Water Transport Properties of pH‐Responsive Hydrogels Based on Poly(methacrylic acid) with Polyether Side Chains by Magnetic Resonance Imaging

Three pH-responsive hydrogel families have been synthesized through the photopolymerization of methacrylic acid (MAA) with: i) a poly(ethylene glycol) macromonomer, P(MAA-co-PEGMEMA), ii) a poly(propylene glycol) macromonomer, P(MAA-co-PPGMEMA), and iii) the two above-mentioned macromonomers, to give a terpolymer P(MAA-co-PEGMEMA-co-PPGMEMA). Their swelling properties at pH 7 have been investigated by magnetic resonance imaging (MRI). Equimolecular compositions of both P(MAA-co-PEGMEMA) and P(MAA-co-PPGMEMA) hydrogels showed the lowest swelling kinetics rates. For P(MAA-co-PEGMEMA-co-PPGMEMA) hydrogels, the different structure of the side chains established an antagonist effect on the swelling. In addition, from the MRI intensity profiles and taking into account the first stage of the swelling, water diffusion coefficients (D) have been estimated.