Rheology and structures of aqueous gels of diblock(oxyethylene–oxybutylene) copolymers with lengthy oxyethylene blocks

Kelarakis, Antonis, Mingvanish, Withawat, Daniel, Christophe, Li, Hong, Havredaki, Vasiliki, Booth, Colin, Hamley, Ian W. and Ryan, Anthony J. (2000) Rheology and structures of aqueous gels of diblock(oxyethylene–oxybutylene) copolymers with lengthy oxyethylene blocks. Physical Chemistry Chemical Physics, 2 (12). pp. 2755-2763. ISSN 14639076

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Official URL: http://dx.doi.org/10.1039/B001557L

Abstract

Aqueous solutions of diblock copolymers E96B18, E184B18, E315B17 and E398B19 (E=oxyethylene unit, B=oxybutylene unit) were investigated by rheometry and small-angle X-ray scattering (SAXS). Storage (G′) and loss (G″) modulus and yield strength (σy) were used to define hard- and soft-gel phases in experiments which covered the concentration range 2–14 wt.% copolymer. Values of G′ correlated with those of yield strength, the ratio G′/σy being ca. 0.03. SAXS was used to explore hard-gel structures, and to confirm hard-gel/soft-gel boundaries. The sol/soft-gel boundary was identified as a percolation threshold. The effect of an increase in E-block length was to move the gel phases to lower concentrations without changing the pattern of their behaviour. In this respect, the critical conditions for hard-gel formation (c*, T*) served as parameters for a ‘universal ’ phase diagram.


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