Multiple phase transitions in block copolymer blends and pressure effects on these transitions. (10th March 2017)

• Record Type: Journal Article
• Authors: Lee, Yonghoon; Jo, Seongjun; Lee, Wooseop; Lee, Hoyeon; Han, Young Soo; Ryu, Du Yeol
• Is Part Of: Polymer. Volume 112(2017)
• Page Start: 427
• Page End: 434
• Publication Date: 2017-03-10
• Subjects: Phase transition -- Block copolymer blends -- Pressure effect; Polymers -- Periodicals; Polymerization -- Periodicals; Polymères -- Périodiques; Polymérisation -- Périodiques; 547.7
• DOI: 10.1016/j.polymer.2017.02.026
• Languages: English
• ISSNs: 0032-3861

Abstract

Abstract: We sought to identify an evident enthalpic-driven transition below an entropic-driven closed-loop phase transition by studying the phase behavior in miscible binary block copolymer (BCP) blends of a polystyrene- b -poly ( n -butyl methacrylate) (PS- b -P n BMA) and a deuterated polystyrene- b -poly ( n -hexyl methacrylate) ( d PS- b -P n HMA), using small-angle x-ray scattering (SAXS) and depolarized light scattering (DPLS). Intriguingly, an order-to-disorder transition (ODT) below the closed-loop transition consisting of a lower disorder-to-order transition (LDOT) and an upper order-to-disorder transition (UODT) was observed in the BCP blends of an asymmetric (PS-rich) PS- b -P n BMA and a symmetric d PS- b -P n HMA. Multiple phase transitions, previously undiscovered in BCP system, were attributed to a delicate balance in the free energy of the dispersive intermolecular interactions, the entropic compressibility, and the combinatorial entropy of mixing at an experimental temperature range between the glass transition temperature ( T g ) and degradation temperature ( T d ). We also characterized the effects of hydrostatic pressure on the transition temperatures to determine the thermodynamic origins of each phase transition. Graphical abstract: Highlights: Phase behavior in miscible binary BCP blends of weakly interacting PS- b -P n BMA/ d PS- b -P n HMA. Multiple phase transitions displaying an ODT to a LDOT and an UODT (in the closed-loop transition) upon heating. 3D phase transition diagram of the BCP blends based on transition behavior. Pressure effects on the transition temperatures to evaluate the pressure coefficient ( dT/dP ).