Micellization and Gelation of Diblock Copolymers of Ethylene Oxide and Styrene Oxide in Aqueous Solution

Abstract

Four diblock copolymers of styrene oxide and ethylene oxide were prepared by oxyanionic polymerization: E45S10, S15E63, S17E65, and S20E67. Surface tension measurements were used to determine critical micelle concentrations of copolymer E45S10 in aqueous solution at several temperatures and thereby its standard enthalpy of micellization. A compilation of known results for copolymers with hydrophobic blocks formed from either styrene oxide or 1,2-butylene oxide shows a discontinuity at S5 or B10 in the block length dependence of the Gibbs energy of micellization which is assigned to lengthy hydrophobic blocks being tightly coiled in the molecular state in water. Light scattering was used to determine micellar association numbers and radii, and scaling exponents were established for the dependence of these parameters on S-block length. Phase diagrams defining regions of hard and soft gel were determined by tube inversion and Couette rheometry.

Micellar and surface properties of a poly(methyl methacrylate)–block–poly(N-isopropylacrylamide) copolymer in aqueous solution

“…Although the exact pattern of cmc(T ) and γ (T ) plots reported here is rather unique, values of cmc that are independent of temperature has been reported in other systems [28,29,31,32]. In each case the behavior has been assigned to collapse of hydrophobic coils, i.e., to the formation of monomolecular micelles.…”

Association properties of diblock copolymer of ethylene oxide and 1,2-butylene oxide: E17B12 in aqueous solution

“…The required amount of dry 1,2-butylene oxide was transferred under vacuum into the ampoule, which was then held in a water bath at 45 • C for 5 days, at 65 • C for 10 days, and finally at 85 • C until reaction was complete. Homopolymer and copolymer were characterized by 13 C-NMR spectroscopy for absolute values of the number-average molar mass, M n , and confirmation of block architecture, and by gel permeation chromatography (GPC, calibrated with poly(oxyethylene) standards) for the width of the molar mass distribution (M w /M n , where M w is the mass-average molar mass). M w /M n was corrected for instrumental spreading by subtraction of ca.…”

“…The longer B block of copolymer E 17 B 12 ensures that micelles of this copolymer are stable down to very low concentrations. The correlation of critical micelle concentration (cmc) with B-block length, obtained for a range of E m B n copolymers [1,13], indicates that the cmc of copolymer E 17 B 12 is at least an order of magnitude lower than that of copolymer E 11 B 8 . As a consequence, effects caused by the unimer/micelle equilibrium are not important in the range of our present observations, i.e., concentrations of E 17 B 12 higher than ca.…”

Characterization of triblock copolymer E67S15E67–surfactant interactions

“…The total intensity of the scattered light normalized with the scattered intensity of toluene ðI tot h Þ was measured at a copolymer concentration of 2.5 g dm À3 and varying SDS concentrations from 7.5 · 10 À6 to 0.1 M at 20°C, with a scattering angle of 90°, because no angular dependence of the static light scattering intensity was observed, as previously shown [17,20] (see Fig. 1).…”

“…However, to our best knowledge, no attention has been paid to the mixtures of surfactants and block copolymer comprising a hydrophilic poly(oxyethylene) block and a second hydrophobic poly(oxyphenylethylene) block. In recent papers, we have studied the micellization and gelation properties of both diblock and triblock architectures of this class of copolymers [17][18][19] (denoted as E m S n or S n E m for diblocks depending on polymerisation sequence, and E m S n E n for triblocks, where E denotes the oxyethylene unit, OCH 2 CH 2 , and S denotes the oxyphenylethylene, OCH 2 CH(C 6 H 5 ), and the subscripts m and n denote the number-average block lengths in repeat units). In a recent paper, we have described the interactions between a diblock (styrene oxide-ethylene oxide) copolymer with cationic and anionic surfactants by different experimental techniques [20][21][22].…”