Effects of Spatial Confinementon Dielectric Relaxation of Block Copolymers having Tail, Loop, and Bridge Conformations.

From a simple calculation considering no thermodynamic requirement of maintaining uniform density, we estimated the effects of spatial confinement on the dielectric relaxation of model block copolymer chains having type-A dipoles. The results were utilized to discuss the relative importancc of these requirement and confinement in the block chain dynamics. For a tail (tethered) chain composed of N segments as well as for loop/bridge chains composed of 2N segments, all confined in a lamella of thickness L=N1/2b (b=segmental step length), the terminal relaxation was moderately faster, its mode distribution was slightly broader, and the dielectric intensity was considerably smaller than those of the same chains in free space. These effects of the spatial confinement were identical for the bridge and loop (either in the knotted or unknotted configuration) and nearly the same also for the tail. The dielectric behavior expected from this calculation was quite different from the behavior of actual type-A blocks. This result strongly suggests that the block chain dynamics is affected much moer significantly by the requirement of maintaining uniform density than by the spatial confinement.