DIELECTRIC EVIDENCE OF SOL-GEL TRANSITION IN FREE RADICAL CROSSLINKING SYSTEM



F.Salehli, O.Kamer, H.Çatalgil-Giz, A.Giz

Faculty of Science and Letters, Istanbul Technical University, 80626 Maslak,Istanbul, Turkey.



ABSTRACT


       Bulk polymerization of methyl methacrylate (MMA), ethyl methacrylate (EMA) and buthyl methacrylate (BMA) monomers with crosslinker ethylene glycol dimethacrilate (EGDM) have been investigated by means of dielectric spectroscopy. The results were compared to the behavior of linear polymers of the same monomers.

      In the crosslinking systems, the dielectric constant was found to peak at the sol-gel transition point. The peak was most pronounced in MMA with short pendant groups and was least pronounced in BMA with long pendant groups. Experiments performed at different temperatures showed that dielectric constant depends on the extent of the reaction. The dielectric constant show power law behavior around the sol-gel transition. The observed singularity of real and immaginary part of dielectric constant was confırmed by time dependent viscosity measurements.