Advanced polymer nanoparticles with nonspherical morphologies

Polymer particles have been the subject of research in various fields for several centuries. The discovery of rubber latex, a class of naturally occurring colloidal dispersions of cis-polyisoprene particles, is usually regarded as the starting point of the development of modern polymer science (Whitby et al. 1933; Hohenstein et al. 1946). Driven by the need for rubber polymers, in the early twentieth century extensive research was carried out in order to find synthetic routes to polymers by mimicking Mother Nature’s process for producing natural rubber (Hofmann 1912; Gottlob 1910, 1912; Pond 1914). In 1912, Kurt Gottlob invented the first process that enabled the preparation of synthetic rubber latex by polymerization of isoprene in viscous aqueous solutions. The process involves the use of naturally occurring polymers such as gelatin, egg albumin, and starch to stabilize a dispersion of monomer droplets, which are then polymerized into solid particles. This process, now widely known as “emulsion polymerization,” has since become one of the dominant methods for synthesizing polymer particles from a wide variety of monomer materials. In most cases, the particles produced using emulsion polymerization or related processes have sizes within the range of 100 nm to 1 ím, although it is not uncommon to find recipes for making particles beyond this range. In this chapter, the term “nanoparticle” is used to broadly cover particles with sizes of a few nanometers to several micrometers.