WO 01/71392 discloses polymerizable macromonomers which are obtained by co-polymerizing N,N-dimethyl acrylamide (DMA) and a crosslinker comprising two or more ethylenically unsaturated double bonds in the presence of a chain transfer agent and capping the resultant copolymer with a compound providing a C—C double bond. The macrocomonomers thus obtained may be crosslinked in a suitable mold in order to yield hydrogel moldings, for example contact lenses. According to the above-outlined process valuable polymers with applicability in the field of medical devices may be obtained. However, the synthesis as described above sometimes suffers from some drawbacks affecting the quality of the resulting products. In particular, the first copolymerization step is complex and proceeds in a manner difficult to control. Due to a lack of kinetic control, the reproducibility of the resulting products is sometimes poor. For example, the water contents of the final molding may vary, or the amount of undesired extractables within the molding, for example, reaction products which are present but not incorporated in the polymer matrix of the molding and which therefore may leach out over time, is sometimes high.
In view of this there is a demand to improve the basic concept as outlined in WO 01/71392 and provide new polymers with further improved properties in a more reproducible manner.
USPTO Backgrounds
USPTO Backgrounds