Polymerizations of Nitrophenylsulfonyl-Activated Aziridines

Abstract

1-((p-Nitrophenyl)sulfonyl)aziridine (pNsAz) and 1-((o-nitrophenyl)sulfonyl)aziridine (oNsAz) were synthesized, and their polymerization chemistry was studied. Upon heating, pNsAz formed an insoluble white powder. In contrast, poly(oNsAz) is soluble in DMF and DMSO. Attempts were made to convert poly(oNsAz) to linear poly(ethylenimine) (lPEI) through removal of the o-nosyl group using sodium thiomethoxide. Although some evidence for the formation of lPEI was found, formation of pure lPEI was not possible. oNsAz is susceptible to spontaneous polymerization when stored neat or in a polar solvent (e.g., DMSO and DMF). Poly(oNsAz), formed from the spontaneous polymerization of oNsAz, was analyzed by MALDI-TOF mass spectrometry and composed of signals consistent with either OH or H2O acting as initiators for an anionic polymerization. Experiments studying the kinetics of oNsAz showed that the rate of polymerization was first order with respect to monomer concentration. It was also possible to initiate the anionic polymerization of oNsAz using BnN(Li)Ms. At low oNsAz:BnN(Li)Ms ratios, some control over molecular weight was achieved; however, at higher ratios, control was no longer possible, likely due to the presence of protic impurities that contaminate the monomer. Chain extension and propargyl chloride termination experiments were also performed with BnN(Li)Ms initiated polymerization of oNsAz.