Rheological and thermal characteristics of a two phase hydrogel system for potential wound healing applications

Hydrogels fabricated from single polymers have been extensively investigated for wound healing applications. However, in many cases a single polymer cannot meet divergent demands in terms of both properties and performance. In this work, a two phase hydrogel was prepared by physically imbedding a xerogel in the core of a freeze thawed hydrogel. The outer hydrogel was prepared by freeze thawing poly (vinyl alcohol) (PVA) and poly (acrylic acid) (PAA) while the xerogels were prepared by UV polymerisation of 1-vinyl-2-pyrrolidinone (NVP). The rheological results indicated that the two phase hydrogels over a period of 2 weeks formed a strong interface and demonstrated greater physical strength. This suggested that the inner gel containing PVP diffused into the PVA/PAA hydrogel, which in turn increased hydrogen bonding, resulting in the overall increase in the stiffness of the gel. Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) confirmed hydrogen bonding had occurred between the constituents of the two phase hydrogels. Thermal analysis suggested that T g of each of the samples was above 80 °C, which indicated no impact on the behaviour of the gel at body temperature, but did however, give an indication of the stiffness of the dry polymer.