Abstract
We have investigated the phase transition behavior of poly(ethylene oxide)-block-poly(4-vinyl pyridine) (PEO-b-P4VP) and its complexes with dodecylbenzenesulfonic acid (DBSA). PEO-b-P4VP was found to exhibite an unusual lower critical ordering transition (LCOT), where the diblock, which was in the disordered state at lower temperature, underwent microphase separation upon heating. The disorder-order transition temperature (TDOT) of PEO-b-P4VP was in general significantly lower than that of PEO-b-P2VP under a given composition and molecular weight. This was attributed to the larger solubility parameter of P4VP than that of P2VP. The complexation of P4VP block with DBSA drastically increased the TDOT due to the shift of the copolymer composition to more asymmetric value and the modification of the χ parameter between the two blocks. The supramolecular comb-coil diblock copolymers thus formed exhibited the structure-within-structure morphology above TDOT.