Abstract: Poly(methacrylic acid co-poloxamer) hydrogel networks were synthesized by free radical solution polymerization and their equilibrium swelling and solute permeation properties were characterized. These gels exhibited pH dependant swelling and solute diffusivity due to the formation or disruption of hydrogen bonded complexation between methacrylic acid (MAA) and etheric (EO). In neutral and basic conditions (above the swelling transition pH), the copolymer swelling was greatly higher than acid condition. In complexed hydrogels, the diffusion coefficients of vitamin B12 (VB12) were in the range of 10^-10 to 10^-7 cm²·s^-1; While in uncomplexed hydrogels, the values were about 2×10^-6 cm²·s^-1. The comonomer composition and synthesis conditions have great effect on the structure, and thereby, swelling and solute diffusion characteristics of the resultant hydrogels. For the copolymers with composition of less than or more than 1:1 MAA/EO molar ratio, the plot of lnD vs 1/H-1 followed two different linear equations of ‘free volume theory', respectively.

Key words: Methacrylic acid, Methacrylic acid, Poloxamer, Poloxamer, pH Sensitive hydrogel, pH Sensitive hydrogel, Equilibrium swelling, Equilibrium swelling, Solute diffusion, Solute diffusion, Free volume theory, Free volume theory