Dynamic and photochemical behavior of amorphous comb-like copolymers with photochromic azobenzene side groups

摘要

A series of amorphous photochromic homo- and copolymethacrylates with an azobenzene moiety in the side group is investigated systematically by optical and dielectric spectroscopy. The aliphatic ester component of the comonomer unit and the concentration of the azobenzene groups within the copolymer are varied. The kinetics and the temperature dependence of the E/Z (trans/cis) photoisomerization and of the thermal Z/E (cis/trans) isomerization is studied for spin-coated films of the polymers. To understand the polarity of the polymeric materials as well as the matrix dependence of the reactions and of the photoinduced reorientation processes in the steady state molecular dynamics is investigated by dielectric spectroscopy. A variety of relaxation processes is observed: a #gamma#-relaxation at low temperatures followed by a #beta#-, and #alpha#-, and a #delta#-process. Additionally at room temperature a new #beta#'-relaxation is detected for polymers containing azobenzene moieties. The temperature dependence of the reaction rate of the thermal Z/E isomerization process measured by optical spectroscopy seems to correlate with the values of the #beta#'-process. A correspondence between dielectric and photochemical behavior is discussed.