Journal
POLYMER INTERNATIONAL
Volume 56, Issue 10, Pages 1230-1239Publisher
WILEY-BLACKWELL
DOI: 10.1002/pi.2264
Keywords
poly(methacryloyloxyalkyloxycinnamate)s; liquid crystalline polymers; thermal properties; UV crosslinking studies
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Three series of liquid-crystalline-cum-photocrosslinkable polymers were synthesized from 4-x-phenyl-4 '-(m-methacryloyloxyalkyloxy)cinnamates (x = -11, -OCH3 and -CN; in = 6, 8 and 10) by free radical solution polymerization using azobisisobutyronitrile as an initiator in tetrahydrofuran at 60 degrees C. All the monomers and polymers were characterized using intrinsic viscosity, and FTIR, H-1 NMR and C-13 NMR spectroscopy. The liquid crystalline behavior of these polymers was examined using a hot stage optical polarizing microscope. All the polymers exhibited liquid crystalline behavior. The hexamethylene spacer-containing polymers exhibited grainy textures; in contrast, the octamethylene and decamethylene spacer-containing polymers showed nematic textures. Differential scanning calorimetry data confirmed the liquid crystalline property of the polymers. Thermogravimetric analysis revealed that all the polymers were stable between 236 and 344 degrees C in nitrogen atmosphere and underwent degradation thereafter. As the methylene chain length increases in the polymer sidechain, the thermal stability and char yield of the polymers decrease. The photocrosslinking property of the polymers was investigated using the technique of exposing the polymer solution to UV light and using UV spectroscopy. The crosslinking reaction proceeds via 2 pi-2 pi cycloaddition reactions of the -CH=CH-of the pendant cinnamate ester. The polymers containing electron-releasing substituents (-OCH3) showed faster crosslinking than the unsubstituted polymers and those containing electron-withdrawing substituents (-CN). (c) 2007 Society of Chemical Industry
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