Fabrication Of Polymer Thin Films With Good Barrier And Gas Separation Properties Via Initiated Chemical Vapor Deposition

Polymer thin films have been extensively used in food packaging,electronic packaging,metal and alloy protection,and reduction of energy consumption.With the development of new preparation methods,it is possible to synergistically realize special functions for various applications.Therefore,it is critical to fabricate thin films using simple,eco-friendly,and energy-saving methods.In this thesis,we study the barrier and gas separation properties of films prepared by the initiated chemical vapor deposition（iCVD）method.Firstly,we fabricated a bilayer thin film on Cu substrate by first treating Cu with a silane coupling agent,followed by grafting a highly crosslinked polyethylene glycol diacrylate（PEGDA）as bottom layer and immediate deposition of a poly（perfluorodecyl acrylate-co-ethylene glycol diacrylate）（P（PFDA-co-EGDA））top layer.We demonstrate conical nanoarrays structure can be achieved for the copolymer layer by manipulating the deposition conditions.Such structure combined with the low surface energy of PFDA moiety enables stable superhydrophobic surface with water contact angle of 159?.The oxygen permeability test showed that the PEGDA film is an effective oxygen barrier with oxygen permeability of 0.0066 Barrer,which is 16-fold smaller than the commercial PET film.The combination of the impermeable bottom layer and the superhydrophobic top layer enables superb corrosion resistance of the bilayer coating.Cu substrate coated by the bilayer film exhibits corrosion rate of only 2.19×10^-7mm/year in 3.5wt%NaCl solution,10⁴-fold decrease compared to bare Cu.Secondly,we synthesized poly（isocyanate ethyl methacrylate-co-4-aminostyrene）（P（IEM-co-AS））films using iCVD.The film composition can be tuned by varying the feed ratio of the two monomers.The isocyanate group reacts with the amino group,resulting in highly crosslinked films.Subsequent annealing treatment ensures complete reaction.Gas transmission and electrochemical tests were used to explore the barrier properties and anti-corrosion ability of the film.The P（IEM-co-AS）film with an equivalent IEM to AS ratios shows a 4,700-fold decrease in oxygen permeability compared to that of PS.Significant decrease of CH₄ and N₂ permeability was also observed.With a thickness of only about 200 nm,the impedance of copolymer-coated Cu reaches¹0⁸Ωcm²,indicating excellent metal protection.Highly-crosslinked polymer film has the rigidity and dense structure required for gas separation.Exploiting the in situ polymerization process of iCVD,we synthesized highly crosslinked PEGDA and poly（divinyl benzene）（PDVB）films on PS sheets.The ideal single-component and bi-component separation efficiency of CH₄,He,CO₂,N₂,and H₂ for the two films were tested.The PEGDA membrane shows low gas permeability and good separation efficiency towards He/CH₄and H₂/N₂.Both the permeability and the separation efficiencies towards most gas pairs of PDVB membrane are higher than that of PEGDA membrane.The solventless synthesis method suggests a novel approach for polymer gas separation membranes.We thus have explored the application of iCVD films for gas barrier,metal protection,and gas separation purpose through the above three projects,proving the promising potential of iCVD as a novel polymer thin film preparation method in these fields.