Dielectric study on two copolymers of vinylidene methylcyanide with 4-fluorostyrene and 4-chlorostyrene

The dielectric properties of 2 copolymers poly[(methyl vinylidene cyanide)- co-(4-chlorostyrene)] and poly[(methyl vinylidene)-co-(4-fluorostyrene)] ha ve been studied. These products are chiefly alternating and have relatively high glass transition temperatures, respectively at 145 degreesC and 160 d egreesC. a relaxation phenomena have been characterised around to these tem peratures. The values of dielectrical increment de have been calculated and compared to those of similar copolymers synthesized from vinylidene cyanid e with various substituted styrenes. The low values are due to the steric e ffect of the bulky aromatic cycles. The orientation abilities of CN dipoles decrease comparatively to that of the copolymer of vinylidene cyanide with vinylacetate and this could explain the low piezo or pyroelectric properti es.