Design,Synthesis And Performance Of Antibacterial Waterborne Polyurethanes

In recent years,due to the enhancement of environmental awareness of people,waterborne polyurethanes（WPU）achieve great development which are gradually replacing solvent-based polyurethanes.Waterborne polyurethanes have been widely used as coatings and adhesives in many fields.However,compared with solvent-based polyurethanes,waterborne polyurethanes materials usually exhibit unsatisfied mechanical properties.In addition,the introduction of hydrophilic components results in insufficient water resistance of WPU materials,waterborne polyurethanes coatings or films are susceptible to microorganism during use which causes adverse impacts of usage.Based on above insufficiencies,we aim to obtain waterborne polyurethane with antibacterial properties by reasonable macromolecular structure design,and further propose effective strategies to improve performance of WPU materials in order to expand the application of WPU materials in different fields.Part 1:We mainly focused on the design and synthesis of antibacterial waterborne polyurethane.Firstly,the functional molecules were synthesized,including:3-（2,3-dihydroxypropyl）-5,5-dimethylimidazolidine-2,4 dione（HD）and（2,3-dihydroxypropyl）-N,N-dimethyloctadecan-1-aminium chloride（DOQA）.The cationic antibacterial waterborne polyurethanes were designed and synthesized by introducing the HD and DOQA;the anionic antibacterial waterborne polyurethane（PU0）was designed and synthesized by introducing the HD.The diluted WPUs were coated onto various fabrics by an ordinary strategy,dipping-drying based layer-by-layer self-assembly（Lb L）strategy,achieving antibacterial and hydrophobic multifunctional fabrics.The original fabrics could be completely wetted by water droplets within 30 s,the water contact angle（WCA）of coated fabrics improved to 122.0-141.1^o.The hydrophobic fabric surface could prevent bacteria from adhering to the fabrics.Furthermore,the coated fabrics presented good antibacterial properties after chlorination.The coated fabrics after chlorination could inactivate 84.7-99.9%of Staphylococcus aureus and 84.1-97.7%of Escherichia coli with contact time of 60 min.The obtained antibacterial and hydrophobic fabrics showed good washing durability,abrasion and adhesion resistance and it is expected to be used in the industrial production of multifunctional textiles.Part 2:In this work,we further improved the mechanical properties of antibacterial waterborne polyurethane materials by adjusting the WPU macromolecular structure,and explored the influence of its structure on its properties.Firstly,1-（2-hydroxyethyl）-3-（（5-（3-（2-hydroxyethyl）ureido）-1,3,3-trimethylcyclohexyl）methyl）urea（HO-IPDI-OH）,a kind of compound with urea groups,was synthesized.A series of WPU were synthesized successfully by introducing the HO-IPDI-OH and adjusting the molar ratio of polyester diols（PEBA）to HO-IPDI-OH.As the decrease of the ratio of PEBA to HO-IPDI-OH,the density of H-bonds increased.The tensile strength and Young’s modulus of obtained WPU films improved significantly,and its tensile strain decreased slowly.The Young’s modulus,tensile strength and strain of PU0 film were 0.5 MPa,0.13 MPa and 3030%,respectively.When the molar ratio of PEBA to HO-IPDI-OH was 1:1,the Young’s modulus and tensile strength of PU1 film were 280.9 MPa and25.1 MPa,which were 560.8 times and 192.1 times more than that of PU0,respectively.While its tensile strain was 710%,which was 3.6 times lower than that of PU0.The obtained PU1 film simultaneously exhibited enhanced fracture energy of 140.0 MJ/m³.The snipped PU1 film could be healed to recover most of its original mechanical properties under 90^oC for 1 h.Tensile strength and elongation of healed PU1film could reach to 24.4 MPa and 610%.The WPU films demonstrated good antibacterial performance and had no apparent cytotoxicity after chlorination.Although the introduction of HO-IPDI-OH improved the mechanical property of WPU films,at the same time the water resistance of WPU film decreased.In addition,the steric hindrance of the ring structure of HO-IPDI-OH and isophorone diisocyanate（IPDI）components might have some influence on performance of the WPU materials.We replaced IPDI by1,6-hexadiisocyanate（HDI）to synthesize WPU and prepared WPU film,and further compared the mechanical properties and water resistance of IPDI-based and HDI-based WPU materials.Compared with the IPDI-based WPU film,the HDI-based WPU film showed better water resistance and flexibility,and lower tensile strength.Part 3:A series of self-cross-linkable waterborne polyurethanes with antibacterial performance were designed and synthesized with 3-aminopropyl trimethoxy-silane（APTMS）used as the end-sealing agent.The methoxy groups on siloxane chain segments could be hydrolyzed and reacted with each other to form Si-O-Si covalent cross-linking networks,which improved water resistance and tensile strength of WPU materials simultaneously.Furthermore,the WPU emulsion was demulsified gradually in Ca Cl₂ solution during the casting film process,because the carboxylate on WPU macromolecular chain could interact with calcium ions(Ca²⁺)to form Ca²⁺chelating structure.The formation of Ca²⁺-cheating structure further enhanced tensile strength of WPU films.The tensile strength and water absorption of PU0 film were 0.13 MPa and19.8%,respectively.When the content of APTMS was 5%,the tensile strength of PUSi5film was enhanced to 10.1 MPa,and its water absorption rate was reduced to 5.4%.After dipping in Ca Cl₂ solution,the tensile strength of WPU film further improved to12.7 MPa.After chlorination,the WPU film could inactivated 97.9%of Gram-positive S.aureus and 92.5%of Gram-negative E.coli within 60 min.In addition,WPU films before and after chlorination had no apparent cytotoxicity,which could expand their applications in functional coatings.Part 4:The components of waterborne polyurethane could influence the properties of final PU materials.Polycaprolactone（PCL）exhibited good biocompatibility and biodegradability,due to its easy crystallization,polyurethanes materials with PCL as soft segments could construct crystalline zone during stretching process,which leaded to higher mechanical properties of the material.In order to obtain WPU materials with good comprehensive performance,we selected PCL diols as the soft segments and synthesized a series of PCL-based WPU in this work,further exploring the effect of the introduction of HD on the mechanical properties and antibacterial efficiency of WPU.In the absence of HD,the tensile strength and fracture energy of HDPU0 film were 21.5MPa and 106.5 MJ/m³.When 2 wt.%HD was introduced,the tensile strength（30.1MPa）and fracture energy（195.7 MJ/m³）of HDPU2 film improved 40%and 84%,respectively.After chlorination,the HDPU0-Cl could inactivate 73.9%of S.aureus and67.1%of E.coli within 60 min.After chlorination,the HDPU2-Cl film exhibited more efficient antibacterial properties,inactivating 100%of S.aureus and 96.2%of E.coli within 60 min.The WPU films were also degradable in the natural soil and the cracks appeared on the surface of films after burying in soil for 18 weeks.In addition,after immersing in water for 24 h,the water absorption rate of HDPU0 and HDPU2 films was 5.6%and 10.0%,respectively.