Cobalt (II) complex catalyzed polymerization of lactide and coupling of CO 2 and styrene oxide into cyclic styrene carbo
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Ó Indian Academy of Sciences Sadhana (0123456789().,-volV)FT3](0123456 789().,-volV)
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Cobalt (II) complex catalyzed polymerization of lactide and coupling of CO2 and styrene oxide into cyclic styrene carbonate HARISH CHANDRA PRADHANa, SOMANATH MANTRIb, ANITA ROUTARAYb, TUNGABIDYA MAHARANAa and ALEKHA KUMAR SUTARb,* a Department
of Chemistry, National Institute of Technology, Raipur 492010, Chhattisgarh, India Research Lab, Department of Chemistry, Ravenshaw University, Cuttack 753 003, Odisha, India E-mail: [email protected]; [email protected] b Catalysis
MS received 23 June 2019; revised 1 October 2019; accepted 1 October 2019
Abstract. In the present study, the cobalt (II) complex [Co-HMBED] has been prepared and characterized by spectrochemical techniques, which confirmed its square planar structure. The catalytic activity of the cobalt complex was evaluated towards solvent-free conversion of CO2 and styrene oxide into cyclic styrene carbonate and polymerization of lactide. Keywords. CO2; Styrene oxide; cyclic carbonate; PLA; Schiff base; Cobalt complex.
1. Introduction Since the early 21st century, modern researchers are searching for bio-renewable resources for the biodegradable, biocompatible and bioassimilable material. Poly(lactic acid)(PLA) is such a polymer,1–3 on degradation it produces environmentally assimilable compounds such as H2O and CO2.4–7 PLA is used in biomedical application.8,9 And also, CO2 is an easily available, economical, nonflammable and non-hazardous renewable carbon resource, available as an attractive raw material for the production of cyclic carbonate.10 These cyclic carbonates have extensive application as electrolytes,11 aprotic solvents,12 synthesis of polycarbonates,13 pharmaceutical intermediate,14 synthesis of urea derivative,15 biodegradable materials,16 etc. An ideal industrial process should employ non-cytotoxic metals, as complete removal of metal never happens. Therefore, metals having no negative effects on living beings must be taken into consideration. However, although different transition metal complexes were used for the synthesis of PLA17–19 and cyclic carbonates.20–26 Nowadays, cobalt complexes with moderate lewis acidity property have given emphasis for in-depth investigation. Furthermore, FDA has approved the CO2 - based polymer such as poly (styrene carbonate), which is
formed from the raw material cyclic styrene carbonate and production of PLA. Presently, we are engaged in synthesizing Schiff base copper complexes,27,28 and nickel complexes29,30 which efficiently catalyzed the polymerization of lactide. Very few literatures say about the activity of cobalt metal catalysts for lactide polymerization and cyclic carbonate formation. Thus, the present paper reports the catalytic activity of cobalt complexes of HMBED (N,N0 -bis (hydroxymethoxybenzaldehyde) ethylenediamine) towards ROP of Llactide and solventless conversion of CO2 and styrene oxide into cyclic styrene carbonate. Finally, based on experimental results, a proposed mechan
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