WO1992007894A1

WO1992007894A1 - Ether-ketone-sulphone copolymers

Info

Publication number: WO1992007894A1
Application number: PCT/GB1991/001857
Authority: WO
Inventors: Ian David Henderson Towle; Richard Harold Whiteley; Christopher John Borrill
Original assignee: Raychem Ltd
Current assignee: Raychem Ltd
Priority date: 1990-10-26
Filing date: 1991-10-23
Publication date: 1992-05-14
Anticipated expiration: 1993-04-26
Also published as: GB9023363D0

Abstract

Polyetherketone/sulphone block copolymers in which the polyetherketone blocks are of sufficient size to render the copolymer partially crystalline at sulphone contents above 40 %, which normally result in amorphous structure in random copolymers.

Description

ETHER-KETONE-SULPHONE COPOLYMERS

This invention relates to ether-ketone-sulphone copolymers, hereinafter referred to as EKS copolymers.

EKS polymers are known to have interesting physical properties, but are limited in their usefulness by the fact that the sulphone linkage groups in the polymer backbone tend to render such polymers amorphous.

Published International Patent Application WO90/00573 describes EKS random copolymers comprising 10 to 45 mol %, more preferably 20 to 40 mol %, and especially 30 to 35 mol % of EKS repeat units having the formula

-aιyl-aryl-O-Ar-SO₂-Ar-O-aιyl-aryl-CO-Ar-CO- in which -aryl-aryl- is inter alia biphenylene, and Ar is inter alia phenylene, together with ether ketone (EK) units of formula (inter alia)

-Ar-O-Ar-CO-Ar-O-Ar-CO-Ar-CO-

It is stated that the proportion of EKS units is preferably selected to produce a partially crystalline copolymer, and in practice it is found that these copolymers tend to become amorphous as the proportion of EKS units increases. At about 40 mol %, at least some of the copolymers in question require commercially unacceptably long periods of annealing at temperatures above the glass transition temperature (Tg) of the copolymer to induce even a few percent of crystallinity. It is also stated that the EK units may be prepolymerised to form a polymer block which is subsequently copolymerised into the finished polymer together with the EKS units. Specific examples of such copolymers are described having up to about 33 mol % of the specified EKS units. EKS copolymers generally are expected to lose their crystalline characteristics and become for practical purposes amorphous as the proportion of EKS units approaches 40 mol %.

Contrary to such expectation, the present invention provides EKS copolymers with the benefits of significantly higher proportions of EKS units, which copolymers are nevertheless partially crystalline and thus have advantageous solvent resistance and other engineering properties over the corresponding amorphous polymers.

The invention accordingly provides an aromatic ether- ketone-sulphone (EKS) block copolymer comprising aromatic EKS repeat units and aromatic ether ketone (EK) blocks (preferably substantially uniformly distributed in the copolymer), wherein the EKS units constitute more than 40 mol % of the copolymer, and the average EK block length is more than 2 repeat units and sufficient to render the copolymer partially crystalline, preferably at least 10%, more preferably at least 15%, crystalline.

By "aromatic" copolymer is meant a copolymer having in its backbone units aromatic moieties which moieties form part of the polymer backbone chain (not merely pendant aromatic rings as in polystyrene), and preferably having no two adjacent aliphatic carbon atoms in the backbone chain. The individual EK and EKS units or blocks will accordingly be "aromatic" in the same sense.

The average block length (hereinafter "block length") may be controlled by varying the molar ratio of the monomers used to prepare the block, which ratio will also be chosen to ensure that the blocks terminate in groups suitable for the further polymerisation of the blocks to form the block copolymer. The average block length in the finished copolymer may be determined by NMR analysis by comparing the number of symmetrical ketone linkages with the number of asymmetrical ketone linkages. For example, when forming an EKS block copolymer from the monomers terephthaloyl chloride (TPC) , 4 , 4' - diphenoxybenzophenone (DPB) , and 4, 4' -bis(4- phenylphenoxy)diphenyl sulphone (BPS), it is possible to calculate the probability of occurrence of the various sequences such as BPS- TPC-BPS, BPS-TPC-DPB, and DPB-TPC-DPB. and from the observed frequencies of occurrence the average block length of the EK blocks can be calculated. A block length of 4 indicates 4 repeat units, for example (DPB-TPC) repeat units in a block of structure DPB-TPC-DPB-TPC-DPB-TPC-DPB-TPC-DPB.

