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

摘要美国阿克伦大学CTS-9320351研究热致液晶聚合物(TLCP)的结构-流变学-磁区织构关系。为了进行研究，我们将通过溶液聚合的方法合成一系列以亚甲基基团(CH2)n为柔性间隔基的芳香族均聚酯--聚(苯磺酰基)-对苯双氧基苯甲酸酯(PSHQ)。在以十甲基亚甲基(CH2)10为柔性间隔基的主要研究者的初步研究的基础上，PSHQ可以作为模型化合物来研究TLCP中的结构-流变-磁区织构关系，因为由于其相对较低的清除温度，PSHQ允许人们通过首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(即初始磁区织构)。在PSHQ的合成中，亚甲基单元的数目(即n=7-16)将是不同的，以考察柔性间隔基的影响，特别是所谓的奇偶效应，对所产生的样品的流变性和磁区织构的影响。该研究项目的主要目的是加深我们对TLCP的区域织构如何影响其流变行为的理解，而TLCP的区域织构既取决于热历史又取决于剪切历史，而后者又受聚合物的取向顺序的影响。因此，我们建议对PSHQ的“奇偶”效应进行如下研究：(1)用流变学研究PSHQ的流变行为与流动诱导织构的关系；(2)通过图像分析确定PSHQ样品中的磁畴尺寸及其分布；(3)通过固体核磁共振确定PSHQ样品的取向有序参数，作为温度的函数；(4)用动态光散射法确定PSHQ的持续长度；(5)建立了PSHQ的排外体积(分子间)势的表达式；(6)通过数值求解DOI动力学方程，预测了PSHQ的流变行为。

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.