Light-Induced Shape Changes in Azobenzene Functionalized Polymers Prepared by Ring-Opening Metathesis Polymerization

A method for producing well-defined azobenzene functionalized polymers via ring-opening metathesis polymerization (ROMP) is described. ROMP of an isomerically pure exo-norbornene ester tethered to an azobenzene unit in the presence of the third generation Grubbs' catalyst was investigated in detail. The polymerization was determined to be living on the basis of a linear relationship between Mn and [M]/[I] and the ability to quantitatively produce chain extended homopolymers. The polymer's physical response to plane-polarized light was studied in thin films and latex particles. A relief grating was inscribed on the surface of a thin film by irradiation with an interference pattern of linearly polarized light. The same material was used to prepare isotropic colloidal particles of the polymer. These latex particles were transformed to ellipsoids in response to irradiation by linearly polarized light perpendicular to the sample surface.