It is preferred that the EKS units are also present as blocks, although it may be acceptable for the EKS units to be present as a random copolymer formed from a number of suitable co-monomers in the presence of the pre-formed EK blocks. Preferably, the copolymer consists substantially only of the EKS blocks and the EK blocks.

Preferred copolymers according to this invention are those wherein the EKS units constitute more than 45 mol % of the copolymer, and copolymers containing at least 50 mol %, or even at least 60 mol % of the EKS units have been successfully prepared without loss of the desirable partial crystallinity. However, even the copolymers according to this invention will tend to become amorphous if the proportion of EKS units becomes too high, and it is accordingly preferred that the EKS units constitute not more than 90 mol %, preferably not more than 80 mol % of the copolymer. Copolymers wherein the EKS units constitute not more than 75 mol %, preferably no more than 70 mol %, of the copolymer have been found particularly useful. The block length which can conveniently be used in the subsequent polymerisation is to some extent determined by the nature of the monomers used. For example, an EK block formed from DPB and TPC tends to gel at a block length above about 6 repeat units, whereas a corresponding EKS block will tend to gel at block lengths over about 12. Gelling before the blocks can be mixed with the other components and further polymerised to form the copolymer is undesirable, and it may therefore be preferred to form the EKS blocks first followed by polymerisation of the EK comonomers in the presence of the pre-formed EKS block. Average block lengths of not more than 12 are thus thought to be achievable, although higher block lengths are not excluded, and it may be preferred to have block lengths of not more than 10.5, or perhaps not more than 9. Lower average block lengths for example not more than 8, or not more than 7, and especially not more than 6 or not more than 5, may be preferred if the EK block is to be formed first. At high sulphone contents, where the EKS block is formed second, EKS block lengths as high as 20 to 25 may be achievable, while EK block lengths of only 5 or 6 are used.

The copolymerisation reaction is preferably continued until the resulting copolymer has an inherent viscosity, measured on a 0.1% solution in concentrated sulphuric acid, of at least 0.6 dl/g, preferably at least 0.8 dl/g, more preferably at least 1.0 dl/g.

The blocks and copolymers may be formed by any convenient method, not excluding the nucleophilic known methods in which aryl ether linkages are formed, but it is much preferred to use the electrophilic methods and materials known, for example, from EP- A-0124276, EP-A-0178183, and the aforementioned WO90/00573, the disclosures of which are incorporated herein by reference. Accordingly, it is preferred that the EKS repeat units are of the form

-Ar-O-Ar-SO₂-Ar-O-Ar-CO-Ar-CO- where each Ar independently is an arylene moiety or represents a number of arylene moieties linked together by -O- or -CO-. Especially preferred are those wherein the EKS repeat units are of the form

-aryl-aryl-O-Ar-SO₂-Ar-O-aryl-aryl-CO-Ar-CO- where each aryl-aryl moiety independently comprises two or more aryl rings which are (a) fused together or (b) twice bonded together directly and/or through linking groups to form a cyclic linking structure between the said rings or (c) directly single-bonded together in the polymer backbone, preferably a biphenylene moiety. In a variation of the latter form, the EKS repeat units are of the form

In many cases it is preferred that the EK blocks comprise repeat units of the form

-Ar-O-Ar-CO-Ar-O-Ar-CO-Ar-CO- or Ar-O-Ar-CO-

or Ar-O-Ar-CO-Ar-CO-

where each Ar independently is an arylene moiety or represents a number of arylene moieties linked together by -O- or -CO-. In all cases it may be preferred that each Ar is a phenylene moiety, although one or more of the Ar moieties may be a naphthyl moiety, for example as described for EK polymers in WO89/04848. The copolymers according to this invention may be prepared by a process wherein the EK blocks are formed separately by polymerisation of appropriate monomers, and the EKS units are subsequently formed by polymerisation of appropriate monomers together with the already-formed EK blocks. In this case, as aforementioned, the EK block length will preferably be not more than 6, more preferably not more than 5. The copolymers may also be prepared by a process wherein the EKS units are formed separately as blocks by polymerisation of appropriate monomers, and the EK blocks are subsequently formed by polymerisation of appropriate monomers together with the already-formed EKS blocks. In this case, block lengths of up to 12, preferably not more than 10.5, are preferred as aforesaid. It will be appreciated that in both of these processes, the block length formed by the subsequent polymerisation step will be determined by that of the pre-formed EK or EKS block and by the relative proportions of EK to EKS, and the second block will form automatically because the EK comonomer has already reacted to form the EK blocks. In a third process for producing the copolymers of this invention, the EKS units and the EK blocks are each formed separately as blocks by polymerisation of appropriate monomers, and are subsequently reacted together to form the copolymer. In this case, the respective block lengths are preferably chosen to ensure that the EKS and EK blocks can be mixed together homogeneously before any significant gelling of the blocks occurs, as aforesaid. In all cases, the blocks may be isolated and purified before the copolymerisation step, but this alters the reaction stoichiometry (by removing unreacted monomers) and it is accordingly preferred to proceed without isolating the blocks.

