Molecular alignment during gel formation from methyl methacrylate: An excimer fluorescence study


Kaya D. , ERDOGAN M., PEKCAN O.

PHASE TRANSITIONS, cilt.78, ss.387-400, 2005 (SCI İndekslerine Giren Dergi) identifier identifier

  • Cilt numarası: 78 Konu: 5
  • Basım Tarihi: 2005
  • Doi Numarası: 10.1080/01411590500114799
  • Dergi Adı: PHASE TRANSITIONS
  • Sayfa Sayıları: ss.387-400

Özet

Glass transition during bulk polymerization was studied in free-radical cross-linking copolymerization (FCC) of methyl methacrylate (MMA) using the steady-state fluorescence (SSF) technique. Naphthalene (N) was used as a monomer and excimer forming probe. Changes in the viscosity of the pregel solutions due to gel formation dramatically enhance both monomer and excimer fluorescent yield of N molecules. The reaction time at which the monomer and excimer intensities exhibit a sudden increase corresponds to the reaction time at which the rate of polymerization becomes maximum resulting from the gel effect. This effect was used to study the gelation of MMA, as a function of time, in various N concentrations. The results were interpreted in the view of percolation theory. The gel fraction, beta, and weight average degree of polymerization, gamma, exponents beta=0.40 +/- 0.02 and gamma=1.70 +/- 0.07 were found in agreement with percolation results for both monomer and excimer measurements, respectively.