WO2000042084A1

WO2000042084A1 - Block copolymers with perfluorinated side-chain blocks and the preparation thereof

Info

Publication number: WO2000042084A1
Application number: PCT/NO2000/000006
Authority: WO
Inventors: Luisa Andruzzi; Emo Chiellini; Giancarlo Galli; Michele Laus; Marit Dahling; Thoralv Undrum
Original assignee: Jotun A/S
Priority date: 1999-01-12
Filing date: 2000-01-11
Publication date: 2000-07-20
Also published as: NO990119D0; AU3084100A

Abstract

A fluorinated diblock, triblock or multiblock copolymer, wherein the blocks are selected from at least two of the following types of polymer blocks: a) polystyrene block, b) polymer block of styrene with a fluorinated phenyl moiety, c) copolymer block of a mixture of counits of styrene and styrene with a fluorinated phenyl moiety. The fluorinated copolymer may be prepared by a sequence of controlled radical polymerization process of styrene and styrene monomers containing a fluorinated phenyl moiety. The copolymers are useful for the preparation of low surface energy materials, in particular marine antifouling materials. An antifouling material may contain said copolymer.

Description

"BLOCK COPOLYMERS WITH PERFLUORINATED SIDE-CHAIN BLOCKS AND THE PREPARATION THEREOF"

BACKGROUND OF THE INVENTION

1. Field of the invention

The present invention relates to the preparation of diblock, triblock and multiblock copolymers containing perfluorinated or partly fluorinated blocks via sequential controlled radical processes in the presence of a stable free radical. Preferred application of the fluorinated block copolymers is as low surface energy materials for marine antifouling coatings.

The copolymer, a process for the preparation thereof, a use of the copolymer and an antifouling material are described in the claims. 5

2. Description of the prior art

The control of the molar mass characteristics and monomer sequence in block copolymers is a necessary prerequisite for the macromolecular engineering o of polymers with suitable properties for advanced applications. Recently, the living radical polymerization or controlled radical polymerization (CRP) was introduced (D. H. Solomon, E. Rizzardo, P. Cacioli, U.S. Pat. 4,581 ,429 (1985)), which involves the combined use of a typical free radical initiator, such as benzoyl peroxide (BPO) or azobis-isobutyronitrile (AIBN), and a stable free radical like the 5 2,2,6,6-tetramethylpiperidinyl-l-oxy nitroxide (TEMPO) or a structurally related nitroxide (P. M. Kazmaier, M. K. Georges, R. P. N. Veregin, G. K. Hamer, Macromolecules, 26, 2987 (1993), G. Moad, E. Rizzardo, Macromolecules, 28, 8722 (1995); C. J. Hawker, G. G. Barclay, A. Orellana, J. Dao, W. Davenport, Macromolecules, 29, 5245 (1996); P. J. McLeod, R. P. N. Veregin, P. G. Odell, M. 0 K. Georges, Macromolecules, 31 , 530 (1998)). The stable free radical works as a reversible capping agent of the active site on the growing polymer chain and regulates the growth of the polymer chains in a usually narrow range of temperatures between 125 °C and 135 °C. The molar mass linearly increases with conversion and polymers with predicted molar mass values and narrow polydispersity can be obtained (B. Keoshkerian, M. K. Georges, D. Boils-Boissier, Macromolecules, 28, 6381 (1995)). Accordingly, this new process should be in principle of great practical relevance in that it allows novel materials to be designed with highly differentiated structures and architectures starting from well known monomers able to undergo free radical polymerization. Furthermore, the controlled radical polymerization process is definitely less sensitive to the experimental conditions, including purity, reaction temperature, moisture etc., than the living anionic and cationic polymerizations.

