一种新型苯半恶嗪中间体的合成及其固化性能的研究

本文采用对氨基酚、苯酚和甲醛为原料合成了一种新型的苯 并恶嗪中间体。运用FTIR和^1H-NMR对中间体结构进行了表征。并采用^1H-NMR方法研究了反应条件对中间体结构的影响，结果表明在70－90℃下反应1－2h有利于形成恶嗪环。同时，对该中间体的固化反应进行了研究，表明该中间体具有较高的反应活性，并能够促进苯并恶嗪树脂的固化反应进行。     

开环聚合酚醛树脂—苯并恶嗪中间体的研究进展

本文综合论述了开环聚合酚醛树脂的研究进展,主要围绕开环聚合酚醛树脂中间体—苯并恶嗪化合物的种类、结构表征方法、中间体的性能及其开环聚合产物的优异性能等展开论述。     

苯并噁嗪树脂——一类新型热固性工程塑料

综述了四川大学在苯并口恶嗪树脂研究和产品应用开发等 5个方面的进展 :a.不同组成和性能的苯并口恶嗪的合成 ;b .苯并口恶嗪化反应和固化动力学 ;c .苯并口恶嗪固化过程的体积变化 -膨胀固化 ;d .纤维增强苯并 口恶嗪树脂性能及应用 ;e.以苯并 口恶嗪为粘合剂的制动材料性能及应用。     

一种新型苯并口恶嗪中间体的合成及其固化性能的研究

本文采用对氨基酚、苯酚和甲醛为原料合成了一种新型的苯并口恶嗪中间体。运用FTIR和     

苯并恶嗪树脂：——一类新型热固性工程塑料

综术字四川大学在苯并恶嗪树脂研究所和产品应用开发等5个方面的进展，a不同组成和性能的苯并恶嗪的合成；b，苯并恶嗪化反应和固化动力学；c。苯并恶嗪固化过程的体积变化－膨胀因化；d。纤维增强苯并恶嗪树脂性能及应用。e以苯并恶嗪为粘合剂的制动材料性能及应用。     

一种新型苯并噁嗪中间体的合成及其固化性能的研究

本文采用对氨基酚、苯酚和甲醛为原料合成了一种新型的苯并 噁嗪中间体。运用FTIR和1H -NMR对中间体结构进行了表征。并采用1H -NMR方法研究了反应条件对中间体结构的影响 ,结果表明在 70～ 90℃下反应 1～ 2h有利于形成 噁嗪环。同时 ,对该中间体的固化反应进行了研究 ,表明该中间体具有较高的反应活性 ,并能够促进苯并 噁嗪树脂的固化反应进行。     

苯并恶嗪树脂的合成及其改性的研究进展

综述了近年来国内外在苯并恶嗪树脂基础研究与应用领域内的最新进展情况;介绍了苯并恶嗪树脂的合成及其改性方法,并对苯并恶嗪树脂的发展趋势进行了展望.     

苯并恶嗪树脂的耐热改性研究进展

分别从分子结构设计、无机粒子改性、共混或共聚改性以及新型苯并恶嗪的合成等方面介绍了近年来国内外对新型热固性树脂苯并恶嗪在耐热改性方面取得的研究性进展,预测了苯并恶嗪树脂的未来发展趋势。分子结构设计是利用苯并恶嗪分子的灵活性,将反应性基团或刚性基团引入到苯并恶嗪中。研究表明,各种改性方法均从不同方面显著地提高了苯并恶嗪树脂的耐热性能。     

取代基电子效应对聚苯并噁嗪热稳定性影响研究

以苯酚/苯胺型苯并噁嗪和苯酚/4,4'–二苯甲烷二胺型苯并噁嗪为参照对象,通过DSC、TGA和TGA-FTIR联用测试,研究了酚羟基对位连有不同电子效应的取代基时,苯并噁嗪中间体开环聚合及其聚合物热稳定性的变化。结果表明,酚羟基对位氯原子的取代降低了苯并噁嗪中间体开环聚合的温度,而甲基的取代使苯并噁嗪中间体开环聚合的温度升高;由于氯原子的吸电子效应导致聚苯并噁嗪Mannich(曼尼希)桥上的C—N和C—C键被削弱,使得其热稳定性下降;甲基的取代使聚苯并噁嗪的交联密度下降,因而也降低了其热稳定性。     

