In situ viscoelasticity and in situ thermo-responsiveness in acrylic acid-based soft hydrogels

This study was aimed at understanding any effects that the presence of acrylic acid dimer could have on thermo-mechanical properties of acrylic acid-based hydrogels. Polymeric hydrogels were systematically synthesised and characterised on the basis of having different concentrations of acrylic acid dimer. The materials show a reversible thermo-responsive behaviour, when heated in situ using light transmittance approaches. The point of cloudiness is significantly influenced as a consequence of the presence of the acrylic acid dimer material. Increasing the amount of the dimer additive up to 2% improves the light transmittance (%) of the soft gels by up to 70%, at 140°C, suggesting that a potential method of altering the lower critical solution temperature of the soft gels is to alter the polymer backbone through copolymerization. As the amount of dimer was increased up to 2%, the values of storage modulus (G') were increased by up to 75%, leading to greater viscoelasticity and stronger gel compositions. (paper)