Three photochromic monomers containing a permanent dipole photochromic azobenzene group separated from the methacryloyl moiety by a polymethylene spacer, namely 4-(4-oxy-4'-cyanoazobenzene)but-1-yl methacrylate, 6-(4-oxy-4'-cyanoazobenzene)hex-1-yl methacrylate, and 8-(4-oxy-4'-cyanoazobenzene)oct-1-yl methacrylate, were synthesized in three steps starting from 4-cyanoaniline. These monomers were homopolymerized and copolymerized with an optically active monomer, (-)-menthyl methacrylate, in the presence of AIBN as a radical initiator. The polymeric materials, having a molar content of photochromic units comprised between 5 and 100% and molecular weights of about 15000, were characterized by an almost random distribution of monomeric units and a glass transition temperature ranging from 35 to 131 degrees C. Polymer samples having a content of aromatic units larger than 75% were characterized by a thermotropic liquid crystalline structure, as evidenced by optical microscopy, X-ray diffraction and DSC measurements. Two-dimensional correlations spectroscopy (COSY) allowed an appreciable contribution by intramolecular charge transfer mesomers to the electronic distribution of the azobenzene chromophore to be highlighted.
|Autori:||A. ALTOMARE; L. ANDRUZZI; F. CIARDELLI; B. GALLOT; SOLARO R|
|Titolo:||Methacrylic polymers containing permanent dipole azobenzene chromophores spaced from the main chain: synthesis and characterization|
|Anno del prodotto:||1998|
|Digital Object Identifier (DOI):||10.1002/(SICI)1097-0126(199812)47:4<419::AID-PI78>3.3.CO;2-D|
|Appare nelle tipologie:||1.1 Articolo in rivista|