Cooperative Motion of Side Groups in Amorphous Polymers: Dipolar Interactions

摘要

Two ester-type monomers with different polarity, BEM and NBEM, copolymerize withthe azo-containing monomer DR1M in random fashion and form amorphous copolymers. The polarity of BEM is comparable to the polarity of DR1M, and the electronic spectra confirm that BEM and DR1M interact with each other more strongly than NBEM and DR1M do. A nonlinear increase of the photoinduced birefringence as a function of azo content is found in DR1M copolymers with the polar BEM group, while the increase is linear in copolymers with the nonpolar NBEM group. Comparison between the two copolymer series suggests that the dipolar association between BEM and DR1M is the major factor causing cooperative motion in these amorphous copolymers enhancing the photoinduced birefringence. jg p.2.