Polymer modification by nitroxyl-mediated radical chemistry

In this work, model compounds are utilized for the development of conditions to label “living” polystyrene chains as well as for the assessment of the potential for controlled radical grafting (CRG) methods for modification of polyethylene and polybutadiene.; A fluorescence method was developed and validated for the measurement of the concentration of nitroxyl-terminated chains in polystyrene samples prepared by controlled free radical polymerization. Extension of model compound studies allowed for the quantitative exchange of TEMPO with a naphthoyloxy derivative to fluoresence-label those alkoxyamine-terminated polymer chains capable of further styrene addition. The efficacy of applying nitroxyl-mediated polymerization chemistry for the graft modification of polyethylene and polybutadiene models was also examined. Screening of potential candidates was performed by monitoring the thermolysis of model alkoxyamines. Model compounds with a high rate of homolytic cleavage versus disproportionation were selected as candidates for CRG of maleic anhydride.; While TIPNO-heptane was considered to be the best candidate for the CRG of maleic anhydride onto saturated models, heating TIPNO-heptane in the presence of maleic anhydride showed no observable grafting.; Both TEMPO-heptene and TIPNO-heptene were considered to be the best candidates for the CRG of maleic anhydride onto unsaturated model compounds. Subsequent heating of these models in the presence of maleic anhydride gave an unsaturated maleic anhydride-graft-heptene product. No evidence of the nitroxyl-capped succinyl radical was found, indicating that this compound is unstable under the reaction conditions studied.