Upper and lower critical solution temperature behavior in thermoplastic polymer blends

Ibe phme behavior of blends of polystyrene (Mw = 115 000, Mw/ Mn < 1.06) (PS 115 ) and a random copolymer of carboxylated poly(2,6-dimethyl-1,4-phenylene oxide) (cY-PPO) has been studied by differential •onminc calorimetry (DSC) and light scattering.In cY-PPO, y represents the carboxyl content (COOH mole pen:ent).'Ibe phme diagrams of caoPPO /PS 115 and cio.appo /PS 115 were found to exhibit both UCST (upper critical aolution temperature) and LCST (lower critical solution temperature) behavior.The phase behavior is revenihle.The miscible region between the UCST and LCST decreases with increasing carboxyl content in the C-PPO, and the critic:al point moves to lower mass fraction of copolymer.In the blends C4. 5 -PPO /PS 115 8Dd c&-7 -PPOfPSm no phase separation was observed during thermal treatment.The results obtained from both DSC mMI light ac:attering are consistent.Introdaetioa fl.Gm = allm -Tfl.Sm