Description

(Per)fluoropolyether derivatives

Cross-reference to related applications

This application claims priority from EP No. 18187172.4. filed on 03 August 2018, the whole content of this application being incorporated herein by reference for all purposes.

Technical Field

[0001] The present invention relates to novel (per)fluoropolyether (PFPE) polymer derivatives having high thermal, chemical and hydrolytic stability, a method for their manufacture and their use as intermediates for the synthesis of a variety of functional derivatives, including notably silane group-containing derivatives.

Background Art

[0002] Various families of (per)fluoropolyethers are known, which are obtained for example by oxidation of (per)fluoroolefins, such as tetrafluoroethylene and hexafluoropropylene, with oxygen, under the action of ultraviolet radiation, and/or by anionic polymerization, possibly under fluoride catalysis, of (per)fluoroolefin oxides, including hexafluoropropylene oxide.

[0003] Functional derivatives thereof, possessing reactive end groups at the ends of the (per)fluoropolyether chain, are also well known in the art since a long time, and have found usefulness in the manufacture of a large variety of derivatives and polymers adapted to cope with high demanding applications, such as, notably, harsh chemical envoronments, high temperatures, etc.

[0004] Among derivatives which have been disclosed in the art, mention can be made of (per)fluoropolyether derivatives possessing chain ends including ethylenically unsaturated double bonds, which have been notably used for being incorporated in polyaddition polymers and/or as intermediate for the manufacture of other derivatives, including those comprising silane groups.

[0005] For instance, US 2003/0139620 ( Shin-Etsu Chemical Co. , Ltd.) discloses an example of perfluoropolyether derivatives having ethylenically unsaturated double bonds, said derivative having formula:

Rf[(CH ₂ )n-0-(CH2)mCH=CH ₂ ]2

wherein Rf is a divalent straight-chain perfluoropolyether radical with n and m being integers ³ 0 and equal to or different from each other.

[0006] The ethylenically unsaturated double bond(s) present as end groups in said (per)fluoropolyether derivatives can be further reacted for providing a variety of derivatives, which may find utility as additives notably in coating compositions and/or in lubricating formulations.

[0007] EP 2915833 (Daikin Industries, Ltd.) discloses perfluoro(poly)ether group containing silane compounds, represented by formula (1a) or (1 b):

A - Rf - X - SiQkYs-k (1a)

Ys-kQkSi-X-RF-X-SiQkYs-k ( 1 b)

It is worth noting that in the above mentioned formulae, linking group -X- is a divalent organic group, which can be selected among a very long list of alternative meanings. Examples 2 to 15 of EP 2915833 disclose the synthesis of polymers having, as the linking group between the

perfluoropolyether chain and the silane-containing group, a hydrocarbon moiety always containing one oxygen atom (i.e., chain complying with formula -CH ₂ OCH ₂ CH ₂ CH ₂ -). Only Example 1 discloses the synthesis of a perfluoropolyether polymer comprising a divalent alkylene chain as the -X- group, notably of formula -CH ₂ CH ₂ CH ₂ CH ₂ -Nevertheless, in compounds taught in the prior art, the ethylenically unsaturated double bond is actually connected to the (per)fluoropolyoxyalkylene chain through an ethereal oxygen atom, which connects the terminal -CF ₂ - moiety of said chain to the double bond-containing moiety, in generally through a -CH ₂ -0-CH ₂ - moiety.

[0008] While ethereal bonds among alkylene groups are generally considered sufficiently stable for withstanding different chemical environments, and for remaining unreacted under several organic chemistry reactions, in

(per)fluoropolyether derivatives, as mentioned above, the presence of vicinal (per)fluorinated groups may have a detrimental effect on the stability of the said moiety, which remains, all in all, a weak point in the otherwise robust, and chemically, hydrolytically and thermally stable (per)fluoropolyether structure.

[0009] The need is therefore felt to provide novel (per)fluoropolyether derivatives comprising one or more than one reactive chain end under the form of an ethylenically unsaturated double bond, said reactive chain end(s) being bound to the backbone of the (per)fluoropolyoxyalkylene chain through a thermally, hydrolytically and chemically stable bridging group.

Summary of invention

[0010] The aim of the present invention is to overcome the aforementioned

drawbacks of the (per)fluoropolyether derivatives of the prior art. More in particular, the aim of the present invention is to provide

(per)fluoropolyether derivatives comprising one or more than one reactive chain end under the form of an ethylenically unsaturated double bond, said reactive chain end(s) being bound to the backbone of the

(per)fluoropolyoxyalkylene chain through a thermally, hydrolytically and chemically stable bridging group.

