Emulsion polymerization is of pivotal importance as a route to the fabrication of water-based synthetic polymer colloids. The product is often referred to as a polymer latex and plays a crucial role in a wide variety of applications spanning coatings (protective/decorative/automotive), adhesives (pressure sensitive/laminating/construction), paper and inks, gloves and condoms, carpets, non-wovens, leather, asphalt paving, redispersible powders, and as plastic material modifiers.
Since its discovery in the 1920s the emulsion polymerization process and its mechanistic understanding has evolved. Our most noticeable past contributions include the first reversible-deactivation nitroxide-mediated radical emulsion polymerization (Macromolecules 1997: DOI 10.1021/ma961003s), and the development and mechanistic understanding of Pickering mini-emulsion (Macromolecules 2005: DOI 10.1021/ma051070z) and emulsion polymerization processes (J. Am. Chem. Soc. 2008: DOI 10.1021/ja807242k). The latest on nano-silica stabilized Pickering Emulsion Polymerization from our lab can be found here.
One quest in emulsion polymerization technology that remains challenging and intriguing is control of the particle morphology. It is of importance as the architecture of the polymer colloid influences its behavioural properties when used in applications. We now report in ACS Nano an elegant innovation in the emulsion polymerization process which makes use of nanogels as stabilizers and allows us to fabricate Janus and patchy polymer colloids.
False coloured SEM images of emulsion polymerizations using nanogels as stabilizers (N1) at 2.8 wt% wrt monomer in which the pH was adjusted to 8.8 (A), 5.5 (B), 5.0 (C) and 4.5 (D) prior to polymerization. Scale bars: 100 nm.
The use of the nanogels in the emulsion polymerization leads to anisotropic Janus and patchy colloids, where a latex particle is decorated with a number of patches on its surface. In the paper we show that control of particle size and patch density can be achieved by tailoring the reaction conditions.
Proposed mechanism for the formation of Janus and patchy particles in the emulsion polymerization of styrene carried out in presence of nanogel particles.
The work was carried out by a team of talented scientists from the BonLab, Andrea Lotierzo, Brooke Longbottom, and Wai Hin Lee. Prof.dr.ir. Stefan Bon says: “ I am absolutely delighted that our work is published in the internationally leading journal ACS Nano. It is a great achievement of the team who have worked tremendously hard in the realisation of this new innovative technology. It shows that the area of emulsion polymerization is very much alive and kicking!”
The link to the paper is here: DOI: 10.1021/acsnano.8b06557