A Solution and Molecular Study of Thermotropic Liquid Crystalline Cellulose Derivatives

制备了完全取代的纤维素醚（三-O-庚基和三-O-癸基纤维素）和纤维素酯（十三烷酸纤维素酯），并将其分馏成具有合理窄的分子量分布（Mw/Mn = 1.1 - 1.3）的许多级分。进行了粘度，光散射和超离心分析，以确定这些聚合物的分子参数。在所有情况下，在30 ° C下的余辉长度P约为9.0 nm，与侧链长度和化学性质无关。得到<-3>庚基醚的温度系数α = 5.0 × 10 ~ 4（α = dln P/dT），并测定了醚和酯的介晶向各向同性相转变温度T_i随主链长度的变化，并与理论预测值进行了比较。这一理论是为一个没有分子间相互作用但有排斥体积的类功圆柱体系统而建立的。醚类衍生物的行为与理论预测非常吻合，表明它们的中间相（α相）基本上是由排阻体积，即β相所稳定的。例如，熵效应和链的半刚性。酯衍生物的T_i点与醚衍生物的T_i点有很大的差别，表明它们的中间相来源不同. X射线衍射和红外光谱分析表明，酯衍生物的低聚物（如二聚体和三聚体）形成分散的柱状相，分子轴垂直于柱轴;关于Polym &gt;30）形成分子轴平行于柱轴的柱状相，两相通过羰基参与的分子间相互作用而稳定。

Fully substituted cellulose ethers(tri-O-hepty1 and tri-O-decy1 celluloses)and a cellulose ester(cellulose tridecanoate)were prepared and fractionated into a number of fractions with a reasonably narrow molecular weight distribution(Mw/Mn = 1.1 - 1.3). Viscometric, light scattering, and ultracentrifugation analyses were carried out to determine the molecular parameters of those polymers. The persistence lengths P were found to be about 9.0 nm at 30ﾟC in all cases, independent of the side chain length and chemistry. A value of 5.0 X 10^<-3> was obtained for the temperature coefficient alpha of the heptyl ether(alpha= dln P/dT).The mesomorphic to isotropic phase transition temperatures T_i of the ethers and esters in the bulk were determined as a function of the main-chain length, and compared with the theoretical prediction. This theory was formulated for a system of worklike cylinders with no intermolcular interactions but the excluded volume. The behavior of the ether derivatives closely agreed with the theoretical prediction, indicating that their mesophase(a cholesteric phase)is stabilized essentially by the excluded-volume, i. e., entropic effect and the semirigidity of the chain. The T_i points of the ester derivatives were, quantitatively, quite different from those of the ethers, which implies that their mesophase is different in origin.X-ray diffraction and infrared spectroscopic analyses of the ester derivatives showed that the oligomers, such as dimer and trimer, form a discotic columnar phase with the molecular axis normal to the column axis, and the polymers(deg. of polym. >30)form a columnar phase with the molecular axis parallel to the column axis, both phases being stabilized by an intermolecular interaction in which the carbonyl groups participate.