However, the reversible dissociation of the adduct polymer chain-TEMPO at high temperatures occurs in a limited number of systems and this restricts the versatility of this technique in controlling the CRP process. In addition, another limitation derives from the occurrence of irreversible bimolecular terminations and transfer reactions. Consequently, the number of monomers whose homopolymerization has successfully been controlled by the living radical polymerization is restricted so far to styrene and styrene derivatives such as acetoxystyrene, chloromethylstyrene (P. M. Kazmaier et al., Macromolecules, 30, 2228, (1997)), bromostyrene (E. Yoshida, J. Polym. Sci. A, Polym. Chem., 34, 2937, (1996)). Occasionally, the random copolymerization of such monomers with a monomer which can not be polymerized by the CRP often gives an unexpectedly good result. For example, acrylonitrile, methyl and ethyl acrylates and 9-vinylcarbazole gave no polymer by CRP, but their copolymerization with styrene proceeded in a controlled fashion at least when the styrene amount in the polymerization mixture was not too low and gave narrow-polydispersity copolymers (T. Fukuda, T. Terauchi, A. Goto, Y. Tsujii, Y. Miyamoto, Y. Shimizu, Macromolecules, 29, 3050 (1996)).

The prior art does not include examples of the CRP of perfluorinated side- chain monomers, such as pentafluorostyrene which shows a very limited tendency to polymerization. Homopolymers and copolymers are normally prepared by conventional free-radical or UV-irradiation initiations for incorporation of different fluorinated monomers (J. Scheirs (ed.), Modern Fluoropolymers, Wiley, Chichester (1997)). In particular, polymerizations of variously fluorinated acrylates or methacrylates have been disclosed in the open literature (for a review, see N. N. Chuvatkin, I. Yu. Panteleeva, in J. Scheirs (ed.), Modern Fluoropolymers, Wiley, Chichester (1997), p.1991; for most recent examples, see D. L. Schmidt, C. E. Coburn, B. M. DeKoven, G. E. Potter, G. F. Meyers, D. A. Fischer, Nature, 368, 39 (1994); S. S. Sheiko, M. Krupers, P.J. Slangen, M. Moller, Am. Chem. Soc, Polym. Div., Preprints, 39(2), 956 (1998); R. R. Thomas, D. R. Anton, W. F. Graham, M. J. Darmon, K. M. Stika, Am. Chem. Soc, Polym. Div., Preprints, o 39(2), 970 (1998); K. Sugiyama, A. Hirano, S. Nakahama, Am. Chem. Soc,

Polym. Div., Preprints, 39(2), 839 (1998)) and in the patent literature (C. R. Pfeifer, U.S. Pat. 4,861,501 (1989)). The controlled polymerization of fluorinated acrylate and methacrylate monomers, such as perfluoroalkylmethyi and perfluoroalkylethyl methacrylates, has successfully been accomplished by a different polymerization s technique, namely the atom transfer radical polymerization (ATRP) by using a bromoalkane as the initiator in conjunction with cuprous bromide and an amine ligand as the catalyst (T. Johnson, J. M. DeSimone, Am. Chem. Soc, Polym. Div., Preprints, 39(2), 824 (1998); Z. Zhang, Z. Shi, S. Ying, Am. Chem. Soc, Polym. Div., Preprints, 39(2), 820 (1998)). While these new initiating systems are able to o polymerize styrene, examples of the polymerization of pentafluorostyrene have not been described.

3. Wider scope of the invention

5 Fluorinated polymers in general are known to be rather low surface energy materials, which renders them suitable candidates for application in coatings towards biological foulants, soil, ice and other undesired contaminants.

Specifically, use of marine antifouling coatings is a contemporary concern of great economical and environmental relevance. In fact, a heavy growth of o marine fouling organisms attached to ship hulls adversely affects operation of the ships, reduces their speed and increases their fuel consumption and maintenance costs. Historically, antifouling marine coatings contain toxicants such as organotin and copper compounds (R. S. Alberte, S. Snyder, B. J. Zahuranec, M. Whetstone, Biofouling, 6, 91 (1992)). Such ablative and toxicant-release materials are becoming environmentally unacceptable because of their effects on non-target marine organisms and the problems associated with their disposal. A potential alternative to toxicant release is a surface to which fouling organisms adhere with difficulty (C. D. Anderson, PCE, 22 (1998)). When incorporated into a coating, such surfaces would be intrinsically fouling resistant, would effect facile fouling release, and would be environmentally benign. The concept of fouling release coatings has been demonstrated in the development of coatings with resin matrices compatible with Teflon fillers (R. F. Brady, J. R. Griffith, K. S. Love, D. E. Field, J. Coat. Technol., 59, 113 (1987)). Later on, research has revolved around the development of low surface energy materials which would reduce the potential chemical interactions between the fouling organisms and the surface of the coating and which would possibly have a low s surface glass transition temperature and remain temporally stable in situ.

