Copolymers incorporated with \u03b2-substituted acrylate synthesized by organo-catalyzed group-transfer polymerization

Motosuke Imada,Hideki Abe,Takeharu Tsuge,Yasumasa Takenaka

doi:10.1038/s41428-021-00493-z

Abstract

Various copolymers incorporated with β-substituted acrylates, such as alkyl crotonates (e.g., methyl crotonate (MC), ethyl crotonate (EC), isopropyl crotonate (iPC), and n-butyl crotonate (nBC)) and methyl cinnamate (MCin), were synthesized by group-transfer polymerization (GTP) using a silicon-based Lewis acid catalyst. In addition to β-substituted acrylates, α-substituted acrylates (e.g., methyl methacrylate (MMA) and n-butyl methacrylate (nBMA)) were examined as comonomers. Proton nuclear magnetic resonance (1H NMR) spectroscopy and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) characterizations of the obtained copolymers revealed that each monomer component was incorporated sufficiently. The thermal stabilities of the resulting copolymers were investigated by dynamic mechanical analysis (DMA), indicating that the glass-transition temperature (Tg) of the copolymers can be widely varied over a relatively high-temperature range by selecting the optimal comonomer. More specifically, the Tg values of poly(MC-random-EC) (MC/EC molar ratio = 50/50), poly(MC-random-nBC) (MC/nBC molar ratio = 50/50), poly(MC-random-MCin) (MC/MCin molar ratio = 54/46), and poly(nBC-random-MCin) (nBC/MCin molar ratio = 56/44) were 173, 130, 216, and 167 °C, respectively.

Highlights

Group-transfer polymerization (GTP) was developed as a controlled living-polymerization method ofacrylates by Webster et al in the 1980s [1]
The preparation of a series of copolymers incorporating two types of β-substituted acrylates (M1 and M2) selected from the methyl crotonate (MC), ethyl crotonate (EC), isopropyl crotonate (iPC), n-butyl crotonate (nBC), and methyl cinnamate (MCin) groups was attempted by GTP using Tf2NSitBuMe2 (generated via the in situ reaction between tBuMe2SKA and Tf2NH (Scheme S1, Supporting Information)) as the catalyst and tBuMe2SKA as the initiator in CH2Cl2 at 0 °C at a molar feed ratio of M1: M2 = 1:1
We reported the preparation of various copolymers incorporated with β-substituted acrylates, such as alkyl crotonates (MC, EC, iPC, and nBC), and MCin, via the GTP process using a silicon-based Lewis acid catalyst and silyl ketene acetals (SKAs) possessing a relatively bulky silyl moiety, such as the tert-butyldimethylsilyl group

Summary

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Group-transfer polymerization (GTP) was developed as a controlled living-polymerization method of (meth)acrylates by Webster et al in the 1980s [1]. MC, EC, iPC, nBC, MCin, MMA, nBMA, methyl isobutyrate, tert-butyldimethylchlorosilane, N,N’-dimethylpropyleneurea, lithium(diisopropylamide) (1.5 M in THF), and bis(trifluoromethanesulfonyl)imide (Tf2NH) were obtained from Tokyo Chemical Industry Co., Ltd. CH2Cl2 and tetrahydrofuran (THF) The second stage of polymerization was conducted for an additional 24 h cMonomer conversions (x1 = M1 conv., and x2 = M2 conv.) were calculated directly using 1H NMR measurements (500 MHz, rt, CDCl3) of the reaction mixture dThe polymer yield was calculated based on the total weight of the feed monomers eThe number-averaged molecular weight (Mn) and dispersity (Đ) were determined using conventional GPC against PSt standards in CHCl3 fInitiator efficiency: f = [molecular weight of polymer calculated by a feed ratio]/[number-average molecular weight of polymers determined by GPC]. The reaction was worked up using the same process that was employed for the one-stage polymerization

Results and discussion

Conclusion

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