The effects of salts and ionic surfactants on the micellar structure of tri-block copolymer PEO-PPO-PEO in aqueous solution
Date
2008
Authors
Bharatiya, Bhavesh
Ghosh, Goutam
Bahadur, P.
Jitendrakumar, Mata
Journal Title
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Publisher
Marcel Dekker Inc.
Abstract
The micelles of two poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) block copolymers, P123 and F127 (same mol wt of PPO but different % PEO) in aqueous solution in the absence and presence of salts as well as ionic surfactants were mainly examined by dynamic light scattering (DLS). The study is further supported by cloud point and viscosity measurements. The change in cloud point (CP), as well as the size of micelles in aqueous solution in presence of salts obeys the Hofmeister lyotropic series. Addition of both cationic cetylpyridinium chloride (CPC) and anionic sodium dodecylsulfate (SDS) surfactants in the aqueous solution of P123 show initial decrease of micellar size from 20 nm to nearly 7 nm and then increasing with a double relaxation mode, further in the presence of NaCl this double relaxation mode vanishes. The effect of surfactant on F127, which has much bigger hydrophilic part is different than P123 and have no double relaxation. The relaxation time distributions is obtained using the Laplace inversion routine REPES. Two relaxation modes for P123 are explained on the bases of Pluronic rich mixed micelles containing ionic surfactants and the other smaller, predominantly surfactant rich micelles domains.
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Keywords
Keywords: Agglomeration; Composition effects; Dynamic light scattering; Laplace equation; Micelles; Polyethylene oxides; Polypropylene oxides; Salts; Surface active agents; Cloud point; Ionic surfactant; Micellar structure; Block copolymers; Agglomeration; Block co Aggregation; Block copolymers; Dynamic light scattering; Surfactant pluronic interaction
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Source
Journal of Dispersion Science and Technology
Type
Journal article
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2037-12-31