Thermo-optical and differential scanning calorimetric observations of mobility transitions in polystyrene-poly(2,6-dimethyl-1,4-phenylene oxide) blends

Transition temperatures by thermo‐optical analysis (TOA) and by DSC were measured on films of polystyrene (PS), poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO resin) and nine homogeneous blends of these polymers. The TOA procedure consists of automatically monitoring light transmission through birefringent scratches in a film during heating at constant rate in a microscope hot stage between crossed (90°) plane polarizers. The TTOA transition temperature, defined as the temperature of birefringence disappearance in the scratches, increased monotonically from 113°C for pure PS to 222°C for pure PPO resin at a 10°/min heating rate. The Tg (DSC) similarly ranged from 99°C to 212°C at a 20°/min heating rate. The TOA technique as described should be a useful addition to thermomechanical studies of transparent polymers and polymer blends.