Liquid crystalline polymers: molecular simulation of some polyethers containing oxetanic rings in the main chain

Molecular simulation of thermophysical properties of aromatic polymers containing oxetane ring in the main chain

“…For the next simulated polyether, PE-3, the calculated order parameter, presented in Table II, predicts a non-liquid-crystalline behaviour for this polyether, which is supported by poorly ordered chain conformation reported in previous conformational analysis study, 9 a relatively low value in the theoretical cohesive energy (Table III) and slightly high chain flexibility of the PE-3 polyether compared with the PE-1 and PE-2 polyethers. The chain flexibility of this polyether is predicted to be higher than that for the PE-1 and PE-2 polyethers, due to the theoretical T g value of the PE-3 polyether (365 K) being lower than the theoretical T g values of the PE-1 (402 K) and PE-2 (401 K) polyethers (Table III).…”

“…The investigated thermophysical properties, such as theoretical and experimental glass transition temperatures, T g , theoretical cohesive energy and theoretical decomposition temperature, T d , are given in Table III. The chain properties and polymer chain geometry corresponding to the PE-1, PE-2, and PE-3 polymers were presented in detail by Pavel et al 9 However, in the present article, only their orientational properties and some of their thermophysical properties are reported and discussed. A helicoidal chain geometry was obtained for the PE-1 and PE-3 polymers, whereas an approximately linear chain geometry was obtained for the PE-2 polymer.…”

“…A previous molecular dynamics study 9 of the PE-1 polyether reflects the arrangement of the oxetane rings inside the helix. For this polyether, the crosslinking processes do not occur and the liquid-crystalline phase transitions are reproducible on the second heating.…”

“…9 This arrangement of oxetane rings of the PE-2 polyether favours initiation of the crosslinking processes. 21,22 According to the experimental data, the crosslinking processes begin at 533 K.…”

“…A helicoidal chain geometry was obtained for the PE-1 and PE-3 polymers, whereas an approximately linear chain geometry was obtained for the PE-2 polymer. 9 Conformational analysis of the chain flexibility (rotational barriers around simple bonds) for the PE-1 polyether shows that the chain is semirigid. 9 These results were confirmed in this study by the high values of both theoretical (402 K) and experimental (399 K) T g s, as indicated in Table III.…”