Changes in molecular dynamics of the tri-ethylene glycol dimethacrylate monomer upon polymerization

The dielectric behavior of the tri-ethylene glycol dimethacrylate monomer was investigated by dielectric relaxation spectroscopy after isothermal polymerization at different temperatures and compared with the unreacted monomer. The relaxation process associated with the monomer glass transition slightly deviates to lower frequencies/higher temperatures in partial polymerized samples. Additionally, it is stronger depleted the higher the polymerization temperature, vanishing after a temperature where the polymerization reached completion. A secondary relaxation process related with localized mobility with the appearance of an excess wing in the bulk monomer previously studied in a narrower frequency range, becomes better defined after partial polymerization due to the depletion of the main relaxation process. Its location and activation energy is independent of the polymerization temperature. Whereas its intensity does not change significantly upon polymerization, the decrease of the intensity of the glass transition process could be taken as a degree of conversion. A αβ splitting scenario was drawn that maintains its pattern in the partial polymerized systems relatively to the bulk monomer. The fragility parameter of the bulk monomer was recalculated (m = 85), slightly increasing when the monomer left unreacted co-exists with the newly formed polymer.