Zinc (II) metal ion complexes of Chitosan: Toward heterogeneous-active catalysts for the polymerization of vinyl acetate

Abstract

A low cost biopolymeric ligand (Chitosan) was used as a stabilizer to synthesize Zinc(II)-chitosan biopolymer (Zn(II)-Chit). The Zn(II)-Chit was prepared by  adding ZnSO to chitosan in acetic acid solution under an inert 4 atmosphere. The Zn(II)-Chit was further used to polymerize vinyl acetate (VAc) in an aqueous  sodium sulphite (Na SO⁴ ). Both the Chitosan and Zn(II)-Chit synthesized were characterized using FT-IR spectroscopy and UV-  visible spectroscopy. The  hydrated Polyvinyl acetate (PVAc) obtained was also characterized using FT-IR spectroscopy. The UV-visible spectrum of chitosan revealed no peak in the range  300 – 800 nm while Zn(II)- Chit showed an absorption band at 360 nm attributed to metal to ligand charge transfer. The FT-IR analyses revealed the presence of  coordinating –NH and –OH functional groups in chitosan, both –NH and –OH   stretching vibrations overlap at around 3441 cm³ . The FT-IR spectrum of the  Zn(II)-Chit indicates coordination of Zn³⁺ with the -NH₂, -OH and >C=O of the N-acetyl group in chitosan. The Application of Zn(II)-Chit for the polymerization of  VAc yielded PVAc in good yield. The catalyst efficiency of Zn(II)-Chit for the polymerization of VAc was considerably high in terms of induction period and  percentage yield of PVAc.

Keywords: Chitosan, Zn(II)-Chitosan Complex, Catalyst, Polymerization, Polyvinyl Acetate