Construction And Functionalization Of Organic Fluorine/silicon Hybrid Epoxy Resin Coatings

Epoxy resins have been widely used in aerospace,transportation,electrical,electronics industry,and 5G/6G communication owing to their good adhesion and excellent corrosion resistance,bonding properties,and dimensional stability.However,the high brittleness,poor hydrophobicity,and poor weathering resistance of epoxy resins,as well as the complex process requirements and easy failure of cured epoxy resin materials resulting from the conventional "A+B"curing mode,have limited the scope of application of these epoxy resins and their curing mode of high-performance and intelligent polymer materials.To meet the high-performance requirements of epoxy resins and expand their application fields,organofluorine/silicone chemicals with low surface energy and good flexibility as well as oligo-sesquioxanes with high weather resistance are used to modify epoxy resins via organic/inorganic hybridization,which can improve the flexibility and weather resistance of epoxy resins and simultaneously endow them with water and oil repellency.Additionally,to break the way between the epoxy resin and curing agent,the development of a latent epoxy resin curing agent and a corresponding curing system has gained prominence in the development of epoxy resins.The following work has been conducted herein to address the aforementioned issues.(1)Density functional theory(DFT)-assisted synthesis of epoxy/anhydridebased bifunctional poly(styrene-co-acrylate)resin and its application in epoxy coatingThe quaternary radical copolymerization reaction system comprising butyl acrylate(BA),styrene(St),maleic anhydride(Ma),and allyl glycidyl ether(AGE)was studied.The free radical reactivity indices of these four monomer molecules were calculated based on DFT using Gaussian 09 software.The optimal ratio of the components was determined to be NBA:NSt:NMa:NAGE=1.2:1.0:0.4:0.5.Based on theoretical calculations,this study also synthesized an epoxy/anhydride bifunctional poly(styrene-co-acrylate)(EMPA)resin copolymer curing agent.This was achieved through free radical copolymerization of BA,St,Ma,and AGE at the optimized theoretical amount ratios——producing the BA-co-St-co-Ma-coAGE resin.The structure,average molecular weight,and film-forming morphology of the EMPA resin and the properties of ER/EMPA coatings prepared using EMPA and epoxy resin(ER)were investigated to reveal the conformational relationships and patterns between the monomer amount of substance ratio and EMPA and ER/EMPA coatings.It showed that the average molecular weight(Mn)of the EMPA resin synthesized with DFT assistance could reach a maximum of 71108 g/mol with a minimum polydispersity index(PDI)of 1.44.In addition,the introduction of EMPA could improve the toughness and impact resistance of the ER/EMPA coating,resulting in elongation at break and impact resistance of 45.5%and 75 cm,respectively.(2)Examining the design and synthesis of the latent polymer curing agent,namely,(fluorinated)poly(styrene-co-acrylate)resin bearing anhydride group and its applications in epoxy functional coatingsWith reference to the aforementioned ratio of NBA:NSt:NMa=1.2:1.0:0.4 and BA being substituted with R(f)A,the(fluorinated)alkyl(meth)acrylate[R(f)A],styrene(St),and maleic anhydride(Ma)radical copolymerization reaction systems were investigated using DFT and Gaussian 09 software.Moreover,the reactivity indices of radical reactions(fa0)of alkenyl carbon atoms in five monomer molecules of R(f)A,including(fluorinated)alkyl(meth)acrylate such as BA,dodecyl methacrylate(LMA),octadecyl methacrylate(SMA),perfluorohexyl ethyl acrylate(C6FA),and perfluorooctyl ethyl acrylate(C8FA),were calculated as follows:fBA0=0.23,fLMA0=0.16,fSMA0=0.15,fC6FA0=0.20,and fC8FA0=0.18.The results indicated that the BA,LMA,SMA,C6FA,and C8FA ratios in the(fluorinated)poly(styrene-co-acrylate)resin bearing anhydride group(MPA)could be optimized for different combinations,maintaining a NR(f)A:NSt:NMa ratio of approximately 1.2:1.0:0.4.Based on the above calculations,R(f)A was subjected to tertiary or multiple radical copolymerizations with St and Ma,resulting in the synthesis of R(f)A-co-St-co-Ma copolymer resins.These resins are a class of poly(styrene-co-acrylate)resins bearing anhydride group(MPA),acting as macromolecular latent curing agents.The structure,average molecular weight and thermal stability of the MPA resin as well as the microscopic morphology of ER/MPA coating were investigated to reveal the conformational relationships and patterns between the side chain groups and the MPA resin and ER/MPA coating.The results indicate that the ER/MPA coatings exhibited microscopic roughness patterns such as "folds" or "islands" owing to the long-chain alkyl C18H37 or perfluoroalkyl C8F17C2H4 oriented arrangement or aggregation state of the R(f)A link in the MPA curing agent structure.Due to the special microscopically patterned roughness mentioned above,the surface contact angle of the ER/MPA coating to reach up to 135° for water and 95° for oil,and reducing surface energy of the coating to 6.7 mJ/m2.