I. Goldmints et al., SMALL-ANGLE NEUTRON-SCATTERING STUDY OF PEO-PPO-PEO MICELLE STRUCTUREIN THE UNIMER-TO-MICELLE TRANSITION REGION, Langmuir, 13(14), 1997, pp. 3659-3664
The structure of(ethylene oxide)(26)(propylene oxide)(40)(ethylene oxi
de)(26) Pluronic P85 block copolymer micelles in the unimer-to-micelle
transition region was studied using small-angle neutron scattering. A
t low concentration (1%), where no intermicellar interactions were evi
dent, aggregation numbers were obtained using the contrast variation m
ethod. At higher concentrations a three parameter model accounting for
the presence of water in the core and corona of the micelle, and for
micelle-micelle interactions, was fitted. The micelle core water conte
nt decreases (from 60 to 10%) with increasing temperature in the trans
ition region, with a corresponding increase in the micelle aggregation
number (35-62). The micelle core radius remains constant (40 Angstrom
). Thus, the broad nature of the unimer-to-micelle transition region m
ay be ascribed to the structural changes which accompany the replaceme
nt of micellar core water by polymer.