Characterization of poly( D , L ‐lactic acid) synthesized by direct melt polymerization and its application in Chinese traditional medicine compound prescription microspheres

From D , L ‐lactic acid and with 0.5 wt % stannous chloride (SnCl 2 ) as a catalyst under an absolute pressure of 70 Pa and at 165–170°C, poly( D , L ‐lactic acid) (PDLLA) with an intrinsic viscosity of 0.2302 dL/g was synthesized after 10 h of melt polycondensation. This directly produced PDLLA was systematically characterized with gel permeation chromatography, Fourier transform infrared, 1 H‐NMR, differential scanning calorimetry, and X‐ray diffraction. The weight‐average molecular weight of PDLLA was 17,800 Da, and the weight‐average molecular weight/number‐average molecular weight ratio was 1.25. It was partly crystalline, and its crystallinity was 20.8%. When first applied to the Chinese traditional medicine compound prescription Osteitis no. 1 PDLLA microsphere (G‐PDLLA‐MS), the optimal conditions for the extraction of the effective components in three raw herbs ( Herba epimedii , Fructus psorakae , and Angelicae ) and for the preparation of G‐PDLLA‐MS were determined with orthogonal testing. After the extractant was obtained by ethanol reflux, G‐PDLLA‐MS was prepared with a gelatin concentration of 8%, an inner water phase/oil phase volume ratio of 1.5:1, a stirring rate of dispersion of 1000 rpm, and a PDLLA concentration of 20%. Differential scanning calorimetry and scanning electron microscopy proved that G‐PDLLA‐MS had a good spherical shape. The practical average particle size of G‐PDLLA‐MS was 8.59 μm, and the particle sum between 2 and 12 μm was greater than 92%; this meets the requirement for an arthritis cure. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 195–200, 2005