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

Abstract

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 Bclick^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.

Functional polymer particles via thiol–ene and thiol–yne suspension “click” polymerization

“…Each of these examples take advantage of the thiol-ene/yne "click" chemistry tenets by using multifunctional alkenes, alkynes, and thiols that provide crosslinked polymer particles with well-dened networks at high yields under ambient reaction conditions. [10][11][12] Here, not only do we expand the range of monomers used in thiol-ene/yne "click" suspension polymerizations, thus providing polymer particles with different compositions, thermo-mechanical properties, and functionality, we also present the rst instance of using thiol-yne radical polymerization in suspension polymerizations. [13][14][15][16][17]24,[27][28][29][30][31][32] In our previous communications outlining the use of thiol-ene suspension polymerizations we focused on a limited set of monomers, used photoinitiation, and examined a range of surfactants and stabilizing agents.…”

Composite Particles From Pickering‐Stabilized Radical Mediated Thiol‐Ene Suspension Polymerizations

“…Previously, we and others developed radical‐mediated thiol‐ene and thiol‐yne polymerizations for the production of colloidal polymer particles . Synthesis of colloidal polymers have been shown to work in different dispersed polymerization modes, such as emulsions, dispersions, miniemulsions and suspensions .…”

“…Synthesis of colloidal polymers have been shown to work in different dispersed polymerization modes, such as emulsions, dispersions, miniemulsions and suspensions . In these prior cases, the particles were emulsified or stabilized using common surfactants, such as sodium dodecyl sulfate (SDS), or natural gums . The use of Pickering stabilization in suspension polymerizations provides a unique avenue to produce composite polymer particles with raspberry‐like morphology.…”

Recyclable cross-linked hydroxythioether particles with tunable structures via robust and efficient thiol-epoxy dispersion polymerizations

“…9 Thiol-ene reactions, for example, gradually revealed their great potential in polymer synthesis and heterogeneous polymerizations. 10,11 Since the rst report of Du Prez and co-workers on the preparation of functional polymer beads via thiol-ene/yne chemistry in a micro-uidic setup, 12 both the nucleophilic thiol-Michael and radicalmediated thiol-ene additions were applied to fabricate polymer particles via suspensions, [13][14][15][16][17][18] emulsions, 19,20 mini-emulsions, [21][22][23][24][25] Pickering emulsion, 26 dispersions, [27][28][29][30][31][32] micro-uidics. 12,33,34 Very recently, thiol-isocyanate reactions have also been implemented to prepare particles and capsules by our group as well as by Ethirajan and co-workers.…”