Synthesis of renewable soybean protein and acrylate copolymers via ATRP in ionic liquid

In this paper, acrylate and glycidyl methacrylate (GMA) were grafted onto the main chain of soy protein isolate (SPI) in 1-butyl-2,3-dimethylimidazole chloride ionic liquid ([BDMIM][Cl]), to prepare a renewable soy protein graft copolymer via atom transfer radical polymerization (ATRP). The effect of unfolding degree of soy protein structure on pretreated SPI was studied via Fourier-transform infrared spectroscopy (FT-IR), hydrogen nuclear magnetic resonance spectroscopy (1 H NMR), surface tension (ST) and contact angle (CA) measurements. The results of FT-IR, 1 H NMR and energy dispersive spectrometry (EDS) indicated the successful synthesis of 2-bromoisobutyryl-functionalized SPI.The analysis of FT-IR and 1H NMR spectra showed that the soybean protein graft copolymer was successfully synthesized. In addition, the grafting of acrylate onto soybean protein enhanced the hydrophobicity of the copolymer, and the static contact angle was above 90°. Differential scanning calorimetry (DSC) analysis revealed that the thermal stability of pretreated SPI was reduced. The new glass transition temperature in the copolymers also proved the successful synthesis of the copolymers. The tensile strength of the carbon fiber multifilament infiltrated with the copolymers was improved, indicating their potential application in the reinforcement of carbon fiber material. [Display omitted] •SPI graft copolymers were synthesized by using Atom Transfer Radical Polymerization.•By destroying the quaternary structure of SPI with Ionic Liquid and NaHSO3.•The functionalities of GMA and MMA were imparted to SPI.•Proving the potential application of the Soy protein adhesive in carbon fiber.