Optical properties of IPN-like networks. I. Polyethylene/poly(butylmethacrylate-co-styrene) copolymer systems

IPN-like systems, made of Low Density Polyethylene (PE) and Poly(butylmetha crylate) (BMA)-co-styrene(S) copolymer networks, were synthesized by a part icular procedure, described in previous papers. The initial PE/copolymer molar ratio was kept equal to one for all the samp les. Different molar BMA/S ratios (50/50,70/30, 80/20, 85/15, 90/10 100/0) of the copolymer and various molar percenttages (0.5, 1.0, 1.5, 2.0%) of th e copolymer crosslinker (DVB) were used. The samples obtained were analyzed by DSC, WAXS, swelling in CCl4, dynamic- mechanical and impact tests. An accurate optical investigation was made in a temperature range going fi- om room temperature (R,T.) up to 180 degrees C, in order to deepen the know ledge of the optical properties of these materials, whose preliminary resul ts were shown in a previous paper. From the experimental data, it was possible to derive an analytical express ion relating the temperature, at which the IPN's become transparent, to syn thetic parameters such as copolymer composition and degree of crosslinking, expressed by the initial mixture BMA/S comonomers ratio and by the amount of the DVB copolymer crosslinker. By the use of this analytical expression, a priori designs of IPN materials with desired optical properties are made possible.