COMPARATIVE-EXAMINATION OF ACRYLIC-ACID AND 4-VINYLPYRIDINE MONOMERS IN LIQUID-PHASE PHOTOGRAFTING ON POLYETHYLENE FILM

The effect of monomer concentration on the location of acrylic acid (AA)- and 4-vinylpyridine (4VP)-grafted chains introduced into low-density polyethylene film (thickness = 30 mum) by liquid-phase photografting (lambda > 300 nm) was investigated together with the grafting behaviours at 60-degrees. Benzophenone was used as a photoinitiator by coating it on the film surface. The grafting rate of AA increased with increasing the AA concentration (1.7, 3.4 and 6.8 wt%). The AA-grafted chains of the sample prepared in the system of 6.8 wt% AA concentration, where the formation of grafted polymer overcomes that of homopolymer, tended to penetrate into the film inside compared to those of the sample prepared in the system of 3.4 wt% concentration, in which the formation of homopolymer proceeds preferentially. With 4VP monomer, on the other hand, the grafting rate decreased while promoting the formation of homopolymer as the monomer concentration increases. The 4VP-grafted chains distributed in the film inside irrespective of the monomer concentration (1.9, 3.8 and 7.6 wt%). The resultant AA- and 4VP-grafted films were subjected to measurement of pH-responsive characters in order to understand relationship between the location of grafted chains and the function.