文摘
Four diblock copolymers of styrene oxide and ethylene oxide were prepared by oxyanionic polymerization: E45S10, S15E63, S17E65, and S20E67. Surface tension measurements were used to determine criticalmicelle concentrations of copolymer E45S10 in aqueous solution at several temperatures and thereby itsstandard enthalpy of micellization. A compilation of known results for copolymers with hydrophobic blocksformed from either styrene oxide or 1,2-butylene oxide shows a discontinuity at S5 or B10 in the block lengthdependence of the Gibbs energy of micellization which is assigned to lengthy hydrophobic blocks beingtightly coiled in the molecular state in water. Light scattering was used to determine micellar associationnumbers and radii, and scaling exponents were established for the dependence of these parameters onS-block length. Phase diagrams defining regions of hard and soft gel were determined by tube inversionand Couette rheometry.