PAA-b-PPO-b-PAA triblock copolymers with enhanced phase separation and inverse order-to-order phase transition upon increasing temperature. (17th December 2019)

• Record Type: Journal Article
• Authors: Lv, Chao; Wang, Ruiyang; Gao, Jia; Ding, Ning; Dong, Shunni; Nie, Jingjing; Xu, Junting; Du, Binyang
• Is Part Of: Polymer. Volume 185(2019)
• Publication Date: 2019-12-17
• Subjects: AxOyAx triblock copolymers -- Enhanced phase separation -- SAXS; Polymers -- Periodicals; Polymerization -- Periodicals; Polymères -- Périodiques; Polymérisation -- Périodiques; 547.7
• DOI: 10.1016/j.polymer.2019.121982
• Languages: English
• ISSNs: 0032-3861

Abstract

Abstract: Enhanced phase separation and inverse order-to-order phase transition with increasing temperature was observed for a series of poly (acrylic acid)- b -poly (propylene oxide)- b -poly (acrylic acid) triblock copolymers with various block lengths by temperature-variable synchrotron small-angle X-ray scattering (SAXS). This abnormal phase behavior was attributed to the change of hydrogen (H)-bonding interaction in block copolymers upon increasing temperature and theoretically explained from thermodynamic viewpoint. The temperature-dependent FTIR analysis revealed that increasing temperature led to the weakening of overall H-bonding interactions and the increase of free CO and C–O–C groups. The Flory-Huggins interaction parameter χ of PAA and PPO blocks was positive and increased with increasing temperature as determined from the SAXS profiles of disordered block copolymer. The thermodynamic calculation indicated that the increase of Δ H was larger than the decrease of – T Δ S with increasing temperature because of the relatively large value of χ, leading to the increase of overall Δ G mix and hence the enhanced phase separation at higher temperature. Graphical abstract: Image 1 Highlights: PAA- b -PPO- b -PAA block copolymers exhibit enhanced phase separation and inverse order-to-order phase transition upon increasing temperature. The interaction parameter between PAA and PPO blocks increases with increasing temperature. The thermodynamic calculation shows that the increase of Δ H was larger than the decrease of – T Δ S with increasing temperature for PAA- b -PPO- b -PAA.