Influence of electronic effects from bridging groups on synthetic reaction and thermally activated polymerization of bisphenol-based benzoxazines

Review on the Accelerated and Low-Temperature Polymerization of Benzoxazine Resins: Addition Polymerizable Sustainable Polymers

Due to their outstanding and versatile properties, polybenzoxazines have quickly occupied a great niche of applications. Developing the ability to polymerize benzoxazine resin at lower temperatures than the current capability is essential in taking advantage of these exceptional properties and remains to be most challenging subject in the field. The current review is classified into several parts to achieve this goal. In this review, fundamentals on the synthesis and evolution of structure, which led to classification of PBz in different generations, are discussed. Classifications of PBzs are defined depending on building block as well as how structure is evolved and property obtained. Progress on the utility of biobased feedstocks from various bio-/waste-mass is also discussed and compared, wherever possible. The second part of review discusses the probable polymerization mechanism proposed for the ring-opening reactions. This is complementary to the third section, where the effect of catalysts/initiators has on triggering polymerization at low temperature is discussed extensively. The role of additional functionalities in influencing the temperature of polymerization is also discussed. There has been a shift in paradigm beyond the lowering of ring-opening polymerization (ROP) temperature and other areas of interest, such as adaptation of molecular functionality with simultaneous improvement of properties.

Propargylamine: an attractive amine source for designing high-performance benzoxazine resins with low polymerization temperatures

A series of benzoxazine resins using propargylamine as the amine source were synthesized to achieve highly thermally stable thermosets with low polymerization temperatures.

Cerium Salts: An Efficient Curing Catalyst for Benzoxazine Based Coatings

The effect of three different cerium salts (Ce(NO3)3.6H2O, CeCl3.7H2O and Ce(OOCCH3)3.5H2O) on the ring-opening polymerization (ROP) of a model diamine-based benzoxazine (4EP-pPDA) was investigated. With the incorporation of the cerium salts, the curing temperature of 4EP-pPDA is reduced substantially, and the glass transition temperatures of the resulting networks are increased significantly. The three cerium salts exhibit different catalytic activities, which were analyzed by FT-IR, NMR, and energy-dispersive X-ray (EDX). Ce(NO3)3.6H2O was found to exhibit the best catalytic effect, which seems to be related to its better dispersibility within 4EP-pPDA benzoxazine precursors.

Electronic effects of asymmetric and meta-alkoxy substituents on the polymerization behavior of bis-benzoxazines

Three isomers of benzoxazine monomers based on m-alkoxyphenol and 4,4′-methylenedianiline were synthesized and successfully isolated by column chromatography.

Development of Hydrogen-Rich Benzoxazine Resins with Low Polymerization Temperature for Space Radiation Shielding

A systematic study has been carried out to develop a material with significant protection properties from galactic cosmic radiation and solar energetic particles. The research focused on the development of hydrogen-rich benzoxazines, which are particularly effective for shielding against such radiation. Newly developed benzoxazine resin can be polymerized at 120 °C, which meets the low-temperature processing requirements for use with ultrahigh molecular weight polyethylene (UHMWPE) fiber, a hydrogen-rich composite reinforcement. This highly reactive benzoxazine resin also exhibits low viscosity and good shelf-life. The structure of the benzoxazine monomer is confirmed by proton nuclear magnetic resonance and Fourier transform infrared spectroscopy. Polymerization behavior and thermal properties are evaluated by differential scanning calorimetry and thermogravimetric analysis. Dynamic mechanical analysis is used to study chemorheological properties of the benzoxazine monomer, rheological properties of the cross-linked polybenzoxazine, and rheological properties of UHMWPE-reinforced polybenzoxazine composites. The theoretical radiation shielding capability of the composite is also evaluated using computer-based simulations.

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%.

Quantitative studies on thep-substituent effect of the phenolic component on the polymerization of benzoxazines

The pure monofunctional benzoxazines substituted by either electron donating or withdrawing groups are synthesized to verify the electronic effect on the polymerization behaviors without any complicated factors of the impurities.

Synthesis and polymerization of benzoxazine molecules with electron-withdrawing group substitution and ring-opening polymerization

The synthesis of strong electron-withdrawing group substituted aromatic amine and phenol-based benzoxazines is hampered due to the poor solubility of the reactant. In this article, a simple methodology is presented to synthesize the strong electron-withdrawing groups substituted benzoxazine monomers from a solution method using a low-boiling polar solvent. In order to achieve this, we used formaldehyde as a reactant as well as a solvent, and the reaction was carried out for a longer time. Also, benzylaniline derivatives were successfully prepared through benzoxazine. The monomers were polymerized by using solution polymerization method using lithium bromide as a catalyst. The structure of the monomers and polymers was confirmed by Fourier transform infrared and nuclear magnetic resonance spectroscopy. The thermally activated polymerization of the monomers was evaluated by differential scanning calorimetry, and thermal properties of polymers were analyzed by thermogravimetric analysis.

Catalytic effect of trifluoroacetamido group on thermally induced ring-opening polymerization of 1,3-benzoxazine and formation of arylamine Mannich bridge structure

The autocatalytic ring-opening polymerization behavior of trifluoroacetamido group containing benzoxazine (FBA) is reported and its curing process was monitored by in situ proton nuclear magnetic resonance and Fourier transform infrared spectra analysis. The ring-opening polymerization temperature of FBA is significantly lower than that of typical 1,3-benzoxazine (BA), which can be attributed to higher stability of benzoxazine zwitterionic ion intermediate due to strong electron-withdrawing effect of trifluoroacetamido substituent. Arylamine Mannich bridge structure is found to form during polymerization, thereby enhancing the thermal stability of FBA homopolymer (poly-FBA). Differential scanning calorimetric analysis indicates that FBA effectively catalyzes the copolymerization of FBA and BA monomers at a temperature even lower than the polymerization temperature of pure FBA monomer, and the resultant copolymer exhibits higher glass transition temperature than either FBA or BA homopolymer, indicating promising possibility of FBA as reactive comonomer of polybenzoxazine systems for curing acceleration and performance improvement.

A study on the chain propagation of benzoxazine

Variation of T_g with conversion of step polymerization, living chain polymerization and non-living chain polymerization of benzoxazine during the curing process.

Preparation and characterization of novel multi-branched polymers in situ cured from benzoxazine/epoxy resin/primary amines blends

Novel high-performance multi-branched copolymers were prepared in situ from benzoxazine, epoxy resin and primary amines through controlling the curing reactions.

The robustness of a thermoset of a main-chain type polybenzoxazine precursor prepared through a strategy of A–A and B–B polycondensation

A polybenzoxazine precursor was prepared via an A–A and B–B condensation, with a much higher molecular weight than those prepared by Mannich condensation. After curing, the thermoset shows robustness in thermal, mechanical, and dielectric properties.

Effect of phenol on the synthesis of benzoxazine

The kinetic parameters of benzoxazine synthesis approximately equaled those of phenol consumption revealing that phenol was the key starting material.

A novel high performance oxazine derivative: design of tetrafunctional monomer, step-wise ring-opening polymerization, improved thermal property and broadened processing window

A novel tetrafunctional oxazine monomer containing benzoxazine and fluorene-oxazine was prepared for the first time using a Mannich condensation reaction of 2,7-dihydroxy-9,9-bis-(4-hydroxyphenyl)fluorene with paraformaldehyde and n-butylamine.

Influence of substituent on equilibrium of benzoxazine synthesis from Mannich base and formaldehyde

Influence of substituents on equilibrium of reaction between Mannich base and formaldehyde to form benzoxazine is the major concern.