[0011] In a first aspect, the present invention relates to a polymer (P) of formula (1a) or (1b) according to present claim 1. The Applicant has surprisingly found that polymer (P) has increased thermal, hydrolytical and chemical stability, both in neutral and basic conditions, when compared to the (per)fluoropolyether derivatives of the prior art having alkenyl moiety(ies) linked to the polymer chain through an ethereal bridging group.

[0012] In a second aspect, the present invention relates to a method for

manufacturing the polymer (P) of formula (1a) or (1 b).

[0013] In a third aspect, the present invention pertains to a process for the

synthesis of a (per)fluoropolyether derivative comprising reacting at least one polymer (P) of any of formulae (1a) and (1b) with at least one compound possessing reactivity towards an ethylenically unsaturated double bond. The present invention notably pertains to a process for the synthesis of a (per)fluoropolyether derivative comprising at least one silane-containing chain end by reacting at least one polymer (P) with at least one hydrosilane.

[0014] In a fourth aspect, the present invention relates to a (per)fluoropolyether group containing-silane compound of formula (6a) or (6b) according to the claims.

Description of embodiments

[0015] For the purpose of the present description and of the following claims:

- the use of parentheses around symbols or numbers identifying the formulae, for example in expressions like“polymer (P)”, etc., has the mere purpose of better distinguishing the symbol or number from the rest of the text and, hence, said parenthesis can also be omitted;

- the acronym“PFPE” stands for "(per)fluoropolyether” and, when used as substantive, is intended to mean either the singular or the plural form, depending on the context;

- the term "(per)fluoropolyether” is intended to indicate fully or partially fluorinated polyether polymer;

- the expression“hydrocarbon group” is intended to denote a group consisting solely of one or more than one carbon atom and a number of hydrogen atoms saturating all free valences of the said carbon atom(s).

[0016] As said, in a first aspect, the present invention is directed to a

(per)fluoropolyether derivative comprising at least one ethylenically unsaturated double bond and complying with any of formulae (1a) or (1 b) [polymer (P) herein below]:

B-R _f -(CFX ^F ) _m -(CR ^H1 R ^H2 ) _n -A (1a)

A-(CR ^H1 R ^H2 ) _n -R _f -(CFX ^F ) _m -(CR ^H1 R ^H2 ) _n -A (1 b),

wherein:

- A is a hydrocarbon group comprising an ethylenically unsaturated double bond; - B is a group of formula Y-CF ₂ -O-, wherein Y is selected from the group consisting of F, Cl, and a C ₁ -C3 perfluoroalkyl group, preferably a -CF3;

- m is an integer different from zero, preferably m is 1 or 2, more preferably m is 1 ;

- n is an integer different from zero, preferably n is 1 or 2, more preferably n is 1 ;

- each of X ^F , equal to or different from each other at each occurrence, is independently selected from the group consisting of F and a C ₁ -C3 perfluoroalkyl group, preferably a -CF3; preferably X ^F is F;

- each of R ^H1 and R ^H2 , equal to or different from each other at each occurrence, is independently selected from the group consisting of H and a C1-C3 fluorine-free alkyl group;

- R _f is a fluoropolyoxyalkylene chain [chain (R _f ) herein below], i.e. a chain comprising a plurality of fluorocarbon segments connected via ethereal bonds.

[0017] Chain (R _f ) of polymer (P) preferably comprises, more preferably consists of, repeating units and said repeating units are independently selected from the group consisting of:

(i) -CFXO-, wherein X is F or CF3;

(ii) -CFXCFXO-, wherein X, equal or different at each occurrence, is F or CF3, with the proviso that at least one of X is -F;

(iii) -CF2CF2CW2O-, wherein each of W, equal or different from each other, are F, Cl, FI;

(iv) -CF2CF2CF2CF2O-;

(v) -(CF ₂ ) _j -CFZ-0- wherein j is an integer from 0 to 3 and Z is a group of general formula -0-R _(f-a) -T, wherein R _(f-a) is a fluoropolyoxyalkylene chain comprising a number of repeating units from 0 to 10, said recurring units being chosen among the following : -CFXO- , -CF ₂ CFXO-, -CF ₂ CF ₂ CF ₂ O-, -CF ₂ CF ₂ CF ₂ CF ₂ O-, with each of X being independently F or CF3 and T being a C ₁ -C3 perfluoroalkyl group.

