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Effect of the linking structure of nonlinear optical side groups on the phase behavior of an aromatic polyester backbone

机译：非线性光学侧基的连接结构对芳族聚酯骨架相行为的影响

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The phase behavior of poly(p-phenylene terephthalate)s (PPT) with pendant side groups, N-(4-nitrophenyl)ethylaminoethanol (NPE) and N-(4-nitrophenyl)-L-prolinol (NPP) has been studied by using differential scanning calorimetry (DSC), wide-angle X-ray scattering (WAXS), and second harmonic generation (SHG). PPT-NPE showed a layered liquid crystalline morphology while PPT-NPP showed a completely amorphous structure. Compressive or shear stress applied on the polymer melt surface at 210 degreesC induced a more prominent layered structure of PPT-NPE whereas the amorphous structure of PPT-NPP remained unchanged under the stress. In order to understand this phase difference in terms of the repeat structure, we attempted theoretical ab initio Hartree-Fock, and DFT calculations for the monomers and molecular dynamics for the bulk state. The results indicated that molecular configurations are a good way of microscopically understanding the phases of rigid backbone polymers with functional side groups: The NPT (constant particle number, pressure, and temperature) simulation data at 210 degreesC agree qualitatively with the experimental data and the difference between PPT-NPE and PPT-NPP could be understood using rotational energy barrier, steric hindrance and inter-chain interactions. X-ray diffractometer (XRD) simulation patterns for the oligomers are also in qualitative agreement with the experimental WAXS I data and the structural parameters of stacks of PPT-NPE chains are estimated to be layer distance (4.6 Angstrom), backbone distance (21.5 Angstrom), and side distance (12 Angstrom).
机译：具有侧基的聚对苯二甲酸对苯二酯（PPT），N-（4-硝基苯基）乙基氨基乙醇（NPE）和N-（4-硝基苯基）-L-脯氨醇（NPP）的相行为已得到研究使用差示扫描量热法（DSC），广角X射线散射（WAXS）和二次谐波产生（SHG）。 PPT-NPE显示出层状液晶形态，而PPT-NPP显示出完全非晶态结构。在210摄氏度的聚合物熔体表面施加压缩应力或剪切应力会导致PPT-NPE的层状结构更加突出，而PPT-NPP的非晶态结构在该应力下保持不变。为了从重复结构的角度理解这种相差，我们尝试从头开始进行Hartree-Fock的理论计算，并对单体的DFT计算和对于本体态的分子动力学进行了尝试。结果表明，分子构型是从微观上理解带有官能侧基的刚性主链聚合物相的一种好方法：210℃时的NPT（恒定粒子数，压力和温度）模拟数据与实验数据在质量上相符。使用旋转能垒，位阻和链间相互作用可以理解PPT-NPE和PPT-NPP之间的关系。低聚物的X射线衍射仪（XRD）模拟模式也与实验WAXS I数据定性一致，并且估计PPT-NPE链堆叠的结构参数为层距（4.6埃），主链距离（21.5埃） ）和边距（12埃）。

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