Synthesis And Material Properties Of Bio-based Imidazole And Its Polymer

Since the advent of polymer materials,they have played a vital role in promoting the rapid development of society.However,most polymer materials are heavily dependent on non-renewable petroleum resources,and people are faced with energy crisis and environmental pollution problems,so the research and development of bio-based polymers have increased rapidly in recent years.Epoxy resins are commonly used as prepolymers in various industries,and in order to convert epoxy resins into cross-linked networks with desirable thermal and mechanical properties,the resins must be cured with hardeners.The curing agent can be a variety of compounds,such as polyamines,anhydrides or Lewis acids or bases.Like epoxy resins,currently commonly used curing agents also come from petroleum-based resources.Many common curing agents are toxic before curing,which brings additional environmental and health concerns.Therefore,the development of safer epoxy curing agents from bio-based,sustainable alternative sources has been the subject of much research worldwide..In this paper,vanillin as raw material,through the molecular structure design,synthesis of biological imidazoldiene（BIM）monomer,using mercapto-ene click as a tool for synthesis of controllable polymer structure,the construction of a series of biological imidazole linear polymers.In addition,the alkylated imidazole was synthesized and a series of imidazole latent curing agents were prepared by mercapto-ene click reaction.The main research contents and conclusions are as follows:（1）Firstly,a series of novel linear polymers based on imidazole were designed and prepared by using vanillin as raw material and the structural characteristics of vanillin.The chemical structure and molecular weight of the product were identified.The thermal properties of the products were characterized,and the glass transition temperatures（T_g）of a series of biobased imidazole linear polymers were 90.2℃,87.9℃,74.7℃,60.4℃,48.7℃and 46.3℃,respectively.Tg changes with the length of the dimercaptan chain.The longer the dimercaptan chain,the smaller the T_g.If there are other heteroatoms in a segment of the same length,the Tg will get smaller.The 5%weight loss temperature(T_5%)of the imidazole linear chain polymer is higher than330℃.The residual carbon content of polymer at 800℃is more than 37%,and the largest residual carbon content is BIM-C₂,which is 49.1%.The maximum thermal decomposition rate temperature is above 348.5℃,and the highest temperature is BIM-C₁₀,which reaches 391.8℃.（2）A series of linear polymers of biobase alkylated imidazole were prepared by substituting the prepared biobase imidazole monomer with n-butane bromide,and then mercapto-ene reaction was performed on different dimercaptan compounds to prepare a series of linear polymers of biobase alkylated imidazole,which were used as macromolecular latent curing agent and mixed with commercial E51 epoxy resin to obtain one-component epoxy resin prepolymers.The storage stability at room temperature and the curing behavior at temperature were studied,and the thermal and mechanical properties of the cured resin were characterized.The results showed that the one-component epoxy resin prepolymers retained fluidity at room temperature for more than 90 days and cured quickly at high temperature.In addition,the introduction of the soft chain effectively increased the impact strength of the cured resin,while the bending strength and bending modulus were not reduced,meaning that the soft chain successfully toughened the cured resin without sacrificing strength.