[0018] Preferably, chain (R _f ) complies with the following formula:

(R _f -I) -[(CFX ¹ 0)gi(CFX ² CFX ³ 0)g ₂ (CF ₂ CF ₂ CF ₂ 0)g3(CF ₂ CF ₂ CF ₂ CF ₂ 0)g ₄ ]- wherein

- X ¹ is independently selected from -F and -CF3,

- X ² , X ³ , equal or different from each other and at each occurrence, are independently -F, -CF3, with the proviso that at least one of X is -F;

- g1 , g2 , g3, and g4, equal or different from each other, are independently integers ³0, such that g1 +g2+g3+g4 is in the range from 2 to 300, preferably from 2 to 100; should at least two of g1 , g2, g3 and g4 be different from zero.

[0019] More preferably, chain (R _f ) is selected from chains of formula:

(Rf-IIA) -[(CF ₂ CF20)al(CF ₂ 0)a2]- wherein:

- a1 and a2 are independently integers ³ 0 such that the number average molecular weight is between 400 and 10,000, preferably between 2,000 and 8,000; both a1 and a2 are preferably different from zero, with the ratio a1/a2 being preferably comprised between 0.1 and 10;

(Rf-IIB) -[(CF2CF ₂ CF ₂ 0)b]- wherein:

- b is an integer > 0 such that the number average molecular weight is between 400 and 10,000, preferably between 2,000 and 8,000;

(Rf-IIC) -[(CF ₂ CF2CF2CF ₂ 0)C]- wherein:

- c is an integer > 0 such that the number average molecular weight is between 400 and 10,000, preferably between 2,000 and 8,000;

(Rf-ll D) -[(CF ₂ CF ₂ 0)di (CF ₂ 0)d2(CF(CF3)0)d3(CF2CF(CF ₃ )0)d4]- wherein:

d 1 , d2, d3, d4, are independently integers ³ 0 such that the number average molecular weight is between 400 and 10,000, preferably between 2,000 and 8,000; preferably d1 is 0, d2, d3, d4 are > 0, with the ratio d4/(d2+d3) being >1 ;

(Rf-ll E) -[(CF ₂ CF ₂ 0)e1 (CF ₂ 0)e2(CF2(CF2)ewCF ₂ 0)e3]- wherein: ew = 1 or 2;

e1 , e2, and e3 are independently integers ³ 0 chosen so that the number average molecular weight is between 400 and 10,000, preferably between 2,000 and 8,000; preferably e1 , e2 and e3 are all > 0, with the ratio e3/(e1 +e2) being generally lower than 0.2;

(R _f -IIF) -[(CF(CF ₃ )CF ₂ 0) _f ]- wherein:

f is an integer > 0 such that the number average molecular weight is between 400 and 10,000, preferably between 2,000 and 8,000.

[0020] Chains (R _f -IIA), (R _f -IIB), (R _f -IIC) and (R _f -IIE) are particularly preferred.

[0021] Still more preferably, chain (R _f ) complies with formula (R _f -IIA), wherein:

- a1 , and a2 are integers > 0 such that the number average molecular weight is between 400 and 10,000, preferably between 2,000 and 8,000, with the ratio a1/a2 being generally comprised between 0.1 and 10, more preferably between 0.2 and 5.

[0022] As said, A is a hydrocarbon group comprising an ethylenically unsaturated double bond. While A may comprise one or more than one ethylenically unsaturated double bonds, it is generally preferred for A to be a

hydrocarbon group comprising solely one ethylenically unsaturated double bond. Besides said ethylenically unsaturated double bond, group A may include other hydrocarbon moieties, such as alkylene groups, arylene groups, and the like. Nonetheless, it is generally preferred for group A to be a group of formula -(CR ^H3 R ^H4 ) _na -CR ^H5 =CR ^H6 R ^H7 , wherein:

- each of R ^H3 , R ^H4 , R ^H5 , R ^H6 and R ^H7 , equal to or different from each other at each occurrence, is independently selected from the group consisting of FI and a C1-C3 fluorine-free alkyl group; preferably each of R ^H3 , R ^H4 , R ^H5 , R ^H6 and R ^H7 is H; and

- na is zero or an integer (preferably an integer of 1 to 3), and more preferably na is zero or 1.

[0023] In a preferred embodiment, A is a vinyl moiety -CH=CH2. In another

preferred embodiment, A is an allyl moiety -CH2-CH=CH2. [0024] The polymer P of formula (1a) above, which contains a single ethylenically unsaturated double bond-containing group A, is also referred to as “monofunctional polymer P”.

[0025] The polymer P of formula (1 b) above, which contains two ethylenically unsaturated double bond-containing groups A, is also referred to as “bifunctional polymer P”.

[0026] In the above formulae, the group -(CR ^H1 R ^H2 ) _n - is recognized to be a linker which connects the group A with the polymer backbone, namely with the monovalent fragment [B-R^(CFX ^F ) _m ]- of the monofunctional polymer P or the divalent fragment -[R - (CFX ^F ) _m ]- of the bifunctional polymer P.

