Characterization of precursors of crosslinked polymers in the free-radicalcrosslinking copolymerization of benzyl methacrylate with polyethylene glycol dimethacrylate

Benzyl methacrylate (BzMA) was copolymerized radically with polyethylene gl ycol dimethacrylate [CH2=C(CH3)CO(OCH2CH2)(23)OCOC(CH3)=CH2] (PEGDMA-23) to provide novel amphiphilic polymers as precursors of crosslinked polymers g overned by Flory-Stockmayer gelation theory (F-S theory). Thus, BzMA/PEGDMA -23 copolymerizations were conducted under the specified conditions where t he occurrence of a thermodynamic excluded volume effect and intramolecular crosslinking as the primary and secondary factors, respectively, for the gr eatly delayed gelation in the free-radical monovinyl-divinyl copolymerizati ons was reduced: Firstly, the reasonable applicability of F-S theory was ve rified by the comparison of the actual gel point with the theoretical one. Secondly, the tailed molecular-weight distribution curves were observed wit h conversion as a result of the predominant occurrence of intermolecular cr osslinking according to F-S theory. Thirdly, the applicability of F-S theor y was supported by both the correlations of molecular weight versus elution volume and r.m.s. radius of gyration versus molecular weight, although the molecular size shrinkage of the resulting prepolymers consisting of rather rigid poly(BzMA) chains and flexible polyoxyethylene crosslinks would be e nhanced with conversion as a result of increased crosslinking. (C) 2000 Els evier Science Ltd. All rights reserved.