Design and Photogrowth of Nanomaterials Through Light Mediated Polymerizations



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As polymer networks present immense potential in the materials field, synthetic tools to access and tune these materials have grown tremendously over the years. Of great significance are reversible deactivation radical polymerization (RDRP) techniques, specifically light-mediated techniques that provide precise spatiotemporal control. In order to further improve this precision over tuning polymer networks, utilization of orthogonal techniques for site-selective manipulations are needed. Although there are numerous reports of polymer network manipulations through light mediated RDRP techniques involving bulk materials, there exists a need to explore these manipulations in the nanoscale, which could provide shortcuts to existing nanomaterials and various novel advanced materials. The aim of this dissertation is to develop nanomaterials capable of experiencing precise site-selective manipulations in size, architecture, and properties as summarized in Chapter 1. Chapters 2 and 3 details the synthesis of photogrowable nanonetworks (PGNNs) through urethane, ester and Diels-Alder adduct linkages and their orthogonal site-selective photogrowth via photoinduced electron/energy transfer reversible addition-fragmentation chain-transfer (PET-RAFT) polymerization, atom transfer radical polymerization (ATRP), or ring opening polymerization (ROP). PGNNs were prepared by reacting scaffold polymer with units capable of either RAFT polymerization, ATRP or ROP on the chain end and crosslinkers with trithiocarbonate (TTC) RAFT moieties. Site-selective photogrowth from the scaffold and the crosslinker were demonstrated and larger dimensions of expanded nanonetworks (ENNs) were observed in comparison to the parent PGNN. Dangling polymer chains formed from the scaffold expansions were shown to orient differently in good and less than good solvents, creating various shapes as evidenced by transmission electron microscope (TEM) images. This study demonstrates the ability to manipulate not only the size and chemical composition of living nanonetworks, but it also provides a gateway to modulate the surface character of particles by collapsing and extending the network filling polymer chains in good or bad solvents. Utilization of polymerization techniques such as ATRP and ROP in Chapter 3 provides new routes to ENNs and broadens the monomer scope beyond vinyl monomers. Chapter 4 discusses photogrowth expansions of TTC RAFT agents undergoing self-assembly to produce materials that can experience morphological changes via light-mediated polymerizations.



Nanonetwork, Polymerization