Biobased Chitosan/Polybenzoxazine Cross-Linked Films: Preparation in Aqueous Media and Synergistic Improvements in Thermal and Mechanical Properties

Abstract

A novel class of polymer blends has been prepared from main-chain-type benzoxazine polymer (MCBP) and chitosan (CTS), a modified biomacromolecule. A water-soluble, main-chain-type benzoxazine polymer, MCBP(BA-tepa), was synthesized from the reaction of bisphenol A (BA), tetraethylenepentamine (TEPA) and formalin. The structure of the MCBP(BA-tepa) was confirmed by proton nuclear magnetic resonance spectroscopy ((1)H NMR) and Fourier transform infrared spectroscopy (FT-IR). The polymer blends were prepared by mixing MCBP(BA-tepa) and CTS in aqueous acetic acid solution (1%). The CTS/MCBP(BA-tepa) films are cross-linked by thermal treatment via the ring-opening polymerization of benzoxazine structures in the main chain to produce an AB-cross-linked network. Differential scanning calorimetry (DSC) and FT-IR were used to study the effects of CTS on the polymerization behavior of benzoxazine. Hydrogen bonding between polybenzoxazine and CTS structures was also observed. The mechanical and thermal properties of cross-linked CTS/MCBP(BA-tepa) films were evaluated, and the results showed unusual levels of synergism. In particular, the tensile strength and thermal stability were significantly enhanced in a nonlinear fashion.

Study on an amine-containing benzoxazine: Homo- and copolymerization with epoxy resin

“…The resonances at 6.8-7.2 ppm are assigned to the protons on aromatic rings. The peaks in the range of 3.7-3.9 ppm were assigned to Ar-CH 2 -N and N-CH 2 -N structures, which has been reported in other literatures as well [16,23,24]. A resonance chemical shift at 3.5 ppm confirms the formation of N-H.…”

“…The thermal stability of all samples was studied by TGA ( Figure 8) and the results have been summarized in Table 1. The decomposition temperature of P-deta homopolymer is similar to MCBP BA-tepa [24] and P-ad6 [32]. The similar aliphatic diamine structure is probably the dominant cause of the initial decomposition.…”

“…The synthesis method is a modification of preparing a main-chain type benzoxazine polymer reported elsewhere [23,24]. Specifically, phenol (18.8 g, 0.2 mol) was dissolved in dichloromethane (50 mL) in a 250 mL flask before adding DETA (10.3 g, 0.1 mol).…”

“…Apparently, rather than crosslink density, Bz fraction is more dominant to determine the char yield of the copolymers. In summary, comparing with a Bz monomer (P-ad6 in [32]) and a main-chain type Bz polymer (BA-tepa in [24]) of similar molecular structures, P-deta homopolymer exhibits higher modulus under room temperature than both while thermal stability and char yield in-between. P-deta/Ep copolymers inherits the high modulus from P-deta homopolymer.…”

Polymer/Carbon-Based Hybrid Aerogels: Preparation, Properties and Applications

“…Polybenzoxazine has excellent molecular design flexibility that allows the properties of the cured materials to be controlled for various applications. Polybenzoxazine has many advantageous characteristics compared with traditional phenolic resin, such as high mechanical strength, near-zero shrinkage upon polymerization of its monomer, and high char yield [134,135]. Interestingly, ring-opening polymerization of benzoxazine in solvents leads to gelation and formation of 3D polymer networks [136,137].…”