composites produced herein represent new material used in bipolar plates for fuel cells and filter press electrolyzers and as composite material for automobiles and aircraft structures.

Description

TITLE: Method to Produce Graphite/Polymer Composites Field of the invention The invention relates to organic/organic polymer composites produced by stable free radical polymerization combined with polymerization compounding approach in bulk, solution and colloidal dispersion.
Background of the invention Graphite/polymer composites are known as materials with improved properties and performance. Such hybrid composites result in a high strength, lightweight composite with ~5 higher electrical properties. Good adhesion between the organic matrix and graphite improves electrical conductivity and mechanical properties.
Graphite is usually used to modify the following properties of products;
conductivity, EMI
shielding, lubricating coatings, self-lubricating bearings, lubricants, heat, chemical and water 2o resistance, flame retardancy, release properties, pigmentation. Purity, crystalline structure, texture, and particle size are factors which control tribological, thermal, electrical, chemical and physical proporties of products manufactured with graphite. The mechanical properties of graphite filled plastic may be tailored to meet requirements. Studies on polypropylene show that addition of graphite increases Young's modulus (ratio between stress and strain) by up to 25 60% with the addition of 30-35 wt% graphite but also results in an improvement of its tensile strength. Polystyrene is another example of a polymer whose tensile strength is increased by the addition of graphite (25%) and its Young's modulus is tripled.
Graphite/polymer composites prepared with exfoliated graphite are described in European 3o patent application publication No.0081004, U.S. Patent No. 3,409,563 and U.S. Patent No.
3,404,061, the entire content of which is incorporated herein by reference.
U.S. Patent No.
4,704,231 describes composites comprising exfoliated graphite flakes in a polymer matrix, which constitutes a small volume fraction. These composites are bound by a polymer, making the flakes preferentially oriented. Polymer/graphite composites described in U.S. Patent No.

4,413,822 has an elastic polymer core, which is bonded to and surrounded by a rigid shell of graphite composite. These composites are used in the structure of a tennis racket.
U.S. Patent No. 4,992,528 describes the preparation of lightweight polymer matrix composite materials. Graphite fluoride fiber polymer composite material, described in U.S. Patent No.
4,957,661 show a high thermal conductivity, high electric resistivity, and high emissivity. It is a high modulus, military-grade graphite composite fiber with an aerospace resin system developed for extreme toughness. This aerospace high modulus graphite and resin system is the same material used in the Stealth B2 Bomber and F-117A fighter. The graphite-filled, 1o polymeric matrix leads to hybrid materials with higher electric and thermal conductivity, resistance to thermal shock, and also a lower absorption coefficient of X-rays and electrons.
Hybrid graphite fiber polymer composite laminates are also used for spacecraft structural and thermal applications. Thermal and stiffness properties offer package designers new ways to accomplish thermal management, while reducing weight. Strength and fracture properties t5 present structural design challenges. Japanese patent application publication No.: JP11070612 describes a technique to produce a graphite/polymer composite holding a polymer between the layers of an alkali metal-graphite interlaminar compound.
Graphite/polymer composite is an ideal material for bipolar plates and electrodes used in fuel 20 cells. European patent application publication No.: 1223630 describes how graphite/polymer composite bipolar plates with high bulk conductivity are subjected to an abrasive surface treatment to improve surface contact, as well as the reactant transfer to the adjacent gas diffusion electrodes. The graphite/polymer composite used as a bipolar plate for a fuel cell is described in international application publication No.: W00227842 and U.S.
Patent No.
25 6,242,124. U.S. Patent No. 6,039,852, describes bipolar plate made of a composite material for use in a filter-press electrolyzer.
International patent application publication No. W09856574 describes the use of heat resistant composite structure in an aircraft weapons' bay or the like to mitigate the danger 3o associated with undesirable ordnance deflagration. The heat resistant composite comprises a graphite reinforced organic matrix composite and at least one layer of fiber-reinforced pre-ceramic polymer which are co-cured.

