the group consisting of (1) reaction products of dianhydrides with molecules containing at least one methacrylate, acrylate or other polymerizable group and also one reactive hydroxyl group, or primary or secondary amino group, (2) 4-methacryloxyethyltrimelliticanhydride and its dicarboxylic acid hydrolysis derivative, (3) other compounds containing at least one group or moiety capable of free rad