Preparation And Applications Of High-adhesion Silver Coating On APTMS Modified Polymer Substrates

As a noble metallic material,silver was widely used in electronic devices,catalysts and biological antibacterial fields because of its excellent ductility,electrical and thermal conductivity,catalytic activity and biological antibacterial properties.Covering a layer of silver on polymer substrates could simultaneously take advantage of the characteristics of silver and polymer material,which could efficiently reduce the costs of using metallic silver.In this paper,silver coating was respectively deposited on polyethylene（PE）and polydimethylsiloxane（PDMS）these two different polymer substrate by the means of electroless plating for biological antibacterial devices and flexible electrode applications.In order to ensure the efficacy of silver coating on polymer substrates when it was utilized for a long period use.So it is supremely essential to enhance the adhesion between the silver coating and the polymer substrate.For this purpose,3-aminopropyltrimethoxysilane（APTMS）was utilized to chemically modify the surface of those two polymer substrates.After the partial self-polymerization of APTMS,the formed oligomers would react with the hydroxyl groups on the polymer surface and form a thin layer of APTMS oligomers,which also called self-assembled monolayers（SAMs）.The formed SAMs chemisorbed with the polymer substrate by covalent bonds.After the sensitization and activation reactions,the palladium particles which served as catalytic activity centers were created on the SAMs and bond with the terminal–NH₂ groups through chemical bonds,which was verified by the results of XPS.The formed palladium particles would initiate the deposition of silver particles on polymer surface in the subsequent electroless silver plating process,and the metallic bonds would be formed between the palladium particles and the silver coating.Therefore,after the APTMS surface modification,the silver coating would link with the polymer substrate through continuous chemical bonds.The formation of continuous chemical bonds would replace the intermolecular force connection that happened in the none-chemical modification treatment and caused the improvement of adhesion between the silver coating and the polymer substrates.The peel tests were applied to qualitatively and quantitatively measure the adhesive strength between the silver coating and the polymer substrate.The results showed that the adhesive strength between the modified substrate and the silver coating was 23 times larger than the polymer substrates without chemical surface modification.With strong affinity of silver coating,the antibacterial test showed that the silver coating on PE substrate possessed excellent antibacterial property,which could guarantee the possible utilization of silver coating on the IUD as antibacterial agents in the future.The tensile test was applied to measure the resistance change of the silver coating on PDMS surface under a certain tensile deformation.The results showed that under the tensile deformation of 10%accompanied with hundreds of cycles,the resistance changed of silver coating on PDMS was maintained in a stable range.And even under the tensile deformation of 30%,the silver coating remains as intact and no obvious cracks were observed.The excellent tensile properties of silver coating on the PDMS surface guarantee that they could be used as flexible electrode applications.