Crystallization of poly(ethylene oxide) in a photopolymerizable monomer under an electric field

The miscibility behavior and crystallization of poly(ethylene oxide) (PEO) from two non-polar solvents when subjected to a high electric field were studied. The two solvents, both photopolymerizable, were urethane dimethacrylate (UDMA) and 1,6-hexanediol dimethacrylate (HDDMA). The electric field was found to decrease miscibility in at least HDDMA, causing liquid–liquid phase separation at temperatures above the PEO melting temperature and well above the dissolution temperature. Cooling the solutions below 45°C under the field caused the irregular spherulites forming in HDDMA (a low-viscosity solvent) to align in groups and, above 0.2 kV/mm, to elongate. Lamellae within the spherulites tended to align with their planes in the field direction. Only branched lamellae formed in UDMA (a high-viscosity solvent), with the longest lamellae in the field direction and the few branches at large angles to these. For both solvents, crystallization was retarded slightly by the field, as was the total amount of crystallinity in HDDMA, and possibly also in UDMA. PEO crystallinity in UDMA was much less than that in HDDMA, with or without the field, presumably because of viscosity.