Modification of polybutadiene with trifluoromethyl and clickable azide groups in one shot

Abstract

Development of facile synthetic routes to endow polybutadiene (PB) with desirable and/or enhanced properties has attracted growing attention owing to the broad application spectrum of PB. Herein, we report an efficient approach to introduce both trifluoromethyl (–CF₃) and azide (–N₃) groups into PB in a one-shot procedure via copper-catalyzed azide-trifluoromethylation of the alkenyls of PB using Cu(CH₃CN)₄PF₆ as the catalyst and commercially available Togni's reagent and TMSN₃ as –CF₃ and –N₃ sources, respectively, without chain cross-linking or chain degradation. The contents of –CF₃ and –N₃ in PB increase with the increasing feed ratio of –CF₃ and –N₃ sources to the alkenyl of PB. After the modification, the glass transition temperatures (T_g) of the resulting PBs increase from about −31.4 °C to 35.7 °C accompanied by a decrease of the thermal stability from ∼343.8 °C to ∼249.6 °C (5% weight loss temperature). The films of the resulting modified PBs exhibit more hydrophobic surfaces than pristine PB and the water contact angles increase with increasing –CF₃ content. By taking advantage of the introduced azide groups as reactive anchoring sites, additional functionalities, including fluorescent pyrenes, perfluoroalkyls and short PEG chains, can be efficiently attached onto PB chains via copper-catalyzed alkyne-azide cycloaddition (CuAAC). In this way, the properties, such as thermal stability, photophysical properties and wetting behavior, of PB can be easily tuned.