[0027] Without being bound by any theory, the Applicant believes that the

increased stability shown by polymer P is due to the presence of a C-C bond between the group A and the -(CR ^H1 R ^H2 ) _n - group, which is more stable from a thermal, hydrolytic and chemical standpoint than an ethereal bond. This will be more evident from the Examples contained in the following Experimental Section.

[0028] According to another aspect, the present invention provides a process for the manufacture of polymer P starting from PFPE halides.

[0029] The monofunctional polymer P of formula (1a) is preferably prepared

starting from monofunctional PFPE halides of formula (2a), i.e. PFPE comprising a halogen at one polymer end only:

B-R _f -(CFX ^F ) _m -(CR ^H1 R ^H2 ) _n -Ha ¹ (2a)

[0030] The bifunctional polymer P of formula (1 b) is preferably prepared starting from bifunctional PFPE halides of formula (2b), i.e. PFPE comprising a halogen at both polymer ends:

Ha ¹ -(CR ^H1 R ^H2 ) _n -R _f -(CFX ^F ) _m -(CR ^{H 1} R ^H2 ) _n -Ha ¹ (2b)

In the above formulae (2a) and (2b), Ha ¹ is a halogen and B, m, n, X ^F , R ^H1 , R ^H2 and R _f are as defined above.

[0031] The process according to the invention comprises reacting the PFPE- halide of formula (2a) or (2b) as defined above with a Grignard reagent of formula A-MgHa ² , wherein Ha ² is a halogen chosen among bromine, iodine and chlorine and A is as defined above. [0032] Preferably, said Grignard reagent has the following formula:

Ha ² Mg-(CR ^H3 R ^H4 ) _na -CR ^H5 =CR ^H6 R ^H7 ,

wherein R ^H3 , R ^H4 , R ^H5 , R ^H6 , R ^H7 , Ha ² and na are as defined above.

[0033] More preferably, said Grignard reagent is selected from allylmagnesium halide and vinylmagnesium halide, preferably from allylmagnesium bromide BrMg-CH2-CH=CH2 and vinylmagnesium bromide

BrMg-CH=CH ₂ .

[0034] Preferably, the reaction between the PFPE-halide of formula (2a) or (2b) and the Grignard reagent is performed under heating, more preferably at a temperature of about 50°C.

[0035] According to a preferred embodiment of the invention, said PFPE-halide is obtained by:

(I) reacting a PFPE-alcohol of formula (3a) or (3b):

B-R _f -(CFX ^F ) _m -(CR ^{H 1} R ^H2 ) _n -OH (3a)

HO-(CR ^{H 1} R ^H2 ) _n -R _f -(CFX ^F ) _m -(CR ^{H 1} R ^H2 ) _n -OH (3b)

with a compound [compound (O) hereinafter] comprising a sulfonyl fluoride moiety, obtaining a PFPE-sulfonate, and

(II) reacting the PFPE-sulfonate obtained in step (I) above with a compound [compound (Q) hereinafter] which is a source of nucleophilic halides, obtaining said PFPE-halide.

[0036] Suitable PFPE-alcohol(s) can be obtained according to methods known in the art and are commercially available, for example from Solvay Specialty Polymers Italy S.p.A. under the trade name Fomblin ^® .

[0037] The compound (O) used in the above step (I) is preferably selected from the perfluoroalkanesulfonyl fluorides. Good results have been obtained using the perfluorobutanesulfonyl fluoride as compound (O).

[0038] Step (I) is advantageously performed in the presence of a base, such as triethylamine.

[0039] Preferably, said step (I) is performed in the presence of an aprotic solvent, such as 1 ,3-bis(trifluoromethyl)benzene

[0040] Preferably, said step (I) is performed under heating, more preferably at a temperature of about 50°C. [0041] The compound (Q) used in the above step (II) is preferably lithium bromide.

[0042] Preferably, said step (II) is performed in the presence of an aprotic solvent, such as sulfolane.

[0043] Preferably, said step (II) is performed under heating, more preferably up to a temperature of about 200°C.

[0044] According to another aspect, the present invention provides methods for the synthesis of (per)fluoropolyether derivatives by conversion of the ethylenically unsaturated double bond of polymer (P) of formula (1a) or (1 b) into different moieties, for example an epoxide, a vicinal diol, a vicinal dibromide, a carboxylic acid, an aldehyde and alkyl substituted saturated groups.

[0045] According to a first embodiment, an epoxide moiety is obtained by reacting the polymer (P) with peroxides, such as hydrogen peroxide, or peracids.

