Aqueous Gels of Diblock Oxyethylene‐Oxypropylene Copolymers

Abstract

Aqueous solutions of diblock copolymers E102P37 and E92P55 (E = oxyethylene unit, P = oxypropylene unit) were investigated by rheometry. Storage (G′) and loss (G″) modulus and yield stress (σy) were used to detect and characterise hard and soft gels in experiments which covered the concentration range 4–28 wt.‐% copolymer and the temperature range 5–85 °C. Comparison is made with phase diagrams reported for other diblock copoly(oxyalkylene)s, and it is shown that the mesophase behaviour of these systems depends on the effective thickness of the E‐block corona and the stability of the micelles at low temperatures. Hard‐gel boundaries (circles) and soft‐gel boundaries (squares) for aqueous solutions of copolymers (○, □) E92P55 and (•, ▪) E96B18.magnified imageHard‐gel boundaries (circles) and soft‐gel boundaries (squares) for aqueous solutions of copolymers (○, □) E92P55 and (•, ▪) E96B18.

Nafion as Cosurfactant: Solubilization of Nafion in Water in the Presence of Pluronics

“…The phase diagram of block polyethers in a selective solvent displays changes of the effective volume fraction of micellar spheres beyond or above a critical value. [48][49][50][51][52][53] The sol/ gel diagram of E 19 P 69 E 19 plotted in Figure 9 is in fair agreement with previous studies. 48 The physics that dictates the temperature effect on phase transitions can be traced back to the negative solubility coefficient of E corona, 30 meaning that the self-assembly and, thus, micellar packing are favored upon heating.…”

“…However, increasing the temperature in a (essentially) fully micellizable solution results in gradual dehydration of E chains and significant shrinkage of the spheres leading to collapse of close packing. 50,52 The rise and fall of G 0 shown in Figure 10 for 35 wt % of E 19 P 69 E 19 is consistent with such a scheme.…”

Poly(ethylene oxide)–poly(styrene oxide)–poly(ethylene oxide) copolymers: Micellization, drug solubilization, and gelling features

“…S3d). Viscous fluids of the present type have been previously identified in aqueous micellar solutions of a wide range of block copolymers, including PEO-PPO [18,[47][48][49][50] and other PEO-PSO block copolymers [21,24,51]. In addition, G 0 and G 00 increased in about three magnitude orders at ca.…”

Novel hydrogels containing Nafion and poly(ethylene oxide) based block copolymers

“…Soft gels are described as defected closely packed systems, where interacting micellar aggregates give rise to a moderate viscoelastic response (e.g. stronger than sol, but weaker than a hard gel) 35 .…”