Preparation And Antibacterial Study Of Natural Borneol-based Polymer Composite Coating

Bacteria are the main branch of pathogens.It causes the biological contamination or degradation of products in industrial and agricultural field.The traditional antibacterial models rely on the use of antibiotics,precious metals,and other antibacterial agents.However,the overuse of antibiotics may lead to bacterial resistance,while precious metals have a certain biological toxicity.Therefore,it is of great significance to establish antibacterial models based on novel antibacterial materials.Natural borneol is extracted from the stems and leaves of Ainacum in Compositae or the branches and leaves of Lauraceae plant camphora.Borneol has a warm nature,which possesses detumescence and sedative effects as medicament.In addition,the unique asymmetric chiral characteristics and stereochemical structure of borneol make the borneol-based polymer have an antibacterial adhesion.Based on the above,a series of borneol-based polymer antibacterial coatings were prepared.The relationship between the chemical composition,surface structure,basic physical properties with antibacterial effects of the coatings was studied.Moreover,the construction of borneol-based superhydrophobic coating and dual antibacterial(antibacterial adhesion and sterilization)model was investigated for the long-term antibacterial activity,and the biological safety of related coatings was further evaluated.The main research contents and conclusions are summarized as follows:(1)Phase separation will occur due to the different polarity of the chain segments during the film forming process of polybornyl acrylate-polyurethane copolymer.And the low surface tension polybornyl acrylate will migrate and enrich to the coating surface which has an antibacterial adhesion effect as the asymmetric chiral structure.Thus,in this paper,seed emulsion polymerization and controllable shell technology are used to prepare polyurethane/polybornyl acrylate core-shell microspheres with polyurethane(PU)latex particles as the core and adjustable shell thickness.By changing the amount of bornyl acrylate(BA),core-shell microspheres with BA content of 0%,23 wt%,37 wt%and 54 wt%were prepared.Dynamic light scattering(DLS)and high-resolution transmission electron microscopy(HR-TEM)results show that the average particle size of the PU core is 52.3 nm,the average particle sizes of the core-shell particles are 75.6 nm,83.2 nm,and 108.9 nm,respectively.The polyurethane/polybornyl acrylate microspheres have a clear core-shell interface,and there is no phase reversal between the hydrophobic shell layer and the hydrophilic core layer.The coatings with different BA contents were prepared by casting the obtained core-shell microspheres in mold.X-ray energy dispersive spectroscopy(EDS),X-ray photoelectron spectroscopy(XPS),and contact angle(CA)tests were performed on the upper and lower surfaces of the coating.The results indicate that the core-shell microspheres collapsed during the process of forming the coating.Due to the polar incompatibility of the core-shell polymer segments,phase separation was occurred in the coating,and BA component was enriched on the upper surface of the coating,while PU component was enriched on the lower surface of the coating,leading to differences in C,N,O element content and hydrophobicity between the upper surface and the lower surface."Prison break"and antibacterial adhesion experiments demonstrate that the coating with BA concentration(37 wt%)show better antibacterial and antibacterial adhesion effects on the upper surface than on the lower surface,which indicates that effective phase separation can enrich borneol-based ingredients on the upper surface of the coating,improve the utilization rate of antibacterial borneol ester,and reduce the cost of borneol-based antibacterial coating.The in vitro cytotoxicity results show that the cell viability of three coatings(23 wt%,37 wt%,and 54 wt%BA)were all higher than90%,and they had good cytocompatibility.(2)When superhydrophobic surfaces contact with the bacteria-containing solution,it can form air pockets physical isolation layer to reduce the initial bacterial adhesion.Besides,on account of the chiral chemical structure,borneol polymer surface can be"recognized"by bacteria,which makes the bacteria"hate"the coating surface and reduce bacterial adhesion.Therefore,in virtue of the superhydrophobic physical isolation and chemical shielding for the borneol polymer,a coating with long-term good antibacterial adhesion can be prepared.Based on that,a series of new polybornyl-based superhydrophobic antibacterial coatings were prepared for long-term resistance to bacterial adhesion.Fourier transform infrared spectroscopy(FTIR)and XPS tests show that the acrylate and BA monomer has been polymerized.Thermogravimetric analysis(TGA)and differential scanning calorimetry(DSC)tests show that the polymer has excellent thermal stability.SEM and DLS tests show that borneol-based polymer nanoparticles with particle sizes of 249 nm,432 nm,and 759nm were formed on the surface of the three coatings(PLB-1,PLB-2,PLB-3),but no nanoparticles were found on the surface of PLB-4 coating.CA measurement result shows that the coatings PLB-1,PLB-2,and PLB-3 are superhydrophobic,while the surface of PLB-4 is hydrophobic.The coating was immersed in water when they were conducted the CA test again 7 days later.The results reveal that PLB-1,PLB-2,and PLB-3 still maintained superhydrophobic even after immersing 7 days,and PLB-3had the best superhydrophobic stability.Antibacterial adhesion experiments show that the general hydrophobic coating PLB-4 could not completely resist the adhesion of E.coli.Moreover,with the increase of time,the bacteria attached to the PLB-4 surface gradually increased,whereas the superhydrophobic coating PLB-3 could maintain long-term stable antibacterial adhesion.Cytotoxicity assay shows that the prepared coatings all exhibit good cytocompatibility and have potential application prospects in the biomedical field.