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UNDERSTANDING THE VIBRATIONAL STRUCTURE, RING-OPENING KINETICS OF OXAZINE RING AND HYDROGEN BONDING EFFECTS ON FAST POLYMERIZATION OF 1,3-BENZOXAZINES

Han, Lu
http://rave.ohiolink.edu/etdc/view?acc_num=case1523026767260573

Abstract Details

2018, Doctor of Philosophy, Case Western Reserve University, Macromolecular Science and Engineering.
Polybenzoxazines are relatively new but already commercialized thermosetting resin. The material has already gathered much attention from not only academia but also industry field due to its superior properties than conventional phenolic, epoxy and bismaleimide resins. However, many people focus on working towards high performance material, much less work has been done on the fundamental study on understanding the vibrational structure, ring-opening kinetics of oxazine ring, which will be a great guidance on future molecular design and higher performance material, resins, composites. Chapter 1: In this chapter, the previous work and current research interest are covered, which leads to my research motivation for understanding the vibrational structure, ring-opening kinetics of oxazine ring and hydrogen bonding effects on fast polymerization of 1,3-benzoxazines. Chapter 2: In this chapter, the characterization band of benzoxazines and polybenzoxazines in FT-IR spectra is reassigned. Polymerization of benzoxazine resins is indicated by the disappearance of a 960-900 cm-1 band in infrared spectroscopy (IR). Historically, this band was assigned to the C-H out-of-plane bending of the benzene to which the oxazine ring is attached. This study shows that this band is a mixture of the O-C2 stretching of the oxazine ring and the phenolic ring vibrational modes. Vibrational frequencies of 3-phenyl-3,4-dihydro-2H-benzo[e][1,3]oxazine (PH-a) and 3-(tert-butyl)-3,4-dihydro-2H-benzo[e][1,3]oxazine (PH-t) are compared with isotope-exchanged and all-substituted compounds. Deuterated benzoxazine monomers, 15N-isotope exchanged benzoxazine monomers, and all-substituted benzoxazine monomers without aromatic C-H groups are synthesized and studied meticulously. The various isotopic-exchanges involved deuteration around the benzene ring of phenol, selective deuteration of each CH2 in the O-CH2-N (2) and N-CH2-Ar (4) positions on the oxazine ring, or simultaneous deuteration of both positions. The chemical structures were confirmed by 1H nuclear magnetic resonance spectroscopy (1H NMR). The IR and Raman spectra of each compound are compared. Further analysis of 15N isotope-exchanged PH-a indicates the influence of the nitrogen isotope on the band position, both experimentally and theoretically. This finding is important for polymerization studies of benzoxazines that utilize vibrational spectroscopy. Chapter 3: In this chapter, the intrinsic ring opening of oxazine ring mechanism is proposed. A phenol/aniline type monofunctional benzoxazine monomer, PH-a, is synthesized and highly purified into single crystals to study the intrinsic thermal ring-opening polymerization of benzoxazines without the influence of any impurity. The successful synthesis of the monomer and its corresponding chemical structure are confirmed by Fourier transform infrared spectroscopy (FT-IR) and 1H nuclear magnetic resonance (1H NMR) spectroscopy. Purity of the compound is evaluated through differential scanning calorimetry (DSC) as well as elemental analysis (EA). Moreover, the thermal behavior of benzoxazine monomer toward polymerization is also studied by DSC, indicating that the highly purified benzoxazine monomer actually polymerize upon heating. The results present evidence of an intrinsic tendency for 1,3-benzoxazines to undergo thermally induced ring-opening polymerization upon heating only without any impurity participating during the reaction. This reveals that polybenzoxazines can be obtained by both the traditional thermally accelerated (or activated) polymerization, where impurities or purposefully added initiators are involved in the reaction; or, by the classic thermal polymerization, where only heat is enough to initiate the reaction. Chapter 4: Base on previous understanding the vibrational structure, ring-opening kinetics of oxazine ring, smart molecular design of ortho-structure containing hydrogen bonding benzoxazine monomer is proposed. Pure para and ortho position amide benzoxazines, pHBA-a and oHBA-a, are synthesized. The hydrogen bonding interactions occurring in pHBA-a, oHBA-a are studied by Fourier transform infrared (FT-IR) spectroscopy and proton nuclear magnetic resonance spectroscopy (1H NMR). FT-IR results show that, while pHBA-a presents intermolecular hydrogen bonding interactions, oHBA-a exhibits an intramolecular five-membered-ring hydrogen-bonding system between the NH in the amide group and the oxygen in the oxazine ring. Differential scanning calorimetry (DSC) is used to study the thermal properties of the resins and their respective polymers. A deeper understanding of the hydrogen bond interactions in this family of resins is attempted to have better insights on how these systems influence the polymerization behavior not only with respect to the polymerization temperature but also with respect to the propagation step. Chapter 5: This chapter focuses on the conclusion that obtained from the previous study. It also demonstrates the great guidance for future study.
Hatsuo Ishida, Dr. (Advisor)
Gary Wnek, Dr. (Committee Member)
Lei Zhu, Dr. (Committee Member)
Daniel Lacks, Dr. (Committee Member)
293 p.
Chemistry; Polymer Chemistry; Polymers
benzoxazine, polybenzoxazine, vibrational structure, ring-opening kinetics, hydrogen bonding, high performance

Recommended Citations

Citations

  • Han, L. (2018). UNDERSTANDING THE VIBRATIONAL STRUCTURE, RING-OPENING KINETICS OF OXAZINE RING AND HYDROGEN BONDING EFFECTS ON FAST POLYMERIZATION OF 1,3-BENZOXAZINES [Doctoral dissertation, Case Western Reserve University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=case1523026767260573

    APA Style (7th edition)

  • Han, Lu. UNDERSTANDING THE VIBRATIONAL STRUCTURE, RING-OPENING KINETICS OF OXAZINE RING AND HYDROGEN BONDING EFFECTS ON FAST POLYMERIZATION OF 1,3-BENZOXAZINES. 2018. Case Western Reserve University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=case1523026767260573.

    MLA Style (8th edition)

  • Han, Lu. "UNDERSTANDING THE VIBRATIONAL STRUCTURE, RING-OPENING KINETICS OF OXAZINE RING AND HYDROGEN BONDING EFFECTS ON FAST POLYMERIZATION OF 1,3-BENZOXAZINES." Doctoral dissertation, Case Western Reserve University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=case1523026767260573

    Chicago Manual of Style (17th edition)

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This open access ETD is published by Case Western Reserve University School of Graduate Studies and OhioLINK.