title: 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 degrees 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.
authors.affiliation: Department of Chemical and Biomolecular Engineering, Clemson University, Clemson, South Carolina 29634, USA.
authors.forename: Rahul M
authors.initials: RM
authors.lastname: Rasal
authors.forename: Douglas E
authors.initials: DE
authors.lastname: Hirt
mesh_terms: D020155:3-Hydroxybutyric Acid / Q000737:chemistry*; D001672:Biocompatible Materials / Q000737:chemistry; D002152:Calorimetry, Differential Scanning; D002208:Caproates / Q000737:chemistry*; D019344:Lactic Acid / Q000737:chemistry*; D008422:Materials Testing; D055668:Photochemical Processes; D011091:Polyesters; D011108:Polymers / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D013314:Stress, Mechanical; D013499:Surface Properties; D013818:Thermogravimetry; D000094122:Polyhydroxybutyrates
chemical_list: D020155:3-Hydroxybutyric Acid; D001672:Biocompatible Materials; D002208:Caproates; D019344:Lactic Acid; D011091:Polyesters; D011108:Polymers; C115940:poly(3-hydroxybutyrate-co-3-hydroxyhexanoate); D000094122:Polyhydroxybutyrates; C033616:poly(lactide)