SynopsisAlthough the rate of heterogeneous nucleation of crystallization in isotactic polystyrene, as studied by photomicroscopy, is markedly increased by addition of fine-particle silica, the rate of subsequent radial growth of spherulites formed is diminished. The latter observation is rationalized on the basis of a modified Hoffman-Lauritzen treatment wherein the nucleant is depicted as a quasicrosslink which impedes the transport of polymer segments.
EXPERIMENTALThe i-PS, with a viscosity-average molecular weight of 6.91 X lo5: was obtained from Polysciences Inc. Its tacticity was confirmed by infrared spectroscopy. The equilibrium melting temperature, measured by DSC, was 231OC.Fine-particle silica (Cabosil M5, surface area 200 m2/g) or (CH3)3SiCl-treated