Free Volume Relaxation in Polymer Blends by the Magnetic Resonance

1.研究了聚环氧乙烷(PE0)与等规聚甲基丙烯酸甲酯(PMMA)共混物中氮氧自由基标记的电子自旋共振(ESR)线形随老化温度和退火温度的变化。还研究了与PMMA结合的氮氧化物自由基标记物和共混物中氮氧化物探针的ESR线形。观测到具有不同运动速率的两个光谱分量--一个“快”分量和一个“慢”分量。在室温下观察到的快组分的分数随时效和热处理温度的变化而变化。随着老化温度的降低，可流动组分在-20ﾟC附近下降，而在55ﾟC附近随退火温度的升高而急剧增加。在上述相同温度下，时效和退火过程中体积收缩和膨胀的C.A.0.5%。这些实验事实归因于与共混物无色区域中自由体积的湮没和形成有关的弛豫现象。以聚四氟乙烯机械断裂形成的机械自由基为引发剂，通过乙烯的嵌段共聚反应，制备了固定在新鲜聚合物表面的聚乙烯分子链端自由基。即使在77K，自由基的分子运动也允许围绕C-C键轴自由旋转。自由基的高迁移率归因于分子间弱相互作用，因为聚四氟乙烯链分离出来的PE链在表面的浓度极低。也就是说，PE相在聚四氟乙烯表面的自由体积非常大。

1. The electron spin resonance (ESR) line shape of nitroxide radical labeles attached to poly(ethylene oxide) (PE0) in a blend with isotactic poly(methyl methacrylate)(PMMA) was studied as a function of aging and annealing temperatures. The ESR line shapes of the nitroxide radical labeles attached to PMMA and the nitroxide probe in the blend were also studied. Two spectral components with different rates of motion -a "fast" component and a "slow" component are observed. The fractional amount of the fast component observed at room temperature changes with aging and annealing temperatures. The mobile fractions decrease around -20ﾟC with decreasing aging temperatures, whereas the fractions increase abruptly around 55ﾟC with increasing annealing temperatures.The specific volume of the blend was measured at room temperature by the dilatometric method. C.a.0.5% of volume contraction and expansion during aging and annealing at the same temperatures mentioned above. These experimental facts are attributed to relaxational phenomena related with annihilation and formation of free volume in an amorhous region of the blend.2. The chain end radical of polyethylene (PE) molecules anchored on a fresh polymer surface was produced by block copolymerization of ethylene which was initiated by mechano-radicals formed by mechanical fracture of a poly(tetra fluoroethylene) and located on the fresh surface. The molecular motion of the radical allows free rotation around the C-C bond axis even at 77K.The high mobility of the radical is attributed to weak intermolecular interaction, because of extremely low concentration of the PE chains on the surface, isolated from PTFE chains. In other words, the free volume of the PE phase on the PTFE surface is extremely large.