A study of the chain extending effect of elongational flow in polymer solutions
A study of the chain extending effect of elongational flow in polymer solutions
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DOI：
10.1007/bf01438032
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发表时间：
1978-08
影响因子：
2.4
通讯作者：
D. Pope;A. Keller
中科院分区：
文献类型：
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作者：
D. Pope;A. Keller
通过观察流场适当区域的局部双折射，研究了拉长流动对溶解大分子取向的影响，目的是将实验观察到的链取向与基本理论联系起来。得益于以往的经验，我们使用了最高分子量的组分，即mw = 2·106的聚苯乙烯，并使用了两个相对的吸入射流来提供所需的高应变速率。双折射设定在临界应变率以上，并迅速上升到最大值，证实了理论的预期。最大双折射和临界应变速率均与浓度无关，表明链之间是相互独立的。双折射值与完全链延伸值一致，而临界应变速率的松弛时间为3·10−5s，与zimm的非自由排水模型计算值一致。其他观察得出了临界纠缠浓度的估计值。讨论了这种实验方法的前景和局限性。
The effect of elongational flow on the orientation of dissolved macromolecules has been studied by observation of localised birefringence within appropriate regions of the flow field, with the objective of linking up experimentally observed chain alignment with basic theory. Benefitting from previous experience the highest available molecular weight fractions were used, i. e. polystyrene ofMw= 2 · 106, and two opposed suck jets were employed to provide the high strain rates required. Birefringence set in above a critical strain rate and rose rapidly to a maximum value, confirming expectations from theory. Both the maximum birefringence and critical strain rate were independent of concentration indicating that the chains are independent of each other. The value of the birefringence was consistent with complete chain extension, while the critical strain rate yielded a relaxation time of 3 · 10−5s in accord with the value calculated fromZimm's non-free draining model. Other observations yielded an estimate of the critical entanglement concentration. The prospects and limitations of the present kind of experimental approach are discussed.