Nanoparticles can impart specific functions, such as magnetism as required in magnetic data storage media or charge transport properties as required in polymer-based photovoltaic devices, to the nano/micro-structures.1 However, controlled assembly of nanoparticles in such nanostructures is a challenging problem. Typically, such assembly is achieved at fluid-fluid or fluid-solid interfaces.

In this work, we are investigating the possibility of using UV-photopatterning as a potential method for controlled assembly of nanoparticles. In this method, a monoacrylate, 2(2-ethoxyethoxy) ethyl acrylate (E3A) is photopolymerized in presence of photoinitiator, 2,2-dimethoxy-1,2-diphenylethan-1-one (DMPA), and 500 nm silica particles using photomasks with micron-size features. The silica particles added to the polymerization mixture also contain red fluorescent dye (rhodamine) so that their movement during photopolymerization can be traced. Preliminary results of photopolymerization of E3A with DPMA as an initiator indicate that as photopolymerization proceeds towards gelation, silica particles migrate from unmasked (UV-illuminated) region, where photopolymerization occurs, to the masked region (dark), where photopolymerization does not occur; thus forming aggregates in the masked region. We expect that by controlling pattern shapes and feature sizes in the photomasks, we can easily control the assembly of nanoparticles.

Reference:

1. Böker, A.; He, J.; Emrick, T.; Russell, T. P. Soft Matter, 2007, 3, 1231-1248.