Micelles of polybutadiene-b-poly(ethylene oxide) in deuterated methanol and deuterated cyclohexane.

Micellization of the diblock copolymer poly(ethylene oxide)-b-polybutadiene, PEO(132)-PB(89), where the subscripts denote the number of monomers in each block, has been studied in solution in deuterated methanol and in deuterated cyclohexane, in order to compare the micellar assembly in deuterated solvents to that in protonated solvents. The methods used were dynamic light scattering and small angle neutron scattering. In CD(3)OD, PEO(132)-PB(89) forms only spherical micelles that change little in size or shape over the temperature range 21-68°C. In CH(3)OH, PEO(132)-PB(89) forms coexisting cylindrical and spherical structures over the entire temperature range. Thus cylindrical micelles form in CH(3)OH, but do not form in CD(3)OD. In C(6)D(12), the copolymer forms flexible, cylindrical micelles at lower temperatures; above about 40°C, spherical micelles and free copolymers appear and coexist with the cylindrical micelles. The behavior in C(6)H(12) is the same as in C(6)D(12), except that no free copolymers are observed in C(6)H(12). The stronger hydrogen bonding in deuterated methanol as compared to protonated methanol is assumed to be the source of the difference in assembly.