Preparation And Performance Of Intrinsic Self-healing Polyimine Resin Based On Schiff Base

A wide variety of polymeric materials are used in various industries and play an important role in people’s production life.However,micro-cracks are created during polymer processing,molding and using,which could eventually lead to material failure and damage.To prevent and stop material failure,new solutions are being offered by polymer chemistry:the introduction of dynamic covalent bonds into polymer polymeric networks which give materials the ability to repair themselves.Schiff base is an imine structure（-C=N-）formed by the condensation of aldehydes or ketones with primary amines.Among many reactions to form imine structures,Schiff base reaction process is simple which can realize dynamic covalent bond exchange without adding catalysts.The raw materials are widely available,cheap and environmentally friendly,so the introduction of Schiff base structure into the field of self-healing intelligent materials hold unique advantages and broad application prospects.In this paper,we designed and synthesized two intrinsic self-healing polyimide resin materials with dynamic cross-linked structures.The mechanical properties of the polyimide resin materials were regulated by adjusting the Schiff base species and hydrogen bonding content,and the dynamic imine bonding and hydrogen bonding formed a double dynamic cross-linked network,which provided strong support for the self-healing properties of the materials.Firstly,a series of linear Schiff base dynamically cross-linked polyimide resins with grafted anhydride were synthesized from terephthalaldehyde,diethylenetriamine,polyetheramine D-230 and methylhexahydrophthalic anhydride,and the ratio of imine bond and anhydride was controlled by adjusting the ratio of diethylenetriamine and polyetheramine D-230 in the long chain of linear Schiff base to effectively regulate the mechanical properties,which could realize the demand of tensile stress of the materials.The materials could be customized from 0.20～7.79 MPa,which were effectively selected from a wide range（-0.8～84.5℃）by the self-healing temperature.The glass transition temperature Tg of polyimide resin SF-Me HHPA_4:1 was 43.52℃and the tensile strength was 5.47 MPa.After the resin was completely destroyed and heated at 100℃for 1 h,the first self-repair efficiency is as high as99.6%,the second time can also reach 98.2%.And the resin still had high mechanical properties after two repairs.The material enabled rapid self-repair at room temperature and in water,broadening the repair conditions of materials and enabling complete recovery in organic solvents.This new polyimide resin could be repaired under mild conditions,providing data to support the study of the self-healing properties in the materials.Second,the vanillin-based polyimide resin was produced by curing and cross-linking the epoxidized vanillin,amidated epoxidized soybean oil,with polyetheramine T-403,and the amidated epoxidized soybean oil as a long-chain structure with the imine network to form a semi-interpenetrating（IPN）supramolecular polymer network.The prepared imine resin had excellent thermal stability with initial decomposition temperature at 260℃,good mechanical properties with the maximum tensile stress of VE-AESO-0%up to 18.81 MPa and 79.6%self-healing efficiency at 80℃for 1 h after complete destruction of the resin and complete degradation in acidic solution.The bio-based polyimide resin provides a new strategy for the preparation of environmentally friendly polymer materials,and offers a new option for reducing environmental pollution and achieving the dual carbon goal.