Shear thickening and properties of polyionomer solutions
| Autor: | Wen-Hong Liu, 劉玟泓 |
|---|---|
| Rok vydání: | 2007 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 95 Using dynamic light scattering (DLS) and capillary dynamic viscoelasticity (DVE) analyzer, we investigated: (1) dilute (0.5 mg/ml) poly(diallyl dimethyl ammonium chloride) (PDADMAC) aqueous solutions properties for three different molecular weights PDADMACs mixed with various concentrations of NaCl; and (2) physical properties of 5 wt% poly(N-isopropyl acryl amide) (poly(NIPAM)) (Mv=3.22x105) semi-dilute solutions in H2O, D2O, and THF (tetrahydrofuran) solvents. PDADMAC is a cationic polyelectrolyte. In the first part of this thesis, the influences of polymer molecular weight and NaCl concentration on the PDADMAC conformations in dilute aqueous solutions were studied. By analyzing dynamic shear viscosity, viscoelastic relaxation times tr, and shear rate at tube wall ŕa of PDADMAC aqueous solutions in oscillatory flows, we proposed polymers chains conformations varied with increasing shear frequency 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 n’ exponent of storage modulus G’with n’< 2, and the polymer chains stretching and inter-polymer aggregations caused shear thickening of PDADMAC aqueous solutions. The behaviors of the lowering of n’ exponent with n’< 2 and the shear thickening were favored by increasing ionic strength of solutions. By comparing data with DLS hydrodynamic radii (Rh) data, we also confirmed the possibility of inter-polymer aggregations in dilute solutions when polymers chains were stretched in oscillatory flows. Poly(NIPAM) is a polymer consists of hydrophilic –NHC=O groups and hydrophobic –CH(CH3)2 groups and hydrophobic –CH2-CH- backbone. In the second part of this thesis, the influences of H-bonding (D-bonding) of H2O and D2O with –NHC=O group and hydrophobic property of polY(NIPAM) in H2O, D2O, and THF solvents were investigated. The DLS data showed that there were poly(NIPAM) slow mode inter-polymer chains associations in H2O and D2O solvents. However, no DLS slow mode was observed in poly(NIPAM)/THF solutions. The DSV data showed that there are shear thickening behavior in these three poly(NIPAM) solutions, resulting in a maximum shear viscosity in the viscosity versus shear frequency curve. The slow mode hydrodynamic radius of DLS measurements and the zero shear rate viscosity data of poly(NIPAM)/H2O and poly(NIPAM)/D2O solutions show two critical transition temperatures with Tcr1 = 30oC~32oC and Tcr2 =32oC~34oC. Poly(NIPAM)/D2O has higher Tcr1 and Tcr2 than poly(NIPAM)/H2O. However, no transition temperatures of poly(NIPAM)/THF solution were observed. The different temperature dependencies of these three solutions were attributed to the “solubility” and “hydrogen bonding” effects between poly(NIPAM) with H2O, D2O, and THF solvents. Without considering the polymer-solvent hydrogen bonding, the solubility of poly(NIPAM) in solvents decreases in the following sequence: THF>H2O>D2O and the degree of polymer-solvent hydrogen bonding increases in the following sequence: THF |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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