The design of inorganic nanoparticles (NPs) for the purpose of exploiting/studying their inherent properties of self-assembly has garnered much interest in recent years. These assemblies of NPs, or colloidal polymers, have been shown to exhibit electronic, magnetic, and catalytic properties distinct from those of the starting colloidal monomers. Often, these properties can be tuned by monomer design and degree of polymerization. As such, polymer science provides a useful framework for understanding the assembly of these colloidal species, as well as unique insight into the design of next-generation materials exhibiting more complex architectures or functionalities. With the concept of applying principles of polymerization to the preparation of new colloidal polymers, we have investigated the synthesis of new colloidal monomer species. These specifically designed monomers allow novel functionalities to be imparted to the final materials. For the first time, we have succeeded in incorporating large, sterically bulky inorganic sidechains into magnetically self-assembled colloidal polymers. Methods were developed to synthesize semiconductor tetrapods (TPs) (40 nm arms) each with a single dipolar tip, which were observed to spontaneously align to form linear assemblies of spherical magnetic NPs (D=20 nm), each with a bulky TP pendant functionality directly attached. The key step to this synthesis was the installation of asymmetry onto the TP framework, which has proven challenging in past research due to the identical nature of the TP arms. Utilizing a novel UV-deposition/ripening process, a single large (~10 nm) Au NP was deposited onto the end of one arm of each TP, providing a site for deposition of dipolar cobalt. These colloidal monomers exhibited spontaneous self-assembly to afford the final polymer with the bulkiest reported semiconductor sidechains. Albeit much larger in overall size, the TP functionalities bear a striking resemblance to traditional “t-butyl” groups. Methods to control the grafting density of TPs in the polymers were established, allowing for random copolymers of modified and unmodified magnetic particles to be prepared, as well as polymers consisting of multiple TP groups per magnetic particle.

Synthesis and dipolar assembly of tetrapod functional colloidal monomers: Colloidal polymers with giant T-butyl groups

251st National Meeting (2016)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.