Polybenzoxazine Films Research Articles

Synthesis and properties of an amide- and Meldrum's acid-functionalized mainchain-type polybenzoxazine and the corresponding crosslinked resin

Mainchain-type polybenzoxazines (PBz) are self-crosslinkable polymers possessing high flexibility of molecular designs and property adjustments. The corresponding crosslinked PBz in different forms, such as films, porous membranes, electrospun fiber mats, have been prepared for various applications. This work aims on functionalization of PBz with amide groups and Meldrum's acid moieties, to bring hydrogen bonding interaction and additional covalent crosslinks to the crosslinked PBz. A bisphenol derivative possessing both MA and amide groups (MA/Am-BP) is synthesized from a biomass-based precursor of 3,4-dihydrocoumarine. MA/Am-BP is utilized as a monomer, together with 4,4′-oxydianiline and formaldehyde, for preparation of amide- and Meldrum's acid-functionalized polybenzoxazine (MA/Am-PBz) and the corresponding crosslinked polybenzoxazine (CR_MA/Am-PBz). The benzoxazine- and Meldrum's acid-involved crosslinking reactions have been investigated with temperature-dependent Fourier transform infrared spectroscopy. CR_MA/Am-PBz has demonstrated film formability and flexibility. In addition to the attractive thermal properties, including a thermal stability of 340 °C, a char yield of 52 wt% at 800 °C, a storage modulus of 1.44 GPa at 50 °C, and a Tg of 295 °C, CR_MA/Am-PBz also exhibits a high tensile strength of 97 MPa, which is superior over the data reported to crosslinked polybenzoxazine films.

Preparation of biphenyl-containing polybenzoxazines with low dielectric constants and high thermal stability

In this work, two biphenyl-containing benzoxazine monomers (C-tfmb and C-dmb) have been synthesized using 2,2′-bis(trifluoromethyl)benzidine/2,2′-dimethylbenzidine, 4-cyclohexylphenol and paraformaldehyde as raw materials. The thermal curing behaviors of the benzoxazine monomers were investigated by Fourier transform infrared spectroscopy and non-isothermal differential scanning calorimetry. After curing, the biphenyl-containing polybenzoxazines (PC-tfmb and PC-dmb) exhibited high thermal stability with the 5% weight loss temperatures at 335 °C and 367 °C, respectively. Moreover, both polybenzoxazine films showed high hydrophobicity and low dielectric properties. Due to the presence of low-polarity and bulky cyclohexyl and trifluoromethyl groups, PC-tfmb had a dielectric constant of 2.78 and a dielectric loss of 0.0035 at 1 MHz.

Sustainable Chitosan/Polybenzoxazine Films: Synergistically Improved Thermal, Mechanical, and Antimicrobial Properties.

Polybenzoxazines (Pbzs) are considered as an advanced class of thermosetting phenolic resins as they overcome the shortcomings associated with novolac and resole type phenolic resins. Several advantages of these materials include curing without the use of catalysts, release of non-toxic by-products during curing, molecular design flexibility, near-zero shrinkage of the cured materials, low water absorption and so on. In spite of all these advantages, the brittleness of Pbz is a knotty problem that could be solved by blending with other polymers. Chitosan (Ch), has been extensively investigated in this context, but its thermal and mechanical properties rule out its practical applications. The purpose of this work is to fabricate an entirely bio-based Pbz films by blending chitosan with benzoxazine (Bzo), which is synthesized from curcumin and furfuryl amine (curcumin-furfurylamine-based Bzo, C-fu), by making use of a benign Schiff base chemistry. FT-IR and 1H-NMR spectroscopy were used to confirm the structure of C-fu. The impact of chitosan on benzoxazine polymerization was examined using FT-IR and DSC analyses. Further evidence for synergistic interactions was provided by DSC, SEM, TGA, and tensile testing. By incorporating C-fu into Ch, Ch-grafted-poly(C-fu) films were obtained with enhanced chemical resistance and tensile strength. The bio-based polymer films produced inhibited the growth of Staphylococcus aureus and Escherichia coli, by reversible labile linkages, expanding Ch galleries, and releasing phenolic species, which was 125 times stronger than bare Ch. In addition, synthesized polybenzoxazine films [Ch/Poly(C-fu)] showed significant dose-dependent antibiofilm activity against S. aureus and E. coli as determined by confirmed by confocal laser scanning microscopy (CLSM). This study suggests that bio-based Ch-graft-polymer material provide improved anti-bacterial property and characteristics that may be considered as a possibility in the near future for wound healing and implant applications.

