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Phase behavior of block co-poly (ethylene oxide-butylene oxide), E18B9 in water, by small angle neutron scattering



A I. Norman, D L. Ho, Alamgir Karim, Eric J. Amis


We present a small angle neutron scattering (SANS) study into the micellar and vesicular structures of diblock copolymer EO6BO11 (where EO represents an ethyleneoxide unit and BO represents a butyleneoxide unit, and 6 and 11 are the number of repeat units of each block) in dilute aqueous solution. SANS measurements were preformed over a range of five different concentrations (0.025 %, 0.05 %, 0.5 %, 5 % and 20 % by mass fraction) at eight different temperatures (10 C, 20 C, 30 C, 40 C, 50 C, 65 C, 80 C and 90 C). At low concentration and temperature worm-like micelles were shown to exist and as the temperature and concentration was increased, these micelles ordered to form spherical lamellae, i.e. vesicles. This work compliments a previous study 10 on the same system, which used microscopy techniques to identify the vesicle phase. The vesicle phase is shown to be stable over a wide temperature and concentration range. The SANS data has been fitted to a model proposed by Kratky and Porod to account for vesicle polydispersity. In addition the pair distance distribution function, p(r), has been calculated, giving information regarding particle dimension. From the calculated p(r), the cross sectional p(r) and subsequent radial contrast profiles were calculated. Such calculations lead to the conclusion that the EO head group exists in a once-folded configuration for vesicles and a random non-folded configuration for the micellar structure. At a critical concentration and temperature these structures are shown to order further into lyotropic liquid crystalline arrays of either hexagonally packed rod-like micelles, or planar lamellar sheets.
Journal of Colloid and Interface Science
No. 1


block copolymers, small angle neutron scattering, vesicles


Norman, A. , Ho, D. , Karim, A. and Amis, E. (2005), Phase behavior of block co-poly (ethylene oxide-butylene oxide), E<sub>18</sub>B<sub>9</sub> in water, by small angle neutron scattering, Journal of Colloid and Interface Science, [online], (Accessed April 23, 2024)
Created August 1, 2005, Updated February 19, 2017