Polymer micro-particles formed by thiol–ene suspension polymerization using canola oil as a diluent solvent

Abstract

This work demonstrates the use of canola oil as a biologically compatible solvent for a thiol–ene driven suspension polymerization that effectively creates micron-sized particles. A 1 : 1 thiol to alkene functional group stoichiometry was maintained for all formulations. Thymol was incorporated into these particles during synthesis as a naturally derived, lipophilic drug with known anti-microbial properties and use in agriculture as a pesticide. UV-Vis spectroscopy demonstrated the removal of surfactant and any excess reagents to be 99% effective. Particle size was dependent on stirring speed with faster stirring resulting in smaller particles. The release of thymol from the selected ten formulations was measured with UV-Vis spectroscopy at a wavelength of 275 nm for ten days and was shown to be tailorable by altering the amount of crosslinker and surfactant used during the creation of the particles. A smaller molar ratio of 2-functional thiol monomer compared to 4-functional thiol monomer (0.1 : 0.9) crosslinker and a higher molar ratio of 2-functional alkene monomer compared to mono-functional alkene surfactant (0.9 : 0.1) resulted in the slower release of thymol. A higher molar ratio of 2-thiol to 4-thiol monomer (0.8 : 0.2) and a lower molar ratio of 2-alkene to surfactant (0.5 : 0.5) resulted in faster-releasing particles. The Peppas–Sahlin equation used to model the thymol release found that a super case II drug release mechanism that relies on physical interactions between the polymer chains determined the amount of thymol released. The utility of canola oil as a solvent for a polymer particle delivery system holds promise for their use in environmentally sensitive applications such as a pesticide carrier and anti-microbial products.