Improvement of thermal properties of polybenzoxazines synthesized from an oligonuclear phenolic compound without sacrificing toughness by introducing crosslinkable groups separated by rigid biphenyl linkers

Novel allyl-, ethynyl-, and furfuryl-containing polyfunctional benzoxazine monomers were synthesized, and the mechanical and thermal properties of their thermosets were investigated. The benzoxazines OP-ala, OP-ea, and OP-fu were successfully synthesized with high yield from an oligonuclear phenolic compound with a 4,4ʹ-dimethylenebiphenyl group as the phenol linker; paraformaldehyde; and the corresponding amines, allylamine, m-ethynylanilline, and furfurylamine, respectively, using a microwave heating technique. Despite the introduction of the crosslinkable groups, the brown polybenzoxazine films obtained via thermal curing up to 240 °C showed sufficient toughness, as shown through tensile testing. Dynamic mechanical analysis revealed that the glass transition temperature (Tg) of the thermosets considerably increase due to the introduction of the crosslinkable groups; POP-ala, POP-ea, and POP-fu films showed Tg values of 289 °C, 272 °C, and 269 °C, respectively. Moreover, thermogravimetric analysis showed that the thermal stability also increased, and the 5% weight-loss temperature of POP-ea was >430 °C.

A Simple Solvent-Free Strategy of Polybenzoxazine Film Elaboration with Controllable Performance via Molecular Weight Regulation between Cross-Linking Knots

A Simple Solvent-Free Strategy of Polybenzoxazine Film Elaboration with Controllable Performance via Molecular Weight Regulation between Cross-Linking Knots

Synthesis of high‐performance bio‐based benzoxazine for flame retardant application

AbstractIn this study, a phosphorous‐containing benzoxazine was synthesized using a bio‐based primary amine, vanillin diamine true sample 2 (VDTS2,IUPAC name: 4‐(([3‐aminopropyl] imino) methyl)‐2‐methoxyphenyl(4‐(([3‐aminopropyl] imino) methyl)‐2‐methoxyphenyl) phenylphosphonate), paraformaldehyde and vanillin and tested for its use as a flame‐retardant. The molecular structure of the synthesized benzoxazines was characterized by FTIR spectroscopy and1H NMR spectroscopy. Polybenzoxazine was obtained through the ring‐opening polymerization of the benzoxazine monomer, and the formation of the same was confirmed through FTIR spectroscopy. The polymerization mechanism of the benzoxazine was investigated using thermogravimetric analysis (TGA). The thermal properties of the benzoxazine were studied using differential scanning calorimetry and TGA. The flame‐retardant properties of the polybenzoxazine films obtained were investigated by the LOI. Due to the highly brittle nature of the polybenzoxazine, the synthesized polybenzoxazine was further crushed and incorporated into an epoxy system to investigate its use as a flame‐retardant additive. The thermal property and flame‐retardant property of the epoxy films were then studied. The flame‐retardant and thermal stability test results of the epoxy‐pbz films showed that the epoxy‐pbz films showed improved thermal stability and achieved a UL‐94 V‐0 rating and an LOI of 28% at 15% by weight of the polybenzoxazine concentration. SEM analysis was also conducted to study the surface morphology of the polybenzoxazine and epoxy‐pbz films pre and post the flame test. FTIR analysis was carried out to study the flame retardant mechanism of the polybenzoxazine and the epoxy‐pbz film. The respective films' mechanical properties were also investigated to study the film‐forming capability of the films.

Effects of the curing atmosphere on the structures and properties of polybenzoxazine films

The effects of four different curing atmospheres, i.e., static air, circulating air, nitrogen and vacuum, on the polymerization mechanism, chemical structure, hydrogen bonding, mechanical property, thermal property, water contact angle, etc., of the polybenzoxazine films were systematically studied. It was found that curing in air caused more oxidation and decomposition, generating more benzoquinones, carbonyl groups and iminium ions in the resultant polybenzoxazine films. Consequently, the films cured in air were less cross-linked, darker in color and more brittle. The films cured in static air (SA) showed tensile strength and elongation at break of 12.59 MPa and 2.16%, respectively, which were 61.24 MPa and 2.74% lower than those of the films cured in nitrogen (N2). Moreover, it was demonstrated that more intramolecular rigid –OH···N hydrogen bonding was formed in the films cured in air, which was believed to be the fundamental reason for the lower chemical cross-linking density and poorer toughness. Nevertheless, these films showed higher char yield due to the formation of more thermally stable groups in oxidation process. Further investigation on chemical structures, hydrogen bonding and water contact angles of the upper and lower surfaces of the films revealed that the upper surfaces were more inclined to be oxidized and decomposed during curing and more intramolecular hydrogen bonding (–OH···N HB) was formed on upper surfaces, which led to increased water contact angles.

