Chain Dynamics and Structure of Polymer Interfaces

聚合物分子是否旋转的问题一直是聚合物物理学中最重要和最有争议的问题之一。旋转模型是由P.G.de Gennes(1971)提出的描述熔体中线性高分子链动力学的模型。我们设计了一个实验来探索这个模型的基本特征，即由于其他链的约束而导致链的蛇形运动，以及相关的标度定律。我们研究了两组匹配的三区块链HDH/DHD的相互扩散，其中链中心在界面的一侧(HDH)，链末端(DHD)在界面的另一侧。如果链旋转，在浓度分布CD(x，t)中形成特征的“波纹”，该波纹增长到最大值，然后衰减。这种波纹是由于链的各向异性运动造成的。我们最初的波纹实验，《自然》，365,235,1993年9月，使用SIMS和匹配的聚苯乙烯三块的中子反射分析为重新启动提供了强有力的支持。仍有几个关键实验需要使用匹配的三块来完成对爬行模型的研究。它们包括(A)分子量在MMc的影响，(B)在MMc(临界缠结分子量)的Rouse动力学的影响，(C)链末端的位置，(D)化学的影响，(E)随时间和相对分子质量的标度行为，(F)计算机模拟和实验之间的定量比较，以及其他。这些实验应该为修正模型的有效性提供一个明确的声明。%表示是线性高分子链运动中的一个关键概念。对这一模型的验证或否定，将在橡胶或塑料裂缝的愈合等领域产生重要后果。

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.