[0046] According to a second embodiment, a vicinal diol moiety is obtained by reacting the polymer (P) with Os0 ₄ providing a complex and then subjecting said complex to hydrolysis. In an alternative embodiment, the vicinal diol is obtained by hydrolysis of the epoxide obtained by reacting polymer (P) with peroxides or peracids, as disclosed above.

[0047] In a third embodiment, a vicinal dibromide moiety is obtained by reacting the polymer (P) with elemental bromine.

[0048] In a forth embodiment, a carboxylic acid moiety is obtained by reacting the polymer (P) with an oxidizing agent, such as potassium permanganate.

[0049] In a fifth embodiment, an aldehyde moiety is obtained by subjecting the polymer (P) to hydroformylation in the presence of carbon monoxide and hydrogen under pressure and in the presence of a suitable catalyst, such as a transition metal complex.

[0050] In a sixth embodiment, an alkyl substituted saturated group is obtained by reacting the polymer (P) with radical species (i.e. by radical addition reaction), optionally in the presence of olefins which can propagate the radical chain. [0051] In another embodiment, a monofunctional silane group is obtained by reacting the polymer (P) with a hydrosilane having at least one

hydrolysable radical.

[0052] According to a further embodiment, the present invention provides a

process for the synthesis of a (per)fluoropolyether derivative of formula (4a) or (4b) comprising at least one silane-containing chain end:

B-Rf-(CFX ^F ) _m -(CR ^H1 R ^H2 ) _n -A ^* -SiM ₃ (4a)

M ₃ Si-A ^* -(CR ^H1 R ^H2 )n-Rf-(CFX ^F ) _m -(CR ^H1 R ^H2 ) _n -A ^* -SiM ₃ (4b) by reacting the polymer (P) of formula (1a) or (1 b) with HSiM ₃ , wherein A ^* is a hydrocarbon group and M is independently halogen or Ci- ₆ -alkoxy.

[0053] Preferably, said process further comprises:

- reacting the derivative of formula (4a) or (4b) with a Grignard reagent of formula Ha ² -Mg-M ^* -CH=CH2, wherein Ha ² is a halogen chosen among bromine, iodine and chlorine and M ^* is a bond or a divalent organic group, and optionally with a compound of formula K _h L wherein K is a hydroxyl group, a hydrolysable group, or a hydrocarbon group, L is a group which is able to bind to K and h is an integer of 1-3, thus obtaining a compound of formula (5a) or (5b):

B-Rf-(CFX ^F ) _m -(CR ^H1 R ^H2 )n-A ^* -Si(K _3-k )(-M ^* -CH=CH2)k’ (5a)

(H ₂ C=CH-M ^* -) _k (K _3-k )Si-A ^* -(CR ^H1 R ^H2 ) _n -R _f -(CFX ^F ) _m -(CR ^H1 R ^H2 ) _n -A ^* -Si(K _3- k’)(-M ^* -CH=CH ₂ )k’ (5b), wherein k’ is independently 2 or 3;

- reacting the compound of formula (5a) or (5b) with HSiM ₃ , wherein M is as defined above, and optionally with a compound of formula RVL’, wherein R ¹ is a hydroxyl group or a hydrolysable group, L’ is a group which is able to bind to R ¹ and h ^* is an integer of 1 -3, and/or with a compound of formula R ^2’ _h** L”, wherein R ^2’ is Ci _-22 -alkyl, L” is a group which is able to bind to R ² and h ^** is an integer of 1 -3, thus obtaining a compound of formula (6a) or (6b):

B-Rf-(CFX ^F ) _m -(CR ^H1 R ^H2 )n-A ^* -SiJkK _3-k (6a)

SiJ _k R ₃ -k-A ^* -(CR ^H1 R ^H2 )n-Rf-(CFX ^F ) _m -(CR ^H1 R ^H2 )n-A ^* -SiJkK _3-k (6b) wherein: k is independently 2 or 3, and

J represents, each independently at each occurrence, -J ^* -SiR ¹ _n* R ² 3- _n* , wherein:

J ^* is a divalent organic group, preferably with the proviso that J ^* is not a group which forms a siloxane bond together with a Si atom;

R ¹ represents, each independently at each occurrence, a hydroxyl group or a hydrolysable group;

R ² represents, each independently at each occurrence, a Ci-22 alkyl group or J’, wherein J’ has the same definition as that of J,

n ^* is an integer selected from 0 to 3, and the total sum of n ^* is 1 or more.