咪唑盐离子液催化苯并恶嗪固化反应的研究

采用DSC、FTIR研究了不同种类阳离子、阴离子以及不同浓度的咪唑盐离子液作为双酚A型苯并恶嗪固化反应的催化剂时体系的固化反应、固化物的交联结构。结果表明,咪唑盐离子液能够降低苯并恶嗪的固化反应温度,固化物中部分生成苯氧醚式结构。咪唑盐阳离子体积越大,因位阻效应固化反应越慢,而阴离子则通过与苯并恶嗪开环产生的中间体阳离子的相互作用改变体系的反应速率。     

Synthesis and polymerization behavior of novel liquid-crystalline benzoxazines

Novel liquid-crystalline (LC) benzoxazines were synthesized by using 4(4′-heptoxybenzoyloxy)benzylidene-4″-aminophenol, various alkylamines, and formalin in chloroform under reflux. Polarized optical microscopy (POM) and differential scanning calorimetry (DSC) were used to analyze the LC behavior of the synthesized benzoxazines. The novel benzoxazines showed nematic and smectic phases upon cooling cycle from the isotropic liquids. The LC benzoxazines also showed a nematic phase upon heating cycle, indicating that the novel benzoxazines are enantiotropic liquid crystals. The ring-opening polymerization behavior of the LC benzoxazines was investigated by DSC and IR analyses. POM observations showed that a polybenzoxazine film, prepared by thermally curing the LC benzoxazine up to 160 °C for 1 h, exhibited birefringence at room temperature.     

Synthesis and characterization of bio-based benzoxazines derived from thymol

In the present study, bio-based benzoxazine resins were synthesized from bio-based phenolic compound; thymol, and three different amines; ethylamine, aniline and 1,6-diaminohexane, and paraformaldehyde by solvent-free condensation reaction. The chemical structures of bio-based benzoxazines; T-ea (thymol, ethylamine), T-a (thymol, aniline), and T-dh (thymol, 1,6-diaminohexane) were characterized by proton nuclear magnetic resonance spectroscopy, Fourier transform infrared (FTIR) spectroscopy, elemental analysis, and high-resolution mass spectrometry. The curing studies of T-ea, T-a, and T-dh bio-based benzoxazines were performed by stepwise thermal treatment at 150, 175, 200, 225, and 250 °C. The polymerization (ring-opening and crosslinking reactions) of T-ea, T-a, and T-dh bio-based benzoxazines was investigated by FTIR spectroscopy. Cure analysis was conducted using differential scanning calorimetry and the changes in thermal properties of the T-ea, T-a, and T-dh bio-based benzoxazine resins and their corresponding thermally crosslinked polybenzoxazines PT-ea, PT-a, and PT-dh were studied by thermogravimetric analyzer. The results indicated that all the thymol-based polybenzoxazines have shown enhanced thermal stability. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47371.     

Hybrid dual-cure polymer networks via sequential thiol–ene photopolymerization and thermal ring-opening polymerization of benzoxazines

Dual-cure hybrid polymer networks were prepared by sequential thiol–ene photopolymerization followed by thermal ring-opening polymerization of benzoxazines with the aim of increasing the glass transition temperature range of thiol–ene based materials and improving the processibility of polybenzoxazines. The hybrid networks are derived from a multifunctional, dually-polymerizable monomer possessing both bis-“ene” and bis-benzoxazine moieties enabling the formation of two networks through a common constituent monomer when combined with a multifunctional thiol. The photopolymerization kinetics of the thiol–ene reaction were investigated by real-time infrared spectroscopy. Sequential thermal ring-opening polymerization of the benzoxazine moieties incorporated into the thiol–ene network was characterized by FTIR and differential scanning calorimetry. The glass transition of the hybrid material was observed at 150 °C; however, competing thiol–ene (radical-mediated) and thiol–benzoxazine (nucleophilic ring-opening) reactions during the UV cure yield a heterogeneous network structure.     