(3)The borneol-based polymer has antibacterial adhesion,but its bactericidal effect is weak.Nano-TiO₂ is a highly effective inorganic bactericidal material.Combining TiO₂ and borneol-based polymer,the dual-resistant polymer composites with anti-bacterial adhesion and bactericidal effect can be prepared.The existence of dual-resistant mode can improve the long-term bactericidal efficacy of the composites.In this section,a novel multifunctional borneol-based polymer/TiO₂ composite coating was synthesized by using a borneol-based polymer with antibacterial adhesion properties as the carrier,nano-TiO₂ as the photocatalyst and bactericide,and polychlorotrifluoroethylene(PCTFE)as the binder.The results of FTIR,atom force microscopy(AFM),SEM,and DLS show that nano-TiO₂ was successfully immobilized on the borneol-based polymer and uniformly dispersed in the composite film.DSC and TGA tests show that the introduction of TiO₂ nanoparticles can improve the thermal stability of the composite film.The photodegradation activity of the composite film with different amounts of TiO₂ to methylene blue(MB)under ultraviolet light irradiation was tested,and the results show that the degradation efficiency of MB gradually increased with the extension of the irradiation time.After irradiation for 240 min,the MB degradation rate of PBT-0,PBT-1,PBT-2,PBT-3 and PBT-4 composite films reached 12.2%,82.6%,91.5%,83.2%and 70.2%,respectively.Compared with PBT-0(without TiO₂),the composite film containing TiO₂ has better photocatalytic degradation ability.Under weak ultraviolet light,the bactericidal effect of PBT-0 and composite film with different TiO₂ content on gram-positive Staphylococcus aureus was tested.The results show that the number of viable bacteria in the control group was 1.92×10⁴CFU/cm²,and that in the PBT-0 group was1.15×10⁴CFU/cm².For PBT-1,PBT-2,PBT-3 and PBT-4,the number of viable bacteria were all below the detection limit(<10CFU/cm²).This suggests that the borneol-based polymer/TiO₂ composite film has superior bactericidal effect in a weak ultraviolet environment.Persistent bactericidal experiment shows that PBT-3 still had good antibacterial effect after 30 days.On the contrary,the control group PMMA/TiO₂ showed good bactericidal effect on the first day,but the bactericidal performance decreased significantly after 20 days,even close to zero at 30 days.It shows that the synergistic effect of nano-TiO₂ and borneol-based polymer can effectively improve the long-term bactericidal efficacy of the composite film.The prepared composite film has excellent photocatalytic performance and long-lasting antibacterial performance,which has potential application in water pollution treatment.(4)Quaternary ammonium salt is a kind of high-efficiency organic bactericidal material.By the copolymerization of quaternary ammonium salt containing double bond and bornyl acrylate,a double-resistant polymer composite coating with antibacterial adhesion and bactericidal effect can be prepared.The synergistic effect of bacterial adhesion and bactericidal effect can extend the bactericidal durability of the composite coating.In this paper,a series of borneol-based polymer antibacterial materials(BRE1?BRE5)with different quaternary ammonium salt content were prepared via soap-free emulsion polymerization,in which bornyl acrylate served as the antibacterial adhesion material,and maleic acid diester-octadecyl poly(ethyleneoxy)20 ethyl ether-ethylene trimethyl ammonium chloride(R303)was used as a bactericide.FTIR and EDS tests prove that R303 was successfully introduced into BRE.TGA experiment confirm that the thermal decomposition temperature of BRE decreased with the addition of R303.The wettability test results show that the higher the content of R303 in BRE,the more hydrophilic the BRE."Prison break"experiment shows that the prepared polymer coating material(BRE)shows good antibacterial activity against Staphylococcus aureus and Escherichia coli.Bactericidal experiments show that compared with the blank group,BRE1 has a weaker bactericidal ability,while BRE2?BRE5 displays highly effective bactericidal ability,indicating antibacterial activity mainly came from R303 containing the active center of quaternary ammonium salt.The antibacterial adhesion test reflects that BRE1?BRE5 possessed good antibacterial adhesion effect,proving that bornyl acrylate played a leading role in the antibacterial adhesion of BRE coating.Long-lasting sterilization experiments show that the control group occurred a decline in germicidal performance on the 10th day,and there is an exponential decline in the30th day.However,the experimental group still maintained a good bactericidal activity on the 30th day,demonstrating that the synergistic effect of BA and R303could significantly improve the long-term bactericidal activity of BRE coating.The cytotoxicity results show that the prepared BRE coating has good cytocompatibility and safety,which has good application prospects and provides the basis for the follow-up research.