Enhanced hydrogel adhesion by polymer interdiffusion: use of linear poly(ethylene glycol) as an adhesion promoter.

The fracture energy required to separate layers of hydrogel films was investigated to evaluate the impact of bulk polymer diffusion on hydrogel/hydrogel adhesion and to obtain molecular information on the fracture energy in polymer mucoadhesion. Poly(ethylene glycol) (PEG) was incorporated in a hydrogel and was used as an adhesion promoter. The influence of PEG molecular weight and contact time on PEG diffusion across the hydrogel/hydrogel interface was investigated by using tensiometric studies and near-field FTIR microscopy. These experiments indicated that linear PEG diffusion enhanced the adhesion between the two hydrogel layers. The enhanced adhesion could not be explained by surface wetting phenomena alone. These results indicated that bulk diffusion of linear polymers such as PEG (adhesion promoter) incorporated into polymer networks (hydrogels) was an effective technique for enhancing gel/gel adhesion in various applications including polymer/mucus interactions in mucoadhesion and development of mucoadhesive controlled drug delivery systems.