The prior art includes examples of poly(dimethylsiloxane-urea-urethane) segmented block copolymers (J. K. Pike, T. Ho, K. J. Wynne, Chem. Mater., 8, 856 (1996)). Polymers with highly fluorinated side chains in one block of a block copolymer are also likely to be used in formulations of marine antifouling coatings o if the block copolymer segregates to the surface, driven there by the low surface energy fluorinated block. Surface segregation and interfacial segregation of block copolymers from a polystyrene matrix have already been demonstrated (D. R. lyengar, S. M. Perutz, C.-A. Dai, C. K. Ober, E. J. Kramer, Macromolecules, 29, 1229 (1996)) as well as in end fluorinated polystyrenes (R. B. Mason, C. A. Jalbert 5 J. F. Elman, T. E. Long, B. Gunesin, J. T. Koberstein, Am. Chem. Soc, Polym. Div., Preprints, 39(2), 910 (1998)). Prior low surface energy materials comprise polystyrene/fluorinated acrylate copolymers (J. Hόpken, M. Mδller, Macromolecules, 25, 1461 (1992)), fluorinated polyurethanes (T. Ho, K. J. Wynne, Macromolecules, 25, 3521 (1992)), fluorinated poly(amide urethane) block o copolymers (T. M. Chapman, K. G. Marra, Macromolecules, 28, 2081 (1995)), perfluorinated polysiloxanes (M. M. Doeff, E. Lindner, Macromolecules, 22, 2951 (1989)), and polyesters (D. U. Pospiech, D. Jehnichen, L. Haussler, D. Voigt, K. Grundke, Am. Chem. Soc, Polym. Div., Preprints, 39(2), 882 (1998)). Fluoropolymer surfaces have also been obtained from variously crosslinked polymers, such as crosslinked fluorinated polymethacrylates (R. F. Brady, Jr., D. L. Schmidt, Am. Chem. Soc, Polym. Div., Preprints, 39(2), 912 (1998)) or fluorinated polydimethylsiloxanes (J. R. Griffith, U.S. Pat. 5,449,553 (1995), M. Bergling, P. Gatenholm, E. Johnston, K. Wynne, Am. Chem. Soc, Polym. Div., Preprints, 39(2), 908 (1998), A. Takahara, K. Kojio, T. Kajiyama, Am. Chem. Soc, Polym. Div., Preprints, 39(2), 914 (1998)). Adsorbed monolayers of perfluorinated surfactants have been shown to have lowest surface free energies (E. Lindner, Biofouling, 6, 193 (1992)), (C. E. D. Chidsey, D. N. Loiacono, Langmuir, 6, 682 (1990)).

JP 61 141 405 discloses optical fibres having a core which is a copolymer of styrene and/or a derivative thereof and dialkyl fumarate. A possible styrene derivative is pentafluorostyrene. The copolymer is prepared by using alkyl peroxides as initiators in combination with chain transfer agents such as mercaptans, as per se known. The resulting copolymers will normally have an alternating sequence of monomeric counits (a), due to the fact that the relative reactivity ratios of the two comonomers, styrene and dialkyl fumarate, are close to zero.

ABABABABABABABAB (a)

This is in contrast to the block copolymers of the present invention with precisely controlled macromolecular architecture, e.g. A-B diblocks (b), A-B-A triblocks (c) and others.

AAAAAAAA-BBBBBBBB (b)

AAAAAAA-BBBBBBB-AAAAAAA (c) Fluorinated copolymers are also disclosed in US 5,352,742 and US 5,907,017 which may be illustrated by the following formulae:

US 5,352,742 US 5,907,017

These are in contrast to the copolymers of this invention which may be illustrated by the formulae:

(present invention)

The process used for preparing the block copolymers of US 5,352,742 has not been disclosed, while the copolymers of US 5,907,017 are obtained by chemical modificaiton of preformed polymers.