Lamellar inorganic particles and organic macromolecules are an inexpensive and versatile route to functional nanometer-scale structures. The layer-by-layer method relies on the exfoliation of solids to produce colloids sheets. It was shown that graphite oxide nanoparticles can be used to prepare multi-layer organic/inorganic composite films using lamellar metal phosphate, titanate, niobate [Keller, S. W., et al., J. Am. Chem. Soc.1994, 116, 8817], silicate [Kleinfeld,E. R. and Ferguson, G. S. Science 1994, 265, 370], and metal chalcogenide [Ollivier, P. J. et al., .J. Chem. Soc., Chem. Commun. 1998, 1563.771 Chem.
Mater. 1999, 11, 771-778] compounds.
1o Developing a polymer composite with certain desired properties requires good control of polymer/solid interactions, wetting by the polymeric matrix and good solid dispersion in the matrix. Intensive mixing and a coupling agent may enhance these particular features. The optimum solution remains, however, a covalent bond between the solid substrate and polymeric matrix and encapsulation of the solid by the polymeric matrix.
Methods for grafting a polymer onto an inorganic molecule such as silica have been reported in the literature [Prucker O, Ruhe J. Macromolecules 1998;31:592-601]. These methods focus on the introduction of various initiators onto the surface of a silica followed by an interfacial dispersion polymerization of vinyl monomers [Tsubokawa N and Ishida H, Polym.
J.
1992;24: 809-816]. However methods for covalently grafting polymers to organic molecules (e.g., graphite) and controlling the polymer/solid interactions and dispersion of the polymer in the matrix has not been found in the literature.
Living free radical polymerization can be carried out using nitroxide and the like as stable free radical. The reaction between carbon-centered radicals and appropriate nitroxides lead to the formation of alkoxyamines initiators. The C-O bond of alkoxyamines and similar species is relatively weak and undergoes reversible homolysis on heating to form an alkyl radical and a stable nitroxide. The reactive carbon-centered radical initiates polymerization while the nitroxide reacts with the propagating radical by primary radical termination to form a new oligo or polymeric alkoxyamine initiator. The advent of nitroxide stable free radicals, such as 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO), to reversibly control the growing polymer chains in free radical polymerization represents a breakthrough in this synthesis route [Georges M. K, Vergin R.P.N, Kazmaier P. M, Hamer G.K. Macromolecules 1993;
26: 2987-2988]. Polymers with narrow molecular weight distribution, as well as block copolymers in which several parameters can be controlled (e.g. size and polydispersity of each block, architecture of the polymer, such as star comb and other complex architectures), can now be obtained using the pseudo-living Stable Free Radical (SFR) polymerization.
U.S. Patents No.
6,271,340, and 4,581,429, the entire content of which are incorporated herein by reference, describes synthesis of monodispersed polymers with controlled molecular weight and architecture with living free radical polymerization. A wider domain of practices and organic grafting reactions will then be accessible. Free radical polymerization is also easy to perform, less sensitive to impurities and, more importantly, can be applied to most vinyl monomers in contrast with living anionic or cationic polymerization techniques, which require rigorous synthesis conditions.
It would be advantageous to develop alternatives methods of producing graphite/polymer composites and also composites with improved properties. Developing new methods for grafting polymers to colloidal graphite would also be particularly advantageous. The present work uses polymerization compounding to develop graphite/polymer composites with enhanced overall properties, such as for example improvement in percentage of grafting, architecture of grafted polymers, the length of chains and polydispersity index, in contrast with mechanical compounding. The approach involves the surface of the solid substrate in the polymerization process of what will represent the matrix in the final composite. For the approach to be used efficiently, competition between polymerization at the surface of the 2o solid and in the bulk, i.e. homopolymerization, must be avoided. For that purpose, polymerization compounding in conjunction with stable free radical polymerizatioon was used. The use of free radical polymerization for generating graphite/polymer composites reduces unwanted side reactions, such as for example, radical coupling, disproportionation, radical transfer). Organic/inorganic hybrid composites comprising silica were generated using the polymerization compounding approach in combination with stable free radical polymerization [Kasseh A., Ait-Kadi A., Reidl B., and Pierson J. F. The polymer Processing Society, seventeenth Annual Meeting, Montreal Canada, May 21-24, 2001].
Grafting of polymers onto fumed silica was obtained only in bulk polymerization using N-tent-butyl-1 diethylphosphono2,2-dimethyl propyl nitroxide as nitroxide stable free radical. The obtained 3o composites gave stable suspensions in toluene and tetrahydrofuran.
Since dispersion properties and interfacial adhesion between the polymeric matrix and graphite are improved in graphite/polymer produced by the method disclosed herein, many properties (e.g., tribological, thermal, electrical, chemical and physical proporties) of the composite may also be improved.
The content of each publication, patent and patent aplication mentioned in the present application is incorporated herein by reference.
SUMMARY OF THE INVENTION
to An alternative method for generating graphite/polymer composite is disclosed herein. This method may allow, for example, the generation of composites with an improved polydispersity index.
The present invention relates to a method for generating a composite comprising a carbon-containing material and a polymer.
The present invention relates, in a first aspect, to a composite substance (material) comprising a substrate (matrix) component a linker component 2o a polymer component, said linker component covalently linking said polymer component to said substrate (matrix) componnet (e.g., wherein said substrate component comprises a carbon containing material e.e, graphite).
In a furher aspect, the present invention provides a method for generating a composite comprising a carbon-containing material and a polymer (covalently linked), said method comprising contacting (mixing, reacting) a modified carbon-containing material, (e.g., by/using polymerization compounding) with a (molecule able to be transformed into a) stable free radical and a (first) monomer in a reaction mixture.
In accordance with the present invention, the carbon-containing material may be a particulate material such as, for example, a particulate material in the form of a fiber, a flake, a colloidal suspension, a film or a powder.