In any of these processes, it may be preferred that the EKS units and/or the EK blocks are formed by polymerising a monomer system comprising

(I) at least one self-polymerising monomer having a carboxylic acid halide group and an aromatic hydrogen activated towards electrophilic substitution (which monomer may include one or more n on-terminal -SO₂- linkages) or at least one self- polymerising monomer having a sulphonic acid halide group and an aromatic hydrogen activated towards electrophilic substitution; or

(II) at least one aromatic dicarboxylic acid dihalide (which may include one or more non-terminal -SO₂- linkages) or at least one aromatic disulphonic acid dihalide together with a substantially stoichiometric amount of at least one aromatic compound having two aromatic hydrogens activated towards electrophilic substitution; or

(III) combinations of the above; in a reaction medium comprising

(A) a Lewis acid in an amount of about one equivalent per equivalent of Lewis basic groups in the monomers (e.g. carbonyl and/or sulphonyl and/or cyclic ether groups) plus one equivalent per equivalent of Lewis base, plus an amount effective to act as a catalyst for the polymerisation;

(B) a Lewis base in an amount from 0.01 to 4 equivalent per equivalent of acid halide groups present in the monomer system; and

(C) a non-protic diluent in an amount from 0 to 93 percent by weight, based on the weight of the total reaction mixture.

This process, using a catalytic excess of Lewis acid over the controlling Lewis base, is generally described in the aforementioned EP-A-0124276 and EP-A-0178183. In an alternative process, described in our copending British patent application 9010175.9, the Lewis base may exceed the amount of Lewis acid, provided that a weak Lewis base is selected. Accordingly, the EKS units and/or the EK blocks may be formed by condensing a reactant system comprising

(I) at least one self-polymerising monomer having a carboxylic acid halide group and an aromatic hydrogen activated towards electrophilic substitution (which monomer may include one or more non-terminal -SO₂- linkages) or at least one self- polymerising monomer having a sulphonic acid halide group and an aromatic hydrogen activated towards electrophilic substitution; or

(II) at least one aromatic dicarboxylic acid dihalide (which may include one or more non-terminal -SO₂- linkages) or at least one aromatic disulphonic acid dihalide together with a substantially stoichiometric amount of at least one aromatic compound having two aromatic hydrogens activated towards electrophilic substitution;

or

(III) combinations of the above; under modified Friedel Crafts acylatiori and/or sulphonylation conditions, preferably at a temperature of not more than 100°C, in the presence of Lewis acid in a molar amount (Z) determined by the equation X + Y< Z< X + Y + E, in which

X is the total number of moles of sulphonyl groups or carbonyl groups or other strongly Lewis basic groups present in the condensation reactants,

Y is the number of moles of strong Lewis base (if any) which is not a condensation reactant, added to control the reaction, and E is a number greater than zero of moles of weak Lewis base which is not a condensation reactant present in the reaction mixture.

These methods can readily be applied to the preparation of the EK or EKS blocks by a suitably skilled technologist, and similar methods can equally well be used for the final copolymerisation stage to produce the copolymers according to the invention, using the preformed EK blocks and/or EKS blocks as reactants. The strong and weak Lewis bases may for example be selected from those mentioned in EP-A-0124276 or from the protic controlling agents mentioned in EP-A-0264194, the disclosures of both of which are incorporated herein by reference.

The copolymers according to this invention are "partially crystalline", by which is meant at least 10%, preferably at least 15% crystalline. The term "crystalline" will be readily understood by persons familiar with this field of technology and the % crystallinity may be determined by, for example wide-angle X-ray diffraction. Copolymers which crystallise spontaneously on cooling from the melt are naturally included, together with those which crystallise relatively slowly, but still at commercially usable rates. For avoidance of doubt, copolymers which can be converted from the amorphous to the partially crystalline state by annealing at suitable elevated temperatures for commercially acceptable times, preferably less than 30 minutes, more preferably less than 15 minutes, and especially less than 7 minutes, are also included.

