Synthesis of dimpled polymer particles and polymer particles with protrusions - Past, present, and future.

Since the development of emulsion polymerization techniques, polymer particles have become the epitome of standard colloids due to the exceptional control over size, size distribution, and composition the synthesis methods allow reaching. The exploration of different variations of the synthesis methods has led to the discovery of more advanced techniques, enabling control over their composition and shape. Many early investigations focused on forming particles with protrusions (with one protrusion, called dumbbell particles) and particles with concavities, also called dimpled particles. This paper reviews the literature covering the synthesis, functionalization, and applications of both types of particles. The focus has been on the rationalization of the various approaches used to prepare such particles and on the discussion of the mechanisms of formation not just from the experimental viewpoint but also from the standpoint of thermodynamics. The primary motivation to combine in a single review the preparation of both types of particles has been the observation of similarities among some of the methods developed to prepare dimpled particles, which sometimes include the formation of particles with protrusions and vice versa. The most common applications of these particles have been discussed as well. By looking at the different approaches developed in the literature under one general perspective, we hope to stimulate a more ample use of these particles and promote the development of even more effective synthetic protocols.

Polymer Colloids: Moving beyond Spherical Particles.

When thinking about colloidal particles, the fist image that comes into mind is that of tiny little polystyrene spheres with a narrow size distribution. While spherical polymer colloids are one of the workhorses of colloid science, scientists have been working on the development of progressively advanced strategies to move beyond particles with spherical shapes, and prepared polymer colloids with more complex morphologies. This short review aims at providing a summary of these developments, focusing primarily on methods applicable to submicron particles, with an eye towards their applications and some discussion about advantages and drawbacks of the various approaches.