[0054] According to a further aspect, the present invention relates to a

(per)fluoropolyether group containing-silane compound of formula (6a) or (6b):

B-R _f -(CFX ^F ) _m -(CR ^H1 R ^H2 )n-A ^* -SiJkK _3-k (6a)

SiJ _k R ₃ -k-A ^* -(CR ^{H 1} R ^H2 )n-Rf-(CFX ^F ) _m -(CR ^{H 1} R ^H2 )n-A ^* -SiJ _k K _3-k (6b) wherein:

- A ^* is a hydrocarbon group;

- B is a group of formula Y-CF2-O-, wherein Y is selected from the group consisting of F, Cl, and a Ci-C ₃ perfluoroalkyl group, said perfluoroalkyl group being preferably -CF ₃ ;

- m is an integer different from zero, preferably m is 1 or 2, more

preferably m is 1 ;

- n is an integer different from zero, preferably n is 1 or 2, more

preferably n is 1 ;

- each of X ^F , equal to or different from each other at each occurrence, is independently selected from the group consisting of F and a Ci-C ₃ perfluoroalkyl group, said perfluoroalkyl group being preferably -CF ₃ ; preferably X ^F is F;

- each of R ^H1 and R ^H2 , equal to or different from each other at each occurrence, is independently selected from the group consisting of H and a Ci-C ₃ fluorine-free alkyl group; - R _f is a fluoropolyoxyalkylene chain [chain (R _f )];

- K represents, each independently at each occurrence, a hydroxyl group, a hydrolysable group, or a hydrocarbon group;

- J represents, each independently at each occurrence, -J ^* -SiR ¹ _n* R ² 3- _n* , wherein:

J ^* is a divalent organic group, preferably with the proviso that J ^* is not a group which forms a siloxane bond together with a Si atom;

R ¹ represents, each independently at each occurrence, a hydroxyl group or a hydrolysable group;

R ² represents, each independently at each occurrence, a Ci-22 alkyl group or J’, wherein J’ has the same definition as that of J, n ^* is an integer selected from 0 to 3, and the total sum of n ^* is 1 or more;

- k is independently 2 or 3.

[0055] Preferably, A ^* is a group of formula: -(CR ^H3 R ^H4 ) _na -CHR ^H5 CR ^H6 R ^H7 -,

wherein:

- each of R ^H3 , R ^H4 , R ^H5 , R ^H6 , and R ^H7 , equal to or different from each other at each occurrence, is independently selected from the group consisting of H and a C1-C3 fluorine-free alkyl group, preferably each of R ^H3 , R ^H4 , R ^H5 , R ^H6 , and R ^H7 is H, and

- na is an integer > 0, preferably na is not higher than 3, more preferably na is 0 or 1 ,

[0056] Preferably, A ^* is -CH2CH2- or -CH2CH2CH2-.

[0057] Illustrative examples of suitable hydrolyzable groups include alkoxy

radicals such as methoxy, ethoxy, propoxy and butoxy, alkoxyalkoxy radicals such as methoxymethoxy and methoxyethoxy, acyloxy radicals such as acetoxy, alkenyloxy radicals such as isopropenoxy, and halogen radicals such as chloro, bromo and iodo. Of these, organooxy radicals such as alkoxy and alkenyloxy radicals and chloro are preferred, with methoxy, ethoxy, isopropenoxy and chloro being most preferred.

[0058] Should the disclosure of any patents, patent applications, and publications which are incorporated herein by reference conflict with the description of the present application to the extent that it may render a term unclear, the present description shall take precedence.

[0059] The invention will be hereinafter illustrated in greater detail by means of the Examples contained in the following Experimental Section; the

Examples are merely illustrative and are by no means to be interpreted as limiting the scope of the invention.

Experimental Section

[060] Materials

[061] Perfluoro-1-butanesulfonyl fluoride, triethylamine, lithium bromide,

allylmagnesium bromide solution 1 M in diethylether, allyl iodide, potassium tert-butoxide, tert-butanol, HCI (37% aqueous solution), methanol, 2- methyl-1 -propanol and sulfolane were purchased from Sigma Aldrich.

[062] 1 ,3-bis(trifluoromethyl)benzene was obtained from Miteni S.p.A.

ZMF-402: CF ₃ 0(CF ₂ CF ₂ 0) _p (CF ₂ 0) _q CF ₂ CH ₂ 0H (p/q = 1.0, F = 1.07, EW = 4570) is available from Solvay Specialty Polymers S.p.A.

[063] Methods

[064] NMR

[065] ¹ H-NMR and ¹⁹ F-NMR were recorded on an Agilent System 500 operating at 499.86 MHz for ¹ H and 470.30 MHz for ¹⁹ F.

