Journal of Polymer Science Part A: Polymer Chemistry, Vol.51, No.21, 4650-4656, 2013
Photoresponsive Polyamides Containing Pentamethylated Norbornadiene Moieties: Synthesis and Photochemical Properties under Sunlight Irradiation
Photoresponsive polyamides containing main-chain pentamethylated norbornadiene (NBD) moieties are obtained in quantitative yields via the Yamazaki-Higashi reaction between a pentamethylated NBD dicarboxylic acid and a series of aromatic diamines. Chemical structures are confirmed by H-1 and C-13 NMR and weight average molar masses measured by SEC are in the range of 21,500-28,600 g mol(-1) with chain dispersities close to 2. Physical properties are investigated by FTIR, differential scanning calorimetry (DSC), thermogravimetric analysis, and viscosimetry. All obtained polyamides are amorphous with glass transition temperatures ranging from 68 to 124 degrees C. They are soluble at room temperature in common organic solvents and exhibit good thermal stabilities with T-d10 values ranging from 175 to 276 degrees C. The photochemical isomerization of the NBD moiety into quadricyclane (QC) is studied by UV/vis spectroscopy after sunlight irradiation of polymer films. For all polyamides, a first-order kinetic rate is observed for the conversion of NBD to QC. The thermal release of the stored energy associated to the reverse transformation of QC groups into NBD ones is about 90-95 kJ mol(-1) as measured by DSC of the irradiated polymer films. (c) 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4650-4656
Keywords:irradiation;isomer;isomerization;polyamides;step-growth polymerization;stimuli-sensitive polymers;UV-vis spectroscopy