Preparation and characterization of polyseudorotaxanes based on adamantane-modified polybenzoxazines and β-cyclodextrin

β-Cyclodextrin (β-CD) forms inclusion complexes (ICs) with adamantane-modified benzoxazines (2 benzoxazine and 3 benzoxazine). These benzoxazines can readily penetrate into the CD's hydrophobic cavity, causing turbidity of their solutions, from which fine crystalline powders are obtained. We characterized these complexes by powder X-ray diffraction, ¹³C and ¹³C CP/MAS NMR spectroscopies, DSC, and TGA. The X-ray diffraction and solid-state ¹³C CP/MAS NMR spectroscopy indicate that the IC domains of the polypseudorotaxanes maintain their channel-type structures after the ring-opening curing reactions have occurred. Furthermore, DSC measurements indicate that complexing the adamantane-modified benzoxazine units with β-CDs result in stiffer main chains and, thus, higher glass transition temperature. TGA also indicates that the inclusion complexes have enhanced its thermal stability.     

Synthesis of liquid–crystalline benzoxazines containing a biphenyl group in the mesogenic moiety

In this work, we describe a process to synthesize novel liquid–crystalline (LC) benzoxazines from a LC phenol that contains biphenyl, ester and azomethine groups in the mesogenic moiety, various alkyl amines and formaldehyde. The LC behavior of the biphenyl-containing benzoxazines was investigated by differential scanning calorimetry and polarized optical microscopy and compared with analogous phenyl-containing LC benzoxazines containing phenyl, ester and azomethine groups in the mesogenic moiety. While the LC benzoxazines containing the phenyl groups only exhibited a nematic phase upon heating, the LC benzoxazines containing biphenyl groups exhibited a smectic phase as well as a nematic phase. Additionally, the LC-isotropic transition temperatures were over 100 °C higher than that for the phenyl-containing LC benzoxazines. A film obtained by curing the biphenyl-containing LC benzoxazine at 180 °C for 1 h exhibited birefringence. Finally, the thermal diffusivity of the cured LC benzoxazines was also investigated.     

Syntheses, thermal properties, and phase morphologies of novel benzoxazines functionalized with polyhedral oligomeric silsesquioxane (POSS) nanocomposites

We have successfully synthesized a novel benzoxazine ring-containing polyhedral oligomeric silsesquioxane (BZ-POSS) monomer by two routes: (1) hydrosilylation of a vinyl-terminated benzoxazine using the hydro-silane functional group of a polyhedral oligomeric silsesquioxane (H-POSS) and (2) reaction of a primary amine-containng POSS (Amine-POSS) with phenol and formaldehyde. The benzoxazine-containing POSS (BZ-POSS) monomer can be copolymerized with other benzoxazine monomers through ring-opening polymerization under conditions similar to that used for polymerizing pure benzoxazines. Thermal properties of these POSS-containing organic/inorganic polybenzoxazine nanocomposites have been improved over the pure polybenzoxazine analyzed by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). The BZ-POSS monomer is poorly miscible with the benzoxazine monomer and tends to aggregate and forms its own domains, both before and after polymerization. At a higher BZ-POSS content, gross aggregation occurs and results in a lower than expected improvement in the thermal properties.     

Quantitative structure-property relationships of new benzoxazines and their electrooxidation as a model of metabolic degradation

The quantitative structure-property relationships study of 40 benzoxazines, that seem to be very promising antimycobacterial drugs, allowed proposing and testing of the equations describing effects of substituents on half-wave potentials of these compounds. Although two structural types of benzoxazines were studied (i.e. thioxobenzoxazinones and benzoxazinedithiones), it is possible to describe the effect of substituent on half-wave potentials of benzoxazines by one general equation. A good correlation for relationship between half-wave potential and energy of HOMO orbital was also found.The study of electrochemical oxidation of these compounds as a model of their possible metabolic degradation was performed. It was possible to propose general scheme of electrochemical oxidation of sulfur containing benzoxazine derivatives. From the metabolic point of view, desulfuration is the corresponding process to this pathway. As these derivatives were not examined in vivo, obtained results represent very beneficial clues, and, moreover, proposed scheme could serve as a support for the explanation of strong antimycobacterial activity of sulfur containing benzoxazines.     