[066] Determination of the average functionality

[067] The average functionality (F):

F = 2 ^* Ef/(Ef+E _n )

wherein E _f is the number of functional end groups and E _n is the number of non-functional end groups,

was determined by means of ¹ H-NMR and ¹⁹ F-NMR according to known methods, for example as disclosed in US 5,919,641.

[068] Thermal stability in neutral conditions

[069] Thermal stability tests in neutral conditions were carried out according to the following procedure: 50 g of product were charged into a round bottom flask equipped with a mechanical stirrer, a refrigeration column, a precision seal septum and a thermometer; the product was heated to a temperature of 150 °C for 24 hours; a sample of the product was taken out every 8 hours and analysed by ¹ H-NMR and ¹⁹ F-NMR.

[070] Thermal stability in basic conditions

Thermal stability tests in basic conditions were carried out according to the following procedure: 50 g of product and dried KOH powder (1.5 molar ratio) were charged into a round bottom flask equipped with a mechanical stirrer, a refrigeration column, a precision seal septum and a thermometer; the mixture was heated to a temperature of 100 °C for 24 hours; a sample of the product was taken out every 8 hours, washed with an aqueous solution of hydrochloric acid (5% w/w) and added with 1 ,3- bis(trifluoromethyl)benzene. The lower fluorinated phase was separated, dried under vacuum and the recovered residue was analysed by ¹ H-NMR and ¹⁹ F-NMR.

In the above tests, the percentage of degraded product was monitored by determining the relative ratios of the formed byproducts and the product submitted to the stability test.

[071] Synthesis examples

[072] Example 1 - Synthesis of Polymer P having the following formula:

CF ₃ 0(CF2CF20)p(CF20)qCF2-CH2CH2CH=CH2

[073] STEP 1 : synthesis of PFPE-lntermediate A having the formula:

CF30(CF2CF20)p(CF20)qCF2-CH20-S(0)2CF2CF2CF ₂ CF3

[074] 125 g of 1 ,3-bis(trifluoromethyl)benzene, 17.2 g of perfluoro-1 - butanesulfonyl fluoride (57 mmol) and 6.2 g of triethylamine (61 mmol) were charged under inert atmosphere into a 500-ml round bottom flask equipped with a mechanical stirrer, a thermometer, a dropping funnel and a refrigeration column and the temperature was raised up to 50 °C.

[075] Then, 200 g of ZMF 402 PFPE of formula

CF ₃ 0(CF ₂ CF ₂ 0) _P (CF ₂ 0) _q CF ₂ CH ₂ 0H (p/q = 1.0, F = 1.07, EW = 4570, 44 meq) were slowly added. The reaction mixture was let under stirring for 3 hours until the signals of the pre-terminal -CF ₂ group shifted from -81.3 and -83.3 ppm (when linked to -CFhOH) to -78.7 and -80.5 ppm (when linked to -CH20-S(0)2CF2CF2CF2CF3). Said shifting was monitored by 1 ⁹ F-NMR analysis.

[076] At the end of the reaction, the reaction mixture was cooled to 20 °C and the lower fluorinated phase was separated and washed with 50 g of methanol and 80 g of an aqueous solution of hydrochloric acid (5% w/w).

[077] The heavier fluorinated phase was dried under vacuum leaving 197.0 g of the PFPE-lntermediate A having the following formula

CF30(CF2CF20)p(CF20)qCF2-CH20-S(0)2CF2CF2CF ₂ CF3

that was confirmed by ¹⁹ F-NMR analysis.

[078] STEP 2: synthesis of the PFPE-lntermediate B having the formula:

CF ₃ 0(CF ₂ CF ₂ 0) _p (CF ₂ 0) _q CF ₂ CH ₂ Br

[079] 5.7 g of dried lithium bromide, 90 g of sulfolane and 160 g of the PFPE- lntermediate A (p/q = 1.0, F = 1.07, EW = 4845, 33 meq) were charged under inert atmosphere into a 250-ml round bottom flask equipped with a mechanical stirrer, a thermometer and a refrigeration column.

[080] The so obtained reaction mixture was gradually heated up to a

temperature of 190 °C and let under stirring for 8 hours until the signals of the pre-terminal -CF2 group shifted from 78.7 and -80.5 ppm (when linked to -CFh0-S(0)2CF2CF2CF2CF3) to -72.9 and -74.7 ppm (when linked to - CFhBr). Said shifting was monitored by ¹⁹ F-NMR analysis.

[081] Then, the reaction mixture was cooled to 20 °C.

[082] Then, 90 g of an aqueous solution of hydrochloric acid (5% w/w), 80 g of 1 ,3-bis(trifluoromethyl) benzene and 40 g of 2-methyl-1 -propanol were added and the mixture was let under stirring for 15 minutes.

