| A series of hydrophobically modified Acrylamide-based copolymers, incorporating linear alkyl side chains containing 8-18 carbons at level of 0.75-7 mol%, hydrolysis level ranging from 0 to 65 mol%, have been prepared by micellar copolymerization and graft reaction of a precursor polymer. These polymers have been characterized by NMR for hydrophobe level, classical light scattering for molecular weight and elemental analysis for hydrolysis level. In addition, novel dispersed-phase hydrogels with hydrophobic microdomains composed of aggregates of the alkyl side chain were made from polymers containing 1.5 mol% C{dollar}sb8{dollar} with hydrolysis levels of {dollar}1.53sim4.81{dollar} mol% acrylate and 1.5 mol% C{dollar}sb{lcub}10{rcub}{dollar} with {dollar}2.28sim23.7{dollar} mol% acrylate in aqueous systems. The hydrogel properties were investigated using rheometry, fluorescence spectroscopy and conductimetry.; A comparison of the two synthetic routes, including the product structure, limitations and procedure of the two routes are presented in this study. Micellar copolymerization can make amphiphilic polymers by one step and is an easier procedure than the graft reaction. However, it is not possible to synthesize amphiphilic polymers with both high molecular weight and high hydrophobe level by this method. On the other hand, the graft reaction has no such structure limitation on the product. The conversions of hydrophobic modifiers are 100% for micellar copolymerization and {dollar}40sim60{dollar}% for the graft reaction, respectively.; Several structure/property relationships between starting polymer and the resulting hydrogel have been identified. First, the gel point (the lowest polymer concentration at which an aqueous polymer solution exhibits a rubbery plateau in the dynamic rheological spectra) increases with backbone charge and decreases with side chain length. Second, the strength of the polymeric network increases with side chain length. Third, formation of hydrophobic aggregates is favored by low hydrolysis level polymer (between 1.53 to 4.81 mol% for C{dollar}sb8{dollar} modified polymer) but not relatively high hydrolysis level polymer (about 24 mol%). Furthermore, the hydrogel properties may be manipulated to some extent by the addition of salt and surfactant. |