By way of illustration, some specific examples of the preparation of copolymers according to the invention will now be described. Unless otherwise specified, the following general method of synthesis is used in these examples. General method of Synthesis

A reaction vessel fitted with a PTFE stirrer, thermocouple, and nitrogen inlet containing the required amount of dichloro- methane diluent was pre-cooled to minus 13°C, and the required amount of aluminium chloride catalyst was added while stirring, keeping the temperature below -5°C, followed by the required amount of dimethylsulphone (Lewis base), which was added slowly, not allowing the temperature to rise above minus 5°C. The required molar quantity of DPB (previously referred to) was then added together with just enough TPC (previously referred to) to produce the EK block. The nitrogen was then turned off and a scrubber attached whilst the temperature was allowed slowly to reach 20°C. After 3/4 of an hour the scrubber was replaced by the nitrogen inlet and the reaction vessel was cooled to below 0°C. The sulphone monomer 4,4'-bis(4-phenylphenoxy)diphenylsulphone, was added in the required molar quantity together with sufficient additional TPC to form the copolymer and together with an appropriate amount of an end capper, 4-phenoxybenzophenone, as known per se. The temperature was then raised slowly to 20°C, and the copolymer gelled as the reaction progressed to completion over a period of about 5 hours. The copolymer gel was decomplexed by vigorous blending in iced water until white, after which it was filtered and washed in known manner. After stirring for more than 6 hours in distilled water, followed by boiling for 30 minutes, the polymer fluff produced was filtered and washed 3 times with distilled water followed by drying overnight at 125°C. The sulphone monomer is added first instead of the DPB if the EKS blocks are to be formed first.

Polymers produced by this method using DPB and TPC are identified as S3 type, and the following Table 1 sets out the observed inherent viscosity (IV); glass transition temperature (Tg) determined by known methods of differential scanning calorimetry (DSC) or by dynamic mechanical thermal analysis (DMTA); and the crystalline melting point (Tm); together with the observed percentage crystallinity (% CRYST); the temperature (Tc) at which shortest time to reach maximum crystallisation rate is achieved; and the value of that shortest time (TIME TO MAX CRYST) determined by DSC. The table shows examples with various EK block lengths (B.L.) and mol % EKS contents (%S), in which connection it will be noted that random copolymers (block length 2.0) containing 45 mole percent EKS were clearly amorphous (AM), and that when the sulphone content was increased to 50 mole percent a block length of 3.5 produced an amorphous copolymer, whereas a block length of 4 or more produced crystalline copolymers.

Where Tg is indicated for both an amorphous (A) sample and a crystalline (c) sample, the amorphous sample was usually a film or plaque produced by rapid cooling ("quenching") from the melt deliberately to prevent the crystallisation which normally occurs on slower solidification, or which at least occurs on annealing at a temperature above Tg but below Tm for an appropriate time. Where the copolymer is indicated generally as "amorphous", the degree of crystallisation was insignificant on cooling and even after such annealing.

The accompanying Figure 1 shows the wide-angle X-ray diffraction plots for the S3S40 polymer of Table 1, in which the smooth curve obtained from quenched amorphous polymer film has been superimposed on the peaked trace obtained after annealing the film for 1¹/₂ hours above Tg to render it crystalline. The relative areas underlying these graphs indicate only 11.6% crystallinity after this long annealing treatment.

The difference between the crystalline and amorphous Tg was unexpectedly increased by blocking, compared to the random S3S40 polymer. The longer the EK block length, the greater the difference between crystalline and amorphous Tg. This can possibly be explained by an increasing segregation of EK and EKS respectively into crystalline and amorphous regions as the block length increases. The crystallites become larger with less internal disruption, giving the observed increase in percent crystallinity, and the amorphous regions become more rich in sulphone giving a higher Tg for the annealed samples. However, the invention is not necessarily limited to this theory.

The following Table 2 indicates the applicability of this invention over a range of S3 block copolymer molecular weights, as indicated by I.V. All the copolymers had a block length of 4 and an EKS content of 40 mol %, and the I.V. (mol.wt.) was controlled by choosing the % "out of balance" (%OOB) of the TPC against the other two monomers (i.e. the mole % deviation from exact stoichiometry).

