Maleki Atoosa, Kjøniksen Anna-Lena, Nyström Bo
Department of Chemistry, University of Oslo, P.O. Box 1033, Blindern, N-0315, Oslo, Norway.
J Phys Chem B. 2005 Jun 30;109(25):12329-36. doi: 10.1021/jp0514271.
Intramolecular and intermolecular associations of dilute aqueous alkali solutions of hydroxyethylcellulose (HEC) in the presence of a chemical cross-linker agent (divinyl sulfone, DVS) are studied with the aid of dynamic light scattering (DLS) and rheological methods. At quiescent state, DLS detected only interchain aggregation of HEC during the cross-linker reaction, and the magnitude and start of this effect depend on the cross-linker concentration. The growth of clusters has been investigated at various stages in the course of the cross-linking process by quenching the reaction mixture to a lower pH. After quenching, no further association of the species occurred. When the dilute reaction mixtures are subjected to shear, intrapolymer cross-linking with contraction of the molecules is observed, and at moderate shear rates this effect is followed by interpolymer cross-linking and the formation of aggregates at longer times. The rate of the growth of the multichain aggregates decreases with increasing shear rate, and at sufficiently high shear rates no cross-linking effect is observed. Depending on the shear rate, the aggregates continue to grow until they reach a certain size where an incipient breakup of interaggregate chains can be observed. The delicate interplay between intramolecular and intermolecular association effects is governed by factors such as the magnitude of the shear rate, polymer concentration, and cross-linker density.
借助动态光散射（DLS）和流变学方法，研究了在化学交联剂（二乙烯基砜，DVS）存在下羟乙基纤维素（HEC）稀碱水溶液的分子内和分子间缔合。在静态下，DLS仅检测到交联剂反应过程中HEC的链间聚集，且这种效应的大小和起始取决于交联剂浓度。通过将反应混合物淬灭至较低pH值，研究了交联过程中不同阶段簇的生长情况。淬灭后，物种之间没有进一步的缔合。当对稀反应混合物施加剪切力时，观察到分子内交联伴随分子收缩，在中等剪切速率下，这种效应之后是聚合物间交联，并在更长时间形成聚集体。多链聚集体的生长速率随剪切速率增加而降低，在足够高的剪切速率下未观察到交联效应。取决于剪切速率，聚集体持续生长直至达到一定尺寸，此时可观察到聚集体间链的初始断裂。分子内和分子间缔合效应之间的微妙相互作用受剪切速率大小、聚合物浓度和交联剂密度等因素控制。
