| Abstract: | Crosslinked xerogels comprising N-vinyl-2-pyrrolidone (VP) and butyl acrylate (BA) with different weight fractions of BA ranging between 0.1 and 0.3 were prepared by γ-ray initiation copolymerization using different concentrations of either hexa- or tetrafunctional crosslinking agents. Methylene bisacrylamide (MBA) was selected as tetrafunctional crosslinker, while 1,1,1-trimethylolpropane trimethacrylate (TPT) was used as a hexafunctional crosslinker. The concentration of both crosslinkers ranged between 0.5% and 2%. Thin disks of the prepared copolymers were swollen in deionized water at 294 K. The final equilibrium water content, volume fraction of polymer and swelling capacity were determined. The effective crosslinking density Ve, the average molecular weight between the crosslinks Mc and the polymer–water interaction parameter were determined from stress–strain measurements. For different compositions of VP/BA, the linear relations between theoretical crosslinking densities Vt and Ve were established. The efficiencies of MBA and TPT crosslinking agents towards VP–BA copolymers were determined. © 1998 John Wiley & Sons, Ltd. |
