From CO₂-based multifunctional polycarbonates with a controlled number of functional groups to graft polymers

Copolymerization of CO₂ and epoxides is employed to generate functional polycarbonates. The introduction of reactive double bonds at a poly(propylene carbonate) (PPC) backbone is realized by the copolymerization of aliphatic alkene epoxides with propylene oxide (PO) and carbon dioxide (CO ₂). A series of copolymers with random structure and varying comonomer content (3-22%) with molecular weights in the range of 22 000-34 000 g mol^-1 is synthesized and characterized with respect to their microstructure and thermal properties. The facile transformation of the double bonds is verified by a thiol-ene reaction, resulting in quantitative conversion of the double bonds. Polycarbonate derivatives with multiple functionalities are prepared, providing suitable moieties for further grafting. Functional aliphatic polycarbonates with tailored functionality are prepared directly from CO₂ and epoxyalkenes. The facile transformation of the double bonds is verified by a thiol-ene reaction, resulting in quantitative conversion of the double bonds. The functional polycarbonates possess M_n between 22 000 and 34 000 g mol^-1 (M_w/M_n = 1.17-1.38) and their multiple functionalities provide suitable moieties for further grafting.