Near neutral waterborne cationic polyurethane from CO2-polyol, a compatible binder to aqueous conducting polyaniline for eco-friendly anti-corrosion purposes†
This work focuses on two meaningful points in green chemistry, one is providing a practical solution for CO2 transformation into a CO2 copolymer, and the other is disclosing the potential application of a CO2 copolymer as a water dispersible binder to overcome the bottleneck in heavy metal free anti-corrosion coatings. For the first point, a CO2-copolymer like CO2-polyol is synthesized from the telomerization of CO2 and propylene oxide using a zinc–cobalt double metal cyanide complex as a catalyst and terephthalic acid as a chain transfer agent. For the second point, for the past 30 years conducting polyaniline, with its unique anti-corrosion behaviour, has been regarded as a heavy metal free anti-corrosion material, but the development of a waterborne polyaniline anti-corrosion coating has encountered an impasse owing to the lack of a compatible binder. Therefore, a water borne cationic polyurethane dispersion (CPUD) was developed for this purpose, in which CO2-polyol was used as a soft segment, and 1,4-butanediol di(3-diethylamino-2-hydroxypropyl alcohol) ether was synthesized as a side-chain cationic extender. Unlike earlier acidic water borne dispersions, this water borne CPUD was near neutral, ensuring good compatibility with an aqueous conducting polyaniline dispersion, and is expected to create significant possibilities for the development of a novel generation of sustainable and eco-friendly metal anti-corrosion materials.