Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
5189951 | Polymer | 2007 | 14 Pages |
Abstract
Using dynamic light scattering (DLS) and capillary dynamic viscoelasticity (DVE) analyzer, we investigated dilute (0.5 mg/ml) poly(diallyl dimethyl ammonium chloride) (PDADMAC) aqueous solution properties for three different molecular weights of PDADMACs mixed with various concentrations of NaCl. The dependence of PDADMAC molecular chain conformations in aqueous solutions on polymer molecular weight and NaCl concentration were studied. By analyzing dynamic shear viscosity ηâ²(Ï), viscoelastic relaxation times tr, and shear rate at tube wall Åa(Ï) of PDADMAC aqueous solutions in oscillatory flows, we proposed that polymer chain conformations varied with increasing shear frequency Ï via the following steps: intra-polymer associations, dissociation of intra-polymer associations, stretching of polymer chains, inter-polymer aggregations, and dissociations of inter-polymer aggregations. The intra-polymer associations lowered the nâ² exponent of storage modulus Gâ²(Ï) (Gâ²(Ï) â¼Â Ïnâ²) with nâ²Â < 2, and the polymer chain stretching and inter-polymer aggregations caused shear thickening (i.e. upturn of ηâ²(Ï)) of PDADMAC aqueous solutions. The behaviors of the lowering of nâ² exponent with nâ²Â < 2 and the shear thickening were favored by increasing ionic strength of solutions. By comparing ηâ²(Ï) data with DLS hydrodynamic radii (Rh) data, we also confirmed the possibility of inter-polymer aggregations in dilute solutions when polymer chains were stretched in oscillatory flows.
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Physical Sciences and Engineering
Chemistry
Organic Chemistry
Authors
Wen-Hong Liu, T. Leon Yu, Hsiu-Li Lin,