Study On Wetting Regulation And Water/humidity Response Characteristics Of Urushiol-based Polybenzoxazine

Benzoxazine resin is a new type of high-performance thermosetting resin.In addition to the advantages of high strength,high modulus,high temperature resistance and no release of small molecular substances in resin ring-opening polymerization,benzoxazine resin also has a near-zero shrinkage during curing process,flame retardancy,low dielectric constant,low surface energy,low water absorption and other unique excellent characteristics.In addition,benzoxazine also has flexible molecular designability,and the molecular structure of the polymer can be changed by changing the phenol source and amine source,so as to realize the high performance and functionalization of the material.Polybenzoxazine is an inherently hydrophobic polymer due to intramolecular hydrogen bonding.This low surface energy characteristic greatly limits the application fields of polybenzoxazines.Based on the flexible molecular designability of benzoxazine resin,different hydrophilic functional groups(melamine,polyethyleneimine,polyethylene glycol amine)were introduced into benzoxazine structure by changing amine source,and the molecular structure and molecular composition(feed ratio,molecular weight)were adjusted to control the wettability of benzoxazine,and the water / humidity response of this new type of benzoxazine was explored.The specific research contents are as follows:1.Eugenol/melamine-based benzoxazine(E-M)and eugenol/polyethyleneimino-based(E-pei)were prepared from eugenol,melamine/diethylamine and formaldehyde aqueous solution with different molar ratios,and the synthesis conditions of E-M and E-pei were optimized.Eugenol/melamine-based benzoxazine polymers(E-MBPs)and eugenol/di-terminal amine polyethyleneimino-based benzoxazine polymers(E-PEIBPs)were obtained by thermosetting.The contact angle test found that changing the molar ratio of eugenol and melamine could slightly affect the contact angle of the coating,but could not effectively control the wettability of E-MBPs.Changing the molar ratio of eugenol and double-terminated amine polyethyleneimine can more effectively improve the wettability of E-PEIBPs,but it still cannot change the hydrophobic properties of traditional polybenzoxazine resins.2.Using polyethylene glycol methyl ether methacrylate(Mn=300,475 and 950)and4-aminothiophenol as raw materials,polyethylene glycol amine(sa PEG)was synthesized by click reaction,and the synthesis conditions of sa PEG were explored and optimized.Eugenol,catechol and urushiol polyethylene glycol benzoxazines((E-PEG,C-PEG and U-PEG)were synthesized by sa PEG,different phenol sources(eugenol,catechol and urushiol)and paraformaldehyde respectively.The preparation methods,structure and thermal curing behavior of monomers E-PEG,C-PEG and U-PEG were studied.Eugenol type,catechol type and urushiol type polyethylene glycol based benzoxazine polymers(E-PEGBPs,C-PEGBPs and U-PEGBPs)were obtained by monomer thermosetting.The thermal stability and contact angle of polymers E-PEGBPs,C-PEGBPs and U-PEGBPs were analyzed.The results show that the contact angle of the polymer coating decreases with the increase of the molecular weight of polyethylene glycol;Secondly,changing the molecular structure of the phenol source can also effectively control the wettability of the polymer;The contact angle of C-PEGBPs coating is the smallest.The contact angle of C-PEG950 BPs coating can reach 29.8 ± 3.3 °,while the contact angle of E-PEG300 BPs coating is the largest,101.3 ± 1.8 °,indicating that changing the molecular weight and phenol type can effectively control the wettability of polyethylene glycol benzoxazine polymer.3.Water/humidity responsiveness of polyethylene glycol-based polybenzoxazines.Using PTFE as a mold,splines of polymers E-PEGBPs,C-PEGBPs and U-PEGBPs were prepared by curing.Fourier transform infrared spectroscopy(FTIR),X-ray photoelectron spectroscopy(XPS),scanning electron microscopy(SEM)and X-ray energy dispersive analysis(EDS)were used to prove that polyethylene glycol-based benzoxazine has a self-stratification effect during curing.The results show that the benzoxazine main chain is enriched in the upper layer and the polyethylene glycol functional group is enriched in the lower layer,and the two endow the polyethylene glycol-based benzoxazine polymer with water-responsive shape deformation properties through a binary synergistic effect.The results show that E-PEG950 BPs has the most excellent water responsive performance,and its spline is immersed in water for only 15 s,and the bending angle of the spline reaches 0.69 π.After being heated,the splines could return to their original state with the reduction of moisture in the splines,indicating that the PEG-based polybenzoxazine has reversible responsiveness.Further,we used E-PEG950 BPs splines to hook the rubber band on water and transport it for release,demonstrating the application potential of its polymer claws.