The Brønsted acid, trifluoromethanesulfonimide (HNTf2), was revealed to act as a highly efficient activator for group transfer polymerization (GTP) of methyl methacrylate (MMA) at ambient temperature. The HNTf2-catalyzed GTP of MMA initiated by 1-methoxy-1-trimethylsilyloxy-2-methyl-propene (MTS) proceeded in a living manner to produce poly(methyl methacrylate)s (PMMA) with controlled molecular weights and narrow molecular weight distributions. Kinetic measurement and postpolymerization experiment further supported that the polymerization proceeded in a living fashion. Furthermore, from the MALDI-TOF MS analysis, only one series of peaks was observed, which was in perfect agreement with the molecular weight of PMMA possessing the MTS initiator residue and the desilylated chain end, showing that the HNTf2-catalyzed GTP of MMA proceeded without any side reactions. The syndiotacticity of the PMMA obtained by the HNTf2-catalyzed GTP increased with the decreasing polymerization temperature; the syndiotactic (rr) triad content was 72% at 27 °C and 90% at −55 °C.
The polymerization of δ-valerolactone (δ-VL) using 3-phenyl-1-propanol (3-Ph-PrOH) as the initiator and trifluoromethanesulfonimide (HNTf 2 ) as the catalyst in CH 2 Cl 2 at 27 °C with the [δ-VL] 0 /[3-Ph-PrOH] 0 /[HNTf 2 ] 0 ratio of 100:1:0.1 proceeded homogeneously to afford a poly(δ-valerolactone) (PVL) with a narrow polydispersity index. The molecular weight determined from the 1 H NMR analysis, M n = 9600 g mol -1 , fairly agreed with that estimated from the initial ratio of [δ-VL] 0 /[3-Ph-PrOH] 0 , M n,theo = 9400 g mol -1 . In addition, the kinetic and chain extension experiments confirmed that the HNTf 2 -catalyzed ROP proceeded in a living fashion. The 1 H NMR, SEC, and MALDI-TOF MS measurements of the obtained PVL clearly indicated the presence of the initiator residue at the chain end, showing that the HNTf 2 -catalyzed ROP of δ-VL proceeded through a living mechanism. The HNTf 2 -catalyzed ROP of δ-VL with functional initiators, such as 6-azido-1-hexanol, 2,3,4,5,6-pentafluorobenzyl alcohol, and N-(2-hydroxyethyl)maleimide, successfully afforded the corresponding end-functionalized PVL with a precise molecular control.
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