The use of a fluorinated block copolymer for applications as low surface energy antifouling material is not known in the prior art. Thus, US 5,907,017 relates to materials having surfaces with anti-stick, non-wetting and low friction properties. DESCRIPTION OF THE INVENTION

The present invention refers to the controlled radical synthesis of block copolymers including diblock, triblock and multiblock copolymers containing structural units deriving from styrene (S) and pentafluorostyrene (PFS) monomers. The block copolymers of the invention have the following general structure:

poly(S) poly(PFS) poly[(S)-st-(PFS)]

with poly(S) being a poly(styrene) block, poly(PFS) being a poly(pentafluorostyrene) block, and poly [(S)-sf-(PFS)] being a polymer block with a statistical distribution of styrene and pentafluorostyrene counits, in which the number and sequencing of the interconnected polymer blocks are both suitably tailored by the appropriate succession of steps in the controlled radical polymerization process.

These block copolymers are prepared via a controlled radical polymerization following a synthetic procedure consisting of different sequential steps, a general illustration of which is given in Figure 1. Specifically, the synthetic routes followed in the invention are outlined in Figures 2-7. More specifically, in the first step (Figure 2), the polymerization of S or a mixture of S and PFS with different PFS compositions from 5 to 95 mole-% is initiated by a free-radical initiator in the presence of a stable radical as an end-capping agent. In the former case, poly(S) homopolymers are obtained, while in the latter case poly[(S)-sf- (PFS)] copolymers with random distribution of the S and PFS counits are produced. Notably, in these conditions the homopolymerization of PFS does not occur.

The free-radical initiators used are benzoyl peroxide (BPO) or azobis- isobutyronitrile (AIBN), most preferably BPO. The free radicals employed are 2,2,6,6-tetramethyM -piperidinyloxy (TEMPO) or 2,2,6,6-tetramethyl-4-hydroxy-1 - piperidinyloxy (TEMPOL) nitroxide radicals, or 2,6-di-tetf-butyl-a-(3,5-di-terfτbutyl- 4-0X0-2, 5-cyclohexadien-1-ylidene)-p-tolyloxy (Galvinoxyl) radical, preferably TEMPO. The TEMPO/BPO molar ratios used range from 1.0 to 2.0, the preferred ratio being 1.3. The polymerization experiments are performed at a constant temperature between 110 °C and 140 °C, preferably 125 °C.

(BPO) (AIBN)

(TEMPO) (TEMPOL)

The molar mass characteristics of the various polymers are determined by size exclusion chromatography (SEC) and the average number molar mass (Mn)

ranges from 2000 to 50000 gmol , and the first polydispersity index (Mw Mn) ranges from 1.10 to 1.25. Figure 8 shows the SEC curves of a series of poly[(S)- sf-(PFS)] isolated from the reaction mixture at different times. The SEC curves are shifted toward lower values along the elution volume scale as the reaction time

increases. Specifically, Mn ranges from 4000 to 29000 gmol and M Mn is in the range 1.10 to 1.20. Furthermore, Mn increases linearly with conversion (Figure 9), and Mw/Mn also increases slightly with conversion. The reaction yield of the polymerizations of S and the copolymerization of the mixtures of S and PFS ranges from 50 to 90%, normally 65-75%. In a second step, diblock copolymers of different structures are obtained. As PFS and S are both liquid at room temperature, the controlled radical block copolymerizations of mixtures of S and PFS with different PFS compositions from 5 to 95 mole-% as initiated by polystyrene homopolymers or the controlled radical polymerizations of S as initiated by poly[(S)-sf-(PFS)] are performed typically in bulk at 110-130 °C, preferably 125 °C to give poly(S)π -[(S)-sHPFS)] and poly[(S)- sf-(PFS)]-6-(S) respectively (Figure 3). Figure 10b shows the SEC curves of the copolymer poly[(S)-sf-(PFS)]-ύ-(S) obtained from poly[(S)-sf-(PFS)] as the macroinitiator as well as the one of the macroinitiator itself (Figure 10a). Both SEC curves are very narrow and no trace of the starting poly[(S)-sf-(PFS)] or of the poly(S), as deriving from a parallel thermally-initiated free radical polymerization can be seen in the curve relevant to the diblock copolymer.

