Acceleration effect of <i>N</i>‐allyl group on thermally induced ring‐opening polymerization of 1,3‐benzoxazine

Oie, Hiroaki; Sudo, Atsushi; Endō, Takeshi

doi:10.1002/pola.24338

Cited by 56 publications

(44 citation statements)

References 24 publications

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“…Recently, Lochab et al have successfully reduced the Bz-C curing temperature from 242 to 161 1C by blending with oxazines containing higher and acidic functionalities [6]. Other functional groups such as allylic [7], methylol [8] etc. has also been reported to lower the curing temperature.…”

Section: Introductionmentioning

confidence: 98%

Microencapsulated cardanol derived benzoxazines for self-healing applications

et al. 2014

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Section: Introductionmentioning

confidence: 98%

Microencapsulated cardanol derived benzoxazines for self-healing applications

et al. 2014

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“…1) 10–16 . Apparently, this design flexibility brings about a huge molecular diversity and control of structure and properties of PBZs.…”

Section: Introductionmentioning

confidence: 99%

Recycling and Self-Healing of Polybenzoxazines with Dynamic Sulfide Linkages

Arslan

Kışkan

Yaǧcı

2017

Sci Rep

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In this work, a recycling and self-healing strategy for polybenzoxazines through both S-S bond cleavage-reformation reaction and supramolecular attractions is described. Both recyclable and selfhealable polybenzoxazines can be prepared from low cost chemicals with a simple procedure in only 30 minutes. For this purpose, inverse vulcanization of poly(propylene oxide)benzoxazine (PPOB) and diallybenzoxazine (B-al) with elemental sulfur was performed at 185 °C. The obtained cross-linked polymer films exhibited thermally driven recycling ability up to 5 cycles. Moreover, the self-healing ability of a test specimen was shown. Spectral characterizations, thermal stability and fracture toughness of the films were investigated after each recycling.In the past few decades, polybenzoxazines (PBZs), also known as benzoxazine resins, emerged as a superior alternative to classical resol and novolac type phenolic resins. The main structural difference of PBZs from classical phenolics is the tertiary amine groups in each repeating unit, which generates immense effect especially on hydrogen bonding types and strength. Due to these unique structural characteristics, PBZs exhibit high tensile strength and modulus (100-125 MPa, and 3.8-4.5 GPa, respectively), and high glass transition temperatures (T g ) (170-340 °C). Accordingly, these materials, particularly rigid ones or those admixed with transition metals, have high service temperatures, char yields, and are stable under acidic/alkali conditions. Unlike the general nature of phenolics, PBZs have low water adsorption stemming from strong intra-molecular hydrogen bonding. Another important aspect is related to their dimensional stability during synthesis. These resins are obtained by ring-opening polymerization of benzoxazine monomers at temperatures between 160-250 °C, sometimes higher, without any additive (Scheme 1) [1][2][3][4][5][6] . It should be emphasized that 1,3-isomers are the only active benzoxazines to undergo such polymerization. According to mechanistic studies, polymerization proceeds via the cationic pathway as oxazine rings have N and O atoms, which are capable of stabilizing cations during polymerization 7-9 .The other appealing side of PBZs is the synthesis of corresponding benzoxazine monomers, which can be accomplished using any suitable phenol, a primary amine, and formaldehyde; therefore, the number of possible benzoxazines is large (Fig. 1) [10][11][12][13][14][15][16] . Apparently, this design flexibility brings about a huge molecular diversity and control of structure and properties of PBZs. For example, crosslinking density of the resins can be increased by introducing dimerizable or polymerizable functionalities on benzoxazines 17,18 . The toughness of PBZs can be manipulated by using long chain amines and other soft or conversely rigid groups [19][20][21][22] . Gas forming moieties can be attached to benzoxazines causing macroporosity to occur during curing; thus, sponge-like materials can be obtained, etc 23,24 . Such suppleness in the properties ...

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“…6 In particular, it is being gradually recognized that the most important and attractive characteristic of polybenzoxazines is the extraordinary exibility in their molecular design. There have been a lot of successful reports on the development of benzoxazine monomers to improve material performance or expand the range of their applications, 8 for example, lowering the polymerization temperature by introducing hydroxyl, 9,10 acetylene, 11,12 N-allyl, 13 and carboxylic acid groups 14 to benzoxazine compounds, increasing the cross-linking density by the incorporation of polymerizable groups, [15][16][17] improving ame retardancy by phosphorylation of the cured products, 18 and others. Desired benzoxazines can be synthesized using specially selected phenol derivatives and primary amines.…”

Section: Introductionmentioning

confidence: 99%

A curing system of benzoxazine with amine: reactivity, reaction mechanism and material properties

et al. 2015

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Five commercially available amines: m-phenylenediamine (A1), m-xylylenediamine (A2), isophorone diamine (A3), trimethylhexamethylenediamine (A4), and 4,4 0 -diaminodiphenyl sulfone (A5), were examined as nucleophilic hardeners for bis-benzoxazine monomers based on aniline paired with bisphenol-A (BA-a) or bisphenol-F (BF-a). The reactivities and reaction mechanisms of their mixtures with BA-a were investigated using FTIR and NMR spectroscopy, DSC, and HPLC techniques. It was found that BA-a rapidly cured with the amines upon heating at 120 C or 150 C. The cure rate was similar to the amine/epoxy curing process in practical uses, and significantly faster than the ring-opening polymerization of bulk BA-a. The possible reaction mechanism was supported by the experimental results and includes three successive steps: (i) nucleophilic substitution at the carbon atom (O-C-N) in the oxazine ring by the amine, (ii) thermal decomposition of the resulting aminomethanaminium structure, and (iii) electrophilic addition of the newly formed iminium ion with the aromatic ring to form stable aminomethylphenol structures. These findings are helpful to improve the thermosetting resins in terms of their chemical structure, material properties, and processability.

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Acceleration effect of N‐allyl group on thermally induced ring‐opening polymerization of 1,3‐benzoxazine

Cited by 56 publications

References 24 publications

Microencapsulated cardanol derived benzoxazines for self-healing applications

Microencapsulated cardanol derived benzoxazines for self-healing applications

Recycling and Self-Healing of Polybenzoxazines with Dynamic Sulfide Linkages

A curing system of benzoxazine with amine: reactivity, reaction mechanism and material properties

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