Abstract: The UV crosslinking reaction of unsaturated polyphosphoester with N-vinyl pyrrolidone was investigated by gel content measurement. The experiment results show that photoinitiators can remarkably improve the gel content of curing product. Among all initiators used in this study, BE, BN and DEAP show high initiating activities. The gel content of curing product increased with the increasing of initiator amount within low concentration, but higher concentration of photoinitiator would reduce the gel content. The optimum amount of BN and BE was 2.4E^-5(mol/g UPPE)and 0.6E^-5(mol/g UPPE), respectively. The gel content of crosslinked network obtained from unsaturated polyphosphoester with M_w = 4040 g·mol^-1 is lower than that of with higher molecular weight when the irradiation time was less than 2 minutes, but an opposite results would obtained by extending irradiation time. The surface layer of sample absorbed the UV light and decreased the pho-tocrosslinking reaction rate of the deep layer. Gel content of the sample with 1.5 mm in thickness would approach to that of sample with 1.0 mm in thickness by extending irradiation time. The crosslinking reaction was uncompleted for the sample with 6.0 mm in thickness after 24 min irradiation.

Key words: unsaturated polyphosphoester, injectable bone repair materials, photocrosslinking, Gel content