Chain Dynamics and Structure of Polymer Interfaces

高分子是否具有伸缩性是高分子物理中最重要也是最有争议的问题之一。 爬行模型是由P. - G. de Gennes（1971）描述了熔体中线性聚合物链的动力学。 我们设计了一个实验来探索这个模型的基本特征，即，由于受到其他链条的限制而产生的链条的蛇形运动，以及相关的比例定律。 我们探讨的相互扩散的两套匹配的三块链，HDH/DHD，其中链中心是氘代的一侧（HDH）和链端（DHD）是氘代的接口的另一侧。 如果链往复运动，则在浓度曲线CD（x，t）中形成特征性的“涟漪”，其增长到最大值，然后衰减。 涟漪是由于链的各向异性运动。 我们最初的涟漪实验自然，365，235，1993年9月使用西姆斯和中子反射分析匹配的聚苯乙烯三嵌段提供了强有力的支持爬行。 几个关键的实验仍然是完成使用匹配的三块爬行模型的调查。 其中包括（a）分子量对分子量的影响，（B）Rouse动力学对临界缠结分子量的影响，（c）链端位置，（d）化学效应，（e）标度行为随时间和分子量的变化，（f）计算机模拟与实验的定量比较等。 这些实验应该为爬行模型的有效性提供一个明确的声明。 爬行是线性聚合物链运动中的一个关键概念。 该模型的验证或否定将在橡胶或塑料裂缝的愈合等领域产生重要影响。

Wool The question of whether polymer molecules reptate or not remains as one of the most important and controversial problems in polymer physics. The reptation model was proposed by P.-G. de Gennes (1971) to describe the dynamics of linear polymer chains in the melt. We have designed an experiment which probes the essential features of this model, i.e., the snakelike motion of chains due to their confinement by the other chains, and related scaling laws. We explore the interdiffusion of two sets of matching triblock chains, HDH/DHD, where the chain centers are deuterated on one side (HDH) and the chain ends (DHD) are deuterated on the other side of the interface. If the chains reptate, a characteristic "ripple" develops in the concentration profile CD(x, t) which grows to a maximum and then decays. The ripple is due to the anisotropic motion of the chains. Our initial Ripple experiments Nature, 365, 235, Sept 1993 using SIMS and Neutron Reflection analysis of matching polystyrene triblocks provide strong support for reptation. Several critical experiments remain to complete the investigation of the reptation model using matching triblocks. These include (a) the effects of molecular weight at M Mc, (b) the effects of Rouse dynamics at M Mc (critical entanglement molecular weight), (c) location of chain ends, (d) effects of chemistry, (e) scaling behavior with time and molecular weight, (f) quantitative comparision between computer simulation and experiment, and others. These experiments should provide a definitive statement on the validity of the reptation model. %%% Reptation is a key concept in the motions of linear polymer chains. A validation, or negation, of this model would have important consequences in such areas as the healing of cracks in rubber or plastics.