(3)Designing and synthesizing polyhedral oligomeric silsesquioxane(POSS)-hybridized fluorinated poly(styrene-co-acrylate)resin bearing anhydride group and constructing superhydrophobic epoxy coatingsPOSS-hybridized fluorinated poly(styrene-co-acrylate)resin bearing anhydride group(POSS-co-FMPA),was synthesized using cage type heptaisobutylmethacryloxypropyl oligomeric sesquisiloxane(MA-POSS)as a nano-modifier,perfluorooctylethyl acrylate(C8FA)as a low surface energy modifier,and octadecyl methacrylate(SMA),St,and Ma as raw materials.These components were facilitating a sequential multiradical copolymerization reaction.The structure of POSS-co-FMPA,average molecular weight distribution,agglomeration morphology,and size of POSS in the POSS-co-FMPA resin as well as the hydrophobicity and dielectric properties of the ER/POSS-co-FMPA coating were investigated to reveal the conformational relationships and patterns between the POSS content and the properties of both the POSS-co-FMPA resin and the ER/POSS-co-FMPA coating.The results showed that the POSS agglomerates were uniformly distributed in the POSS-co-FMPA resin,forming a "cage-like"pattern with agglomerate sizes ranging from 27 to 38 nm.When 2wt%POSS was added,the ER/2wt%POSS-co-FMPA coating exhibited surface energy as low as 6.2 mJ/m2.In addition,the static water contact angle and oil contact angle reached 155° and 86°,respectively.The ER/2wt%POSS-co-FMPA coating at 1 MHz exhibited a reduced dielectric constant of 2.64 and a dielectric loss tangent of 0.021.(4)Fabrication of a silver/silicon cohybrid antibacterial anticorrosion ER coating and investigation of the antibacterial mechanism.The intermediate compound 2,2,4,6,6-pentamethyl-4-{3-[(oxepropan-2ylmethyl)oxy]propyl}-3,5-dioxa-2,4,6-trisiloxyheptane,denoted as PTODT,was synthesized via a silica-hydrogen addition reaction.Subsequently,PTODT and y-aminopropyltriethoxysilane(KH550)were used as raw mater-ials for the synthesis of a silyl compound with a secondary amine group in the structure,3[(4,4-diethoxy-3-oxa-4-silylheptan-7-yl)amino]-1-({2,2,4-trimethyl-4[(trimethylsilyl)oxy]-2,4-disilyl-3-oxaheptan-7-yl}oxy)propan-2-ol,denoted as TAK550,via an aminolysis ring-opening reaction.TAK550 was used as the organic modification component and silver hybridized amino-modified silica nanoparticles(NH2-SiO2@Ag)as the inorganic nano-bactericidal component to modify the ER through hybridization,thus obtaining an Ag/organic silicon cohybridized antimicrobial anti-corrosion epoxy coating(Ag/TAK550/E-51).The structures of the synthesized intermediate compound PTODT and the target compound TAK550 were investigated by FTIR,TEM,nanoparticle sizer,FESEM and XPS,as well as the micromorphology and size of NH2-SiO2@Ag,the microscopic morphology of the coating,the nanoparticle morphology of the coating surface and the surface elemental composition.The results revealed that NH2-SiO2@Ag,featuring a "pyramid-like" shape,was uniformly distributed on the surface of the Ag/TAK550/E-51 coating.Further,the static hydrophobic angle of the Ag/TAK550/E-51 coating surface to water reached 130° under the influence of the nanograded rough structure.The Ag/TAK550/E-51 coating exhibited excellent electrochemical corrosion resistance owing to the synergistic effect of Ag and polvsiloxane,where the corrosion voltage of this coating reached 0.46 V and the corrosion current decreased to 1.92×10-11 A·cm-2.Moreover,the Ag/TAK550/E-51 coating benefited from the strong slow-release bactericidal effect of Ag on the coating surface,which proved highly effective against E.coli and Staphylococcus aureus with a kill rate of up to 99.9%.Further,the corrosion cycle of the Ag/TAK550/E-51 coating against sulfate-reducing bacteria increased from 21 days to 75 days compared to that of the pure ER coating.