(526d) Direct Small Molecule Sequestration By Macroporous Polymer Resin Synthesis

The goal of this work was to sequester a small molecule in a single synthetic step using approaches adopted from macroporous polymer resin synthesis.  Unlike macroporous resin synthesis that traditionally produces particles greater than 100 um; a method has been introduced that produces particles between 400 and 3000 nm.  A wide range of synthetic parameters were studied to both direct the interfacial and interior structure of the nanoparticles.  These parameters included monomer type and composition ratios, particle size, surfactant type, stabilizing agent, initiator type, and small molecule loading.  The ideal structure has been imagined to be a macroporous polymer that has a self-assembled cross-linked shell capable of controlling the diffusion of the small molecule in application requiring controlled release.  Conditions to reproduce or deterministically direct shell synthesis will be discussed. 

A series of synthetic experiments were performed to prepare a stable sequestered small molecule in a macroporous polymer.  It was determined that the highest level of intrinsic pore filling by the small molecule of interest was achieved for systems approaching 100% divinyl benzene (DVB) cross-linker.  However, imaging by SEM suggested a lack of surface shell or “skin” layer which correlated with an inability to control diffusion.  Shell layers have been shown to self-assemble in prior work to produce conventional macroporous polymer resins.  Therefore, experiments were rationally designed to examine if these conditions could be reproduced for resins in the size range of 400-3000 nm using the small molecule of interest as the porogen.  Using SEM, it was shown that by increasing the hydrophilicity of the monomer, the surface of the particle can be smoothed resulting in a thin shell.  In addition, if a second monomer emulsion is introduced, the monomer will diffuse and react at the pore entrance to form a capping layer.