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Synytska, A. ; Berger, S. ; Ionov, L. ; Stamm, M.
Smart bicomponent polymeric janus particles: Synthesis and stimuli-responsive properties

Asymmetry is intrinsic to natural systems and is widely used by living organisms for efficient adaptation and mimicry. Janus particles (JPs) i.e. the colloidal particles having different properties (such as charge, polarity, optical and magnetic properties) at opposite sides are an example of synthetic asymmetrical systems. Recently, the JPs demonstrated huge potential as drug-carriers, emulsion stabilizers, micro rheological probes and functional elements for design of electronic paper. Moreover, due to asymmetrical structures, the JPs are able to aggregate into fascinating hierarchical structures, thereby, building blocks for complex superstructures.
A particularly interesting group of JPs comprises the ones specifically responding to change of environmental conditions. For, example, immobilization of stimuli-responsive polymers to one side of colloidal silica particles was recently used for synthesis of temperature/pH sensitive Janus particles. Apparently, grafting of two polymers with different sensitivities on opposite sides can further diversify responsive properties of JPs.
In this work, we report on the preparation of stimuli-responsive bicomponent polymeric Janus particles and investigation of their switching behavior. First polymer was immobilized on one side of silica particles using surface-initiated atom transfer radical polymerization, “grafting from” approach. Second polymer was immobilized using “grafting to” method by reaction between reactive terminating groups of polymer chains and functional groups on the particle surface. On the example of mixed oppositely charged polyelectrolyte Janus particles decorated with polyacrylic acid and poly(2-vinylpyridine) chains, we demonstrate stimuli-responsive aggregation/stabilization behavior upon pH changes.

Polymeric Materials: Science and Engineering 101



October 2009


Polymer Interfaces