Polymershells

Polymershells are hollow or solid shells composed of polymer material that enclose a core particle or liquid droplet, forming core-shell or capsule-like structures. They are engineered to control properties such as permeability, stability, and surface functionality, and can be designed to respond to environmental stimuli.

Several fabrication routes exist: template-assisted methods where a core is coated with a polymer shell and the core is removed to yield hollow capsules; layer-by-layer assembly of polyelectrolyte layers; emulsion polymerization to form hollow spheres; and self-assembly of amphiphilic block copolymers into micellar shells. These approaches allow tuning of shell thickness, porosity, and mechanical properties.

Common shell polymers include poly(ethylene glycol) derivatives for biocompatibility, poly(lactic-co-glycolic acid) for biodegradability, polyacrylates and polyacrylamides for mechanical strength, and temperature- or pH-responsive polymers such as PNIPAM or poly(acrylic acid). Shell properties such as thickness, crosslink density, and surface functionalization determine permeability and interactions with the core and environment.

Applications span drug delivery, where shells control release and protect cargo; imaging and diagnostic agents; protective coatings for particles and devices; catalysis where shells confine reactive sites; and sensing where functional groups enable binding of analytes.

Characterization uses electron microscopy to image morphology, dynamic light scattering and zeta potential for size and surface charge, and spectroscopy to assess composition. Challenges include achieving uniform shells, maintaining stability in complex media, and avoiding undesired immune responses.