The Regioregularity Effects on the Thermotropic Liquid Crystalline Phase Transition of Poly(3-dodecylthiophene)
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In this work, the thermotropic LC phase transition of regioregularity-controlled poly(3-dodecylthiophene) (RR-controlled P3DDTs) are investigated, while producing different strengths of LC interactions with RR with the same molecular structure. As the RR reduces, the RR-controlled P3DDTs exhibit progressively decreased transition temperatures upon heating. Since the P3DDTs with lower RR consist of more regio-defects, they finally yield weaker interchain interactions and faster rod-to-coil conformations and disruption of ordered/oriented LC pahse. Furthermore, the formation of Form II polymorph and the increasing ratio of Form II/Form I polymorphs towards to lower RR are founded. The Form II, having higher melting entropy, is melted at lower temperature than Form I, the larger Form II at lower RR can promotes fatigues of LC structures, resulting in lower transition temperatures at lower RR.