Abstract
The interactions in poly(oxyethylene) (E) – poly(oxybutylene) (B) of EB or EBE type block copolymers-sodium dodoecyl sulfate (SDS) or dodecyltrimethylammonium bromide (DTAB) and/or t-octylphenoxy polyethoxyethanol, (TX-100) have been monitored as a function of surfactant concentration and temperature. The addition of ionic surfactants to copolymer micellar solutions in general induced not only shape transition from spherical to prolate ellipsoids at 30∘C in the copolymer micelles but also destabilize them and even suppress the micelle formation at high surfactant loading. DTAB destabilizes the copolymer micelles more than SDS. TX-100, being nonionic, however, forms stable mixed micelles. The block copolymer-surfactant complexes are hydrophilic in nature and are characterized by high turbid and cloud points. Triblock copolymer micelles got easily destabilized than the diblock copolymer ones, indicating the importance of the interaction between the hydrophilic E chains and surfactants. The effects of destabilization of the copolymer micelles are more dominating than the micellar growth at elevated temperatures, which is otherwise predominant in case of copolymer micelles alone.
Highlights
Amphiphilic block copolymers of type EnBm or EnBmEn (E = oxyethylene and B = oxybutylene, and m and n indicate the number of units) have several advantages over EPE (P = oxypropylene) copolymers
Detailed investigations dealing with the establishment of binding isotherms, measurement of critical micelle concentrations, determination of size and aggregation number in mixed systems have indicated that the surfactant molecules interact with the hydrophobic as well as hydrophilic parts of the copolymers and induce interesting and dramatic changes in association characteristics depending upon the molecular characteristics of copolymers, namely, length of E or P blocks, P/E ratio and on the type of hydrophobic block and concentration of the surfactants, and so forth
Diblock copolymer, has lower turbidity point (Tp) and cloud points (Cp) values as compared to triblock copolymer and the temperature range over which the turbidity persisted in the solutions has been found to be more for B-2 than B-1 copolymer
Summary
Amphiphilic block copolymers of type EnBm or EnBmEn (E = oxyethylene and B = oxybutylene, and m and n indicate the number of units) have several advantages over EPE (P = oxypropylene) copolymers. Detailed investigations dealing with the establishment of binding isotherms, measurement of critical micelle concentrations, determination of size and aggregation number in mixed systems have indicated that the surfactant molecules interact with the hydrophobic as well as hydrophilic parts of the copolymers and induce interesting and dramatic changes in association characteristics depending upon the molecular characteristics of copolymers, namely, length of E or P blocks, P/E ratio and on the type of hydrophobic block and concentration of the surfactants, and so forth. It has been emphasized that the mixing behavior deviated from ideality and the systems exhibited synergistic interactions
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