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

Broadband dielectric spectroscopy (10(-1) Hz - 10(6) Hz) has been employed to study the molecular dynamics of poly-(gamma-benzyl-L-glutamate) (PBLG) i n 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 alum inium electrodes directly on the sample and (ii) the use of a solid electro de. The latter was prepared by evaporating aluminium on freshly cleaved mic a sheets. Both in the bulk and in the grafted layer two relaxation processe s are observed: (i) the fluctuation of the helical main chains ("chop-stick -motion") and (ii) the dynamic glass transition of the side chains. This se cond process is found to be slightly slowed down in the grafted layer. In c ase of evaporated electrodes, the "chop-stick-motion'' could not be observe d in the grafted layer.