Aqueous Solutions and Gels of Diblock Copolymers of 1,2-Butylene Oxide and Ethylene Oxide Studied by Light Scattering and Rheology

Abstract

Copolymers B 20 E 430 , B 20 E 510 , and B 20 E 610 (B ) oxybutylene repeat unit, E ) oxyethylene repeat unit, subscripts indicate chain length in repeat units) were synthesized and characterized by gel permeation chromatography (for distribution width) and 13 C NMR spectroscopy (for absolute molar mass and composition). Dynamic and static light scattering were used to determine micellar properties in dilute aqueous solution: e.g., micelle association numbers and radii. A tube-inversion method was used to define the mobile-immobile (hard gel) phase boundary. For copolymer B 20 E 610 , immobile gels form at concentrations as low as 2.9 wt %. Rheological measurements of dynamic modulus and yield stress served to characterize the gel properties and to confirm the phase boundaries. The results are combined with those from previous work on related block copolymers to obtain scaling relationships for the dependence of micellar and gel properties on E-block length, thus enabling prediction of the requirements for and properties of very dilute aqueous gels. The validity of treating the micelles as hard spheres is discussed.

Effect of Ethanol on the Rheological Properties of Water‐Rich Gels of Diblock Copolymer E43B11

“…The solution at 65 8C is within the soft gel range, and the frequency scan illustrates very well the sensitivity of the modulus of this solution to frequency. As a consequence, and as pointed out previously, [21,31] temperatures at the softgel/sol boundary are dependent on the frequency used, and those drawn in Figure 1 give only an indication of the viscoelasticy of the three systems. Frequency scans characteristic of a stable hard gel were obtained for 30 wt.-% hard gels of the copolymer in 20 wt.-% aqueous ethanol at 5 and 25 8C.…”

Aqueous Gels of Diblock Oxyethylene‐Oxypropylene Copolymers

“…The notation is consistent with early reports of the rheology of aqueous micellar solutions of E m P n E m block copolymers [2,3] and we have used it our previous work. [9][10][11][12][13][14][15] Hard gel corresponds to the immobile region of the phase diagram depicted in Figure 1 and is characterised by high storage modulus and a high yield stress (s y ). Of the mobile region, those solutions with very low values of G 0 and s y and with G 0 < G 00 are denoted sols, and solutions with moderate values of G 0 and s y and with G 0 > G 00 are denoted soft gels.…”

“…This value is consistent with a Poisson distribution for the E-blocks and a somewhat wider distribution for the P blocks caused by the transfer reaction. 13 C NMR spectroscopy was used to obtain absolute values of number-average chain length and composition, hence the molecular formulae quoted, and to confirm the diblock architecture and sample purity. In the same study, a range of techniques was used to confirm micellisation in dilute aqueous solution, and tube-inversion was used to detect gelation in more concentrated solution.…”

“…Recently we have described small-angle X-ray scattering (SAXS) experiments which show that aqueous gels of diblock E m P n copolymers closely related in composition to those of present interest comprise body-centred cubic (bcc) arrays of packed spherical micelles. [8] There is related rheological and structural information for aqueous gels of other diblock copoly(oxyalkylene)s, notably copolymers of ethylene oxide and 1,2-butylene oxide, [9][10][11][12][13] but also copolymers of ethylene oxide and styrene oxide. [14,15] Experimental Part…”

Rheological properties of multisticker associative polyelectrolytes in semidilute aqueous solutions

“…81 The most striking features of the N7 polymer solutions, that is, gel-like properties with an apparent yield stress and frequency-independent relaxation spectra, have been observed for aqueous solutions of amphiphilic block copolymers, such as Pluronics 82 or oxyethylene-oxybutylene copolymers. 83,84 For these polymers, the peculiarities in the rheological behavior were attributed to the presence of ordered phases composed of packed cylindrical micelles. 85 In our case, as previously pointed out, the supramolecular structure is formed by the interconnection of the multichain clusters.…”