Dielectric relaxation in carbosilane dendrimers with cyanobiphenyl end groups

Carbosilane dendrimers of generation 1 and 2 are functionalized with mesoge nic end groups (cyanobiphenyl) via spacers of 5 and 11 carbons. The dielect ric relaxation is measured over broad frequency (1 Hz-l GHz) and temperatur e (170-470 K) ranges. Two relaxation regimes are observed and characterized as delta and beta relaxation. The delta relaxation is nearly a single Deby e process and varies strongly with temperature. The SE to SA transition obs erved for the dendrimers with long spacers causes a jump in the relaxation rate of the delta process. The beta process displays an Arrhenius-type temp erature dependence with an activation energy of 35 kJ/mol. The relaxation t ime depends on spacer length. The dielectric relaxation reflects the mutual distortion of the dendrimer scaffold and the smectic layers.