MISCIBILITY IN POLY(VINYLETHYLENE) POLY(ISOPRENE) BLENDS/

Poly(vinylethylene) (PVE) and polyisoprene (PIP) do not chemically int eract; nevertheless, miscibility extends to infinite molecular weight of the components, indicating that the interaction parameter for the b lend is negative. This inference has been directly demonstrated by sma ll angle neutron scattering, which showed, moreover, that the negative sign has an enthalpic origin. The present solid state nuclear magneti c resonance (NMR) cross-polarization/dipolar dephasing results are con sistent with a greater degree of spatial intimacy between PVE and PIP chains in the blend relative to the neat polymers. The greater intimac y suggested by the NMR results is consistent with stronger van der Waa ls bonding in the blends, and hence the negative mixing enthalpy.