We previously explored a series of CO2 adducts from alkylated polyethylenimines with C4 to C16 alkyl side chains, serving as climate‐friendly blowing agents for polyurethanes (PUs). Among them, the polyethylenimine with C8 alkyl (2‐ethylhexyl) side chains demonstrated the highest foaming efficiency. In this study, we further changed the grafting rate of the C8 alkyl, from 7 to 16%, and investigated the effects of the resulting blowing agents on the foaming process. For both foaming systems containing a castor oil‐derived polyol (Polycin T‐400) or a poly(propylene glycol) polyol (Polyether 4110), the CO2 adducts with a grafting rate of 13% displayed the best foaming performance in terms of high dispersibility in the foaming systems, homogenous cellular morphology, and good mechanical properties. Moreover, the 13%‐C8‐alkylated blowing agent demonstrated high suitability for the foaming systems from biomass‐sourced polyols (like Polycin T‐400). Therefore, the optimized CO2‐adduct blowing agent could replace the currently used climate‐changing hydrochlorofluorocarbons and hydrofluorocarbons, as well as might contribute to the development of future renewable PU foams. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48752.

Based on previous endeavors on antimicrobial polyurethane (PU) foams and CO2‐releasing environment‐friendly blowing agents, we explored a series of modified polyethylenimine (PEI)–CO2 adducts, serving as both blowing and antimicrobial agents for PUs. For this purpose, a quaternary ammonium chain with a C12 alkyl (C12+), either alone or together with neutral (C8 and C12) alkyls, was grafted onto branched PEI (Mn = 25,000 Da) backbones prior to saturation with CO2. The resultant four CO2 adducts, 5C12+5C8‐, 5C12+5C12‐, 10C12+‐ and 15C12+‐PEI‐CO2 (where the number indicates grafting rate in percentage of each side chain), all can well disperse into PU foaming mixtures, generating flexible PU foams with antimicrobial activity. 15C12+‐PEI‐CO2 displays the best dispersibility and highest foaming efficiency, while 10C12+‐PEI‐CO2 is the most antimicrobial toward both Gram positive and negative bacteria. The relatively high grafting rate in 15C12+‐PEI‐CO2 drives the formation of micelle‐like particles in the foaming system; the outermost hydrophobic chains can somewhat prevent the internal quaternary ammoniums from accessing to the negatively charged cell membrane of bacteria, causing a reduction in antimicrobial efficacy compared with that of 10C12+‐PEI‐CO2. The developed PEI–CO2 adducts might replace the traditional ozone depletion and/or global warming blowing agents, and would show prolonged antimicrobial activity over rapidly leachable small molecule antimicrobial agents.