Molecular Aggreagtion Structure and Molecular Motion of Ultrathin Polymer Films

结晶聚合物的分子聚集结构与其化学结构和结晶条件有关。在含有聚酯和尼龙等极性基团的结晶聚合物中，高分子链之间会产生范德华相互作用、偶极-偶极相互作用、静电相互作用和氢键。这些链间相互作用强烈地影响着链的构象、晶体结构、片层表面的链折叠结构和片层堆积结构。人们认为，这些极性基团作为链中的结构缺陷停留在折叠链表面而不是晶体中。然而，高阶结构中极性基团的空间分布细节还没有从实验上得到揭示。阐明脂肪族聚酯的分子聚集结构和化学结构之间的关系提供了关于分子…的重要信息通过原子力显微镜、偏光显微镜、衰减全反射红外光谱和静态接触角的测量，研究了含长亚甲基和短氟亚甲基的线型脂肪族聚酯薄膜中的分子聚集结构。以短全氟二元酸和长α-ω烷烃二元醇为原料，采用熔融缩聚法制备了线型脂肪族聚酯[O(CH2)IOCO(CF2)JCO]n(i=12，22，j=2，8，10：ih-jf)。聚酯的重均相对分子质量约为15,000。用溶剂浇铸法制备了聚酯薄膜，然后从熔体中进行了等温结晶。薄膜的厚度约为1.5微米，所有聚酯的POM图像中都观察到负球晶。22H系列聚酯的消光环也被观察到，这表明链的取向从球晶的中心周期性地改变。根据AFM观察到的表面形态，所有聚酯都形成了结晶片层。ATR-FTIR光谱测量表明，随着亚甲基数目的增加，聚酯的亚甲基序列呈构象有序化。相反，随着含氟亚甲基数目的增加，亚甲基序列变得无序，含有Guche键。随着亚甲基与氟亚甲基数目之比的增加，CO基团周围的链间相互作用减弱。由静态接触角数据估算的薄膜表面自由能表明，与亚甲基序列相比，氟亚甲基序列相对集中在表面区。较少

Molecular aggregation structure of crystalline polymers depends on their chemical structure as well as crystallization conditions. In the case of crystalline polymers containing polar groups such as polyesters and nylons, the van der Waals interaction, the dipole-dipole interaction, the static electric interaction, and the hydrogen bonding are induced between the polymer chains. These inter-chain interactions strongly influence chain conformation, crystal structure, chain folding structure on the lamellar surface, and lamellar stacking structure. It is considered that these polar groups as structural defects in chains stay rather at the chain-folding surface than in the crystal. However, the detail of spatial distribution of the polar group in the higher-order structure has not experimentally been revealed yet. Clarification of the relationship between the molecular aggregation structure and the chemical structure of aliphatic polyesters provides significant information regarding molec … More ular design of new biodegradable polymers controlled their structural and physical properties.In this study, molecular aggregation structure in thin films of linear aliphatic polyesters containing long methylene and short fluoromethylene sequences was investigated by atomic force microscopy (AFM), polarized optical microscopy (POM), attenuated total reflection (ATR) FTIR spectroscopy, and static contact angle measurements.Linear aliphatic polyesters [O(CH2)iOCO(CF2)jCO]n (i=12, 22, j=2,8,10 : iH-jF) used as samples were synthesized by melt-polycondensation of short perfluorinated dicarboxylic acids and long α-ω alkane diols. The weight-averaged molecular weight, Mw, of the polyesters was ca. 15,000. Thin films of the polyesters were prepared by the solvent-casting method, and then were isothermally crystallized from the melt. Thickness of the films was ca. 1.5 micrometers.For all the polyesters, negative spherulites were observed in their POM images. The extinction ring was also observed for the 22H-series polyesters, which indicated that chain orientation was periodically changed from the center of a spherulite. Based on the surface morphology observed by AFM, it was suggested that crystalline lamellae were formed for all the polyesters. From ATR-FTIR spectral measurements, it was revealed that methylene sequences of the polyesters became conformationally order with increasing the number of methylene groups. The methylene sequences, on the contrary, became disorder containing the gauche bonds with increasing the number of fluoromethylene groups. The inter-chain interactions around the CO groups became weaker with increasing the ratio of the number of methylene groups to that of fluoromethylene groups. The surface free energy of the films estimated from the static contact angle data implied that the fluoromethylene sequences were relatively concentrated in the surface region compared with the methylene sequences. Less