Light scattering loss and glass transition temperature of optical polymer glass

The glass transition temperature (T_g) was the critical temperature for determining the excess light scattering of poly(methyl methacrylate) (PMMA) glasses. When PMMA glass is polymerized or heat-treated above the T_g, the excess scattering intensity disappears and the isotropic light scattering loss is reduced to the value calculated from the refractive index and the isothermal compressibility using the thermally induced fluctuation theory. The isotropic light scattering loss of the amorphous polymer can be estimated from its molecular structure by assuming a frozen model around T_g.