Polymeric blends with zwitterionic groups

A polymer blend consisting essentially of:

• (A.sub.2) a polymer formed from a radical polymerisable zwitterionic monomer of formula (I)
• Y--B--X (I)
• wherein B is a straight or branched alkylene, an oxaalkylene or an oligo-oxaalkylene chain optionally containing one or more fluorine atoms up to and including perfluorinated chains or, if X contains a carbon-carbon chain between B and the zwitterionic moiety or if Y contains a terminal carbon atom bonded to B, a valence bond;
• X is an anionic-moiety-containing zwitterionic group in which the anionic moiety is a phosphate group,
• Y is an ethylenically unsaturated polymerisable group selected from ##STR41## wherein:
• R is hydrogen or a C.sub.1 -C.sub.4 alkyl group;
• A is --O-- or --NR.sup.1 -- where R.sup.1 is hydrogen or a C.sub.1 -C.sub.4 alkyl group or R.sup.1 is --B--X where B and X are as defined above;
• and
• K is selected from the group consisting of:
• --(CF.sub.2).sub.p OC(O)--, --(CH.sub.2).sub.p C(O)O--, --(CH.sub.2).sub.p OC(O)O`--, O(CH.sub.2).sub.p NR.sup.2 --, --(CH.sub.2).sub.p NR.sup.2 C(O)--, --(CH.sub.2).sub.p C(O)NR.sup.2 --, --(CH.sub.2).sub.p NR.sup.2 C(O)O --, --(CH.sub.2).sub.p OC(O)NR.sup.2 --, --(CH.sub.2).sub.p NR.sup.2 C(O)NR.sup.2 --, (in which the R.sup.2 groups are the same or different) --(CH.sub.2).sub.p O--, --(CH.sub.2).sub.p SO.sub.3 --, and, optionally in combination with B, a valence bond and p is from 1 to 12 and R.sup.2 is hydrogen or a C.sub.1 -C.sub.4 alkyl group;
• and the blend further consisting essentially of:
• (B.sub.2) a polymer having desirable mechanical and/or physical properties which is less hydrophilic than polymer (A.sub.2),
• whereby polymer (B.sub.2) in the blend has improved biocompatibility rendered by polymer (A.sub.2).

A method of producing a blend, consisting essentially of the steps of:

• providing a preformed polymer (A.sub.3) bearing zwitterionic pendant groups and a polymer (B.sub.3) having desirable mechanical and/or physical properties, wherein polymer (A.sub.3) is more hydrophilic than polymer (B.sub.3) and polymer (A.sub.3) and polymer (B.sub.3) ere both in solid particulate form;
• and
• blending polymer (A.sub.3) and polymer (B.sub.3) by a technique selected from roll-milling, Banbury mixing, screw extrusion and disk compounding, to form a polymer (A.sub.3)/polymer(B.sub.3) blend, the blend having a superior biocompatability than polymer (B.sub.3) alone;
• whereby the lubricity of the blend in the presence of aqueous liquid is higher than the lubricity of polymer (B.sub.3) in the presence of aqueous liquid.

A polymer blend consisting essentially of:

• {a} a polymer comprised of residues of one or more radically polymerisable ethylenically unsaturated monomers including a zwitterionic monomer;
• and
• {b} a polymer having desirable mechanical and/or physical properties selected from the group consisting of a polyolefin, a vinylhalide polymer, an (alk)acylate polymer, a polyurethane, a natural rubber and a synthetic rubber, wherein polymer {b} is thermoplastic and/or elastomeric;
• said blend containing 1 to 90% by weight of polymer {a} and 10 to 99% by weight of polymer {b}, whereby the biocompatibility of polymer {b} is improved by being blended with polymer {a}.