Macromolecules, Vol.33, No.18, 6834-6839, 2000
Miscibility of poly(n-butyl acrylate)/poly(propylene glycol) blends. 1. Phase behavior and dielectric relaxation
We report the cloud point, glass transition temperature T-g, and dielectric relaxation for blends composed of poly(n-butyl acrylate)s (PBA) and a linear poly(propylene glycol) (PPGD) and for blends of PEA and a star-shaped PPG having three arms (PPGT). The phase diagram is of the upper critical solution type (UCST), and the critical temperature varies from 340 to 220 K depending on the molecular weight of the PEA. The interaction parameter chi for PBA/PPGD is higher than that for PBA/ PPGT. For blends of high molecular weight PEA and PPGD, a sharp glass transition and a subsequent broad glass transition were observed by differential scanning calorimetry, but for mixed blends a relatively sharp single T-g was observed. The temperature dependence of the dielectric loss factor is an element of'' of phase-separated blends exhibited two loss maxima. The low-temperature peak can be assigned to the segmental mode relaxation (alpha-process) of PPG and the high-temperature peak to the normal mode of PPG and the segmental mode of PEA. Mixed blends exhibited a single loss maximum having an asymmetrical shape, indicating that there is local heterogeneity.