Toughness decrease of PLA‐PHBHHx blend films upon surface‐confined photopolymerization

Abstract The present research investigates the effect of photoinduced grafting reaction on the bulk properties of melt processed poly(L‐lactic acid) (PLA)‐poly[(3‐hydroxybutyrate)‐co‐(3‐hydroxyhexanoate)] (PHBHHx) blend films. PLA‐PHBHHx blend films, comprising 10 wt % PHBHHx showed a remarkable toughness improvement. From dynamic mechanical analysis of melt processed PLA‐PHBHHx blend films, the blend appears to be noncompatible. Unfortunately, PLA‐PHBHHx blend films underwent rapid physical aging as characterized using differential scanning calorimetry, resulting in a significant toughness loss. Physically aged films regained the original toughness on annealing at 60°C for 30 min. Annealed PLA‐PHBHHx blend films also underwent physical aging leading to a significant toughness loss. Hydrophilic monomers like acrylic acid and acrylamide were successfully photopolymerized from the film surface using a sequential, two‐step photografting approach. The resultant films were characterized using water contact angle goniometry, ATR‐FTIR spectroscopy, and mechanical testing. PLA‐PHBHHx blend films lost their toughness significantly on surface modification and this was assigned to UV‐assisted solvent induced crystallization as characterized using wide‐angle X‐ray diffraction analyses. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2009