Sulfonic acid-containing benzoxazine surfactant and its waterborne benzoxaizne resins

A sulfonic acid-containing benzoxazine surfactant, sodium 3-dodecyl-3,4-dihydro- 2H-1,3-benzoxazine-6-sulfonate (SBZ), was synthesized via Mannich reaction using sodium 4-hydroxybenzenesulfonate and n-dodecylamine as raw materials. The chemical structure of SBZ was characterized by 1H NMR and FT-IR. Using SBZ as the surfactant, a series of waterborne benzoxazine resin (WBR) emulsions were prepared. The effects of SBZ concentration and oil–water ratio on the behavior of WBR emulsions were studied. Furthermore, polybenzoxazine film was prepared via curing a WBR emulsion with 50 vol% oil phase. The results showed that SBZ had a strong emulsifying ability. Only using low SBZ concentration of 2.0%, the high solid contents of 50–80 vol% and stable WBR emulsions were obtained. After polymerizing the WBR emulsion, a transparent and flexible polybenzoxazine film was fabricated. The SBZ surfactant was incorporated into the cross-linked polybenzoxazine network after polymerization. The film had a moderate mechanical property and a high glass transition temperature of 288 °C. This work provides a new strategy for the development of high heat-resistant and environmentally friendly waterborne benzoxazine coatings.

Synthesis of high-molecular-weight benzoxazines having azomethine linkages in the main-chain and the properties of their thermosetting resins

High-molecular-weight benzoxazines having azomethine linkages in the main-chain were synthesized by a two-step method consisting of 1) the synthesis of benzoxazine-containing dialdehydes from diamines, formaldehyde, and hydroxybenzaldehyde and 2) the polymerization of the dialdehydes and diamines. Free-standing precursor films were easily obtained by casting the solutions of the benzoxazines on glass plates, followed by drying. By the thermal curing of the precursor films up to 240 °C, brown-colored, transparent, and tough polybenzoxazine films were obtained. The toughness was confirmed by the tensile test; the tensile strength (sb) and elongation at break (eb) of the polybenzoxazine films were 41–67 MPa and 2.2–4.9%, respectively, which were higher than those of the typical bisphenol A-aniline type polybenzoxazine, PB-a, film (sb = 30 MPa and eb = 1.1%). The glass transition temperatures of the polybenzoxazines derived from the high-molecular-weight benzoxazines were determined to be over 280 °C by dynamic mechanical analysis, which was approximately 100 °C higher than that of PB-a. The polybenzoxazines also showed a high thermal stability as evidenced by the 5% weight loss temperatures in the range of 379–391 °C observed via thermogravimetric analysis.

Sustainability and antimicrobial assessments of apigenin based polybenzoxazine film

The present study reports for the first time the use of bio-based apigenin for polybenzoxazine synthesis. Apigenin comes under flavonoids family that is naturally available in fruits, vegetables, and many herbals abundantly. In this work, apigenin was reacted with furfurylamine/stearylamine and formaldehyde to form multifunctional bio-based benzoxazine monomers (AP-f and AP-s). This interaction was investigated by means of FT-IR, 1H-NMR, 13C-NMR spectroscopic techniques. The as-synthesized monomers, AP-f and AP-s are converted to bio-films by means of ring-opening polymerization with thermal treatment to form a well cross-linked network structure. DSC was used to study the curing behavior of benzoxazine, exhibiting lower curing temperature of 178 °C for AP-f and 226 °C for AP-s than the commercially available benzoxazine. The mechanical and thermal properties of the above-mentioned bio-films are characterized by UTM and TGA. These results reveal that apigenin and furfurylamine based bio-film has better tensile (94 MPa) and thermal stability up to 350 °C. Moreover, both the bio-films, poly(AP-f) and poly(AP-s) have been further investigated for bio-activity with S. aureus. It was confirmed that the bio-films was effective in preventing bio-film associated infection. In a similar way, both the bio-films acts against C-albicans and thus prevents the formation of fungal infection. This information reveals that apigenin-based polybenzoxazine bio-films are capable to be considered as anti-microbial and anti-fungal agents.