[083] The lower fluorinated phase was separated and the solvents were

removed by distillation under reduced pressure (T = 80°C, P = 2 Pa).

PFPE-lntermediate B having the formula

CF30(CF ₂ CF ₂ 0)p(CF ₂ 0) _q CF ₂ CFl ₂ Br was recovered in an amount of 145 g. The chemical structure was confirmed by ¹⁹ F-NMR and ¹ H-NMR analyses.

[084] STEP 3: synthesis of the Polymer P having the formula:

CF ₃ 0(CF ₂ CF ₂ 0) _p (CF ₂ 0) _q CF ₂ -CH ₂ CH ₂ CH=CH2 [085] 125 g the PFPE-lntermediate B (p/q = 1.0, F = 1.07, EW = 4617, 27 meq) were charged under inert atmosphere into a 250-ml round bottom flask equipped with a magnetic stirrer bar, a thermometer, a refrigeration column and a dropping funnel.

[086] The temperature of the so obtained reaction mixture was then raised up to 50 °C and 55 ml of allylmagnesium bromide solution 1 M in diethylether were slowly added. The so obtained solution was kept under stirring at reflux for 15 hours until the signals of the pre-terminal -CF2 group shifted from -72.9 and -74.7 ppm (when linked to -CFhBr) to -70.4 and -72.6 ppm (when linked to the hydrogenated alkenyl group). Said shifting was monitored by ¹⁹ F-NMR analysis.

[087] Then, the reaction mixture was cooled to 20 °C and 80 ml of deionized water were slowly added. The so obtained solution was then kept under vigorous stirring for 30 minutes.

Then, 40 g of an aqueous solution of hydrochloric acid (5% w/w) and 40 g of 1 ,3-bis(trifluoromethyl)benzene were charged into the flask. The lower fluorinated phase was separated and dried by distillation under reduced pressure (T = 80°C, P = 2 Pa). The obtained residue was filtered through a 0.2 pm PTFE membrane leaving 117.0 g of polymer P having the following formula: CF ₃ 0(CF ₂ CF ₂ 0) _p (CF ₂ 0) _q CF ₂ -CH ₂ CH ₂ CH=CH2. The chemical structure was confirmed by ¹⁹ F-NMR and ¹ H-NMR analyses.

[088] Example 2 (comparative) - Synthesis of Polymer C having the following formula:

CF ₃ 0(CF2CF20)p(CF20)qCF2-CH20CH2CH=CH2

[089] 200 g of ZMF 402 PFPE of formula CF ₃ 0(CF ₂ CF ₂ 0) _p (CF ₂ 0) _q CF ₂ CH ₂ 0H

(p/q = 1.0, F = 1.07, EW = 4570, 44 meq), 100 g of 1 ,3-bis(trifluoromethyl) benzene and 53 g of a 12% w/w solution of potassium tert-butoxide in tert- butanol were charged into a 500-ml round bottom flask equipped with a mechanical stirrer, an additional funnel, a thermometer and a refrigeration column. The reaction mixture was heated up to 50 °C and let under stirring for 5 hours. [090] Then, the temperature was raised up to 80 °C and 9.6 g of allyl iodide (57 me) were added. The reaction mixture was then kept under stirring at this temperature for 5 hours until the signals of the pre-terminal -CF2 group shifted from -81.3 and -83.3 ppm (when linked to -CH2OH) to -78.2 and - 80.1 ppm (when linked to -CFhOCFteCF^CFh). Said shifting was monitored by ¹⁹ F-NMR analysis.

The reaction mixture was cooled to 20 °C, added with 80 g of an aqueous solution of hydrochloric acid (5% w/w) and 40 g of 2-methyl-1 -propanol and let under stirring for 30 minutes. The lower fluorinated phase was separated and the solvents were removed by distillation under reduced pressure (T = 80°C, P = 2 Pa). The PFPE-lntermediate B having the following formula CF30(CF2CF20) _p (CF20) _q CF2-CFl20CFl2CFI=CFI2 was recovered in an amount of 195 g. The chemical structure was confirmed by ¹⁹ F-NMR and ¹ H-NMR analyses.

[091] Stability tests

Polymers P and C, prepared according to the Examples 1 and 2 above, were submitted to thermal stability tests in neutral and basic conditions according to the above described procedures.

The percentage of degraded product in neutral conditions was 18, 29, 36% respectively after 8, 16, 24 hours in the case of Polymer C, while no degraded product was observed in the case of Polymer P.

The percentage of degraded product in basic conditions was 8, 14, 18% respectively after 8, 16, 24 hours in the case of Polymer C, while no degraded product was observed in the case of Polymer P.