Also in accordance with the present invention, the modified carbon-containing material may be a material comprising a (grafted) initiator or a material comprising a vinyl group. Without being restricted to the following, initiators may include, for example, hydroperoxide (e.g., tert-butyl hydroperoxide) and AIBN (2,2'-azobis(isobutyronitrile)). Vinyl groups may include, for example, a vinyl group originating from 7 oct-1-enyl dimethyl chlorosilane (OEDCS) or 3-(trimethoxysilyl) propyl methacrylate.
In accordance with the present invention, the carbon-containing material may be graphite (e.g., graphite oxide, carbon black or the like, suitably activated, as described herein, to be 1o linked to an initiator). It is to be understood herein, that once the initiator has reacted with the carbon-containing material, for example, graphite (i.e., (activated) graphite oxide) both graphite and the initiator are changed at the molecular level. Nervertheless, it is to be understood herein that the result is a graphite grafted with an initiator. The same apply with the addition of a vinyl precursor to graphite.
Further in accordance with the present invention, the stable free radical may be selected from the group consisting of nitroxide molecules (nitroxides). Examples of nitroxide molecule may include, for example, 2,2,6,6-tetramethylpiperidinyloxy (TEMPO) and N-tert-butyl-1-diethylphosphono2,2-dimethyl propyl nitroxide (DEPN) or any other suitable nitroxide 2o molecule such as those described in U.S. patent No.:4,581,429, the entire content of which is incorporated herein by reference.
Also in accordance with the present invention, the monomer may be selected, for example, from the group consisting of vinyls (vinyl chlorosilane, methoxy vinyl groups, ethoxy vinyl groups, ethoxy methacrylic, methoxy methacrylic), styrene, n-butyl acrylate, methyl acrylate, ethyl acrylate, methyl methacrylate, methacrylonitrile, and olefins (modified (e.g., polyfluorinated olefin) or not).
In accordance with the present invention, the method may further comprise adding a second 3o monomer (a further monomer), said second monomer being either the same or different from the (first) monomer added previously. The (molecule able to be transformed into a) stable free radical may be added to the generated composite to further continue polymerization, for generating, for example, a block copolymer or a longer polymer. Alternatively, the stable free radical may still be part of the composite (e.g., as a dormant species) and the free radical may still be regenerated to further continue polymerization with said second monomer. The method also encompass adding a further (a third, a fourth, etc.) monomer.
The addition of a second monomer thus permits the generation of block copolymer, when the second monomer is different from the first monomer or to form a longer polymer, when the second monomer is the same as the first monomer. Accordingly, the second monomer may also be selected, for example, from the group consisting of vinyls (vinyl chlorosilane, methoxy vinyl groups, ethoxy vinyl groups, ethoxy methacrylic, methoxy methacrylic), styrene, n-butyl acrylate, methyl acrylate, ethyl acrylate, methyl methacrylate, 1o methacrylonitrile, an olefin modified (e.g., polyfluorinated olefin) or not.
Block copolymers may also be generated by adding a polymer of a defined length and/or composition. Thus, in accordance with the present invention, the method may further comprise adding a polymer. Without being restricted to the following, the polymer may be selected, for example, from the group consisting of a thermoplastic resin, an aromatic resin, a polyester (e.g., a polycarbonate, a polysulfonate), a polyamide, a polycarbamate, a polyurea, a polycarbodiimide, a copolymer and mixture thereof. It may be of use to generate a composite where the polymer may be selected from the group consisting of a polynucleotide, a polyamine or a polysaccharide.
2o In yet a further aspect, the present invention provides a method for generating a graphite/polymer composite, said method comprising contacting a graphite (graphite oxide) (e.g., by/using polymerization compounding) with a (molecule able to be transformed into a) stable free radical and a monomer in a reaction mixture.
In accordance with the present invention, graphite may be a modified graphite, such as, for example, a graphite comprising a grafted initiator (e.g., AIBN, hydroperoxide (e.g., tert-butyl hydropereoxide) or a graphite comprising a vinyl group, the vinyl group originating for example from 7 oct-1-enyl dimethyl chlorosilane (OEDCS) or 3-(trimethoxysilyl) propyl 3o methacrylate. For this purpose, a suitable graphite may be, for example, an activated graphite oxide.
Also in accordance with the present invention, the (molecule able to be transformed into a) stable free radical may be selected from the group consisting of nitroxide molecules, such as, for example, 2,2,6,6-tetramethylpiperidinyloxy (TEMPO) and DEPN or any other suitable nitroxide molecule such as those mentioned above.
Further in accordance with the present invention, the monomer may be selected, for example, from the group consisting of vinyls, styrene, n-butyl acrylate, methyl acrylate, ethyl acrylate, methyl methacrylate, methacrylonitrile, an olefin (i.e., hydrocarbon having a double bond) modified or not, etc.
In accordance with the present invention, the method may further comprise adding a second to monomer, said second monomer being either the same or different from the (first) monomer, allowing the formation of a block copolymer. The second monomer may be selected, for example, from the group consisting of vinyls, styrene, n-butyl acrylate, methyl acrylate, ethyl acrylate, methyl methacrylate, methacrylonitrile, an olefin modified or not.
15 Also in accordance with the present invention, the method may further comprise adding a polymer (of a defined length/composition), such as, for example, a polymer selected from the group consisting of a thermoplastic resin, an aromatic resin, a polyester (e.g., a polycarbonate, a polysulfonate), a polyamide, a polycarbamate, a polyurea, a polycarbodiimide, a polynucleotide, a polyamine, a polysaccharide, a copolymer and mixture thereof. This method 2o also allows the formation of a block copolymer.
In another aspect, the present invention relates to a method for generating a graphite/polymer composite, said method comprising contacting a graphite/polymer macroinitiator with a monomer or polymer. In accordance with the present invention, the graphite/polymer 25 macroinitiator may comprise a stable free radical. The monomer or polymer may be as defined herein. Graphite/polymer macroinitiator are described herein and may comprise for example graphite (GO), polystyrene and DEPN (i.e., GO-PS-DEPN) or comprise graphite (GO), poly(n-butyl acrylate) and DEPN.
3o In accordance with the present invention, addition of a monomer or polymer to a modified carbon-containing material, to a modified graphite or to a graphite/polymer macrocomposite may further comprise heating. Heating may be performed up to a temperature allowing the formation of the radical (e.g., from hydroperoxide) andlor the formation of a (nitroxide) stable free radical. Suitable temperature are in the range of between 90 to 130 °C more particularly, a suitable temperature may be, for example, 120°C. The reaction may be performed, for example, under a N2 atmosphere.
In an additional aspect, the present invention relates to a composite comprising a carbon-containing material and a polymer, said carbon-containing material and polymer being covalently linked.
In accordance with the present invention, the carbon-containing material (e.g., graphite) may be a particulate material, such as, for example, a particulate material that may be in the form of a fiber, a flake, a colloidal suspension, a film or a powder.
In accordance with the present invention, the composite may further comprise an initiator (e.g., hydroperoxide, AIBN) or a vinyl group (originating from OEDCS, 3-(trimethoxysilyl) propyl methacrylate (TPM)).
Further in accordance with the present invention, the composite may further comprise a (molecule able to be transformed into a) stable free radical.
In accordance with the present invention, the polymer may be selected, for example, from the 2o group consisting of a thermoplastic resin, an aromatic resin, a polyester (e.g., a polycarbonate, a polysulfonate), a polyamide, a polycarbamate, a polyurea, a polycarbodiimide, a polynucleotide, a polyamine, a polysaccharide, a copolymer and mixture thereof.
Further in accordance with the present invention, the composite may further comprise a second polymer (e.g., forming a (block) copolymer). The second polymer may also be as described above.
In yet an additional aspect, the present invention relates to a graphite/polymer composite, wherein said graphite and said polymer are covalently linked.
In accordance with the present invention, the composite may further comprise an initiator (e.g., tert-butyl hydroperoxide, AIBN) or a vinyl group (OEDCS, TPM, etc.)).
The composite may also further comprise a (molecule able to be transformed into a) stable free radical.
to In accordance with the present invention, the polymer may be selected from the group consisting of a thermoplastic resin, an aromatic resin, a polyester (e.g., a polycarbonate, a polysulfonate), a polyamide, a polycarbamate, a polyurea, a polycarbodiimide, a polynucleotide, a polyamine, a polysaccharide, a copolymer and mixture thereof.
Also in accordance with the present invention, the composite may further comprise a second polymer (forming a (block) copolymer).
In a further aspect, the present invention provides a graphite/polymer hybrid composite prepared using polymerization compounding combined with stable free radical polymerization.
In accordance with the present invention, the composite may be prepared with vinyl monomers, thermoplastic resins, aromatic resins, polyamides, polyfluorinated olefins, mixtures and copolymers thereof.
In accordance with the present invention, graphite may be in fiber, flake, colloidal suspension or powder form.
2o Further in accordance with the present invention, the composite may be prepared by the stable polymerization method (i.e., using stable free radical(s), such as, for example, nitroxides).
Also in accordance with the present invention, the composite may be prepared using radical initiators (e.g., tert-butyl hydroperoxide or AIBN ) grafted onto graphite surface or it may be prepared using a vinyl group grafted onto graphite surface as precursors for polymerization compounding.
In accordance with the present invention, the vinyl groups may be selected from the group consisting of vinyl chlorosilane , methoxy vinyl groups, ethoxy vinyl groups, ethoxy 3o methacrylic, methoxy methacrylic.
In accordance with the present invention, the composite may be obtained in bulk polymerization.

