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Title: Effects of End-Caps on the Atropisomerization, Polymerization, and the Thermal Properties of ortho-Imide Functional Benzoxazines.
Authors: Zhang, K
Liu, Y
Shang, Z
Evans, CJ
Yang, S
First Published: 1-Mar-2019
Publisher: MDPI
Citation: Polymers, 2019, 11 (3), 399
Abstract: A new type of atropisomerism has recently been discovered in 1,3-benzoxazines, where the intramolecular repulsion between negatively charged oxygen atoms on the imide and the oxazine ring hinders the rotation about the C⁻N bond. The imide group offers a high degree of flexibility for functionalization, allowing a variety of functional groups to be attached, and producing different types of end-caps. In this work, the effects of end-caps on the atropisomerism, thermally activated polymerization of ortho-imide functional benzoxazines, and the associated properties of polybenzoxazines have been systematically investigated. Several end-caps, with different electronic characteristics and rigidities, were designed. ¹H and 13C nuclear magnetic resonance (NMR) spectroscopy and density functional theory (DFT) calculations were employed to obtain structural information, and differential scanning calorimetry (DSC) and in situ Fourier transform infrared (FT-IR) spectroscopy were also performed to study the thermally activated polymerization process of benzoxazine monomers. We demonstrated that the atropisomerization can be switched on/off by the manipulation of the steric structure of the end-caps, and polymerization behaviors can be well-controlled by the electronic properties of the end-caps. Moreover, a trade-off effect were found between the thermal properties and the rigidity of the end-caps in polybenzoxazines.
DOI Link: 10.3390/polym11030399
eISSN: 2073-4360
Version: Publisher Version
Status: Peer-reviewed
Type: Journal Article
Rights: Copyright © the authors, 2019. This is an open-access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Description: Supplementary Materials: The following are available online at, Figure S1. 1H-13C HMQC 2D NMR spectrum for oMHI-a, Figure S2. 1H-13C HMQC 2D NMR spectrum of oHHI-a, Figure S3. 1H-13C HMQC 2D NMR spectrum of oHTI-a, Figure S4. FTIR spectra of benzoxazine monomers.
Appears in Collections:Published Articles, Dept. of Chemistry

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