Preparations And Applications Of Dynamic Crosslinking Imine-epoxy Polymer

Crosslinking polymers are usually considered to be not reprocessable,non-recyclable or non-degradable thermosets.But in these years,the concept of dynamic crosslinking polymer starts to break the boundary between thermoplastics and thermosets.These crosslinking network polymers could rearrange their structures when the dynamic bonds embedded in undergo associative or dissociative dynamic reaction,activated by external stimuli such as hear or light.The rearrangement of the networks could change the viscoelasticity,interface properties and chemical features of the polymers,bringing themselves special properties such as reprocessing,recycling,self-healing and degradation.Therefore,dynamic crosslinking materials are potential in future applications,and their concepts and designing could also promote the designing,production and applications of exiting industrial polymers.Among many dynamic covalent bonds,imine bond is a common and active dynamic bond which could undergo associative or dissociative dynamic reaction when activated by heat,water or acid solution.In addition,since the industrial products of aldehyde and amine are abundant,the crosslinking networks with imine bonds are more potential to be introduced to large production.Therefore,imine dynamic network polymers are popular in the research field.However,recent imine networks face problems such as expensive ingredients,remnants of active groups,and incomplete degradation,which are needed to be improved.In this article,new methods were designed for developing dynamic imine-epoxy network polymers,which have solved the problems above.Features as dynamic network polymer are characterized,and their potential applications were also explored.The work of this paper includes:(1).Linear polyimines with secondary amines were designed from p-phthalaldehyde,diethyltriamine and polyether amine D-230,and then had it reacted with biphenyl A type epoxy resin E-51.The synthesized polymers could at least be reprocessed for 3 times and maintain their mechanical properties.Besides,the dynamic networks built by this method have the advantage of using cheap raw materials,simple procedures and possessing good performance.This design has solved the recent problems of remaining active groups,which leads to unstable properties of imine networks.(2).We used the biobased vanillin as raw material,and transferred its phenol group to prepare its epoxide intermediate,which was then cured with diamines to prepare polymers.The synthesized polymers could at least be reprocessed for 3 times and maintain their mechanical properties.In addition,the polymers can be chemically degraded by 10 wt% acetic acid,and the degradation product could be regenerated to be polymer.Using biobased raw material,reprocessing and recycling the crosslinking polymer,having the polymer degraded and reusing the degradation product,the design trys to fulfill the idea of green chemistry and sustainability.(3).The potential application of the two polymers above were explored: Benefited from imine natures,polymers(1)were found effective in carbon steel corrosion protection.In addition,the low viscosity of polymers(2)acid-degradation product allowed monodispersed polystyrene particles to self-assemble in,filming into a composite film with structural color,which could change its color,responding to swelling-drying process.