Fluorescence Probe Studies of Poly(Acrylic Acid) Interchain Complexation and Chain Rigidity Indyced by High Shear Flow. Influence of Molecular Environment

Abstract

The mode and strength of poly(acrylic acid), PAA, interchain complexation was strongly influenced by the presence of salts and cationic surfactants. Addition of salts to the shearing PAA solution disrupted the complexation, while modification of the PAA with surfactant enhanced the complexation but only below a critical concentration that depended on the surfactant chain length and pH employed. The chain morphology developed by such interchain complexation of PAA is a rigid rod-like chain cluster. The PAA self-complexation in the presence of poly(ethylene oxide), PEO, is strongly affected by pH and PEO molecular weight. With a high molecular weight PEO, the PAA self-complexation is drastically suppressed, whereas the PAA complexation and thus, the chain rigidity is markedly enhanced in the presence of a low molecular weight PEO, probably due to physical crosslinking of the PEO between the elongated PAA molecules.