Physical Gels Based on Charge-Driven Bridging of Nanoparticles by Triblock Copolymers

• Published in: Langmuir Vol. 28; no. 33; pp. 12311 - 12318
• Main Authors: Lemmers, Marc, Spruijt, Evan, Akerboom, Sabine, Voets, Ilja K, van Aelst, Adriaan C, Cohen Stuart, Martien A, van der Gucht, Jasper
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 21.08.2012
• Subjects: adsorption; aqueous-solution; Chemistry; colloidal silica; Colloidal state and disperse state; dynamic light-scattering; Exact sciences and technology; formulation process; Gels; General and physical chemistry; Hydrogen-Ion Concentration; macromolecules; micelles; nanocomposite hydrogels; Nanoparticles - chemistry; Physical and chemical studies. Granulometry. Electrokinetic phenomena; Polymers - chemistry; reversible gels; Rheology; Salts - chemistry; shear-induced gelation; Silicon Dioxide - chemistry; Stress, Mechanical; Water - chemistry; Aggregation; Water; Particle; Elastic modulus; Binary compound; Triblock copolymer; Nanoparticle; Shear stress; Polymer; Silica; Relaxation time
• ISSN: 0743-7463; 1520-5827
• DOI: 10.1021/la301917e

We have prepared an aqueous physical gel consisting of negatively charged silica nanoparticles bridged by ABA triblock copolymers, in which the A blocks are positively charged and the B block is neutral and water-soluble. Irreversible aggregation of the silica nanoparticles was prevented by precoating them with a neutral hydrophilic polymer. Both the elastic plateau modulus and the relaxation time increase slowly as the gel ages, indicating an increase both in the number of active bridges and in the strength with which the end blocks are adsorbed. The rate of this aging process can be increased significantly by applying a small shear stress to the sample. Our results indicate that charge-driven bridging of nanoparticles by triblock copolymers is a promising strategy for thickening of aqueous particle containing materials, such as water-based coatings.