Structure-Rheology-Domain Texture Relationships in Thermotropic Liquid-Crystalline Polymers

摘要：提出了热致液晶聚合物（TLCPs）结构-流变-域织构关系的研究。本研究采用溶液聚合法制备了以亚甲基（CH2）n为柔性间隔剂（PSHQ）的邻苯磺酰-对苯双（4-氧苯甲酸酯）芳香均聚酯。在以十亚甲基（CH2）10作为柔性间隔剂进行的初步研究的基础上，PSHQ可以作为TLCP中结构-流变-域织构关系的模型化合物，因为PSHQ由于其相对较低的清除温度，可以通过先加热到各向同性状态，然后缓慢冷却到各向异性状态来控制初始条件（即初始域织构）。在PSHQ的合成中，亚甲基单位的数量（即n=7-16）将会改变，以研究柔性间隔剂的影响，特别是所谓的“奇偶”效应，对样品中产生的流变行为和结构域的影响。该研究项目的主要目的是增强我们对TLCP的结构域的理解，它取决于热历史和剪切历史，如何影响其流变行为，而流变行为又受聚合物取向顺序的影响。因此，我们建议对PSHQ的“奇偶”效应进行以下研究：(1)进行流变光学研究，以了解PSHQ的流变行为与流动诱导织构之间的关系；(2)在控制良好的退火条件下，通过图像分析确定PSHQ样品中的畴大小及其分布；(3)通过固体核磁共振波谱法确定PSHQ试样的取向序参数作为温度的函数；(4)利用动态光散射确定PSHQ的持续长度；(5)将开发PSHQ的排除体积（分子间）电位表达式；(6) PSHQ的流变行为将通过数值求解Doi动力学方程来预测，使用排除体积势的表达式，这将在本研究中得到发展。

ABSTRACT CTS-9320351 University of Akron P.I.: Chang D. Han It is proposed to investigate structure-rheology-domain texture relationships in thermotropic liquid-crystalline polymers (TLCPs). For the investigation, a homologous series of aromatic homopolyester, poly (phenylsulfonyl)-p-phenylene bis(4-oxybenzoate) with methylene units (CH2)n as flexible spacers (PSHQ), will be synthesized via solution polymerization. On the basis of the preliminary study performed by the principal investigator who used decamethylene (CH2)10 as flexible spacers, PSHQ can be used as a model compound to study structure-rheology-domain texture relationships in TLCP because, owing to its relatively low clearing temperature, PSHQ allows one to control the initial condition (i.e., initial domain texture) by first heating to an isotropic state and then cooling slowly down to an anisotropic state. In the synthesis of PSHQ the number of methylene units (i.e., n=7-16) will be varied, in order to investigate the effect of flexible spacer, especially the so-called 'odd-even' effect, on the resulting rheological behavior and domain texture in the specimen. The major thrust of the proposed research project is to enhance our understanding as to how the domain texture of TLCP, which depends on both thermal and shear histories, influences its rheological behavior, which in turn is affected by the orientational order of the polymer. Therefore we propose to conduct, with emphasis on the 'odd-even' effect, the following investigations: (1) A rheo-optical study will be conducted to understand the relationship between the rheological behavior and the flow-induced textures of PSHQ; (2) The domain size and its distribution in PSHQ specimen will be determined, via image analysis, under well-controlled annealing conditions; (3) The orientational order parameter of PSHQ specimens will be determined, via solid-state nuclear magnetic resonance spectroscopy, as a function of temperature; (4) The persistence length of PSHQ will be determined using dynamic light scattering; (5) An expression for the excluded volume (intermolecular) potential will be developed for PSHQ; and (6) The rheological behavior of PSHQ will be predicted by numerically solving the Doi Kinetic equation, by using the expression for the excluded volume potentia, which is to be developed in the proposed study.