The effect of increasing the EK block length is further illu strated in Table 3 for S3 copolymers, some having a 40 mol % EKS content and some having a 50 mol % EKS content.

Although the IVs of these polymers are not the same, some general trends can be seen: Tg appears to be unaffected by block length whilst Tm increases slightly with increasing block length. This suggests that the longer block lengths have a higher % crystallinity. There was also some evidence that the crystallisation rates increased with increasing block length and the DSC crystallisation exo therm width decreases.

The effect of increasing the EKS content is further illustrated in table 4, using a block length of 8.

The data demonstrates that increasing the % mole sulphone content in the block copolymers increases Tg but also increases the melting point. Interestingly, Tc (the temperature at which the crystallisation rate is a maximum) decreases with increasing mole % sulphone.

The following Examples 1 to 4 further illustrate the preparation of S3 type copolymers according to this invention, and Example 5 illustrates for comparison a modified S3 copolymer, in which the EK block includes units derived from 2,6-bis(4- phenoxybenzoyl) naphthalene in addition to the usual DPB and TPC units of the S3 type. In all cases, the strong Lewis base dimethylsulphone was used with a catalytic excess of AICI₃ as the Lewis add, and the aforementioned general method was followed as appropriate. The End Capper in each case was 4- phenoxybenzophenone. Example 1

Synthesis of S3B4S40 (see Table 1) using the general method of synthesis, first forming the EK block then subsequently polymerising the EKS block in the same reaction vessel without isolating the EK block. % OOB was 1.5%

Solvent = Dichlorome thane of which 450 ml was added at start with a further 25 ml used to wash in the reactants.

I.V. of this polymer was 1.03 dl/g

* sulphone monomer used was 4,4'-bis(4-phenylphenoxy) diphenyl sulphone)

Example 2

S3B8S50 (see Table 1) synthesis using the general method but preforming the EKS block then subsequently polymerising the EK block in the same reaction vessel without isolating the EKS block. % O.O.B was 1.5%.

Solvent = dichloromethane of which 180 ml was added at the start with a further 20 ml used to wash in the reactants.

I.V. of this polymer was 1.02 dl/g

* sulphone monomer used was 4,4'-bis(4-phenylphenoxy) diphenyl sulphone.

Example 3

S3B4S40 using 4,4'-bis(phenoxy)diphenyl sulphone monomer, with block length 4 and 40 mol % EKS.

The EK block was preformed and the subsequent polymerisation was carried out in the same reaction vessel.

% OOB was 1.5%

Solvent - dichloromethane of which 50 ml was added at the start with a further 20 ml used to wash in the reactants

Tg (DSC) = 171°C

Tc (DSC) = 214°C

Tm (DSC) = 369°C Example 4

S3B4S40 synthesis as in Example 3 except that the sulphone monomer was

Solvent = dichloromethane of which 50 ml was added at the start, with a further 20 ml used to wash in the reactants.

Tg (DSC) = 194°C

Tc (DSC) = 252°C

Tm (DSC) = 363°C Example 5

S3(N)B4S40 synthesis using the general method preforming the EK block then subsequently polymerising in the same reaction vessel without isolating the block. % OOB was 1.5%, block length 4, 40 mol % EKS.

The EK block was a modified S3 (Naphthalene) arrangement derived from DPB and 2,6-bis(4-phenoxybenzoyl)naphthalene.

Solvent = dichloromethane 50 ml of which were added at the start, with a further 20 ml used to wash in the reactants. sulphone used was 4,4'-bis(4-phenylphenoxy) diphenyl sulphone

Claims

CLAIMS:

1. An aromatic ether-ketone-sulphone (EKS) block copolymer comprising aromatic EKS repeat units and aromatic ether ketone (EK) blocks, wherein the EKS units constitute more than 40 mol % of the copolymer, and the average EK block length is more than 2 repeat units and sufficient to render the copolymer partially crystalline.

2. A copolymer according to claim 1, which is at least 10%, more preferably at least 15%, crystalline.

3. A copolymer according to claim 1 or 2 wherein the EKS units are also present as blocks and the copolymer preferably consists substantially only of the EKS blocks and EK blocks.

4. A copolymer according to any preceding claim, wherein the EKS units constitute more than 45 mol %, preferably at least 50 mol %, of the copolymer.

