Photochemical Isomerization of Norbornadiene-Containing Polytriazoles Obtained by Click Chemistry Polyaddition

Polyesters and polyethers containing norbornadiene (NBD) and 1,2,3-triazole units in the main chain are prepared by step growth polymerization of diester or diether NBD-based dialkynes with different aromatic diazides using copper-catalyzed azide-alkyne cycloaddition. The solubility and the physical properties of the resulting polytriazoles are investigated by differential scanning calorimetry, thermogravimetric analysis, size exclusion chromatography, and H-1 NMR spectroscopy, and are discussed taking into account of the chemical structures of the monomers. All of them are amorphous with glass transition temperatures ranging from 51 to 117 degrees C, number average molecular weight (M-n) values from 16 to 43 kDa and thermal degradation (T-d10) values from 175 to 292 degrees C. The photochemical valence isomerization (PVI) of the NBD units into quadricyclanes (QC) is investigated using UV-vis spectroscopy of polymer films spin-coated onto quartz substrates. For the first time the PVI of NBD into QC is demonstrated by H-1 NMR spectroscopy. (c) 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 223-231