Synthesis and Physical Properties of Reactive Amphiphilic Hydrogels Based on Poly(p-chloromethylstyrene) and Poly(ethylene glycol): Effects of Composition and Molecular Architecture

This paper describes the design, synthesis, and characterization of amphiphilic conetworks using linear or starlike poly(ethylene glycol), PEG, and linear or hyperbranched poly(p-chloromethylstyrene), PPCMSt. The initial synthetic strategy is based on the reaction between the hydroxyl end groups placed in the PEG and the primary and/or secondary alkyl chloride groups dispersed in the linear or hyperbranched component, respectively. It was found that the hybrid conetworks form in 55%-99% yields depending on the stoichiometric ratio of the two building blocks (19-0.5 g PEG per 1 g PPCMSt) and the type of polymer architecture. The dynamic swelling studies showed that the hydrogels absorb water quickly and reach equilibrium in 1-3 h. The architecture of starting polymer, PEG compositions, and temperature were the main factors affecting the equilibrium hydration of the cross-linked materials (700%-4200%). The observed high degree of swelling of these hydrogels in both water and organic solvents was attributed to the high network porosity, which was revealed by scanning electron microscopy (SEM) on freeze-dried specimens. The different states of water in the hydrated cross-linked matrices were measured by differential scanning calorimetry (DSC). The amounts of nonfreezing water, freezing bound water, and free water in the amphiphilic conetworks were dependent on their physicochemical structure.