M. Villacampa et al., DIBLOCK COPOLYMER MICELLES IN SOLVENT BINARY-MIXTURES .2. SELECTIVE SOLVENT GOOD SOLVENT/, Macromolecules, 28(12), 1995, pp. 4144-4149
Solutions of polystyrene-b-poly(ethylene/propylene) block copolymer in
mixtures of 4-methyl-2-pentanone (a selective solvent of the polystyr
ene block) and 2-chlorobutane (a good solvent of both copolymer blocks
) were studied by static and dynamic light scattering and viscometry,
Micelle structural parameters and micellization thermodynamics have be
en analyzed as a function of the solvent composition. The micelle mola
r mass decreased as the 2-chlorobutane percentage in the binary mixtur
e increased. However the apparent radius of gyration, the second viria
l coefficient, and the hydrodynamic radius hardly showed variations. S
tatic light scattering was used to establish the dependencies of the c
ritical micelle temperature on concentration. The standard Gibbs energ
ies, enthalpies, and entropies of micellization have been calculated f
or the different solvent mixtures from these relationships, The three
thermodynamic magnitudes became less negative as the good solvent perc
entage increased.