Ring-opening copolymerization of CHO and MA catalyzed by mononuclear [Zn(L2)(H2O)] or trinuclear [Zn3(L2)2(OAc)2] complex based on the asymmetrical bis-Schiff-base ligand precursor

• Published in: Journal of molecular catalysis. A, Chemical Chemical, 2014-02, Vol.382, p.136-145
• Main Authors: Liu, Deng-Feng, Wu, Li-Ying, Feng, Wei-Xu, Zhang, Xing-Mei, Wu, Jing, Zhu, Lu-Qun, Fan, Dai-Di, Lü, Xing-Qiang, Shi, Qi
• Format: Article
• Language: English
• Subjects: Applied sciences; Catalysis; Chemistry; Copolymerization; Exact sciences and technology; General and physical chemistry; Mononuclear or trinuclear Zn2+ complex based on asymmetrical bis-Schiff-base ligand precursor; Organic polymers; Physicochemistry of polymers; Polyester and poly(ester-co-ether); Preparation, kinetics, thermodynamics, mechanism and catalysts; Ring-opening copolymerization from CHO and MA; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry
• ISSN: 1381-1169; 1873-314X
• DOI: 10.1016/j.molcata.2013.11.002

•Mononuclear or trinuclear Zn2+-containing catalysts based on asymmetrical bis-Schiff-base precursor.•Polyester or poly(ester-co-ether) polymers from CHO and MA.•Effect of coordination environments of metal active species on catalytic behaviors. Based on the half-unit Schiff-base ligand precursor HL1 and the asymmetrical bis-Schiff-base ligand precursor H2L2 synthesized from the reaction of 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone (PMBP), o-phenylenediamine and/or o-vanillin, three complexes containing low toxicity Zn2+ ions, mononuclear [Zn(L1)2] (1), [Zn(L2)(H2O)] (2) and trinuclear [Zn3(L2)2(OAc)2] (3), are obtained, respectively. Complex 1 proves to be inactive, resulting from its saturated octahedral coordination environment around the central Zn2+ ion, while in complex 2 or 3, the unsaturated five and/or four-coordinate coordination environment for the catalytic active centers (Zn2+ ions) permits the monomer insertion for the effective bulk or solution copolymerization of CHO (cyclohexene oxide) and MA (maleic anhydride). All the bulk copolymerizations afford poly(ester-co-ether)s, while some of the solution copolymerizations produce perfectly alternating polyester copolymers. Moreover, higher polymerization temperature, lower catalyst and co-catalyst concentration and shorter reaction time are helpful for the formation of alternating copolymers in bulk or solution copolymerization. Of the three co-catalysts, DMAP (4-(dimethylamino)pyridine) is found to be the most efficient, while an excess thereof is detrimental for chain growth of the copolymers.