Researches On Functional Film Graft,metal Coating Fabrication And Coating-substrate Interface Based On Molecular Bonding

Recently,organic films have aroused considerable attentions in various fields due to their excellent properties and great application potentiality.Surface metallization endows polymer materials with merit properties,such as electrical conductivity and reflectivity,broadening their applications in electronic,automobile,appliances,aerospace and so on.However,the inherent physicochemical properties of polymer make the adhesive metal coating difficult to deposit onto the surfaces.Organic functional films,which can be grafted onto the surfaces and induce metal deposition to form coatings,resulting in surface metallization.At the meantime,there are chemical covalent bondings forming at the interfaces of coatings and substrates and then improving the joint stability of coatings.This dissertation starts from optimizing traditional ABS surface finishing technology and develops palladium-free activation process.Various polymer surfaces have been modified via molecular bonding and metallized with spray-plating.Composition,morphology,physicochemical properties,interfacial adhesion and its mechanism of surface coatings were studied in details.Moreover,the molecular bonding technique and spray-plating were applied to modify flexible substrate surface and fabricate conductive circuits.The main results were listed as follows:（1）Micro structures have formed on ABS surfaces after etching treatment.Then,silver coatings with faced centered cubic structure were deposited by electroless silver plating instead of traditional palladium activation.The coatings’surfaces are smooth and uniform,and the thickness is only 90 nm.After optimizing the processes of electroless silver plating,Cu electroplating was performed on silver-coated ABS,and the stable plating potential is 0.5 V.The metal coatings are with smooth surfaces and adhesive to the substrate,because no block has been peeled off after tape test.（2）Molecular bonding technique was used to graft organic functional triazine films onto ABS surfaces,resulting in that pTES molecules were activated and grafting onto the surfaces.The nTES molecules were coupled with pTES with Si-O-Si via dehydration condensation reaction of silanes.The UV light of 254 nm wavelength is more effective to active azides of pTES.Using molecular bonding technology to modify LCP surfaces,the grafted films are as thin as 3 nm.As nTES molecule’s concentration,assemble time and treating pass increase,surface grafting amounts and rough structures increase.Studying reactivity of thiol groups in nTES with typical metallic ions,there are 17.87%oxides in Ag absorbed films.The Cu layer is thick,while Ni layer is thin.Ag⁺and Cu²⁺will absorb with nTES via Ag-S or Cu-S bond,but Ni²⁺will attach onto nTES films only with physical adsorption.As the adsorption time increases,contact angles of these three surfaces decrease.When adsorption amounts of Ag⁺and Cu²⁺rise,the surfaces’Zeta potential increases,but the Ni²⁺layers are oxidizing and the Zeta potential steps up.（3）The Ag coatings by spray assisted layer by layer deposition show distinct metal luster and smooth morphology with high purity.Their surfaces exhibit more uniform if the reducing agent is formaldehyde.The crystalline structure is face centered cubic and the grain size is nano level.With different spray solution,the Ag surfaces show homogeneous and continuous micro particles,with lowest surface resistance of 0.456Ω/sq.The resistivity was calculated as 6.2×10^-8Ω·m via multiply surface resistance and thickness,and it is close to the standard resistivity of bulk Ag.Reflectance of Ag coatings would be larger than 90%in infrared spectrum and increase as the incident wavelength,concentration of the spray solution,thickness and roughness of Ag coatings.When the spray passes are 10,the Ag particles seem to be spherical and the roughness is lowest.By analyzing the XPS peaks and auger parameters,the Ag coatings include Ag and its oxides in the respect of chemical element.The surface deposition weights of Ag coatings prepared in different atmospheres show diverse increment tendencies.For Ag coatings prepared in air,there are-0.2 eV shifts in the Ag 3d peaks when spray passes of reducing agents increase,but the shifts become+0.5 eV when spray passes of Ag salt increase.For Ag coatings prepared in N₂,the shifts maintain negative in the Ag 3d peaks whether spray passes of reducing agents or Ag salt increase.These results indicate that Ag coatings preparing in air may be hybrid laminated composite of Ag and its oxides,but the Ag coatings preparing in N₂ may be Ag oxides on the topmost surfaces and Ag beneath the surfaces.Changing pH value of the Ag salts,the solutions keep completely transparent even after 20 days storing in dark,proving the stability of these Ag solutions.Ag coatings prepared by initial Tollens’agents exhibit the smoothest surface morphology with the highest Ag element contents and deposition weights,which are 92.8 wt.%and 17.8μg/cm² respectively.（4）Ag coatings are adhesive onto ABS surfaces,owing to the efficient chemical bonding at the interface to connect the metals and polymers.Adhesion strength will be up to 26 N/cm,when the p TES molecules were activated by UV light.Metal coatings on LCP surfaces have passed the tape test,and their adhesion can be improved by surface modification processes.After peeling coatings on modified plastic surfaces,the interfaces show obvious stripping cracks.The metallic elements from coatings do not remain on the plastic side,showing that the interfacial failure should take place at the topmost surfaces of polymer substrates,instead of the metal-polymer interface.Atomic force microscopy-based nano infrared spectroscopy was firstly used to study metal-polymer interfaces,and the results show that there are different chemical functional groups at substrate,molecule films and metal coatings respectively.Thickness of molecule films is only 10 nm.（5）Molecular bonding technology was used to modify flexible surfaces.During modification processes,UV radiation intensity and assemble time impact the grafting molecules amounts.The coatings are smooth and pure,with a nano thickness.Ag particles in the right position toward spray gun are the most uniform and finest,the best spray distances are 15-20cm.Ag coatings are adhesive onto the substrates.Obvious stripping cracks appear on the peeled surfaces,indicating the interfacial failure should be at the topmost surfaces of substrates.Integrated with laser printer,conductive circuits were prepared onto the flexible surfaces.The surface resistances are only 2.5 times of initial resistance,showing that the Ag circuits process excellent deformation resisting capability and electrical properties.