Segmental dynamics of chains tethered at interfaces of varying curvatures

The segmental dynamics of a low glass transition temperature T_g polymer under different conditions of morphological confinement are shown to manifest the influence of the frustration of the local "packing" of chain segments at interfaces of varying curvatures, unique to the morphology. Of particular interest are the polyisoprene (PI) segmental dynamics in polystyrene-b-polyisoprene (PS-b-PI) micelles and in layered onion-like structures in high T_g, "frozen," polystyrene (PS) hosts. At temperatures close to the T_g of PI domains, the segmental relaxation times of PI chains in the micellar structures, τ_micelle, are more than 1 order of magnitude shorter than those of PI chains in the onion-like structures, τ_onion. These rates are appreciably faster than those of homopolymer PI and of PI in the neat copolymers possessing lamellar and gyroid phases, τ_homo ∼ 0.5τ_lam ∼ 0.5τ_gyroid, respectively. At high temperatures τ_homo ∼ τ_lam ∼ τ_gyroid ∼ τ_onion ∼ τ_micelle. These observations are readily reconciled with trends in the local T_g of the PI phase in each sample.