Notably, poly[(S)-sf-(PFS)] copolymers and poly(S) homopolymers are able to initiate the controlled radical polymerization of PFS, at 120-130 °C, preferably at 125°C, thus leading to poly[(S)-sf-(PFS)]-b-(PFS) and poly(S)-b-(PFS) as illustrated in Figure 4. The reaction yield of all the polymerizations of S, PFS and the mixtures of S and PFS ranges from 50 to 90%, typically 70%.

Subsequently, triblock copolymers with various structures are synthesized by dissolving diblock copolymers, e.g. poly(S)-/>-[(S)-sHPFS)], poly[(S)-sf-(PFS)]- b-(S), poly[(S)-sf-(PFS)]-b-(PFS) and poly(S)-6-(PFS) in S, PFS or mixtures of S and PFS with different PFS compositions from 5 to 95 mole-% and by performing the reaction at 110-130 °C, preferably at 125 °C without any added catalyst or solvent, as illustrated in Figures 5 and 6. As a typical example, Figure 10c shows the SEC curve of a triblock copolymer poly[(S)-sf-(PFS)]-b-(S)-6-[(S)-sf-(PFS)] together with those of the starting copolymer poly[(S)-s£-(PFS)] and diblock copolymer poly[(S)-sf-(PFS)]-b-(S). The SEC curve of the triblock copolymer is rather narrow although a shoulder can be seen in the high retention volume region. Comparison of the SEC curve of the triblock copolymer with the one of the diblock copolymer suggests that the shoulder is due to a minor amount (< ca. 5%) of the starting diblock copolymer which remains inactive during the triblock copolymerization reaction. Figure 11 illustrates the trend of the average molar mass value of the third block as a function of conversion. The linear trend of Mn vs. conversion clearly reveals the controlled nature of this thirdradical copolymerization step.

In a subsequent step triblock copolymers are used to initiate one further polymerization of S, PFS or mixtures of S and PFS with different PFS compositions from 5 to 95 mole-% at 125 °C without any added catalyst or solvent

(Figure 7). Figure 10d shows the SEC curve of a multiblock copolymer, namely a copolymer poly[(S)-sf-(PFS)]-5-(S)-b-[(S)-sf-(PFS)]-6-(PFS) comprising four different polymer blocks, along with those of the corresponding parent block copolymers. Whilst specific examples of more complex multiblock copolymers are not described in the invention, their preparation will be possible by the controlled radical process of this invention and does not depart from the spirit and scope thereof.

The following examples will serve to illustrate comprehensively the principles of the present invention but are not meant to limit the boundary of the invention.

Example 1

Controlled Radical Polymerization of Styrene

10 mL (87.2 mmol) of styrene, 0.0709 g (0.45 mmol) of TEMPO, 0.0846 g (0.35 mmol) of BPO are placed in a polymerization ampoule. The content is degassed by freeze and thaw cycles and sealed under nitrogen. The polymerization reaction is performed at 125 °C for 2 h. At the end of the reaction, the ampoule is rapidly cooled to room temperature in cold water and the reaction mixture is diluted with tetrahydrofuran. The poly(S) is then precipitated into methanol, washed with methanol and purified by precipitations from tetrahydrofuran solution into methanol. The polymer is dried on silica gel in vacuo for several hours. Conversion of styrene (yield 80%) is evaluated by weighing the polymer obtained. Example 2

