Effect of N-substituents on the surface characteristics and hydrogen bonding network of polybenzoxazines

Corrosion Resistance of Mild Steel Coated with Phthalimide-Functionalized Polybenzoxazines

Herein, we synthesized two new phthalimide-functionalized benzoxazine monomers, pPP-BZ and oPP-BZ, through Mannich reactions of 2-(4-hydroxyphenyl)isoindoline-1,3-dione (pPP) and 2-(2-hydroxyphenyl)isoindoline-1,3-dione (oPP), respectively, with p-toluidine and paraformaldehyde. The structures of these two monomers were confirmed using Fourier transform infrared (FTIR) and nuclear magnetic resonance spectroscopy. We used differential scanning calorimetry, FTIR spectroscopy, and thermogravimetric analysis to study the polymerization behavior and thermal stability of the monomers and their corresponding polybenzoxazines. Poly(pPP-BZ) and poly(oPP-BZ) were formed on mild steel (MS) through spin-coating and subsequent thermal curing polymerization. We used various corrosion testing methods to examine the effect of the curing temperature on the corrosion resistance of the coated MS samples in 3.5 wt.% aqueous solution of NaCl. Among our tested systems, the corrosion rate reached a low of 2.78 µm·Y−1 for the MS coated with poly(pPP-BZ)180 (i.e., the coating that had been cured at 180 °C); this value is much lower than that (4.8 µm·Y−1) reported for a maleimide-based benzoxazine compound (MI-Bz)/33 wt.% ACAT (amine-capped aniline trimer) blend. Thus, the incorporation of the imide functional group into the PBZ coatings is an effective strategy for affording high-performance corrosion resistance.

Ring-Opening Polymerization of 1,3-Benzoxazines via Borane Catalyst

Tris(pentafluorophenyl)borane was used as Lewis acid catalyst to lower the ring opening polymerization temperature (ROP) of 1,3-benzoxazines. Dynamic scanning calorimeter studies revealed that on-set ROP temperatures were decreased as much as 98 °C for model benzoxazine compounds. Catalytic polymerization was traced by both FTIR and ¹H NMR, and revealed that tris(pentafluorophenyl)borane acted rapidly and fast curing achieved. Moreover, thermal properties of resulting polybenzoxazines were investigated by thermogravimetric analysis (TGA) and found out that the catalyst has high impact on char yield and even 3 mol % catalyst augmented char yields up to 13%.

Combining benzoxazine and ketene chemistries for self-healing of high performance thermoset surfaces

The use of oxoketene chemistry for self-healable polybenzoxazines is described.

Corrosion protection of hydrophobic bisphenol A-based polybenzoxazine coatings on mild steel

Hydrophobic bisphenol A-based polybenzoxazine coatings with excellent corrosion resistance were prepared through a simple dip coating and thermal curing method.

Fluorine-free superhydrophobic/hydrophobic polybenzoxazine/TiO2 films with excellent thermal stability and reversible wettability

A thermally stable superhydrophobic film with strong adhesion to glass substrates and reversibly switchable behavior was prepared from polybenzoxazine and TiO₂.

Triphenylbenzene core based dendritic benzoxazines and their heat-resistant and photoluminescent polymers

A facile and efficient synthetic route to connect 1,3,5-tri( p-hydroxyl-phenyl)benzene (TP) molecules into polymers was introduced. Specifically, a series of triphenylbenzene core based dendritic benzoxazines were synthesized via Mannich reaction using TP, paraformaldehyde, and amine derivatives including n-propylamine, cyclohexylamine, and aniline. The chemical structure of benzoxazines was characterized by nuclear magnetic resonance spectroscopy (proton and carbon nuclear magnetic resonance) and Fourier transform infrared spectroscopy. Thermally ring-opening polymerization of the dendritic benzoxazines yielded the cross-linked polymers. We found that N-substituents had the significant influence on polymerization temperature, glass transition temperature ( Tg), thermal stability, and char yield. Polybenzoxazine with the N-phenyl group exhibited the highest Tg of 276°C, char yield of 70%, and excellent thermal stability (5 and 10% weight loss temperatures at 356 and 411°C, respectively). Photoluminescent analysis indicated that the cross-linked structure did not quench the triphenylbenzene’s photoluminescence, while only the relative photoluminescent intensity of polybenzoxazines reduced compared with TP.

Synthesis and surface properties of low surface free energy silane-functional polybenzoxazine films

A series of low surface free energy silane-functional polybenzoxazine films were prepared from alkylphenol, paraformaldehyde, and 3-aminopropyltrimethoxysilane (3-APTMOS) using a facile one-step thermal curing method. The chemical structures of these benzoxazine monomers were confirmed by FTIR and (1)H NMR. The surface properties of the series of polybenzoxazine films were proved through contact angle measurement, and the lowest surface energy of these films was 14.91 mJ/m(2). Moreover, the hydrogen bond network of the polybenzoxazine systems was studied using the FTIR spectra. The result showed that the intramolecular hydrogen bonding transformed into intermolecular hydrogen bonding with increasing curing time. Based on these findings, the transformation mechanism between the intermolecular and intramolecular hydrogen bonding during the progress of curing was proposed. The thermogravimetric analysis (TGA) results indicated that the silane-functional polybenzoxazine, with a high char yield of 57.01%, possessed excellent thermal stability.

Preparation and surface properties of novel low surface free energy fluorinated silane-functional polybenzoxazine films

A novel fluorinated silane-functional benzoxazine monomer is synthesized, and the structure is characterized by FTIR and (1)H NMR. Chemical bonds Si-O-Si linkage between the benzoxazine monomer and the substrate are identified through the variation of water contact angles. The low surface free energy calculation and mechanism of the benzoxazine polymer films are proved through contact angle measurement and FTIR. The film formation property and thermal stability of the polybenzoxazine are also investigated. These results clearly show that this novel polybenzoxazine can not only bond to the substrate but also possess even lower surface free energy which is 15.5 mJ/m(2). The polymer also possesses well thermal stability with a glass transition temperature of 188 °C and the 5% weight loss temperatures of 276 °C.