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The synthesis of aromatic polyphosphonates based on the step polymerization of various bisphenols and dichlorophenyl phosphine oxide was investigated. The effect of catalyst, type, concentration, and polymerization time were systematically varied to obtain high molecular weight polymers. Very high molecular weight tough, ductile materials with a high degree of optical clarity were synthesized. In contrast with the aromatic polycarbonates, the refractive index was increased from 1.58 to 1.60 (for the bisphenol A-based system) and 1.64 for a biphenol-based system. The latter was still an amorphous soluble polymer as a result of the non-coplanar nature of the phenyl phosphine oxide bond, unlike the analogous polycarbonate. Hydrolytically stable meltprocessable cumyl phenol end-capped polyphosphonates were successfully achieved for the first time. Rheological studies show that these end-capped systems are melt-stable at 200°C, whereas the systems of initially higher molecular weight but without any well-defined end capping clearly degraded quickly probably as a result of an acidcatalyzed hydrolysis process. Extensive high char yields were produced upon pyrolysis in either nitrogen or air, suggesting good fire resistance.

Organic-redox initiated polymerization technique based on the co-initiators system comprising benzoyl peroxide and N-phenyldiethanolamine was used at ambient temperature to fabricate pH-responsive hydrogels. The effects of changes in the concentration of the co-initiators system, the ratio in which the co-initiators combined, the type of the polymerization solvent, the pH of the hydrating medium, the concentration of the cross-linking agent based on azo-bond and the pH-sensitive cross-linking agent on the properties of the hydrogels were investigated. Increasing the concentration of the co-initiators system, decreasing the concentration of the two types of cross-linking agents, and replacing DMSO by ethanol as the polymerization solvent resulted in hydrogels with increased equilibrium swelling ratio and increased molecular weight between cross-links at pH 7.4. Increasing the concentration of N-phenyldiethanolamine while keeping the concentration of benzoyl peroxide constant gave hydrogels with increased equilibrium swelling ratios. The equilibrium swelling ratios of the hydrogels at pH 2.0 were not affected by the factors investigated. The polymerization technique may be suitable for the design of drug delivery systems containing thermolabile bioactive agents like peptides and proteins.

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