Preparation Of Novel Helical Polyacetylene Nanocomposites And Its Infrared Emissivity Properties

Polymers with anti-corrosion,low density,functional diversity and excellent physical and chemical properties have great potential in the field of optoelectronic applications.In particular,the structural changes of materials at molecular scale and the tunability of the composition provide a new way to control the emissivity artificially.Spiral polymer with orderly molecular structure has become a class of low-infrared emissivity materials with practical values.Precise and orderly helical structures can effectively reduce the degree of hydrogen deficiency of unsaturated groups in macromolecules,thus changing the molecular vibration mode.So the infrared emissivities of helical polymers can be reduced to ideal values.In addition,the hybridization of the helical polymer with the nano-materials can make full use of the quantum size effect and surface effect of inorganic nanoparticles and enhance the interface effect between the polymer and the inorganic nanoparticles,thus reducing the infrared radiation energy of the organic and inorganic hybrid system.In this paper,two propargylamide monomers which were based on chiral stigmasterol and achiral pivalic acid were prepared by amidation reaction,respectively(M1 and M2).Then,the homopolymer of M1 and copolymers of M1 and M2 were synthesized by coordination polymerization of rhodium metal catalyst.Nanocomposites were prepared by compositing the copolymer PA which has stabilized helical conformation with nano-carbon materials such as acidified multi-walled carbon nanotube(f-MWNTs)and oxidized grapheme(GO).Fourier transform infrared spectroscopy(FT-IR),nuclear magnetic resonance(NMR),UV-vis spectroscopy,circular dichroism(CD)spectroscopy,GPC,X-ray diffraction XRD,scanning electron microscopy(SEM),transmission electron microscopy(TEM),X-ray photoelectron spectroscopy(XPS)and thermogravimetric analysis(TGA)were used to characterize the structure and properties of the nanocomposites.And heir infrared emissivities at 8-14 ?m were also measured.The experimental results are summarized as follows:1.Synthesis,characterization and infrared radiation characteristics of helical polymersThe chiral N-propargylamide M1 based on stigmasterol was polymerized into poly(Ml)with moderate molecular weight and homogeneous distribution under the coordination polymerization of rhodium metal catalyst.The asymmetric interaction between N-H bonds and C=O bonds in side chains is the important driving force to construct and maintain helical conformation.Among them,the N-H bonds and C=O bonds of amide groups are involved in intermolecular and intramolecular hydrogen bonds,while the C=O bonds in ester structures are mainly involved in the formation of intramolecular hydrogen bonds.The stability and regularity of helical structures are affected by many factors,such as catalyst content,solvent and so on.From the circular dichroism spectrum,we found that the helical structure of copolymers changed significantly with changing components.When the molar ratio of M1 to M2 was 1:2,the hydrogen bond interaction and spatial repulsion achieved the best synergistic effect and Poly(M10.33-co-M20.67)showed the highest optical activity.The infrared emissivity of Poly(M10.33-co-M20.67)can be as low as 0.536.2.The hybridization of helical polyacetylene and multi-walled carbon nanotubes and its infrared radiation characteristicsThe multi-walled carbon nanotubes were oxidized with high temperature concentrated sulfuric acid and oxygen-containing reactive groups were formed on the surface.The PA@f-MWNTs nanocomposites were prepared by solution blending.From the characterization results,it can be seen that the recombination process only occurs on the surface of carbon nanotubes.The polymers are evenly coated on the surface of f-MWNTs and the crystal structures inside f-MWNTs are not damaged.The composite nanoparticles still have good optical activity and thermal stability.Compared with pure CNTs,the infrared emissivity of PA@f-MWNTs nanocomposites decreased,indicating that ?-? conjugation and electron transfer between polymers and carbon nanotubes significantly contribute to the decrease of infrared emissivity.3.The hybridization of helical polyacetylene and oxidized graphene and its infrared radiation characteristicsPA@GO nanocomposites were prepared by mixing the polymers with oxidized graphene by solution blending.During the compounding process,polymers still retain helical secondary structures and are attached to the surface of the graphene oxide layer in an irregular island-like state.The formation of hydrogen bonding between functional groups in PA structures and oxygen-containing groups on graphene oxide layer has a great effect on improving the stabilities of helical PA.The infrared emissivity of the PA@GO nanocomposites(s=0.593)is lower than that of mixture(s=0.704),indicating that the interaction between the organic and inorganic interfaces can reduce the infrared emissivity effectively.