Structure, morphology, mechanical and thermal characteristics of the in situ composites based on liquid crystalline polymers and thermoplastics

Thermotropic liquid crystalline polymers (LCPs) with rigid molecular backbones exhibit unique physical, mechanical, theological and thermal properties. The use of LCPs as the minor phase of polymer blends has attracted considerable attention in the past two decades. This is because LCPs can improve the processability and mechanical properties of thermoplastics. LCPs tend to deform into elongated fine fibrils under appropriate processing conditions. The LCP fibrils reinforce thermoplastic matrix effectively, producing the so-called in situ polymer composites. Reinforcing effect arises from improved compatibility between the matrix and dispersed LCP phase. However, the mechanical properties of LCP/thermoplastic blends are far behind expectations, mainly because of poor compatibility between the dispersed LCP phase and thermoplastic matrix. To increase the compatibility between them, graft polymers or copolymers and ionomers have been introduced in the LCP/ thermoplastic blends to promote the interfacial interactions. Transesterification reactions between certain phase components of in situ composites can also enhance the interfacial adhesion. In this review paper, current developments in fabrication, theology, morphology, mechanical and thermal properties of in situ polymer composites will be addressed. Particular attention is paid to the processing-structure-property relationships of several in situ polymer composites. (C) 2003 Elsevier B.V. All rights reserved.