Preparation of porous urushiol-based polybenzoxazine films with chemical resistance by breath figures method

A novel benzoxazine monomer (UPA) had been synthesized by the reaction of urushiol with formaldehyde and propylamine. From the ring-opening reaction of UPA, the corresponding new biobased resin polybenzoxazine (PUPA) was obtained. The PUPA was used to fabricate honeycomb-structured porous films using the breath figures technique. The obtained films were characterized by scanning electronic microscopy. The results showed that PUPA films were highly ordered porous films. Furthermore, the PUPA porous films possess excellent acid, alkali and organic solvent resistance properties.

High‐Performance Polybenzoxazine Derived from Polyfunctional Benzoxazine Composed of an Oligonuclear Phenolic Compound Having a 4,4′‐Dimethylenebiphenyl Linker

AbstractA novel polyfunctional benzoxazine monomer, OP‐a, is synthesized from aniline, formaldehyde, and an oligonuclear phenolic compound (OP) with a 4,4′‐dimethylenebiphenyl group as the phenol linker. After thermal curing of OP‐a up to 240 °C, a brown‐colored, transparent polybenzoxazine (POP‐a) film is obtained. The mechanical and thermal properties of the POP‐a film are investigated by tensile test, dynamic mechanical analysis (DMA), and thermogravimetric analysis (TGA). The POP‐a film is extremely tough compared with a typical polybenzoxazine (PB‐a) film. The elongation at break of the POP‐a film is 7.6%, which is surprisingly large for the highly cross‐linked thermoset. The high cross‐link density is suggested from the very high storage modulus (over 1 GPa) above the glass transition temperature (T g) observed by DMA. The T g of POP‐a is also improved significantly to T g = 223 °C, which is approximately 50 °C higher than that of PB‐a. Moreover, TGA reveals that the thermal stability of POP‐a is also enhanced.

Sustainability and antimicrobial assessments of bio based polybenzoxazine film

Renewable materials are abundantly available in nature and have the capability to degrade within a short period of time. In the present study, a novel class of chitosan-based polybenzoxazine has been synthesized for the first time. Water, an edible solvent was used for the benzoxazine synthesis, adopting moderate reaction temperature. This bio-based benzoxazine monomer was crosslinked by thermal treatment via ring-opening polymerization to form free-standing polymer films [poly(E-Ch)] without the evolution of volatiles. Hydrogen bonding interactions were found to exist between chitosan and polybenzoxazine. This type of interactions significantly enhance the thermal and mechanical properties with T10 of about 260 °C; ε′ of about 3.6 GPa; and Tg of about 135 °C showing unusual levels of synergism. Interestingly, both the bio-films-poly(E-Ch) and CH do not affect the cell growth. In particular, poly(E-Ch) is effective in preventing bio-film associted infections.

DEVELOPMENT OF POLY(D,L-LACTIC ACID) WITH POLYBENZOXAZINE VIA SOLUTION BLENDING

Polybenzoxazine was synthesized by using bisphenol A, formaldehyde and diamine as precursor via condensation reaction. Triethylenetetramine was used as diamine precursor. Polybenzoxazine was characterized by FTIR technique in order to confirm the obtained polybenzoxazine. The ratio of poly(D,Llactic acid)/polybenzoxazine (Mw = 10,000 and 20,000 g/mol) was 0:100, 1:99, 3:97 and 5:95, respectively. The poly(D,L-lactic acid)/polybenzoxazine films were characterized by using Scanning Electron Microscope (SEM). The results showed homogenous and smooth films. Thermal stability of poly(D,L-lacticacid)/polybenzoxazine films was better than pure polybenzoxazine film. Moreover, 3:97 ratio of polybenzoxazine mixed with poly(D,L-lactic acid) (Mw = 20,000 g/mol) film showed good tensile strength,because the stress at break was 24.06 ± 7.99 when determined by Universal Tenting Machine. It was concluded that poly(D,L-lactic acid) improved the property of the polybenzoxazine film.

Preparation of Transparent and Flexible Shape Memory Polybenzoxazine Film through Chemical Structure Manipulation and Hydrogen Bonding Control

Polybenzoxazines consisting of chemical structures that differ from conventional polybenzoxazines were obtained at relatively lower temperature with the aid of Lewis acids. It is confirmed by FTIR spectra that the new polybenzoxazines mainly consist of arylamine Mannich-type linkage other than phenolic Mannich-type linkage in conventional polybenzoxazines. Owing to the unique chemical structures, the arylamine Mannich polybenzoxazines possess more weak −OH···π hydrogen bonding but less strong and rigid chelated hydrogen bonding. As a result of the special chemical structures and hydrogen bonding distribution, the arylamine Mannich polybenzoxazines possess many unique properties. For example, they are more flexible. Tensile tests show that the arylamine Mannich polybenzoxazines could be stronger and tougher than phenolic Mannich polybenzoxazine. The highest tensile strength increases 83% while elongation at break value increases 115% for 002P180 (arylamine Mannich polybenzoxazine) compared with PBA-a200 (p...

