Preparation of switchable polymer latexes under elevated CO2 pressure by using 4,4'-(diazene-1,2-diyl) bis(N-(3-(dimethylamino)propyl)-4-methylpentanamide) as a novel CO2-switchable inistab

Abstract

Switchable polystyrene (PS) latexes were prepared by using newly synthesized CO2-responsive inistab (initiator + colloidal stabilizer), 4,4'-(diazene-1,2-diyl) bis(N-(3-(dimethylamino)propyl)-4-methylpentanamide) (DABPA) through surfactant-free emulsion polymerization (SFEP) under elevated CO2 pressure. The synthesized latexes can be easily aggregated by adding NaOH or N2 and heat, and readily redispersed by introducing CO2 with 10 min of sonication. The redispersed latexes had almost similar zeta potential, particle size and polydispersity (PDI) as the original latexes. The influence of elevated CO2 pressure along with adding CO2-switchable comonomer, 2-(diethyl)amino ethyl methacrylate (DEAEMA) on the stability and solid content of PS latexes were studied. The results showed that by increasing CO2 pressure up to 60 bar, solid content of latex could be enhanced to 30% by employing 0.25 mol% (with respect to the styrene monomer) of inistab, DABPA and 0.54 mol% of DEAEMA. The obtained polymer particles, ranging in diameter from 230 to 525 nm, are spherical as established by SEM and DLS. This method of using inistab at elevated CO2 pressure yields relatively high solid content and less amount of required stabilizer during the emulsion polymerization.