Further in accordance with the present invention, the composites may have a graphite volume fraction ranging from 6 to 88 °Io.
In accordance with the present invention, the composite may be used, for example, as a bipolar plate for fuel cell and filter press electrolyzers, it may also be used in the aeronautic industry, or in the automobile industry.
As used herein "polymerization compounding" is to be understood as a process in which the surface of a solid substrate participates in the polymerization process of the matrix of the 1o composite.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 illustrates the activation and grafting of the AIBN initiator onto the surface of the graphite oxide, TDI means toluene di-isocyanate, ACPA means 4,4-Azo-bis(4-cyanovaleric acid).
Figure 2 is a graph illustrating styrene monomer conversion into polymer as a function of time.
Figure 3 is a graph illustrating n-butyl acrylate monomer conversion into polymer as a function of time.
DETAILED DESCRIPTION OF THE INVENTION
Graphite/polymer hybrid composites were prepared using polymerization compounding combined with Stable free radical polymerization. Highly filled and well-dispersed polymer solid composites using stable free radical polymerization have been developed.
Grafting 3o polymers onto graphite was obtained in bulk polymerization at 120°C
in the presence of stable free radical nitroxides. The percentage of grafting, the architecture of grafted polymers, the length of chains, and the polydispersity index can be controlled at will using this approach.
The synthesis performed in this work gave grafting percentages of polymers and copolymers ranging from 12 to 88 wt °70. These materials may be used as a bipolar plate for fuel cells and filter press electrolyzers and as composite material for automobiles and aircraft structures in the aeronautic industry.
The combination of living free radical polymerization with the polymerization compounding approach to design new composite materials is illustrated here using graphite oxide (GO) particles. Graphite oxide was synthesized from natural graphite powder [Rummers, W.;
Offeman, R. J. Am. Chem. Soc. 1958, 80, 1339], Hydroperoxide and AIBN were used as the initiators for the polymerization process. The surface of GO substrate must first be activated in order to covalently graft the initiator onto the solid.
to Introduction of AIBN or tert-butyl hydroperoxide initiator onto GO surface Introduction of AIBN (2,2'-azobis(isobutyronitrile) initiator onto graphite oxide surface Figure 1 describes the activation and grafting of the Azo initiator onto the surface of the graphite oxide. The introduction of Azo groups onto the graphite oxide was achieved in two steps. The first step consists on reacting toluene di-isocyanate (TDI) with hydroxyl and acid groups on the graphite surface and then in the second step 4,4-Azo-bis(4-cyanovaleric acid) (ACPA) reacts with isocyanate groups introduced onto the graphite surface.
Introduction of tert-butyl hydroperoxide initiator onto graphite oxide surface Grafting the initiator was carried out in two steps. The first step consisted of chlorinating the silanol groups using thionyl chloride. In the second step, the introduction of tert-butyl peroxide (THP) was achieved by the reaction of chlorosilyl groups on the surface with THP in the presence of sodium bicarbonate as a dehydrogenation catalyst. The chlorination of the silanol groups was followed by the introduction of the initiator onto the graphite oxide.
Introduction of vinyl group onto graphite oxide surface Introduction of 7 oct-1-enyl dimethyl chlorosilane (OEDCS) The grafting of vinyl groups reactions were carried out in a glovebox filled by dry nitrogen in order to prevent some water traces in the surrounding atmosphere. Colloidal graphite particles were transferred by centrifugation from water into methanol and next into ethanol by successive centrifugation-redispersion cycles. At each cycle, the supernatant was replaced by the same volume of pure solvent. Reaction occurred in a glass reactor containing 1 liter of organic colloidal suspension of GO in anhydrous ethanol (5.9% in weight) in which 0.12 mol/1 and 0.11 mol/1 of 7 oet-1-enyl dimethyl chlorosilane (OEDCS) and tri-ethyl amine, respectively, were added. The mixture was then stirred for 30 min. at ambient temperature.
The modified solid substrate was washed by a large excess volume of ethanol and dried under vacuum at ambient temperature during 48 hours.
Introduction of 3-(trimethoxysilyl) propyl methacrylate (TPM) Anhydrous colloidal suspension of GO oxide in ethanol at 5.4 wt % has been prepared.
to Reaction occurred in a glass reactor containing 1200 ml of ethanol, 120 ml of aqueous solution of NH3 at 28 wt %, and 30 ml of TPM. The mixture was then stirred for 30 minutes at ambient temperature. The suspension has been distilled under vacuum at ambient atmosphere and 300 ml of the solvent was removed. The obtained suspension is stable.
Polymerization Procedures Living free radical polymerization of styrene and butyl acrylate The kinetic parameters (polymerization rate and conversion) of grafted polymers are very important in the preparation of composites. Bulk polymerization of styrene and butyl acrylate with THP as the initiator and DEPN as a stable free radical at 120°C
has also been studied.
Molecular weight, polydispersity index (PI) and monomer conversion are summarized in Tables 1 and 2 (see also Fig. 2 and Fig. 3), respectively. It was found in all cases that polymerization proceeds in accordance with a living mechanism. The molecular weight of the resulting polymers was, in fact, found to be proportional to conversion. The same kinetic parameters were used in the presence of silica on the kinetic. Several studies on the polymerization of styrene and methyl methacrylate did indeed show that the presence of filler does not affect the rate of polymerization. It was also observed during the synthesis of composites that the conversion times of monomers are similar to those obtained in the bulk polymerization of the homopolymers.
Bulk polymerization of styrene. In a typical reaction, a 2 liter glass tube reactor with a screw-type agitator was cleaned, dried and then filled with styrene (8.7 mol/1), THP (3.56 mmoUl) and DEPN (8.9 mmol/1). The mixture was purged by nitrogen for 1 hour before heating. The polymerization reaction was carried out at 120°C under N2 (see Table 1).

