Poly(L-Lactic Acid)-Based Microcapsule Containing Phase-Change Material: Influence of Polymer Shell on Particle Morphology

Abstract

The preparation of poly(l-lactic acid) (PLLA)-based microcapsules containing phase change material Rubitherm 27 (RT27) by microsuspension polymerization was first developed. Before polymerization, a commercial PLLA was depolymerized via glycolysis to produce a shorter molecular chain as in PLLA glycosates (GPLLA). The influence of the polymer shell on particle morphology was studied by Optical microscope and Scanning electron microscope. The chemical structures of the obtained polymer microcapsule were characterized by Fourier-transform infrared spectroscopy and Nuclear magnetic resonance spectroscopy. The thermal properties and content of encapsulated RT27 were measured by Differential scanning calorimetry and Thermogravimetric analysis. Phase separation was clearly observed after droplet generation with methyl methacrylate, ethylene glycol dimethacrylate, and polyethylene glycol diacrylate as comonomers. After polymerization, broken particles were obtained. In contrast, a spherical microcapsule with a smooth surface was obtained with copolymerization between GPLLA and glycidyl methacrylate. In addition, high encapsulation efficiency (96 %) was obtained. The latent heats of encapsulated RT27 in the term of J/g-RT27 were 202 and 200 J/g-RT27 for the heat of melting and crystallization, respectively, which were close to those of the pristine RT27. Moreover, a supercooling phenomenon was not observed.