Mesoscopic study of cylindrical phases of poly(styrene)-poly(isoprene) copolymer: Order-order phase transitions by temperature control

Phase transitions of cylindrical structures of poly(styrene)-poly(isoprene) copolymer (PS-PI) toward spherical and gyroid structures were explored using DPD simulations and a coarse-grained model. Cylindrical phases were first obtained within a composition interval (predominance region) 0.2 < f(ps) < 0.26 (volume fraction of poly(styrene)). The predominance region of cylindrical structures was then subject to thermal heating cycles. The thermodynamic instabilities of cylindrical microdomains induce anisotropic composition fluctuations and phase transitions. A transition from the cylindrical phase at low composition limit to a spherical arrangement was observed during the thermal heating process. The cylindrical phase at the intermediate and high composition limit within the predominance region exhibits a transition towards a gyroid arrangement. The phase transition control during thermal heating on the cylindrical phases was governed by small variations in composition. The results are consistent with experimental studies. (C) 2009 Elsevier Ltd. All rights reserved.