Bulk polymerization of butyl acrylate. Butyl acrylate (6.9 mol/1), THP
(2.86mmo1) and DEPN (7.15 mmol/1) were introduced into a glass tube reactor and the mixture was purged by nitrogen for 1 hour. The polymerization was performed following a procedure similar to the one described for styrene (see Table 2).
Composites Synthesis Example 1 GO - Polystyrene Composites synthesis (GOPS). The preparation of GOPS
composites was earned out as follows: GO containing THP initiators, DEPN , and styrene were degassed under a continuous nitrogen flux for 1 hour. The polymerization was earned out in two steps.
The first step consists in the preparation of a composite GO - Polystyrene macro-initiators (GO-PS-DEPN). The GO-PS-DEPN composite was re-dispersed in toluene. This stable suspension was washed by successive centrifugation-redispersion cycles (15000 rpm, 30 min) in order to remove non grafted PS-DEPN polymer produced by the decomposition of THP.
Then, the composite was redispersed in styrene and the polymerization was conducted for 7 hours at 120°C. The GO-PS composite was re-dispersed in toluene, washed by centrifugation-2o re-dispersion cycles as described previously, and dried under vacuum at 90°C. The first step is performed in order to avoid competition between polymerization on the surface of the solid substrate and polymerization in the bulk.
Example 2 GO- Poly(n-butyl acrylate) - Polystyrene Composites synthesis (GO-PBuA-b-PS).
GO-PBuA-b-PS composites were prepared as follows: GO containing THP initiator, DEPN , and butyl acrylate were degassed under nitrogen atmosphere for 1 hour. The mixture was polymerized for 3 hours at 120°C. Then the obtained composite (GO-PBuA) was re-dispersed 3o in THF (stable suspension), washed by successive centrifugation-re-dispersion cycles, and dried in vacuum at ambient temperature. This composite was then re-dispersed in butyl acrylate and degassed in nitrogen atmosphere for 1 hour. This mixture was heated for 7 hours at 120°C. The GOPBuA composite was washed in toluene, and then re-dispersed in styrene.

