Effects of different feed molar ratio on poly(D, L-lactic acid) modified by cholic acid

Using functional molecule cholic acid (CA) as starting material, poly(D, L-Lactic acid) (PDLLA) was modified via direct melt copolycondensation. The copolymer poly(D, L-lactide-cholate) was systematically characterized with intrinsic viscosity [η], FT-IR, 1H-NMR, DSC and GPC. The effects of feed molar ratio were discussed in detail. With the decrease of feed molar ratio of CA to lactic acid (LA), the number of CA unit as the core embedded in the copolymer reduced. When the feed molar ratio of CA to LA was 1:15, the copolymer embedded 4 CA units, and its weight average molecular weight (Mw) was maximal (Mw=12700, Mww/Mnn=1.68). When just one CA unit core was embedded in the star-shaped copolymer, certain crystallinity was detected.