Synthesis of Cyclic Poly(methyl methacrylate) Directly from Dihalogenated Linear Precursors

摘要: Cyclic poly(methyl methacrylate) (PMMA) is prepared by intramolecular radical trap-assisted atom transfer coupling (RTA-ATRC) of dihalogenated PMMA precursors. The inclusion the trap nitrosobenzene (NBz) in sequence affords high yields cyclic polymers, as observed gel permeation chromatography and confi rmed 1 H NMR electrospray ionization mass spectra, which show presence aromatic group from NBz incorporated into cycle. Analogous reactions absence do not lead to appreciable cyclization or even intermolecular elongation, consistent with chain-end sterics preventing radical–radical predominant termination pathway. Thermolysis PMMA, possible because labile C O bond alkoxyamine linkage contained macrocycle, causes a reversion back linear form role sequence. Differential scanning calorimetry also used compare its analog, marked increase glass transition temperatures found after cyclization.