Reversible addition-fragmentation chain transfer (RAFT) polymerization has been widely used for the synthesis of varying polymer architectures, including polymer brushes on nanoparticles for incorporation into polymer nanocomposites. Surface modification of nanoparticles allows for control of the surface properties and therefore the interface between a nanoparticle and the polymer matrix. Adverse interactions between the nanoparticles, grafted polymer, and polymer matrix can lead to aggregation and autophobic de-wetting. This can be suppressed when the enthalpic and entropic effects are decoupled for their independent study, using a bimodal system containing a small number of long polymer chains on a surface that primarily consists of a short dense brush. Here we demonstrate a sequential RAFT polymerization process for the synthesis of bimodal polymer brush anchored nanoparticles. This process allows for the control of brush parameters such as composition, graft density, and molecular weight for both populations separately and independently. The bimodal brush grafted silica nanoparticles show superior dispersion and thermomechanical properties over monomodal brush grafted particles in polymer nanocomposites. In addition, the synthesis and properties of mixed bimodal brushes (brushes of mixed chemical composition) will be discussed. With mixed bimodal, short brushes offer an enhancement in properties while long brushes help retain matrix compatibility. Analogous to block copolymers, the addition of a polymer chain population with different chemical composition can lead to materials with added and differing properties compared to materials with only a single chemical composition.

Synthesis and properties of mixed bimodal brush grafted nanoparticles

248th National Meeting (2014)

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