Amphiphilic ABA Triblock Copolymers Via Combination Of ROMP And ATRP In Ionic Liquid: Synthesis, Characterization, And Self-assembly

The bromo-terminated chain transfer agent (CTA) and monomer of functionalized norbornene with the pendant of oligoethyleneoxy group were synthesized. The characterization of the synthesized compounds was carried out by NMR and elemental analysis.Ring-opening metathesis polymerization (ROMP) with functionalized CTA for the preparation of telechelic polymers has the ability to control the polymer molecular weights through the ratio of monomer to CTA ([M]/[CTA]). The bromo-terminated macroinitiator was prepared via ROMP of norbornene derivative, in conjunction with a CTA in [bmim][BF₄] and in organic solvent. The obtained polymer was characterized via ¹H NMR spectroscopy. The alkene proton signals of the norbornene ring appeared approximately at 6.24ppm. Upon ring-opening and subsequent polymerization, these proton signals shifted upfield to approximately 5.64-5.16ppm, this indicated the polymerization had occurred. The resonances of methylene protons adjacent to the ester bond (CH=CHCH₂OCO) shift from 4.82ppm in the CTA to 4.56ppm in the polymer. These characteristic ¹H NMR resonances indicate that the CTA have been incorporated into the polymer chain. Furthermore, other types of end-groups were observed in their expected regions of the ¹H NMR spectroscopy. Thus, the polymer should be a difunctionalized telechelic macroinitiator with a high degree of bromine end functionalization.ROMP with CTA in [bmim][BF4] exhibited a different performance compared to that in CHCl_, and there has been a better control over polymerization process in [bmim][BF₄] than that in CHCl₃.Based on the telechelic macroinitiator, the amphiphilic ABA triblock copolymer was synthesized by atom transfer radical polymerization (ATRP) in [bmim][BF₄]. The prepared PDMAEMA-PNBEDE-PDMAEMA triblock copolymer can self-assemble spontaneously in H₂O to form polymeric micelles, which was characterized by a DLS, AFM, and TEM.