Dynamic simulations of potentially auxetic liquid-crystalline polymers incorporating swivelling mesogens

Dynamic simulations under stress were carried out on a series of main-chain polymers containing two types of mesogen. One mesogen is orientated in-line with the chain (end-to-end) and the second (swivelling) has the main chain passing at right angles through it. Under strain the swivelling mesogens are expected to rotate, pushing apart the neighbouring chains. Polymers incorporating 50% of both mesogens showed a reduced Poisson's ratio. In particular, swivelling mesogens of seven rings length produced a negative Poisson's ratio, and thus should be auxetic. In contrast, polymers containing only end-to-end mesogens had relatively high Poisson's ratios of 0.53–0.59.