Small-Angle X-Ray Scattering Study of Micelle Formation in Mixtures of Butadiene Homopolymer and Styrene-Butadiene Block Copolymer.
CINCINNATI UNIV OH DEPT OF MATERIALS SCIENCE AND METALLURGICAL ENGINEERING
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The small-angle X-ray scattering technique is utilized to study the formation of micelles in mixtures containing polybutadiene homopolymer Mn 2350 with much smaller amounts 0.5 to 8 wt of styrene-butadiene diblock copolymer Mn 25000, 52.2 wt styrene. The following quantities, characterizing the structure of the micelle core consisting of styrene blocks swollen with polybutadiene, have been evaluated as a function of temperature and the copolymer concentration the radius of gyration of the core, the degree of swelling of the core, the number of block copolymer molecules forming a micelle, and the volume of a core. In addition, the critical micelle concentration i.e., the minimum copolymer concentration necessary for micelle formation and the number density of micelles as a function of the concentration were also determined. The degree of swelling of micelle cores by polybutadiene increases steadily with increasing temperature. The micelle core size is fairly independent of the concentration and, as the temperature is raised, at first remains unchanged but then increases rapidly before it finally dissolves completely. The temperature of dissolution increases with concentration of the copolymer. The micelle core volumes, determined by two independent methods one by the Guinier analysis and the other from the ratio IOQ, agree well with each other.
- Physical Chemistry
- Polymer Chemistry