Synthesis and characterization of a novel acetylene- and maleimide-terminated benzoxazine and its high-performance thermosets

Synthesis of lignin-modified cellulose nanocrystals with antioxidant activity via Diels-Alder reaction and its application in carboxymethyl cellulose film

Multifunctional polymers derived from renewable organic substances have received significant attention. In this work, the Diels-Alder "click" reaction was used to synthesize a renewable copolymer with the mechanical strength of cellulose nanocrystals (CNCs) and the natural antioxidant activity of lignin. Chemical structural analysis and molecular weight results confirmed that lignin was successfully attached to the CNCs. Phenolic hydroxyl groups were introduced into CNCs, resulting in good antioxidant activity with an IC₅₀ value of 1.49 mg/mL, although a slight decrease in the crystallinity index and thermal properties was observed. Additionally, carboxymethyl cellulose (CMC) films containing lignin-modified CNCs were prepared by solution casting. The lignin-modified CNCs endowed film with antioxidant activity and also contributed to increasing the tensile strength by 70%. This indicated that the lignin-modified CNCs with good antioxidant activities and mechanical strength have promising applications in multifunctional materials.

Preparation and properties of bismaleimide resin blended with alkynyl-terminated modifiers

A kind of modified bismaleimide resin, with good processability, heat resistance, and impact strength was developed, using 4,4′-dipropargyloxydiphenyl ether (DPEDPE), N-(4-propargyloxyphenyl)maleimide (4-PPM), and 3-ethynylphenyl maleimide (3-EPM) as modifiers. The DPEDPE, 4-PPM, and 3-EPM were synthesized and characterized by Fourier transform infrared spectroscopy (FTIR) and 1H-nuclear magnetic resonance (1H NMR), and used to modify the N,N′-(4,4′-diphenylmethane)bismaleimide (BDM)/2,2′-diallyl bisphenol A (DABPA) resin system (BD) to obtain the different blend resin systems of DPEDPE-modified BD (BDD), 4-PPM-modified BD (BDP), and 3-EPM-modified BD (BDE). The curing temperature of BD resin increases with increase of the alkynyl-terminated modifier content. The processability of BD resin was improved with addition of the propargyloxy-terminated compounds. The temperature of 5% weight loss, residual yield at 800°C and glass transition temperature of the cured BD resin increase with increase of the alkynyl-terminated modifier content and can reach 443°C, 46.7% and higher than 380°C. The tensile strength of the cured BD resin decreases with increase of alkynyl-terminated modifier content. The impact strength of the cured BD resin increases with increase of the propargyloxy-terminated compound content and can increase by 65%. The tensile strength, elastic modulus, and impact strength of the cured BD resin blended with DPEDPE can be 73.7 MPa, 4.1 GPa, and 19.6 kJ m−2, respectively. Moreover, the cured BD resin blended with DPEDPE has good water absorption resistance.

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.

Synthesis of a benzoxazine monomer contained hyperbranched polysiloxane and the characteristics of its polymer alloys blend with bismaleimides

A novel benzoxazine monomer contained hyperbranched polysiloxane structure (HBPSi-BOZ) was synthesized via a solvent process based on the polyformaldehyde, aniline, and a new hyperbranched polysiloxane with terminal amino groups (HBPSi-NH2). The HBPSi-BOZ was then used as modified phase to blend with bismaleimides (BMIs) resin, and a polymer alloy HBPSi-BOZ/BMI was successfully prepared. The thermal resistant properties, mechanical properties, and tribological properties of HBPSi-BOZ/BMI resins with different contents of HBPSi-BOZ prepared were researched to get an optimal ratio. The thermogravimetric analysis was also carried out to study the polymerization process and stability of HBPSi-BOZ/BMI resins. The results showed that as the thermal resistance increased, the wear resistance and mechanical properties of HBPSi-BOZ/BMI resins were also enhanced.

Study on the catalytic prepolymerization of an acetylene-functional benzoxazine and the thermal degradation of its cured product

The network structures of Polypre(Ph-apa-ca) and Poly(Ph-apa).

A simple method to introduce phosphoester groups into a polybenzoxazine backbone as multifunctional modifiers

Phosphoester groups were conveniently introduced into benzoxazine monomers by chemical bonding through nucleophilic reaction of a benzoxazine ring with diethyl phosphite (DEP).

Synthesis of novel imide-functionalized fluorinated benzoxazines and properties of their thermosets

In this study, two novel imide-functionalized fluorinated benzoxazines, N,N′-bis( N-phenylacetylene-3,4-dihydro-2H-1,3-benzoxazinyl)-(4,4′-hexafluoroisopropylidene)bisphthalimide (6FIBZ-apa) and N,N′-bis( N-phenyl-3,4-dihydro-2H-1,3-benzoxazinyl)-(4,4′-hexafluoroisopropylidene)bisphthalimide (6FIBZ-a), were successfully synthesized. The structures of the benzoxazines were confirmed by Fourier transform infrared and proton nuclear magnetic resonance spectroscopies. The novel benzoxazines were easily dissolved in common organic solvents. The differential scanning calorimetric curve of 6FIBZ-apa showed only a single exothermic peak since oxazine ring-opening and acetylene addition polymerization occurred simultaneously in the same temperature range. The introduction of rigid and thermally stable imide moiety led to rigid molecular structure, thus resulting in an increase in the glass transition temperature and improvement in thermal stability. The thermal properties were further improved significantly by the incorporation of cross-linkable acetylene groups to increase the cross-linking density as evidenced by thermogravimetric analysis.