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Issue 36, 2017
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A preorganized dual H-bond donor promotes benzoic acid active in the polymerization of δ-valerolactone

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Abstract

Ring-opening polymerization (ROP) of lactones catalyzed by a (super)strong Brønsted acid offers a valuable approach to important biodegradable aliphatic polyesters. However, the need for a mild acidic catalyst in ROP has been long sought after but unmet. Here, we describe a truly weak Brønsted acid, benzoic acid, in combination with a dual H-bond donor (dHBD), which catalyzes the ROP of δ-valerolactone (VL) in solution at room temperature. A unique preorganized sulfonyl guanidine type of dHBD, 3-amino-1,2,4-benzothiadiazine-1,1-dioxide (ABTD), proves optimal to work with benzoic acid as a cocatalyst, promoting benzoic acid activity in the ROP of VL. Poly-δ-valerolactones of predictable molecular weights (from 2.13 to 9.33 kg mol−1) and narrow dispersities (Đ ≤ 1.16) are synthesized. The controlled character of the ROP is verified by NMR, SEC, and MALDI-ToF MS measurements. NMR titration experiments imply that ABTD preferentially binds with benzoic acid, and the benzoic acid/ABTD pair protonates the VL monomer. Weak benzoic acid is not weak for the first time in the efficient cationic ROP of VL by the protonation mechanism.

Graphical abstract: A preorganized dual H-bond donor promotes benzoic acid active in the polymerization of δ-valerolactone

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Publication details

The article was received on 18 Jul 2017, accepted on 03 Aug 2017 and first published on 07 Aug 2017


Article type: Paper
DOI: 10.1039/C7PY01192J
Citation: Polym. Chem., 2017,8, 5570-5579
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    A preorganized dual H-bond donor promotes benzoic acid active in the polymerization of δ-valerolactone

    H. Sun, S. Xu, Z. Li, J. Xu, J. Liu, X. Wang, H. Wang, H. Dong, Y. Liu and K. Guo, Polym. Chem., 2017, 8, 5570
    DOI: 10.1039/C7PY01192J

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