Swelling and drying kinetics of polytetrahydrofuran and polytetrahydrofuran-poly (methyl methacrylate) gels: A photon transmission study

A bifunctional polytetrahydrofuran (PTHF) macromonomer was synthesized by termination of the living polymerization of tetrahydrofuran (THF) initiated by triflic anhydride and the subsequent termination by sodium methacrylate. The PTHF macromonomer thus prepared was polymerized and copolymerized with methyl methacrylate (MMA) by free-radical polymerization to yield a network and a segmented network of PTHF, both being homogeneous, respectively. These PTHF and PTHF-PMMA gels were used for swelling experiments in chloroform and chloroform vapor. Drying processes were monitored after removing the gels from the solvent and solvent vapor. Photon transmission from PTHF and PTHF-PMMA gels was monitored during swelling and drying processes using a UV-visible (UVV) spectrophotometer. Transmitted light intensities, I_tr, from these gels increased when they were immersed in chloroform and/or subjected to its vapor. The increase in I_tr was attributed to the homogeneous lattice structure of PTHF and PTHF-PMMA gels which appeared during swelling. The increase in I_tr was modeled using the Li-Tanaka equation from which time constants, τ₁, and cooperative diffusion coefficients, D_C, were determined. A decrease in I_tr after removing choloform and/or its vapor from the cell was observed and attributed to the decrease in homogeneity of lattice structures during drying of the corresponding gels. Time constants, τ2, for the drying processes were also determined.