Controlled Radical Polymerization of Styrene/Pentafluorostyrene Mixtures 5 mL (43.6 mmol) of styrene, 5 mL (18.3 mmol) of pentafluorostyrene, s 0.0709 g (0.45 mmol) of TEMPO, 0.0846 g (0.35 mmol) of BPO are placed in a polymerization ampoule. The content is degassed by freeze and thaw cycles and sealed under nitrogen. The copolymerization reaction is performed at 125 °C for 8 h. At the end of the reaction, the ampoule is quenched in cold water and the reaction mixture diluted with tetrahydrofuran. The copolymer is then precipitated o into methanol, washed with methanol and purified by precipitation from tetrahydrofuran solution into methanol. The copolymer poly[(S)-sf-(PFS)] is dried on silica gel in vacuo for several hours. Conversion of styrene and pentafluorostyrene (yield 75%) is evaluated by weighing the copolymer obtained.

The composition is determined by ^"Η-NMR. 5

Example 3

Synthesis of Poly(S)-6-[(PFS)-sf-(S)]

0.30 g of the poly(S) of example 1 and a mixture of styrene and o pentafluorostyrene in different ratios with a total weight of 1.0 g are placed in a polymerization ampoule. The content is degassed by freeze and thaw cycles and sealed under nitrogen. The copolymerization reaction is performed at 125 °C for 10 h. The copolymer is then precipitated in methanol, washed with methanol and purified by precipitations from tetrahydrofuran solution into methanol. The polymer 5 is dried on silica gel in vacuo for several hours. Conversion of styrene and pentafluorostyrene (yield 75%) is evaluated by weighing the obtained polymer.

The composition is determined by 1 H-NMR. Example 4

Synthesis of Poly[(PFS)-sf-(S)]π -(S)

0.30 g of the poly[(PFS)-sf-(S)] of example 2 and 2.0 g (17.4 mmol) of styrene are placed in a polymerization ampoule. The content is degassed by freeze and thaw cycles and sealed under nitrogen. The copolymerization reaction is performed at 125 °C for 3 h. The copolymer is then dissolved in tetrahydrofuran, precipitated in methanol, washed with methanol and purified by precipitations from tetrahydrofuran solution into methanol. The polymer is dried on silica gel in vacuo for several hours. Conversion of styrene (yield 70%) is evaluated by weighing the obtained polymer. The composition is determined by 1 H-NMR.

Example 5

Synthesis of Poly(S)-b-(PFS)

0.30 g of the poly(S) of example 1 and 1.7 g of pentafluorostyrene are placed in a polymerization ampoule. The content is degassed by freeze and thaw cycles and sealed under nitrogen. The copolymerization reaction is performed at 125 °C for 10 h. The copolymer is then dissolved in tetrahydrofuran and precipitated in methanol, washed with methanol and purified by precipitations from tetrahydrofuran solution into methanol. The polymer is dried on silica gel in vacuo for several hours. Conversion of pentafluorostyrene (yield 65%) is evaluated by weighing the obtained polymer. The composition is determined by ^H-NMR.

Example 6

Synthesis of Poly[(PFS)-sf-(S)]-b-(PFS)

0.30 g of the poly[(PFS)-sf-(S)] of example 2 and 2.0 g of pentafluorostyrene are placed in a polymerization ampoule. The content is degassed by freeze and thaw cycles and sealed under nitrogen. The copolymerization reaction is performed at 125 °C for 10 h. The copolymer is then dissolved in tetrahydrofuran, precipitated in methanol, washed with methanol and purified by precipitations from tetrahydrofuran solution into methanol. The polymer is dried on silica gel in vacuo for several hours. Conversion of pentafluorostyrene (yield 70%) is evaluated by weighing the obtained polymer. The composition is determined by ^H-NMR.

Example 7

Synthesis of Poly(S)-b-[(PFS)-sf-(S)]-b-(S)

0.30 g of the diblock copolymer poly(S)-b-[(PFS)-sf-(S)] of example 3 and 2.0 g of styrene are placed in a polymerization ampoule. The content is degassed by freeze and thaw cycles and sealed under nitrogen. The copolymerization reaction is performed at 125 °C for 3 h. The triblock copolymer is then dissolved in tetrahydrofuran and precipitated in methanol, washed with methanol and purified by precipitations from tetrahydrofuran solution into methanol. The polymer is dried on silica gel in vacuo for several hours. Conversion of styrene (yield 70%) is evaluated by weighing the obtained polymer. The composition is determined by

1H-NMR.

