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High interfacial activity of polymers "grafted through" functionalized iron oxide nanoparticle clusters
Lynn M Foster1, Andrew J Worthen, Edward L Foster
1McKetta Department of Chemical Engineering and ‡Department of Chemistry, The University of Texas at Austin , Austin, Texas 78712-0231, United States.
Langmuir : the ACS Journal of Surfaces and Colloids
|August 12, 2014
Summary
Grafting polymers onto inorganic nanoparticles creates hybrid particles that significantly lower interfacial tension and stabilize emulsions. These particles exhibit a much lower critical concentration for interfacial activity compared to free polymers.
Area of Science:
- Materials Science
- Colloid and Surface Chemistry
- Polymer Science
Background:
- Particle-stabilized emulsions and foams are of great interest, but the mechanism by which grafted polymers on inorganic nanoparticles reduce interfacial tension is poorly understood.
- Understanding interfacial phenomena is crucial for designing advanced materials and processes.
Purpose of the Study:
- To investigate the mechanism of interfacial tension reduction by polymers grafted to inorganic nanoparticles.
- To develop a versatile method for creating hybrid inorganic/polymer particles with enhanced interfacial and rheological properties.
- To explore the application of these hybrid particles in stabilizing oil-in-water emulsions.
Main Methods:
- A free radical "grafting through" technique was employed to graft poly(oligo(ethylene oxide) monomethyl ether methacrylate) onto iron oxide clusters without catalysts.
- Characterization of the resulting hybrid particles, including their size, composition, and interfacial behavior.
- Measurement of interfacial tension, critical particle concentration (CPC), adsorption energy, bulk viscosity, and emulsion stabilization capabilities.
Main Results:
- Hybrid particles (∼1 μm) with high organic fractions exhibited significantly low interfacial tensions (0.003 w/v %) due to high local polymer concentration and particle adsorption.
- The CPC for interfacial tension reduction was over 30-fold lower than the critical micelle concentration of the free polymer.
- Hybrid particles demonstrated greatly enhanced bulk viscosity and effectively stabilized oil-in-water emulsions at low concentrations (0.01 w/v %) with small drop sizes (30 μm).
Conclusions:
- Grafting polymers onto inorganic nanoparticle clusters creates amphiphilic hybrid particles with superior interfacial activity and rheological properties.
- The unique structure of hybrid particles, including deformable nanocluster cores, facilitates efficient interfacial adsorption and stabilization.
- These findings suggest broad applicability of inorganic/polymer hybrid particles for stabilizing emulsions and foams.