Studies on thermal behavior of imidazole diamine based benzoxazines

The objective of the present work is to develop a novel type of structurally modified benzoxazines with improved performance characteristics using imidazole core based diamine with formaldehyde and different types of phenolic compounds in order to utilize them for high‐performance applications. In this work, an attempt has been made to bring down the polymerization temperature of the benzoxazine monomers, which is one of the most deficient factor restrict the applications of benzoxazines, when used in the form of adhesives, sealants, encapsulants, and matrices with other substrates, though they possess numerous advantages and valuable properties than those of other available thermosets. In this context, in this study, two approaches have been adopted to bring down the polymerization temperature, viz., (i) the development of structurally modified benzoxazine monomers with imidazole core and (ii) an incorporation of varying nature of chemical compounds as catalysts, to lower the polymerization temperature and to enhance the thermal stability and char yield. Three types of benzoxazines were developed using imidazole core based diamine with monohydric phenols and formaldehyde, at appropriate conditions. The molecular structure of benzoxazines was confirmed from Fourier transform infrared spectroscopy and ¹H‐nuclear magnetic resonance analysis. From data, it was observed that the imidazole diamine based benzoxazines prepared from 1‐naphthol exhibits lower curing temperature of about 192 °C than that of other samples studied in this work. In addition, the influencing effect of catalysts viz., 4‐hydroxy acetophenone, 4‐hydroxy benzaldehyde, 4‐hydroxyphenyl maleimide, and thiodipropionic acid (TPA) on thermal properties of benzoxazines also was studied. Among the catalysts, it was found that the TPA is the most efficient catalyst. In the case of imidazole diamine based benzoxazines prepared from cyanophenol, the TPA reduces value of polymerization temperature (T_p) from 217 to 167 °C. The thermogravimetric analysis indicates that thermal stability of the benzoxazines are improved to a significant extent when 10 wt % catalysts were incorporated into the system. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46562.     

High dielectric,low curing with high thermally stable renewable eugenol-based polybenzoxazine matrices and nanocomposites

In the present work, a new type of bio-based benzoxazines were prepared by using aniline, N, N-dimethyl amino propyl amine (DMAPA) and caprolactam modified DMAPA with eugenol. The benzoxazines resulted were characterized for their molecular structure by Fourier transform infrared and nuclear magnetic resonance spectroscopy. The polymerization process of benzoxazines and their thermal behavior were studied by differential scanning calorimetry and thermogravimetric analysis, respectively. Moreover, the effect of chemical blending of the synthesized benzoxazines with conventional benzoxazines [bisphenol A benzoxazine (BPAb) and bisphenol F benzoxazine (BPFb)] and bismaleimide was studied to bring down the polymerization temperature by creating supplementary potential sites for polymerization. Furthermore, to reduce the polymerization temperature, the benzoxazines synthesized in the present study were partially incorporated with 10 wt % of catalysts (4-hydroxy phenylmaleimide, 4-amino phenol, and 4-hydroxy acetophenone). The graphene reinforced polybenzoxazine composites were also prepared by incorporating varying weight percentages (1, 3, 5, 7, and 10 wt %) of graphene oxide to obtain hybrid nanocomposites. From the results obtained, it was observed that the polymerization temperature (T_p) was significantly reduced (more than 31 °C) in both the cases of blends of conventional BPAb and BPFb. It was also observed that the values of the dielectric constant of graphene reinforced hybrid composites are significantly enhanced. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47050.     

Polymerization behavior of methylol-functional benzoxazine monomer

This study focuses on methylol functional benzoxazines as precursors to build a network structure utilizing both benzoxazine and resole chemistry. The first part is a review of systems that contain methylol groups which play a role on their crosslinking formation. The polymerization mechanism and properties of resoles will be highlighted as the most abundant polymers that are characterized by polymerization through condensation reaction of methylol group. In the second part, the effect of incorporating methylol group into benzoxazine monomers is studied. Differential scanning calorimetry (DSC) is used to study the effect of methylol group on the rate of polymerization. Kissinger and Ozawa methods using non-isothermal DSC at different heating rates show that methylol monomer exhibits lower average activation energy compared to the un-functionalized monomer. The effect of adding catalysts into the monomers is also studied. p-Toluene sulfonic acid (PTSA) is found to be more efficient than 1-methyl-imidazole (IMD) and lithium iodide (LiI) in the case of methylol monomer due to its ability of accelerating both the methylol condensation and ring-opening polymerization. Additionally, thermal behavior of the monomers is studied using thermogravimetric analysis (TGA).