Influence of Poly(L-lactic acid) Molecular Weight on the Encapsulation Efficiency of Urea in Microcapsule Using a Simple Solvent Evaporation Technique

Poly(L-lactic acid) microencapsulated urea was prepared in water-in-oil-in-water (W₁/O/W₂) system by the solvent evaporation technique. The influence of poly(L-lactic acid) molecular weight on the percent loading, encapsulation efficiency, and the microcapsule morphology was studied using poly(L-lactic acid) having different number average molecular weights (M_n). Using the higher M_n, the smoother shell with complete encapsulation microcapsules was formed. Moreover, the percent loading and encapsulation efficiency of urea also increased with the poly(L-lactic acid) molecular weight. At 80,000 g/mol of poly(L-lactic acid), the obtained microcapsule gave the highest both percent loading (32%) and encapsulation efficiency (56%). The urea control release study of the prepared microcapsules was implemented by in vitro testing. The encapsulated urea was gradually released from the microcapsules, approximately 53, 29, and 22% of poly(L-lactic acid) at 3,000, 30,000, and 80,000 g/mol, respectively, for a month. These results presented the possibility of the prepared poly(L-lactic acid) microcapsules-encapsulated urea for urea control release that could be utilized in agricultural applications.