Preparation and properties of poly-(N-butylmethacrylamide) networks

The gel-effect influences the copolymerization of N-butylmethacrylamide with methylene-bis-acrylamide similarly to other vinyl-divinyl copolymerizations. The fraction of crosslinks wasted in cycles is very high at the gel point, reaching 0.84–0.95; it decreases with increasing content of the crosslinking agent and with decreasing content of dimethylsulphoxide (DMSO) in the polymerization mixture. The effect of residual time processes on the mechanical characteristics in the rubberlike region decreases with increasing concentration of elastically active network chains, ν_e. The equilibrium deformational behaviour obeys the kinetic theory of rubber elasticity. With increasing dilution of the system, the efficiency of the cross-linking reaction decreases and so does the effect of trapped entanglements. A comparison of the gel points and the mechanical characteristics for poly(N-butylmethacrylamide) and poly(N-ethylmethacrylamide) networks swollen in DMSO indicates that the substituent at the amide nitrogen atom has a dilution effect depending on its size. The interaction parameter of the system poly(N-butylmethacrylamide)-DMSO increases linearly with the volume fraction of the polymer in the swollen gel, ν₂; χ = 0.498 + 0.362 ν₂ for ν₂? (0.1, 0.33) and 25°.