Capillary Imbibition, Crystallization, and Local Dynamics of Hyperbranched Poly(ethylene oxide) Confined to Nanoporous Alumina

Abstract

The crystallization and dynamics of hyperbranched poly (ethylene oxide) (hbPEO), obtained from the direct random copolymerization of EO and glycidol (PEO-co-PG), are studied both in bulk and within nanoporous alumina (AAO). Copolymerization decreases the degree of crystallinity and lowers the crystallization and melting temperatures as compared to linear PEO. The dynamics of capillary imbibition within AAO followed the t(1/2) prediction but is slower than predicted by the classical Lucas-Washburn equation. The most prominent effect of confinement is the change in nucleation mechanism-from heterogeneous nucleation in bulk to homogeneous nucleation inside AAO. The homogeneous nucleation temperatures for the hyperbranched PEOs agree with those of linear ones provided that the branch molecular weight is used instead of the total molecular weight. Confinement and interfacial effects futher suppress the degree of crystallinity and speed up the segmental dynamics.