Molecular dynamics in grafted layers of poly(γ-benzyl-L-glutamate)

Abstract

Broadband dielectric spectroscopy (10 -1 Hz - 10 6 Hz) has been employed to study the molecular dynamics of poly-(y-benzyl-L-glutamate) (PBLG) in the bulk and prepared as ultra-thin grafted film. In order to contact the ultra-thin layer, two techniques were applied: (i) the evaporation of aluminium electrodes directly on the sample and (ii) the use of a solid electrode. The latter was prepared by evaporating aluminium on freshly cleaved mica sheets. Both in the bulk and in the grafted layer two relaxation processes are observed: (i) the fluctuation of the helical main chains (chop-stick-motion) and (ii) the dynamic glass transition of the side chains. This second process is found to be slightly slowed down in the grafted layer. In case of evaporated electrodes, the chop-stick-motion could not be observed in the grafted layer.