Preparation Of Polysiloxanes Modified By Cyanoacryloyloxycarbonyl Group

Polysiloxane products have good mechanical properties,low temperature resistance and excellent weather resistance.Linear polysiloxane or branched polysiloxane and polysiloxanes with lower degree of cross-linking have poor mechanical properties.In order to exert the most excellent performance of polysiloxane,it is usually necessary to cure before industrial applications.Depending on the way of cross-linking,polysiloxane curing system can be separated in four types,namely,condensation curing,hrdrosilylation,free-racdical peroxide-induced curing and photoinitiated curing.However,the application of these curing methods in some fields such as criminal investigation,aerospace,and repair of large pipes still has certain limitations.In this paper,the cyanoacryloyloxy functional group is introduced into the molecular chain of polysiloxane to facilitate a quick vulcanization characteristic to traditional silicone polymers in humid environment with good mechanical properties.This new structure of polysiloxane not only expands the curing system of polysiloxane,but also enriches the application fields of silicone products.In this paper,five synthetic routes were designed and the feasibility of each route was analyzed.The intermediates used in each route were characterized in detail.The optimal route for the preparation of cyanoacryloyloxy functionalized polysiloxane was screened,and the performance of crosslinked polysiloxane was tested and analyzed.This paper mainly includes the following five parts:In the first chapter,the curing methods and mechanisms of the traditional polysiloxanes and those of ?-cyanoacrylate compounds were briefly introduced.The advantages and disadvantages of the cross-linking curing system of silicones and those of ?-cyanoacrylate system were analyzed,together with a summary on researches on cyanoacryloyloxy functionalized polysiloxanes reported in literatures.In the second chapter,the preparation process of anthracene-protected cyanofunctionalized intermediates was explored,including anthracene/2-cyanoacrylic acid adduct,anthracene/2-cyanoacrylic acid potassium adduct,anthracene/2-cyanoacrylic acid sodium adduct and anthracene/2-cyanoacryloyl chloride adduct.Their structures were determined by single crystal diffraction,NMR spectra and FT-IR spectra.In the third chapter,the preparation process of each kind of polysiloxane intermediates including vinyl MT-type polysiloxane with low hydroxyl content,branched-chain polysiloxane containing hydrogen,polysiloxane containing hydrogen atoms at both ends and side groups,hydroxypropyl terminated polysiloxane and hydroxypropyl functionalized polysiloxane,were studied in detail.The optimal synthesis method for the preparation of vinyl MT-type polysiloxane with low hydroxyl content and the method for reducing the hydroxyl content were explored.The optimal synthesis route of hydroxyl alkyl functionalized polysiloxane was also screened.In the fourth chapter,five designed synthetic routes were verified and screened.The anthracene-protected cyano functionalized intermediates prepared in the second chapter and the polysiloxane intermediates prepared in the third chapter were used as the raw materials.Firstly,the route for the preparation of anthracene-protected cyano acryloyloxy functionalized polysiloxane was screened.Subsequently,the cyano acryloyloxy functionalized polysiloxanes with different contents of cyano acryloyloxy functional group were prepared by the Retro Diels-Alder reaction.The curing time,crosslinking density and thermal properties of the cured polysiloxane were tested.In the fifth chapter,the experimental routs designed in this paper were analyzed and summarized.Problems encountered and needed to be solved in the future were proposed,which might help to overcome the drawback like controlling the speed of vulcanization of cyano acryloyloxy functionalized polysiloxane networks and made this kind of novel polysiloxane a really interesting material.Through a series of experimental explorations,an experimental route that is easy to implement and can freely regulate the content of cyanoacryloyloxy functional groups on polysiloxane was screened out.The crosslinking curing speed of the cyanoacryloyloxy functional polysiloxane increases with the increase of the content of the cyanoacryloyloxy functional group.By adjusting the content of cyanoacryloxy functional groups,a series of cyanoacryloxy functional polysiloxanes with different curing speeds can be prepared.