Rheological properties of homogeneous and heterogeneous poly(2-hydroxyethyl methacrylate) hydrogels

The swelling and rheological behaviour of hydrogels of morphology varying from non-porous to highly porous was investigated. The hydrogels were prepared by redox free radical copolymerization of 2-hydroxyethyl methacrylate with 0.1 to 5 mol% of di(ethylene glycol) dimethacrylate in the presence of water varying from 40 to 80 wt%. Various compositions led to clear, turbid or macroporous gels. The morphology of the gels was characterized using optical microscopy and cryoscan electron microscopy. The oscillatory shear and creep of swollen gels revealed that there was a pronounced difference between homogeneous or microheterogeneous and macroporous gels with communicating pores. The achievement of optimum conditions for the correct determination of shear modulus was also analysed. (C) 2011 Society of Chemical Industry