Confinement effects on the structure and dynamics of polymer systems from the mesoscale to the nanoscale

In this article, we review some of our recent progress in experimental and simulation methods for generating, characterizing, and modeling polymer microparticles and nanoparticles in a number of polymer and polymer-blend systems. By using instrumentation developed for probing single fluorescent molecules in micrometer-sized liquid droplets, we have shown that polymer particles of nearly arbitrary size and composition can be made with a size dispersion that is ultimately limited by the chain length and number distribution within the droplets. Depending on the timescale for solvent evaporation - a tunable parameter in our experiments - the phase separation of otherwise immiscible polymers can be avoided by confinement effects, and homogeneous polymer-blend microparticles or nanoparticles can be produced. These particles have tunable properties that can be controlled by the simple adjustment of the size of the particle or the relative mass fractions of the polymer components in solution. Physical, optical, and mechanical properties of a variety of microparticles and nanoparticles, differing in size and composition, have been examined with extensive classical molecular dynamics calculations in conjunction with experiments to gain deeper insights into the fundamental nature of their structure, dynamics, and properties.