聚｛11-[(4′-正庚氧基-4-联苯基)羰基]氧-1-十一炔｝的相结构与相转变

采用示差扫描量热法(DSC)、一维(1D)、二维(2D)广角X-射线衍射(WAXD)和偏光显微镜(PLM)等研究手段对聚{11-(4′-正庚氧基-4-联苯基)羰基]氧-1-十一炔}(PA-9,7)的本体相转变和相结构进行研究,并采用分子动力学方法对相结构进行模拟.结果表明,样品的相转变为近晶B相(SmB)近晶A相(SmA)各向同性态(Iso).在近晶B相中,侧链在层状结构中排列成具有六次对称性的准长程有序结构。

PHASE TRANSITIONS AND STRUCTURES OF POLY(11-{[(4'-HEPTOXY-4-BIPHENYLYL)CARBONYL]OXY}-1-UNDECYNE)

A side chain liquid crystalline(LC) polyacetylene with long spacers,namely,poly(11-{(4'heptoxy-4-biphenylyl)carbonyl]oxy}-1-undecyne)(PA-9,7),with high trans configuration was synthesized and the phase structures and transition behaviors were studied using differential scanning calorimetry(DSC),one-and two-dimensional(1D and 2D) wide-angle X-ray diffraction(WAXD)and polarized light microscopy(PLM).The molecular packing was simulated by Materials Studio(Accelrys) and the energy was minimized using Smart Minimizer incorporated in the Discover Molecular Simulation Program.The long spacer of PA-9,7 decouples the side chain mesogen and the rigid polyacetylene backbone and results in the formation of smectic phases,but not the frustrated highly ordered smectic phase of its cousin with short spacer.DSC and 1D WAXD results showed that the sample possesses two LC phases.Based on structural results obtained from 2D WAXD experiments on oriented sample,the phase structures of PA-9,7 were determined to be smectic B phase(SmB) below 70℃,smectic A phase(SmA) in the temperature ranges 70 ～ 118℃,and isotropic phase(Iso) higher than 118℃.For the SmB phase,the side chains can pack into the pseudo-long range order with hexagonal symmetry within the smectic layers.The LC phase transition of PA-9,7 follows the sequence of SmBSmA Iso.