Abstract:

In this paper， PVA/starch composite membranes were grafted with dimethylaminoethyl methacrylate （DMAEMA） as a modifier. The composite membranes were endowed with a selective transmission function of CO₂ gas through introducing tertiary amine groups. The CO₂ transmission volume was optimized through exploring the relationship between the molecular structure and performance. Based on the characterization results from infrared spectroscopy， X⁃ray photoelectron spectroscopy （XPS）， atomic force microscopy， and permeability tests， the composites exhibited selective permeability to CO₂ after grafting DMAEMA into starch. The CO₂ transmittance of the DMAEMA⁃grafted starch increased by 28.03 times from 1.577 to 45.786 cm³/（m²∙24 h∙0.1 MPa） at a graft rate of 55.3 wt% and a copolymer amount of 1.5 wt%. The XPS results indicated a decrease in binding energy at 399.8 eV in N1s spectrum and an increase in binding energy at 401.8 eV after CO₂ permeates the composite membranes. CO₂ can react with tertiary amine groups on the composite membranes to realize an internal transfer. Therefore， the surface roughness of the composite membranes increased， and there was a transition from the curled state to the extended state for the molecular chains on the membrane surface， resulting in an increase in the contact with CO₂.

Key words: poly（vinyl alcohol）, corn starch, modified membrane, grafting, carbon dioxide membrane, mechanism