The polymerization in styrene was conducted under nitrogen atmosphere for 7 hours. This hybrid composite was then dried under vacuum at 90°C.
Nanocomposites synthesis These nanocomposites were obtained via a OEDCS vinyl precursor as described in section entitled "Introduction of 7 oct-1-enyl dimethyl chlorosil".
Example 3 GO/PS synthesis. Polystyrene is chemically bonded to GO surface via OEDCS, which is grafted silica nanoparticles and engaged in the dispersion polymerization.
Styrene monomer can react at the surface of the modified GO and co-polymerize with the reactive vinyl end group of the coupling agent, to give bonded polymer chains at the GO surface.
The free polymer was extracted by successive sedimentation - redispersion cycles in toluene.
GO/PS (1). A colloidal suspension at 12 wt % in ethanol, styrene (0.87 mol/1), THP (3.2 mmol/1) and DEPN (8 mmol/1) were introduced in a glass reactor and then the mixture was degassed with dry nitrogen for 1 hour. The polymerization reaction was carried out at 120°C
for 3 hours under mechanical stirring and inert atmosphere.
GO/PS (2). Styrene (0.87 mole) were added to the GO/PS (1) suspension and the mixture was diluted four times in methanol (total volume is equal to four liters). The polymerization was then carried out at 120°C for 24 hours under mechanical stirring and inert atmosphere in 12 liters reactor.
GO/PS (3). GO/PS (2) suspension was centrifuged at 6000 tr/mn during 24 hours.
The modified solid particles (108 g) were then redispersed in styrene (3.46 motes) giving a stable suspension. Bulk polymerization was carned out, in the same conditions described before, at 120°C for 7 hours ( conversion of 70 %).

Example 4 Nanocomposite synthesis of GO/PABu/PS
A suspension of modified GO by OEDCS was used for the GO/PABu/PS nanocomposite synthesis. In a glass reactor (2 liters) containing 1 liter of GO/OEDCS
suspension in ethanol at 5.9 wt %, we have introduced 0.87 mole of n-butyl acrylate, 3.2 mmoles of tert-butyl hydroperoxide (THP) and 8 mmole of DEPN nitroxide. The mixture was degassed under nitrogen atmosphere. The polymerization reaction was earned out at 120°C under stirring during 6 hours.
GO/ TPM / PS nanocomposites synthesis These nanocomposites were synthesized via a methacrylic precursor as described in section entitled "3-(trimethoxysilyl) propyl methacrylate'".
Example 5 8.8 g of GO/TPM , 0,2 mole of styrene, 1.1 mole of THP and 3 mmole of DEPN
were introduced in a glass reactor and the mixture were degassed under nitrogen atmosphere. The 2o polymerization process was conducted for 16 hours under stirring and continuous nitrogen atmosphere. The composite was then washed in toluene solvent by successive centrifugation-redispersion cycles.
Example 6 GO nanoparticles modified by TPM ( 10.7 wt %), 0.2 mmole of THP (solution of THP in decane at 5.5 moles), 0.5 mmole of DEPN nitroxide and 32 ml of Toluene were introduced in glass reactor. The mixture was degassed under nitrogen atmosphere and heated at 100°C
during 15 minutes. Then, 0.35 mmole of styrene was added to mixture. After one hour, a supplementary 3.5 mmoles of styrene was added to mixture. The polymerization process was 3o then conducted for 3 hours. Another 67.3 mmole of styrene was also added and the polymerization was continued for 7 hours at 120°C under nitrogen atmosphere. The prepared composite is washed in toluene solvent by successive centrifugation-redispersion cycles.

