Deviation from time-composition equivalence in polymer solutions with selective cosolvents

Time-composition superpositioning (tCS) permits determination of the mechanical properties of polymeric materials over a widely extended time (or frequency) domain by systematically varying composition under isothermal conditions. We have recently reported (Soft Matter, 6, 4331, 2010) the existence of such equivalence in technologically relevant triblock copolymers swollen with miscible, midblock-selective cosolvents differing in chemical constitution and viscosity. In this study, chemically homologous homopolymer and copolymer systems exhibiting rheological properties that deviate from tCS are investigated. With regard to the particular case of selectively solvated triblock copolymers, the source of deviation is explained in the context of endblock hopping.