Preparation And Infrared Radiation Properties Of Composites Based On Helical Polysilane

Low infrared emissivity materials has attracted the attention of researchers due to their applications of infrared stealth.Helical polymers possess the advantages of good compatibility,easy processing and corrosion resistance,which are regarded as ideal organic bond in infrared coating material,their adjustable helical structure and polymerization ratio are able to modulate the infrared emissivity of material precisely.Helical polymers with unsaturated functional groups bring about the unsaturation degree.Helical structure promote the formation of noncovalent interaction which includes the hydrogen bond.The abovementioned factors reduce the infrared emissivity of helical polymers.Pristine helical polymers can’t fulfill the application requirement of infrared stealth.Thus,the selection of appropriate low infrared emissivity packing became an important target.Nanomaterial is a kind of low infrared emissivity packing,the helical polymer are interacted with rodlike,sheet and spherical nanomaterials in different ways.The different ways of combination pattern bring about the different infrared emissivity values.Optical active methyl lactates are utilized as the starting material to prepare chiral dichloro(methoxycarbonyl ethyl propyl ether)methylsilane(DCMMS).DCMMS are copolymerized with dichlorodihexylsilane(DCDHS)to prepare helical polysilane copolymers(HPS).The HPSs are utilized as the matrix to prepare polysilane/nanomaterial composites,the inorganic nanomaterial including multi-walled carbon nanotubes,graphene oxide and hollow spherical indium oxide.Infrared spectroscopy(IR),raman spectroscopy(Raman),nuclear magnetic resonance(NMR),ultraviolet spectrum(UV),circular dichroism(CD),differential scanning calorimetry(DSC),polarized light microscopy(PLM),gel permeation chromatography(GPC),X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),scanning electron microscope(SEM)and transmission electron microscopy(TEM)are utilized to characterize the HPS copolymer and its composite material.The infrared emissivity of materials in 8~14 μm are also investigated.The main contents are as follows:1.Dichloromethylsilane and methyl(S)-2-(allyloxy)propanoate were connected to synthesize monomer with the help of platinum catalysts.Wurtz-coupling reaction were conducted in tetrahydrofuran to polymerize the helical polysilane(HPS).The infrared radiation performance of obtained helical polysilanes were investigated at the same time.With the help of the polysilane helical structure,the side-chain unsaturated functional groups could form intra-and intermolecular hydrogen bonds with the alkyl groups which reduce the infrared emissivity of HPSs.In order to modulate the infrared emissivity of the helical polysilane,we adjusted the copolymerization ratio between dichlorodihexylsilane(DCDHS)and dichloro(methoxycarbonyl ethyl propyl ether)methylsilane(DCMMS).The obtained HPSs expand the boundary of low infrared emissivity polymers and provide a theoretical basis for the design and synthesis of similar helical polymers,which show great prospect in the application field of infrared stealth.2.Preparation of racemic and right-handed helical polysilane(R-HPS and D-HPS)was prepared by according to synthesis route of left-handed helical polysilane(L-HPS).The helical configuration of HPSs and infrared emissivity were investigated.In order to compare the polysilanes with different configurations,all of monomers were copolymerized according to the same ratio.HPSs with similar polymerization degree was obtained by dialysis and other type of post-treatments.Due to the strongest intermolecular hydrogen bond,D-HPS possess the lowest infrared emissivity.Molecular dynamics calculation combined with computer simulation were utilized to calculate the specific molecular pitch and screw diameter.The research of HPS’s configuration provides the mathematical and computational models to explain the mechanism of low infrared emissivity.3.The multi-wall carbon nanotubes(MWNTs)were placed in reaction kettle which contains nitric acid.After high temperature and high pressure acidizing treatment,the carboxyl-functionalized multiwall carbon nanotubes(f-MWNTs)were obtained.The HPS/f-MWNTs composites were prepared by solution blending,the surface of f-MWNTs were wrapped by HPS.The preparation route of HPS/f-MWNTs composites provide readily combination method between helical polymers and carbon nanotubes.The method of solution blending also simplify the treatment of nanoparticle without complex surface modification.Because of the abundant surface carboxyl and hydroxyl groups,there are strong noncovalent interactions between carbon nanotubes and helical polysilanes.The synergistic effect of unsaturated functional groups and hydrogen bonds of HPS and f-MWNTs bring about the low infrared emissivity of HPS/f-MWNTs.Thus,the composites show great prospect in the application of infrared stealth.4.Graphene oxide(GO)and HPS were dispersed in polar solvent,then the HPS solution was dropped into the GO dispersion.After ultrasonic dispersion,removing solvent to obtain the HPS/GO composites.There are abundant oxygen containing groups on GO surface such as carboxyl,epoxy groups and hydroxyl.With the help of intermolecular noncovalent interaction,HPS could change its backbone structure,and tightly covered on the GO surface.The unsaturated groups of HPS/GO and their intermolecular hydrogen bonds contribute to the reduction of infrared emissivity,which leading to the application of infrared stealth.5.Glucose was applied as the carbon source,ethanol and water were used for the hydrothermal solution.The size of the carbon ball were controlled by the time and temperature of the hydrothermal reaction.Then,the obtained carbon spheres were added to indium nitrate solution again.After second hydrothermal reaction,indium oxide was coated on the surface of carbon sphere.Then,the inner carbon ball was calcined to prepare the hollow oxide sphere.The solution of hollow oxide indium spheres and helical polysilane were blending to prepare the HPS/In2O3 composite.Since the hollow structural In2O3 spheres possess abundant hydroxyl groups,a large amount of HPS can be encapsulated in composites.The unsaturated group of HPS In2O3 and internal molecular hydrogen bonds contribute to the reduction of infrared emissivity,which can be applied in the application of infrared stealth.In conclusion,this thesis focus on the synthesis of HPS and its application in low infrared emissivity composite materials.This research helps us understand the relationship between intermolecular hydrogen bond and infrared emissivity,and further explain the chemical and optical properties of materials.In addition,molecular dynamics calculation and computer simulation were applied to quantitatively reveal the relationship between polymer morphology and infrared emissivity.A variety of analyses were utilized and a series of explanations were put forward to analyze materials’ physical and chemical properties.Our research provide the theoretical and experimental basis for the design and modulation of polymers’ structures and properties,which promote the development of infrared materials.