Table 1 Polymerization of Styrene at 120°C, [DEPN) = 2.5 [THP]
[Styrene][THPJ Time ConversionM", eXPa~Mn, exP/Mn,MW/Mns) cnb~

(mole/1)(mmole/1)(min) (%) (g/mole) 8.7 3.56 30 8 10464 1.07 1.1 8.7 3.56 75 20 27130 1.11 1.3 8.7 3.56 210 50 58134 0.95 1.3 8.7 3.56 420 70 86447 1.01 1.2 a Experimental number of average molecular weight determined by SEC using polystyrene standards.
b Theoretical number of average molecular weight calculated as: Mn,cn =
([Monomer]/2x[Initiator]) X Mu, monomer x conversion Polydispersity index determined by SEC

Table 2 Polymerization of n- butyl acrylate at 120°C, [DEPN] = 2.5 [THP]
[BuA] [THP] Time Conversion Mn. expat Mn, exp~n, thh? Mw/Mns) (mole/1) (mmole/1) (h) (°lo) (g/mole) 6.9 2.86 3 14 25900 1.20 1.14 6.9 2.86 8 31 58200 1.21 1.20 6.9 2.86 14 50 85800 1.11 1.23 6.9 2.86 24 70 113700 1.05 1.22 6.9 2.86 43.5 98.9 155800 1.02 1.23 a Experimental number of average molecular weight determined by SEC using polystyrene standards.
b Theoretical number of average molecular weight calculated as: Mn,~, -([Monomer]/2x[Initiator]) X MW monomer x conversion Polydispersity index determined by SEC

Claims (67)

1. A method for generating a composite comprising a carbon-containing material and a polymer, said method comprising contacting said carbon-containing material, by polymerization compounding, with a stable free radical and a monomer.

2. The method of claim 1, wherein said carbon-containing material is a modified carbon-containing material.

3. The method of claim 1, wherein said carbon-containing material is a particulate material.

4. The method of claim 3, wherein said particulate material is in the form of a fiber, a flake, a colloidal suspension, a film or a powder.

5. The method of claim 2, further comprising heating.

6. The method of claim 5, wherein said modified carbon-containing material is a material comprising an initiator.

7. The method of claim 5, wherein said modified carbon-containing material is a material comprising a vinyl group.

8. The method of claim 6 or 7, wherein said material is graphite.

9. The method of claim 8, wherein said stable free radical is selected from the group consisting of nitroxide molecules.

10. The method of claim 9, wherein said nitroxide molecule is selected from the group consisting of 2,2,6,6-tetramethylpiperidinyloxy and N-tert-butyl-1-diethylphosphono2,2-dimethyl propyl nitroxide and the like.

11. The method of claim 1, wherein said monomer is selected from the group consisting of vinyls, styrene, n-butyl acrylate, methyl acrylate, ethyl acrylate, methyl methacrylate, methacrylonitrile, an olefin modified or not.

12. The method of claim 6 or 7, further comprising adding a second monomer, said second monomer being either the same or different from the monomer of claim 1.

13. The method of claim 12, further comprising heating.

14. The method of claim 13, wherein said second monomer is selected from the group consisting of vinyls, styrene, n-butyl acrylate, methyl acrylate, ethyl acrylate, methyl methacrylate, methacrylonitrile, and olefins modified or not.

15. The method of claim 6 or 7, further comprising adding a polymer.

16. The method of claim 15, further comprising heating.

17. The method of claim 16, wherein said polymer is selected from the group consisting of a thermoplastic resin, an aromatic resin, a polyamide, a polynucleotide, a polyamine, a copolymer and mixture thereof.

18. A method for generating a graphite/polymer composite, said method comprising contacting a graphite with a stable free radical and a monomer.

19. The method of claim 18, wherein said graphite is a modified graphite.

20. The method of claim 19, further comprising heating.

21. The method of claim 19, wherein said modified graphite is a graphite comprising a grafted initiator.

22. The method of claim 21, wherein said initiator is selected from the group consisting of 2,2'-azobis(isobutyronitrile) and hydroperoxide.

23. The method of claim 19, wherein said modified graphite is a graphite comprising a vinyl group.

24. The method of claim 21 or 23, wherein said stable free radical is selected from the group consisting of nitroxide molecules.

25. The method of claim 24, wherein said nitroxide molecule is selected from the group consisting of 2,2,6,6-tetramethylpiperidinyloxy and N-tert-butyl-1-diethylphosphono2,2-dimethyl propyl nitroxide.

26. The method of claim 25, wherein said monomer is selected from the group consisting of vinyls, styrene, n-butyl acrylate, methyl acrylate, ethyl acrylate, methyl methacrylate, methacrylonitrile, an olefin modified or not.

