Azidation of polyesters having pendent functionalities by using NaN3 or DPPA–DBU and photo-crosslinking of the azidopolyesters

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In this article, we performed dehydration polycondensation of bromosuccinic acid and methylsuccinic acid with 1,4-butanediol at 80 °C to synthesize aliphatic polyesters containing pendent bromo groups without dehydrobromination using scandium trifluoromethanesulfonate (Sc(OTf)3) as the catalyst. Azidation of the resultant polyesters was carried out readily in N,N-dimethylformamide at room temperature using sodium azide (Mn=8.3 × 103 (Mw/Mn=2.17)). 1H nuclear magnetic resonance analysis of the product revealed that 65% contained azide functionality, and dehydrobromination occurred in 35% during the azidation process. On the other hand, azidation of poly(butylene bromoadipate-co-butylene methylsuccinate) (poly(BBA-co-BMS)) proceeded successfully under the same conditions to generate poly(butylene azidoadipate-co-butylene methylsuccinate) (poly(BAA-co-BMS)) without dehydrobromination (Mn=10.4 × 103 (Mw/Mn=2.71)). We successfully photo-crosslinked the resultant azidopolyester by ultraviolet irradiation and examined it using scanning electron microscope. We also described azidation of polyesters having pendent hydroxyl groups by using the ‘DPPA (diphenylphosphoryl azide)–DBU (1,8-diazabicyclo[5.4.0]undec-7-ene) substitution strategy’ to produce water-soluble polyesters containing pendent azido groups (Mn=7.5 × 103 (Mw/Mn=2.25)). These azidopolyesters might be extremely useful not only for their derivatization by simple chemical modification but also for their effective utilization as photolithography material. Dehydration polycondensation of bromoadipic acid and methylsuccinic acid with 1,4-butanediol was performed at 80 °C to synthesize aliphatic polyesters containing pendent bromo groups without dehydrobromination using scandium trifluoromethanesulfonate as the catalyst. Azidation of poly(butylene bromoadipate-co-butylene methylsuccinate) also proceeded to generate poly(butylene azidoadipate-co-butylene methylsuccinate) (Mn=10.4 × 103). We successively photo-crosslinked the resultant azidopolyesters by UV irradiation. We also described azidation of polyesters having pendent hydroxyl groups by using the ‘diphenylphosphoryl azide-1,8-diazabicyclo[5.4.0]undec-7-ene substitution strategy’ to produce water-soluble polyesters containing pendent azido groups (Mn=7.5 × 103).