Synthesis of syndiotactic-rich star-shaped poly(methyl methacrylate) by core-first group transfer polymerization using N-(trimethylsilyl) bis(trifluoromethanesulfonyl)imide

摘要

The N-(trimethylsilyl)bis(trifluoromethanesulfonyl)imide-catalyzed (Me 3SiNTf 2-catalyzed) group transfer polymerization (GTP) of methyl methacrylate (MMA) has been studied for synthesizing stereospecific star-shaped poly(methyl methacrylate)s (PMMAs). The catalytic property of Me _3SiNTf _2 for the GTP of MMA using 1-methoxy-1- trimethylsilyloxy-2-methyl-propene as the initiator was confirmed by a kinetic investigation and matrix-assisted laser desorption ionization time-of-flight mass spectrometry measurement. The initiating efficiency (f) of Me _3SiNTf _2 was 0.94-1.00, which was estimated by the value of M _(n(calcd))/M _(n(SEC)). The Me _3SiNTf _2-catalyzed GTP of MMA was carried out using initiators possessing three, four, and six MTS groups (MTS _3, MTS _4, and MTS _6, respectively) under the condition of [MMA] _0/[MTS _3, MTS _4, or MTS _6] _0 = 120 at -55 °C. All the obtained PMMAs exhibited unimodal and narrow molecular weight distributions as M _w/M _ns = 1.03-1.04 and the M _(w(MALS))s of the 3-, 4-, and 6-armed star-shaped PMMAs (PMMA _3, PMMA _4, and PMMA _6, respectively) were 12.9, 12.9, and 13.4 kgmol ~(-1), respectively, which fairly agreed with the calculated M _(w(calcd)) values. The syndiotacticities, rrs, of PMMA _3, PMMA _4, and PMMA _6 were in the range of 87-89%. The stereoblock synthesis of PMMA _3, PMMA _4, and PMMA _6 was performed by the first and second polymerizations at -55 and 45 °C; the rrs of the first and second PMMA blocks were 87.0, 87.0, and 86.0% and 65.0, 65.0, and 64.0%, respectively. The glass transition temperatures (T _gs) were 118.1, 115.8, and 111.5 °C for the respective syndiotactic-rich PMMA _3, PMMA _4, and PMMA _6 and 111.5, 109.7, and 107.6 °C for the respective stereoblock ones.