| Abstract: | Proton spin magnetization relaxation in the rotating frame is a simple exponential for poly(2,6-dimethylphenyleneether) (PPO) (23K)/polystyrene (PS) (9K) blends of various compositions; these blends are truly homogeneous at the spin-diffusion distance scale of a few nanometers. Blends of PPO with high molecular weight PS exhibit nonexponential decays for the PS component but exponential decays for the PPO component, indicating compositional fluctuation for PS. In some blends, the relaxations are nonexponential for both components. Three factors have been identified to promote microheterogeneity of nanometer dimensions: high polymer molecular weight, increase of temperature, and preparation of blend using solvent that induces crystallization of PPO such as toluene. |
