Long‐Chain Branched Poly(Lactide)s Based on Polycondensation of AB 2 ‐type Macromonomers

A series of long‐chain branched poly( d‐/l ‐lactide)s is synthesized in a two‐step protocol by (1) ring‐opening polymerization of lactide and (2) subsequent condensation of the preformed AB 2 macromonomers promoted by different coupling reagents. The linear AB 2 macromonomers are prepared by Sn(Oct) 2 ‐catalyzed ROP of D ‐ and L ‐lactide with 2,2‐bis(hydroxymethyl)butyric acid (BHB) as an initiator. Optimization of the polymerization conditions allows for the preparation of well‐defined macromonomers ( M w / M n = 1.09–1.30) with adjustable molecular weights (760–7200 g mol −1 ). The two‐step approach of the synthesis comprises as well the coupling of these AB 2 macromonomers and hence allows precise control over the lactide chain length between the branching units in contrast to a random polycondensation.