Welp KA, Wool RP, Satija SK, Pispas S, Mays J
Department of Chemistry, University of Alabama at Birmingham, Birmingham, Alabama 35294.
Macromolecules. 1998 Jul 28;31(15):4915-25. doi: 10.1021/ma971692n.
We explore the interdiffusion of oppositely labeled triblock polystyrene chains, HDH/DHD, during welding in the melt using dynamic secondary ion mass spectroscopy (DSIMS) and specular neutron reflectivity (SNR). The HDH chains have the central portion of the chain deuterated (D) approximately 50% while the two ends (H) each have approximately 25% protonation; the DHD is oppositely labeled, but each set of chains contains about 50% deuteration. During welding, the deuterium depth profile exhibits "ripples" whose characteristic features, such as the time and molecular weight dependent shape, amplitude, and position, are very sensitive to the microscopic details of the polymer dynamics. The ripple experiment is especially sensitive to the presence, or absence, of topological constraints and anisotropic motion of chains. The current work significantly extends the molecular weight range up to 400 000. This allows greater separation of the six key ripple features used in deciphering the correct polymer dynamics model at the polymer-polymer interface. The DSIMS and SNR experimental results are compared to theoretical predictions and ripple simulations for Rouse, polymer mode-coupling, reptation (with and without tube broadening), and other phenomenological dynamics models. The six ripple characteristics were found to be perfectly correlated and convincingly consistent with the predictions of the reptation dynamics model. The ripple results are in significant disagreement with the polymer mode-coupling model proposed by Schweizer and other tubeless models. We conclude that the reptation model, proposed by DeGennes in 1971 with parallel developments by Edwards, is the correct model to describe the dynamics of polymer interdiffusion.
我们使用动态二次离子质谱（DSIMS）和镜面中子反射率（SNR），研究了在熔体焊接过程中，带有相反标记的三嵌段聚苯乙烯链HDH/DHD的相互扩散。HDH链的链中央部分约50%被氘化（D），而两端（H）各有大约25%的质子化；DHD则是相反的标记，但每组链都含有约50%的氘化。在焊接过程中，氘的深度分布呈现出“波纹”，其特征，如与时间和分子量相关的形状、幅度和位置，对聚合物动力学的微观细节非常敏感。波纹实验对链的拓扑约束和各向异性运动的存在与否特别敏感。目前的工作显著扩展了分子量范围至400000。这使得在聚合物 - 聚合物界面处，用于解读正确聚合物动力学模型的六个关键波纹特征能有更大的区分度。将DSIMS和SNR实验结果与Rouse模型、聚合物模式耦合模型、蛇行模型（有和没有管扩张）以及其他唯象动力学模型的理论预测和波纹模拟进行了比较。发现这六个波纹特征完全相关，并且令人信服地与蛇行动力学模型的预测一致。波纹结果与Schweizer提出的聚合物模式耦合模型以及其他无管模型存在显著分歧。我们得出结论，1971年由DeGennes提出并由Edwards进行平行发展的蛇行模型，是描述聚合物相互扩散动力学的正确模型。
