NMR Relaxation Observations of the Constrained Segmental Motions of Block Copolymers in the Narrow Channels of Their Inclusion Copound Crystals Formed with Urea

摘要

Over the past several years we have undertaken the formation and study of several polymer-urea(U)-inclusion compounds (ICs) for the purpose of observing the behavior of isolated and extended polymer chains in the narrow channels created by the host urea lattice (1-10). Comparison of observations made on polymer-U-ICs with those on the corresponding bulk polymers provide a means to assess the relative contributions made by the inherent behavior of individual chains and the cooperative response of closely packed chains to the properties of ordered, bulk polymers. In this report we describe our effort to compare the motional behavior of the segments in two block copolymer-U-ICu, each containing a common block, with the motions of the same segments in the homopolymer-U-IC and bulk homo- and block copolymer samples. We employ "C NMR relaxation measurements (T, , TlP ) to probe these motions, and we also observe T,p ('H) relaxations to learn about the morphologies of the IC and bulk block copolymer samples and to compare the potentially 1 -dimensional and 3-dimensional characters, respectively, of their 'H spin diffusion. Because "C T, and T,p relaxation times are sensitive to motions in the MHz and kHz regimes, we may probe the affects of different ordered, solid-state environments on both motional regimes by observing these relaxation times for PCL chains in bulk and U-IC homo- and block copolymer samples. At the same time T,P ('H) measurements of 'H spin diffusion provide a means to assess the morphological differences between these samples.