27. The method of claim 21 or 23, further comprising adding a second monomer, said second monomer being either the same or different from the monomer of claim 16.

28. The method of claim 27, further comprising heating.

29. The method of claim 28, wherein said second monomer is selected from the group consisting of vinyls, styrene, n-butyl acrylate, methyl acrylate, ethyl acrylate, methyl methacrylate, methacrylonitrile, an olefin modified or not.

30. The method of claim 21 or 23 further comprising adding a polymer.

31. The method of claim 30, further comprising heating.

32. The method of claim 31, wherein said polymer is selected from the group consisting of a thermoplastic resin, an aromatic resin, a polyester, a polyamide, a polycarbamate, a polyurea, a polycarbodiimide, a polynucleotide, a polyamine, a polysaccharide, a copolymer and mixture thereof.

33. A method for generating a graphite/polymer composite, said method comprising contacting a graphite/polymer macroinitiator with a monomer or polymer.

34. The method of claim 33, wherein said graphite/polymer macroinitiator comprises a stable free radical.

35. The method of claim 34 wherein said monomer is selected from the group consisting of vinyls, styrene, n-butyl acrylate, methyl acrylate, ethyl acrylate, methyl methacrylate, methacrylonitrile, an olefin modified or not.

36. The method of claim 34, wherein said polymer is selected from the group consisting of a thermoplastic resin, an aromatic resin, a polyester, a polyamide, a polycarbamate, a polyurea, a polycarbodiimide, a polynucleotide, a polyamine, a polysaccharide, a copolymer and mixture thereof.

37. A composite comprising a carbon-containing material and a polymer.

38. The composite of claim 37, wherein said carbon-containing material is a particulate material.

39. The composite of claim 38, wherein said particulate material is in the form of a fiber, a flake, a colloidal suspension, a film or a powder.

40. The composite of claim 37, further comprising an initiator.

41. The composite of claim 40, further comprising a vinyl group.

42. The composite of claim 41, further comprising a stable free radical.

43. The composite of claim 37, wherein said carbon-containing material is graphite.

44. The composite of claim 37, wherein said polymer is selected from the group consisting of a thermoplastic resin, an aromatic resin, a polyester, a polyamide, a polycarbamate, a polyurea, a polycarbodiimide, a polynucleotide, a polyamine, a polysaccharide, a copolymer and mixture thereof.

45. The composite of claim 37, further comprising a second polymer.

46. A graphite/polymer composite, wherein said graphite and said polymer are covalently linked.

47. The composite of claim 46, further comprising an initiator.

48. The composite of claim 47, further comprising a vinyl group.

49. The composite of claim 48, further comprising a stable free radical.

50. The composite of claim 46, wherein said polymer is selected from the group consisting of a thermoplastic resin, an aromatic resin, a polyester, a polyamide, a polycarbamate, a polyurea, a polycarbodiimide, a polynucleotide, a polyamine, a polysaccharide, a copolymer and mixture thereof.

51. The composite of claim 46, further comprising a second polymer.

52. A graphite/polymer hybrid composite prepared using polymerization compounding combined with stable free radical polymerization.

53. The graphite/polymer composite according to claim 52, wherein the composite are prepared with vinyl monomers, thermoplastic resins, aromatic resins, polyamides, polyfluorinated olefins, mixtures and copolymers thereof.

54. The graphite/polymer composite according to claim 52, wherein the graphite is in fiber, flake, colloidal suspension or powder form.

55. The graphite/polymer composite according to claim 52, wherein said composite is prepared by the stable polymerization method.

56. The graphite/polymer composite according to claim 52, wherein the composite is prepared using stable free radicals.

57. The graphite/polymer composite according to claim 52, wherein the composite is prepared using nitroxides as stable free radicals.

58. The graphite/polymer composite according to claim 52, wherein the composite is prepared using radical initiators grafted onto graphite surface.

59. The graphite/polymer composite according to claim 58, wherein the grafted initiators are tert-butyl hydroperoxide or 2,2'-azobis(isobutyronitrile).

60. The graphite/polymer composite according to claim 52, wherein the composite is prepared using vinyl group grafted onto graphite surface as precursors for polymerization compounding.

61. The graphite/polymer composite according to claim 60, wherein the vinyl groups are vinyl chlorosilane, methoxy vinyl groups, ethoxy vinyl groups, ethoxy methacrylic, methoxy methacrylic.

62. The graphite/polymer composite according to claim 52, wherein the composite is obtained in bulk polymerization.

63. The graphite/polymer composite according to claim 52, wherein the composites have a graphite volume fraction ranging from 6 to 88 %.

64. The graphite/polymer composites according to claim 52, wherein the composite is used as a bipolar plate for fuel cell and filter press electrolyzers.

65. The graphite/polymer composites according to claim 52, wherein the composite is used in the aeronautic industry.

66. The graphite/polymer composite according to claim 52, wherein the composite is used in the automobile industry.

67. A composite substance (material) comprising a substrate (matrix) component a linker component a polymer component, said linker component covalently linking said polymer component to said substrate (matrix) componnet (e.g., wherein said substrate component comprises a carbon containing material e.e, graphite).