Interactions and Temperature Transitions of Ethylene Oxide - Propylene Oxide - Ethylene Oxide tri-block Copolymers in Water Media

摘要

ATR FTIR spectra of two ethylene oxide - propylene oxide - ethylene oxide (EO)_n-(PO)_m-(EO)_n tri-block copolymers (Pluronics) with different lengths of the EO blocks were investigated in water media at various temperatures. The observed wavenumber shifts and intensity changes of the bands of different chemical groups of polymers and of water molecules served as a basis for the estimation of structural changes and interactions of polymers with the surrounding water molecules. Two types of such interactions, i.e. hydrophilic (ether group - water) and a hydrophobic (methyl group - water) are detected. In the copolymer with shorter length of the EO blocks, an interchain H2O bridge in a liquid crystalline phase was discovered and confirmed by ab initio calculations. A model for the structural changes during the temperature transitions is specified.