Ring-opening copolymerization of maleic anhydride or L-Lactide with tert-butyl glycidyl ether by using efficient Ti and Zr benzoxazole-substituted 8-Hydroxyquinolinate catalysts

- Effective catalysts for nearly alternative co-polymers of MA with tBGE and block like copolymers of L-LA with tBGE.
- Understanding the role of ligand substituents towards ROCOP.
- Thorough characterization of co-polymers using NMR methods, GPC, MALDI-TOF, TGA, DSC, SEM and AFM.

Ring-opening polymerization (ROP) of maleic anhydride (MA) or L-Lactide (L-LA) with tert-butyl glycidyl ether (tBGE) were carried out in the presence of Ti and Zr complexes of benzoxazole substituted 8-hydroxyquinoline ligands (1a-3a and 1b-3b), delivering nearly alternative P(tBGE-co-MA) and block-like P(tBGE)-b-PLLA co-polymers with high molecular weight (Mn) and narrow to broad molecular weight distributions (Mw/Mn). The molecular structures of the Ti and Zr complexes (1a and 3b) were confirmed by single-crystal X-ray diffraction analysis. The Zr complex 3b exhibited superior reactivity and produced copolymers within one hour at 80 °C in dry toluene (Mn,GPC = 14-40 Kg mol-1 and Mw/Mn = 1.19-1.55). In case of P(tBGE-co-MA) copolymer synthesis, the polymer arm with tBGE fraction was building faster (82-100 unit%) compared to MA (52-99 unit%). In contrast, incorporation of L-LA was higher (82-99 unit%) compared to tBGE insertion (20-60 unit%) in P(tBGE)-b-PLLA copolymer synthesis.

Polyesters such as nearly alternative poly(tBGE-co-MA) and block-like P(tBGE)-b-PLLA of varied compositions of the monomers were prepared by using benzoxazole-substituted 8-hydroxyquinoline based Ti and Zr complexes as catalysts. The best catalytic activity was observed by using complex 3b, which efficiently catalyse MA or L-LA with tBGE with high molecular weight (Mn > 40 000 g mol-1) and high ester linkage content (>98%).250