I.r. dichroism measurements were used to study the orientation in stretched networks of cis-1,4-polyisoprene (PIP) containing atactic poly(vinylethylene) (PVE). When both components are part of a network, their relaxation behaviour and equilibrium orientation are essentially identical. In blends of crosslinked PIP with linear PVE, the orientation of the latter is reduced relative to that of the former; however, the PVE retains an equilibrium orientation by virtue of its presence in the strained network. Consistent with earlier results on isotropic crystallization of PIP in this blend, strain induced crystallization evidently entraps some of the amorphous PVE when it is high in molecular weight, thus enhancing the extent of orientational coupling. In amorphous networks, the coupling is dependent on the degree to which the PVE chains can be accommodated within the network mesh; hence, coupling is enhanced for lower molecular weight PVE in less crosslinked PIP. The addition of diluent weakens the coupling in a manner consistent with the excluded volume origin of the interchain interactions.
Посилання на статтю:
Orientational correlations in polyisoprene/poly(vinylethylene) mixtures / I. S. Zemel and C. M. Roland* // Polymer. – 1992. – Vol 33. – P. 4522-4526.