Interpenetrating polymer networks (IPN) based on gelatin/poly(ethylene glycol) dimethacrylate/clay nanocomposites: Structure-properties relationship

The effects of cross-linking sequence (simultaneous or sequential) and incorporation of exfoliated sodium-montmorillonite (Na+-MMT) nanoclay on the structure and properties of interpenetrating polymer networks (IPNs) based on gelatin/poly(ethylene glycol)dimethacrylate were studied by means of different complementary techniques. Gelatin and PEGdmA phases were cross-linked via chemical and in-situ UV curing, respectively. 2,2-dimethoxy-2-phenylacetophenone (DMPA) (1.5% w/w) was used as photoinitiator to cross-link PEGdmA. The results showed that the incorporation of small amount of Na+-MMT nanoplatelets accelerates the kinetics of chemical cross-linking of gelatin by glutaraldehyde (1.0% w/w). This led to a new hypothesis concerning the tuning structural evolution of the IPNs by the Na+-MMT content. In the case of simultaneous IPNs, in which both phases cross-linked at the same time, the accelerated cross-linking of gelatin in the presence of exfoliated sodium-montmorillonite led to increased structural homogeneity, improved mechanical and thermal properties. Incorporation of nanoclay did not show any significant effect on the structure and properties of the IPNs synthesized via sequential method in which gelatin and PEGdma phases were cross-linked separately. For the semi-IPNs, however, Na+-MMT induced macroscopic phase separation and resulted in lower mechanical properties. These results might shed light on the mechanisms underlying structure property relationship in biohybrid IPNs based on gelatin as promising candidates for tissue engineering and drug delivery applications. (C) 2013 Elsevier B.V. All rights reserved.