Example 8

Synthesis of Poly(S)-6-[(PFS)-sHS)]-6-(PFS)

0.30 g of the diblock copolymer poly(S)-6-[(PFS)-sf-(S)] of example 3 and 2.0 g of pentafluorostyrene are placed in a polymerization ampoule. The content is degassed by freeze and thaw cycles and sealed under nitrogen. The copolymerization reaction is performed at 125 °C for 10 h. The triblock copolymer is then dissolved in tetrahydrofuran and precipitated in methanol, washed with methanol and purified by precipitations from tetrahydrofuran solution into methanol. The polymer is dried on silica gel in vacuo for several hours. Conversion of pentafluorostyrene (yield 60%) is evaluated by weighing the obtained polymer. The composition is determined by ^H-NMR. Example 9

Synthesis of Poly[(PFS)-sf-(S)]-b-(S)-b-[(PFS)-sf-(S)]

0.30 g of the diblock copolymer poly[(PFS)-sf-(S)]-jb-(S) of example 4 and a mixture of styrene and pentafluorostyrene in different ratios with a total weight of 2.0 g are placed in a polymerization ampoule. The content is degassed by freeze and thaw cycles and sealed under nitrogen. The copolymerization reaction is performed at 125 °C for 10 h. The triblock copolymer is then dissolved in tetrahydrofuran, precipitated in methanol, washed with methanol and purified by precipitations from tetrahydrofuran solution into methanol. The polymer is dried on silica gel in vacuo for several hours. Conversion of styrene and pentafluorostyrene (yield 65%) is evaluated by weighing the obtained polymer. The composition is determined by 1 H-NMR.

Example 10

Synthesis of Poly[(PFS)-sf-(S)]-6-(S)-b-(PFS)

0.30 g of the diblock copolymer poly[(PFS)-sf-(S)]-£»-(S) of example 4 and 1.7 g of pentafluorostyrene are placed in a polymerization ampoule. The content is degassed by freeze and thaw cycles and sealed under nitrogen. The copolymerization reaction is performed at 125 °C for 10 h. The triblock copolymer is then dissolved in tetrahydrofuran, precipitated in methanol, washed with methanol and purified by precipitations from tetrahydrofuran solution into methanol. The polymer is dried on silica gel in vacuo for several hours. Conversion of pentafluorostyrene (yield 65%) is evaluated by weighing the obtained polymer. The composition is determined by 1 H-NMR.

Example 11

Synthesis of Poly[(PFS)-sf-(S)]-6-(S)-b-[(S)-sf-(PFS)]π -(PFS)

0.30 g of the triblock copolymer poly[(PFS)-sf-(S)]-b-(S)-b-[(S)-sf-(PFS)] of example 9 and 1.7 g of pentafluorostyrene are placed in a polymerization ampoule. The content is degassed by freeze and thaw cycles and sealed under nitrogen. The copolymerization reaction is performed at 125 °C for 10 h. The triblock copolymer is then dissolved in tetrahydrofuran, precipitated in methanol, washed with methanol and purified by precipitations from tetrahydrofuran solution into methanol. The polymer is dried on silica gel in vacuo for several hours. Conversion of pentafluorostyrene (yield 70 %) is evaluated by weighing the obtained polymer. The composition is determined by ^H-NMR.

This invention is not limited to the above specific examples of polymers and block copolymers. It must be understood, therefore, that the details involved in the descriptions of the specific examples are presented for the purpose of illustration only, and that reasonable variations and modifications, which will be apparent to those skilled in the art, can be made in this invention without departing from the spirit and scope thereof.

Static contact angle measurements

Static contact angle measurements with water as a wetting liquid are performed on polymer films (approximately 100 mm thickness) as a function of the immersion time in water over a period of 15 days at intervals of 24 h. The measurements are carried out with a Reinhart goniometer by applying a 4 ml drop of water on a polymer film. Each contact angle value is averaged over six measurements performed on different spots of the same polymer film.

