The Surface Roughness And Wettability Of Cotton Fabric Based On Fiber Surface-induced Carbene Polymer Crystallization

As environmentally friendly fiber materials in nature,cotton fabrics have become the most promising renewable natural materials due to their softness,widespread applicability and biodegradability under the current trend of environmental protection and sustainable development.However,the application of cotton fabric is restricted in anti-infiltration fields because of the high concentration of hydroxyl groups on cotton surface which makes the fabrics easily wetted and stained by liquids.Therefore,how to effectively improve the wetting resistance of cotton fabric has become a hot research topic.This paper focused on the preparation and application of superhydrophobic cotton fabric via covalent graft copolymerization.A series of different short fluoroalkyl side-chain polymers were grafted onto the surface of cotton fiber by carbene polymerization as well as surface-induced crystallization-drivesn self-assembly.The fluorine containing materials with low surface energy were coated successfully and generated roughened surface on cotton fiber,which effectively improved the water-repellent property of cotton fabric.The main discussions were as follows:(1)Construction of grafting sites on the surface of cotton fiber and attempts of tert-Butyldiazoacetate carbene grafting polymerization:Using p-toluenesulfonylhydrazide and p-toluenesulfonyl chloride as starting materials,1,2-Ditosylhydrazine was synthesized with pyridine as catalyst.After introducing the C-Br through the reaction between bromoacetyl bromide and hydroxyl groups,the fiber was then reacted with 1,2-Ditosylhydrazine to give the diazo group on the fibers.The EDS result shows that grafting sites were successfuly constructed on the fiber surface.Tert-Butyl diazoacetate was synthesized by one-step reaction between tert-Butyl bromoacetate and 1,2-Ditosylhydrazine.Poly-tert-butyl acetate was successfully grafted onto the surface of the fiber by carbene polymerization under the catalysis of(π-allylPdCl)2 and NaBPh4.The polymer was induced to crystallize on the surface of fiber.The effects of technological conditions on the morphology of the grafting polymer were explored.(2)Synthesis of short carbon chain fluoroalkyl diazoacetate with different fluorine content and modification of cotton fiber via carbene polymerization:Using short-chain fluoroalkyl alcohols such as 2,2,2-trifluoroethanol,3,3,3-trifluoro-1-propanol,3,3,4,4,5,5,6,6,6-nonafluorohexa-1-ol and 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl-1-ol as raw materials,different fluoroalkyl bromoacetates were prepared by substitution reaction with bromoacetyl bromide.The intermediates were reacted with 1,2-Ditosylhydrazine under the catalysis of DUB to produce short carbon chain fluoroalkyl diazoacetate with different fluorine content.All the chemical products were identified by FT-IR and 1H-NMR.The cotton fiber was modified by carbene grafting copolymerization of diazoacetate as well as coustructed roughness morphology on the surface of fibers by surface-induced crystallization-driven self-assemble.The elemental distribution and surface structure of cotton fiber were investigated by SEM,EDS,ATR,XPS and XRD.The water contact angle(WCA)showed that the treated cotton fabric was superhydropbobicwith the value of CA more than 150°.(3)Synthesis of aromatic diazocompounds and the construction of micro-nano complex structures through carbene polymerization grafing:Using phenyl bromoacetate and 4-(trifluoromethyl)phenacyl bromide as starting materials,phenyl diazoacetate and p-trifluoromethyl diazoacetophenone were synthesized by substitution reaction with 1,2-Ditosylhydrazine under the catalysis of DBU.The aromatic diazoacetes were throwed into carbene grafting polymerization and modification of cotton fabric.It was found that the rough surface obtained by aromatic monomers was quite different from that obtained by aliphatic diazo compounds,which formed cubes,peanut leaves and spherical/hemispherical micro structures.After treating with phenyl diazoacetate and p-trifluoromethyl diazoacetophenone,the surface of fibers was covered with dense hill-like roughness structure,and plenty of nanoscale mastoids were found to distribute on each hill evenly.The resulted micro-nano complex structure gave the grafted fabric a water contact angle(WCA)of more than 155° and lower rolling angle.Lastly,the process and mechanism of fiber modification by carbene polymerization as well as surface-induced crystallization-driven self-assembly was researched in this dissertation.The different polymer crystal morphology formed by self-assembly was analyzed and discussed.