Controlling Morphology of Polymer Particles Synthesized from Condensed Monomer Droplets

摘要

Non-spherical polymer nanoparticles with tunable morphology are an emerging class of functional materials with enormous potential in drug delivery, sensing, and soft robotics. However, their development is currently limited by the laborious synthesis with limited control over particle morphology. To bridge that gap, we demonstrate the capability of a facile synthesis technique, namely, condensed droplet polymerization (CDP), to obtain non-spherical particles with disparate morphologies in a vapor deposition apparatus. The morphological control is enabled by a unique in situ digital microscopy, which reveals the evolution of particle morphology development in real time as the unreacted monomer was removed from the partially polymerized droplets through evaporation. To guide particle morphology design, the effect of fundamental properties, such as the monomer propagation constant (kp) and polymer glass transition temperature (Tg), on the resulting particle morphology was investigated using benzyl methacrylate (BzMA, low kp and low Tg) and acrylic acid (AA, high kp and high Tg) as examples. Partially polymerized BzMA droplets shrank isotropically during monomer evaporation, giving rise to compact polymer domes, whereas partial polymerization led to a polymerized layer encompassing unreacted AA monomer, which became wrinkled polymer shells or granular particles upon monomer removal. Such insight provides a framework for understanding the fundamental mechanisms of particle morphology formation. The process–property correlations serve to advance the control over polymer morphology in CDP with useful applications ranging from drug delivery to soft robotics.