Synthesis of Eugenol-Based Silicon-Containing Benzoxazines and Their Applications as Bio-Based Organic Coatings

In this work, several bio-based main-chain type benzoxazine oligomers (MCBO) were synthesized from eugenol derivatives via polycondensation reaction with paraformaldehyde and different diamine. Afterwards, their chemical structures were confirmed by Fourier Transform Infrared Spectroscopy (FT-IR) and Nuclear Magnetic Resonance Spectroscopy (1H-NMR). The curing reaction was monitored by Differential Scanning Calorimetry (DSC) and FT-IR. The polybenzoxazine films were prepared via thermal ring-opening reaction of benzoxazine groups without solvent, and their thermodynamic properties, thermal stability, and coating properties were investigated in detail. Results indicated that the cured films exhibited good thermal stability and mechanical properties, showing 10% thermal weight loss (Td10%) temperature as high as 408 °C and modulus at a room temperature of 2100 MPa as well as the glass transition temperature of 123 °C. In addition, the related coatings exhibited high hardness, excellent adhesion, good flexibility, low moisture absorption, and outstanding solvent resistance.

Surface properties and hydrogen bonds of mono-functional polybenzoxazines with different N-substituents

A series of mono-functional benzoxazine monomers with different N-substituents were synthesized from phenol, formaldehyde, and various amines (ammonia, methylamine, n-butylamine, dodecylamine), named P-am, P-m, P-b, and P-da, respectively. The surface properties of these polybenzoxazine films were proven by contact angle measurements. The hydrogen bond network of the polybenzoxazine systems was studied using the FTIR spectra. And the results showed that the surface free energy increased with increasing the fraction of intermolecular hydrogen bonding when the N-substituent was an alkyl chain. However, the rule was not suitable when the N-substituent was H. That was because there was one more kind of intramolecular hydrogen bond in the poly(P-am). Based on these findings, we proposed that both the N-substituent alkyl group and the fraction of intermolecular hydrogen bonding had effects on the surface free energy.

Copolymerization of fluorene‐based main‐chain benzoxazine and their high performance thermosets

A series of fluorene‐based benzoxazine copolymers were synthesized from the mixture of 9,9‐bis(4‐hydroxyphenyl)fluorene and bisphenol A, and 4,4′‐diaminodiphenyloxide and paraformaldehyde. And the cured polybenzoxazine films derived from these copolymers were also obtained. Fourier transform infrared spectroscopy (FTIR) and hydrogen nuclear magnetic resonances confirmed the structure of these benzoxazines. Their molecular weight was estimated by gel permeation chromatography. The curing behavior of the precursors was monitored by FTIR and differential scanning calorimetry. Dynamic mechanical analysis and thermogravimetric analysis were performed to study the thermal properties of the cured polymers. The cured polybenzoxazines exhibit excellent heat resistance with glass transition temperatures (Tg) of 286–317°C, good thermal stability along with the values of 5% weight loss temperatures (T5) over 340°C, and high char yield over 50% at 800°C. The mechanical properties of the cured polymers were also measured by bending tests. Copyright © 2015 John Wiley & Sons, Ltd.

Characterization of Carbon Films Prepared from Polybenzoxazine Films

Characterization of Carbon Films Prepared from Polybenzoxazine Films

Novel near-infrared and multi-colored electrochromic polybenzoxazines with electroactive triarylamine moieties

Two triarylamine-containing flexible polybenzoxazine films with Tg up to 312 °C were prepared by the thermally induced curing reaction of the corresponding polybenzoxazine precursors, which were synthesized by the reaction of paraformaldehyde with bisphenol A and 4,4′-diamino-4′′-methoxytriphenylamine (1) or N,N′-bis(4-aminophenyl)-N,N′-di(4-methoxyphenyl)-1,4-phenylenediamine (2). By introduction of triarylamine units into the polybenzoxazine precursors, the resulting solution-processable polybenzoxazine precursor films not only exhibited interesting multi-colored electrochromic behavior with a high contrast ratio both in the visible range and near infrared region (NIR) but also could effectively increase the oxidation stages when compared with their corresponding polyamides.