Abstract
Forced Rayleigh scattering was employed to measure diffusion coefficients for a ternary system comprising camphorquinone or diacetyl in poly(methyl methacrylate) with methyl isobutyrate as the diluent. Measurements were made at polymer weight fractions, w p, over the range 0.78–0.90 and temperature 25–50°C for camphorquinone (which spans the glass transition regime), and at w p=0.9 and 0.95 and at room temperature for diacetyl. Results for camphorquinone show a strong temperature dependence, with diffusion coefficients changing as much as two orders of magnitude between 25 and 50°C, and showing high activation energies for diffusion≈125 kJ mol −1. No sharp change in the activation energy for diffusion was observed as the glass transition is crossed. The pre-exponential factor for the diffusion coefficient decreased dramatically through the glass transition. The diffusion coefficients of small penetrants in glassy polymers appear strongly dependent on the molecular size.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have