5. A copolymer according to claim 4, wherein the EKS units constitute at least 60 mol % of the copolymer.

6. A copolymer according to any preceding claim, wherein the EKS units constitute not more than 90 mol %, preferably not more than 80 mol %, of the copolymer.

7. A copolymer according to claim 6, wherein the EKS units constitute not more than 75 mol %, preferably not more than 70 mol %, of the copolymer.

8. A copolymer according to any preceding claim, having an inherent viscosity, measured on a 0.1% solution in concentrated sulphuric acid, of at least 0.6 dl/g, preferably at least 0.8 dl/g, more preferably at least 1.0 dl/g.

9. A copolymer accordin g to any preceding claim, wherein the EKS repeat units are of the form

-Ar-O-Ar-SO₂-Ar-O-Ar-CO-Ar-CO- where each Ar independently is an arylene moiety or represents a number of arylene moieties linked together by -O- or -CO-.

10. A copolymer according to claim 9, wherein the EKS repeat units are of the form

-aryl-aryl-O-Ar-SO₂-Ar-O-aryl-aryl-CO-Ar-CO- where each aryl-aryl moiety independently comprises two or more aryl rings which are (a) fused together or (b) twice bonded together directly and/or through linking groups to form a cyclic linking structure between the said rings or (c) directly single-bonded together in the polymer backbone chain, preferably a biphenylene moiety.

11. A copolymer according to claim 10, wherein the EKS repeat units are of the form -

12. A copolymer according to any preceding claim, wherein the EK blocks comprise repeat units of the form

-Ar-O-Ar-CO-Ar-O-Ar-CO-Ar-CO- or Ar-O-Ar-CO- or Ar-O-Ar-CO-Ar-CO- where each Ar independently is an arylene moiety or represents a number of arylene moieties linked together by -O- or -CO-.

13. A copolymer according to claim 9, 10, 11 or 12 wherein each Ar is a phenylene moiety.

14. A copolymer according to any of claims 9 to 12, wherein one or more of the Ar moieties is a naph thyl moiety.

15. A process for producing a copolymer according to any preceding claim, wherein the EK blocks are formed separately by polymerisation of appropriate monomers, and the EKS units are subsequently formed by polymerisation of appropriate monomers together with the already-formed EK blocks.

16. A process for producing a copolymer according to any of claims 1 to 14, wherein the EKS units are formed separately as blocks by polymerisation of appropriate monomers, and the EK blocks are subsequently formed by polymerisation of appropriate monomers together with the already-formed EKS blocks.

17. A process for producing a copolymer according to any of claims 1 to 14, wherein the EKS units and the EK blocks are each formed separately as blocks by polymerisation of appropriate monomers, and are subsequently reacted together to form the copolymer.

18. A process according to claim 15, 16 or 17, wherein the EKS units and/or the EK blocks are formed by polymerising a monomer system comprising

(I) at least one self-polymerising monomer having a carboxylic acid halide group and an aromatic hydrogen activated towards electrophilic substitution (which monomer may include one or more non-terminal -SO₂- linkages) or at least one self polymerising monomer having a sulphonic acid halide group and an aromatic hydrogen activated towards electrophilic substitution; or

(III) combinations of the above; in a reaction medium comprising

(C) a non-protic diluent.

19. A process according to claim 15, 16 or 17, wherein the EKS units and/or the EK blocks are formed by condensing a reactant system comprising

or

(III) combinations of the above; under modified Friedel Crafts acylation and /or sulphonylation conditions, preferably at a temperature of not more than 100°C, in the presence of Lewis acid in a molar amount (Z) determined by the equation X + Y< Z<X + Y + E, in which

X is the total number of moles of sulphonyl groups, or carbonyl groups or other strongly Lewis basic groups present in the condensation reactants,

Y is the number of moles of strong Lewis base (if any) which is not a condensation reactant, added to control the reaction, and

E is a number greater than zero of moles of weak Lewis base which is not a condensation reactant present in the reaction mixture.

20. A process according to claim 15, 16 or 17, wherein the subsequent copolymerisation step is performed by a process corresponding to claim 18 with the pre-formed EK blocks and/or EKS blocks serving as reactants.

21. A process according to claim 15, 16 or 17, wherein the subsequent copolymerisation step is performed by a process corresponding to claim 19 with the pre-formed EK blocks and /or EKS blocks serving as reactants.

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