title: Intramolecular Hydrogen Bonding in Benzoxazines: When Structural Design Becomes Functional.
abstract: The future evolution of benzoxazines and polybenzoxazines as advanced molecular, structural, functional, engineering, and newly commercial materials depends to a great extent on a deeper and more fundamental understanding at the molecular level. In this contribution, the field of benzoxazines is briefly introduced along with a more detailed review of ortho-amide-functional benzoxazines, which are the main subjects of this article. Provided in this article are the detailed and solid scientific evidences of intramolecular five-membered-ring hydrogen bonding, which is supposed to be responsible for the unique and characteristic features exhibited by this ever-growing family of ortho-functionalized benzoxazines. One-dimensional (1D) (1)H NMR spectroscopy was used to study various concentrations of benzoxazines in various solvents with different hydrogen-bonding capability and at various temperatures to investigate in detail the nature of hydrogen bonding in both ortho-amide-functionalized benzoxazine and its para counterpart. These materials were further investigated by two-dimensional (2D) (1)H-(1)H nuclear Overhauser effect spectroscopy (NOESY) to verify and support the conclusions derived during the 1D (1)H NMR experiments. Only highly purified single-crystal benzoxazine samples have been used for this study to avoid additional interactions caused by any impurities.
authors.affiliation: Department of Macromolecular Science and Engineering, Case Western Reserve University, Cleveland, Ohio, 44106-7202, USA. pxf106@case.edu.|Design and Chemistry of Macromolecules Group, Institute of Technology in Polymers and Nanotechnologies (ITPN), UBA-CONICET, School of Engineering, University of Buenos Aires, Las Heras 2214, CP 1127AAR, Buenos Aires, Argentina. pxf106@case.edu.
authors.forename: Pablo
authors.initials: P
authors.lastname: Froimowicz
authors.affiliation: Department of Macromolecular Science and Engineering, Case Western Reserve University, Cleveland, Ohio, 44106-7202, USA.|School of Materials Science and Engineering, East China University of Science and Technology, Shanghai, 200237, China.
authors.forename: Kan
authors.initials: K
authors.lastname: Zhang
authors.affiliation: Department of Macromolecular Science and Engineering, Case Western Reserve University, Cleveland, Ohio, 44106-7202, USA. hxi3@case.edu.
authors.forename: Hatsuo
authors.initials: H
authors.lastname: Ishida
keywords: benzoxazines; hydrogen bonds; polybenzoxazines; polymers; structure-activity relationships; substituent effects