Suspension "click" polymerizations: thiol-ene polymer particles prepared with natural gum stabilizers

The impact of different natural gum species employed as stabilizers in the suspension photopolymerization of water-borne thiol-ene polymer particles is reported. The focus of analysis was on how hydrocolloids impact the synthesis of polymer particles prepared using a "click" thiol-ene polymerization approach. The use of renewable and naturally occurring gums as particle stabilizers provide a shift toward greener methods of polymer particle synthesis. The natural gum species examined include gum Arabic, guar gum, and xanthan gum. In particular, gum Arabic was examined in thiol-ene particle synthesis due to inherent colloidal stabilizing properties that allow it to be utilized at concentrations comparable to synthetic stabilizers (1 wt% or greater). The use of these naturally occurring polysaccharides led to the development of spherical, cross-linked thiol-ene polymer particles in the size range of several micrometers to hundreds of micrometers. Polymer particle synthesis was completed within minutes via photopolymerization. Parameters examined include variation of natural gum species, natural gum concentration, monomer content, and stabilizer solution viscosity. Thiol-ene polymer particles can be successfully developed at very low stabilizer concentrations (0.005-0.5 wt%) due to the unique viscosity-enhancing properties of natural gum solutions compared to reactions stabilized by synthetic surfactant stabilizers.