Polymer Colloids from Step-Growth Thiol-X Polymerizations

This review article covers recent developments in thiol-X polymerizations as applied to the production of polymer colloidal particles. These polymerizations include thiol-ene, thiol-yne, thio-Michael, and thio-isocyanate polymerizations. Such thiol-X chemistries are facile reactions that offer high yields, rapid synthesis using mild conditions, orthogonality with other methods of organic synthesis, compatibility with a variety of monomer species, and can be radical or base mediated. Recent years have seen the employment of these reactions for the synthesis of polymer colloids in heterogeneous polymerizations such as suspension, dispersion, emulsion, and miniemulsion polymerizations, using microfluidic and batch production methods. A particular feature of thiol-X chemistries is their step-growth mechanism for molecular weight development, which contrasts with chain-growth polymerizations that are more commonly used in heterogeneous polymerizations. This aspect of thiol-X polymerizations allows for straightforward polymer functionalization simply through controlling the functional group stoichiometry. Another benefit is that radical-mediated thiol-X chemistries can be conducted with photo, thermal, or redox initiation, which epitomizes the practicality/adaptability of these reactions. Examples of highly functionalized thiol-X colloidal polymers are provided along with how such functionalization can be leveraged in order to provide desired properties. Therefore, polymer colloids made by thiol-X chemistries are expected to be a platform upon which many new technologies can be built.