Liquid crystal main-chain polymers for high-performance fibre applications

The chemistry and physics of high-performance fibre spinning based on main-chain liquid crystal polymer (MCLCP) solutions and melts is discussed, which is the largest industrial application of liquid crystal technology. The high modulus and strength of liquid crystal polymer-based high-performance fibres is due to the exceptionally high orientational order that can be achieved, reaching values of 0.95 and higher. Together with the chemistry that ensures strong intermolecular interactions, often based on hydrogen bonding, it is possible to make fibres with unusual mechanical and thermal properties. The modulus and strength of such fibres can reach values at about 50-75% of the theoretical limit. Within materials science high-performance fibres are especially interesting, as they are one of the few systems where the material properties can be successfully predicted based on molecular models for the orientational order together with rather simple assumptions on the effect of flow on the director alignment. The most studied MCLCP systems for high-performance fibre spinning PPTA/H2SO4, cellulose/phosphoric acid, PIPD(M5)/PPA and melt-spun Vectran (TM) are discussed.