The films are prepared by casting a solution of 15 mg of polymer in 100 ml of solvent, either CHCI₃, xylene or mixtures therefrom depending on the solubility of the polymers, on glass cover slides with a diameter of 1 ,5 cm. The films are then dried at room temperature for 2 days and subsequently for 3 days under vacuum.

All the dry polymer films have a contact angle greater than 100°, typically

101-106°, which is stable over prolonged periods of immersion time in water and does not decrease. The trends of contact angle vs. immersion time in water for the films prepared from the polymers of Example 3 and Example 5 are shown in

Figure 12 as typical illustrations. The fluorinated polymers of the present invention are useful materials for non-stick surfaces to prevent accumulation of biological fouling, for non-toxic fouling release coatings, more specifically as low surface energy materials for marine antifouling application. There is a direct correlation between the values of contact angle and surface tension that can be quantified on the basis of the semiempirical method referred as Zisman plot. Accordingly, the higher the contact angle, the lower the critical surface energy.

For contact angle values in the range of 100-115°, one can estimate critical surface tension (γ_c) comprised between 20-10 dyne cm^"1 that can be considered as a relatively low surface tension [J. Wang, G. Mao, C. K. Ober, E. J. Kramer, Macromolecules, 30, 7580 (1997), J. Wang, C. K. Ober, Macromolecules, 30, 7560 (1997) and E. Lindner, Biofouling, 6, 193 (1992)].

Concerning measurements on reference standards no measurements were carried out on polystyrene.

The literature reports for polystyrene a contact angle value against water of 90° corresponding to a critical surface tension value of 32 dyne/cm (J. E. Mark, "Physcal Properties of Polymers Handbook", AlP-Publ., Woodbury, N.Y., USA, 1996, pag. 673). A measurement done on a glass cover slide gave a contact angle value of

35° that should correspond to a surface tenison between 50 and 60 dyne/cm.

Claims

P a t e n t c l a i m s

1. A fluorinated diblock, triblock or multiblock copolymer, characterized in that the blocks are selected from at least two of the following types of polymer blocks:

a) polystyrene block b) polymer block of styrene with a fluorinated phenyl moiety c) copolymer block of a mixture of counits of styrene and styrene with a fluorinated phenyl moiety.

2. A fluorinated copolymer according to claim 1 , characterized in that when it contains three blocks, they are of said three different types a)-c).

3. A fluorinated copolymer according to claim 1 , characterized in that when it comprises three blocks, two of the blocks are of the same type.

4. A fluorinated copolymer according to claim 1 , characterized in that when it comprises four or more blocks, the blocks are of two or three of the types a)-c) in any desired order.

5. A fluorinated copolymer according to any of claims 1-4, characterized in that the styrene with a fluorinated phenyl moiety is pentafluorostyrene.

6. A fluorinated compound according to any of claims 1-5, characterized in that the copolymer block of a mixture of styrene and styrene with a fluorinated phenyl moiety is a polypentafluorostyrene-styrene copolymer block with a random distribution of the counits and with a styrene content of 5 to 95 mole-%.

7. A fluorinated copolymer according to any of claims 1-6, characterized in that the polymer blocks each have a predetermined number average molecular weight from 2.000-50.000 gmol^"1 and a narrow molecular weight distribution from 1.05 to 1.25.

8. A process for preparing a fluorinated copolymer of any of claims 1-7, characterized by a sequence of controlled radical polymerization processes of styrene and styrene monomers containing a fluorinated phenyl moiety.

9. A process according to claim 8, characterized by using an initiator acting as a source of primary free radicals and a stable free radical acting as an end- capping agent at a constant temperature.

10. A process according to claim 9, characterized in that said initiator is benzoyl peroxide, said free radical is 2,2,6,6-tetramethylpiperidinyl-l-oxy nitroxide, and said polymerization temperature is between 110°C and 140°C, preferably 125°C.

11. Marine antifouling material having low surface energy, characterized in that it contains a fluorinated copolymer according to any of claims 1-7, prepared according to any of claims 8-10.