Formaldehyde-Free Synthesis of Fully Bio-Based Multifunctional Bisbenzoxazine Resins from Natural Renewable Starting Materials

Abstract

Although bio-based benzoxazines (BZs) have been explored widely as sustainable thermosetting resins, few high-performance BZs have been prepared completely from natural renewable resources. In this study we synthesized a fully bio-based multifunctional bisbenzoxazine (AP-fa-BZ) in high yield and purity from apigenin (AP), furfurylamine (fa), and benzaldehyde by using both solvent and solventless approaches. Fourier transform infrared (FTIR) spectroscopy, high-resolution mass spectrometry, and one- and two-dimensional nuclear magnetic resonance spectroscopy confirmed the chemical structure of AP-fa-BZ. We then used dynamic mechanical analysis, differential scanning calorimetry (DSC), thermogravimetric analysis, and in situ FTIR spectroscopy to examine the thermal characteristics of AP-fa-BZ before and after its ring-opening polymerization (ROP). DSC revealed that the temperature required for the formation of poly­(AP-fa-BZ) through ROP (236.3 °C) was significantly lower than that of a typical 4-phenyl-3,4-dihydro-2H-1,3-benzoxazine (Pa-type) monomer due to the positive catalytic effect of the phenolic OH groups in the AP structure. After thermal polymerization at 250 °C, the resulting poly­(AP-fa-BZ) possessed a high thermal decomposition temperature (T d10 = 395 °C), a high char yield (52 wt %), and a high glass transition temperature (T g = 283 °C). Contact angle measurements revealed the tunable surface properties of AP-fa-BZ. Finally, the AP-fa-BZ resin functioned as an antibacterial agent against both Staphylococcus aureus and Escherichia coli.

Biobased Bisbenzoxazine Resins Derived from Natural Renewable Monophenols and Diamine: Synthesis and Property Investigations

“…As a result, poly­(G-pa) , poly­(S-pa) , and poly­(P-pa) show relatively higher surface-free-energy values compared to other reported petroleum-derived polybenzoxazines . Nevertheless, the surface-free-energy values obtained from these newly developed biobased polybenzoxazines are still much lower than recently reported bio-polybenzoxazines …”

“…42 Nevertheless, the surface-free-energy values obtained from these newly developed biobased polybenzoxazines are still much lower than recently reported bio-polybenzoxazines. 41 Thermal Properties of Polybenzoxazines Derived from Biobased Bisbenzoxazine Resins. A series of biobased polybenzoxazine film samples, poly(G-pa), poly(Spa), and poly(P-pa), were obtained by curing of G-pa, S-pa, and P-pa using stepwise procedures, respectively.…”

“…Polybenzoxazines, which possess both inter- and intramolecular hydrogen bonding network structures, have been reported as a novel class of low surface-free-energy thermoset polymers . The manipulation of hydrogen bonding interactions in polybenzoxazine networks has been determined to be an efficient approach to achieve low surface-free-energy polymeric materials without needing to incorporate fluoro-containing segments. − …”

Crown Ether- and Benzoxazine-Linked Porous Organic Polymers Displaying Enhanced Metal Ion and CO2 Capture through Solid-State Chemical Transformation

“…Polymers incorporating benzoxazine (BZ) linkages, synthesized through Mannich condensation from primary amines, phenols, and CH 2 O, can feature strong intramolecular and intermolecular hydrogen bonds after they undergo thermal ring-opening polymerization (ROP) of their BZ units and these H-bonding interactions could improve the properties of PBZ materials. − Without the need for any thermal curing agent or catalyst, the thermal ROPs of BZ rings can result in poly­(benzoxazines) exhibiting low surface free energy, low dielectric constant, and high thermal stabilities. − As a result, several syntheses of BZ-linked POPs have appeared recently. For example, Xu et al reacted a triphenol, a diamine, and CH 2 O to prepare a BZ-linked POP possessing a high surface area (231 m 2 g –1 ) .…”

Facile Strategy for Room Temperature Knitting of Sulfur in Polybenzoxazine: A New Class of Solution Processable Copolymers

“…Polybenzoxazines (PBzs) have emerged as a popular choice among phenolic thermosets due to their superior physicochemical and thermomechanical properties over conventional resins. , A benzoxazine (Bz) monomer is usually synthesized by a condensation reaction of a phenol and amine in the presence of aldehyde to form a six-membered 1,3-oxazine ring. − The monomer undergoes ring-opening polymerization (ROP) to form PBzs in the presence of an initiator, catalyst, or simple heat treatment (180–280 °C). − A wide variety of precursors are utilized to tune the structure of the monomer and tailor the polymer properties. In this direction, incorporating additional functionality in the monomer, utility of biorenewable feedstocks, and alloying with other (bio)­polymers are well-reported. , …”