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Calorimetric Study of Order-Disorder Transition of Block Copolymers

嵌段共聚物有序-无序转变的量热研究

基本信息

批准号：
07455385
负责人：
ADACHI Keiichiro
金额：
$ 4.54万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1996
项目状态：
已结题

项目摘要

Block copolymers such as stirene-isoprene diblock copolymers (SI) exhibit the microphase separation with a regular crystalline lattice structure. With increasing temperature, they transform from the ordered phase structure to a disordered state. Around the order-disorder transition temperature (ODT), the dynamics of the chains and the physical properties change dramatically. This study aims to clarify the relationship between the thermodynamic properties and the chain dynamics. Firstly we constructed an adiabatic calorimeter for the accurate measurements of heat capacity of block copolymers. For thermometer, a resistance thermometer (Rd-Fe) calibrated at Oxford instrument Co.was used and the resistance was measured with a bridge made by ASL Co. Thus we measured temperatures before and after the supply of electric energy E at a precision of 0.0001K.The sample cell was doubly surrounded by adiabatic walls and the temperature of the wall was regulated to be the same as the sample cell within the error of 0.01K.The cell was gold-plated to prevent the radiation. The readings of the meters and the temperature control were performed with two computers. The heat capacity of toluene solution of SI (20wt%) was measured. The SI with total molecular weight of 142000 and the stirene content of 35.9% was prepared by anionic polymerization. Small lambda type anomaly is found around 228K and can be ascribed to the ODT.The extra heat capacity due to the ODT is compared with the Leibler theory. Although the temperature dependence of the heat capacity agrees with the theory, the intensity was ca.ten times higher than the theory. Beside the calorimetric study, we investigated the dielectric relaxation and small angle X-ray scattering for semi dilute solutions of SI.It was found that the dielectric relaxation time for the normal mode process of the isoprene block chain is bimodal in the ordered state but it changes into unimodal above the ODT.

嵌段共聚物如苯乙烯-异戊二烯二嵌段共聚物（SI）表现出具有规则晶格结构的微相分离。随着温度的升高，它们从有序相结构转变为无序状态。在有序-无序转变温度附近，链的动力学和物理性质发生了显著的变化。本研究旨在阐明热力学性质与链动力学之间的关系。首先，我们建立了一个精确测量嵌段共聚物热容的绝热量热计。对于温度计，电阻温度计（Rd-Fe）采用牛津仪器公司校准的1000 Ω电阻，用ASL公司的电桥测量电阻，从而测量了在提供电能E之前和之后的温度，精度为0.0001K。样品池用绝热壁双重包围，壁温调节到与样品池相同，误差为0.01K。电池被镀金以防止辐射。仪表的读数和温度控制由两台计算机执行。测定了SI（20wt%）甲苯溶液的热容。采用阴离子聚合法合成了苯乙烯含量为35.9%、总相对分子质量为142000的苯乙烯-丁二烯共聚物。在228 K附近发现了小的λ型反常，并将其归因于ODT，将ODT引起的额外热容与Leibler理论进行了比较。虽然热容量的温度依赖性与理论一致，但强度比理论高约10倍。除了量热研究外，我们还研究了SI半稀溶液的介电弛豫和小角X射线散射，发现异戊二烯嵌段链的正常模式过程的介电弛豫时间在有序态下是双峰的，但在ODT以上变为单峰。