New polymer syntheses, 17. Cis/trans isomerism of 1,4‐cyclohexanedicarboxylic acid in crystalline, liquid‐crystalline and amorphous polyesters
New polymer syntheses, 17. Cis/trans isomerism of 1,4‐cyclohexanedicarboxylic acid in crystalline, liquid‐crystalline and amorphous polyesters
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DOI：
10.1002/macp.1987.021880606
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发表时间：
1987-06
影响因子：
2.5
通讯作者：
H. Kricheldorf;Gert Schwarz
中科院分区：
文献类型：
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作者：
H. Kricheldorf;Gert Schwarz
在回流（约 280°C）下用各种可能的异构化催化剂处理 1,4-环己烷二甲酸二甲酯。氯化锂和磺酸引起快速异构化。二苯酯和 1,4-环己烷二甲酰二氯也被异构化，并且在所有情况下都获得了具有 66 ± 2% 反式异构体的热力学控制平衡。对于由1,4-丁二醇、1,6-己二醇或苯基氢醌和1,4-环己烷二甲酸制备的熔融聚酯，发现了相同的顺式/反式比率。由苯基氢醌和反式1,4-环己烷二甲酰二氯在20℃下制备的聚酯，在250℃以上呈现介晶相；然而，这种 LC 相在热力学上不稳定，会异构化为含有 66 ± 2% 反式异构体的各向同性熔体。然而，当将游离二酸或来自氢醌和1,4-环己烷二甲酸的结晶聚酯加热或在约100℃下合成时。 300°C，100%反式异构体含量是热力学最佳值。对于由甲基或氯对苯二酚制备的聚酯的液晶相也是如此。含有不同摩尔比的对苯二酚和苯基对苯二酚单体单元的LC-共聚酯的反式含量随这些摩尔比在66%至100%之间变化。显然，含有 100% 反式异构体的 LC 结构域和含有 66% 反式异构体的各向同性结构域的共存是造成这一结果的原因。
Dimethyl 1,4-cyclohexanedicarboxylate was treated with various potential isomerization catalysts under reflux (ca. 280°C). Lithium cloride and sulfonic acids caused rapid isomerization. Also the diphenyl ester and 1,4-cyclohexandicarbonyl dichloride were isomerized, and in all cases a thermodynamically controlled equilibrium with 66 ± 2% trans-isomer was obtained. The same cis/trans ratio was found for the molten polyesters prepared from 1,4-butanediole, 1,6-hexanediole or phenylhydroquinone and 1,4-cyclohexanedicarboxylic acid. The polyester, prepared at 20°C from phenylhydroquinone and trans-1,4-cyclohexanedicarbonyl dichlorid, exhibits a mesogenic phase above 250°C; yet, this LC-phase is thermodynamically unstable and isomerizes to an isotropic melt containing 66 ± 2% trans-isomer. However, when the free diacid or the crystalline polyester from hydroquinone and 1,4-cyclohexanedicarboxylic acid are heated or synthesized at ca. 300°C, a content of 100% trans-isomer is the thermodynamical optimum. This is also true for the LC-phase of polyesters prepared from methyl- or chlorophydroquinone. The trans content of LC-copolyesters, containing variable mole ratios of monomeric units of hydroquinone and phenylhydroquinone, varies with these mole ratios between 66 and 100%. Obviously, the coexistence of LC-domains containing 100% trans-isomer and isotropic domains containing 66% trans-isomer are responsible for this result.