STRESS-INDUCED ORIENTATION IN POLYMER BLENDS CONTAINING A SIDE-CHAIN LIQUID-CRYSTALLINE POLYMER

In this paper, we show that mechanically stretching an immiscible blend made from a nematic side-chain liquid crystalline polymer and a conventional polymer is an efficient way to induce a rapid macroscopic orientation of the mesogenic groups along the stretching direction. The basic condition for this achievement is to perform the mechanical stretching at temperatures between the glass transition temperature and the clearing temperature of the nematic polymer in order to take advantage of the intermolecular co-operativity which is indispensable for a rapid alignment of the nematic domains. The alignment is monitored by determining the orientation of the mesogenic groups using the i.r. dichroism technique. The liquid crystalline polymers investigated are two nematic polyacrylates, and the conventional polymers used are a styrene-butadiene-styrene triblock copolymer, which is a thermoplastic elastomer, and a poly(vinyl chloride).