Preparation And Properties Of Cellulose/Catechol Adhesive Materials

Cellulose is the most abundant natural polymer in the world with low cost,good mechanical properties,biodegradability,and biocompatibility.At present,the low value-added cellulose has weak adhesion,which limited its application.The traditional epoxy resin,phenolic resin,and urethane resin adhesives have poor water resistance,which are harmful to human health and environment during the fabrication and usage.Thus,it is of great significance to develop functional cellulose-based adhesive materials by physical or chemical modification of cellulose,which can utilize cellulose effectively and widen the application of cellulose.In this thesis,to increase the adhesion strength and water resistance,cellulose nanofibril/poly（hydroxyethyl methacrylate-co-dopamine methacrylamide）（CNF/P（HEMA-co-DMA））composite adhesive with green and high adhesion strength,calcium chloride/TEMPO-oxidized cellulose nanofiber-dopamine/polyacrylamide（Ca Cl₂/TOCNF-DOPA/PAM）adhesive hydrogel with good mechanical properties and conductivity at extreme temperatures,monobasic-grafted and binary-grafted catechol-containing cellulose-based adhesive with water resistance and high adhesion strength were prepared by introducing different functional materials into cellulose.The morphology,structure,swelling behavior,biocompatibility,and adhesion strength of adhesive materials were analyzed in detail.The adhesion and water-resistance mechanism was investigated.The main research contents are as follows.P（HEMA-co-DMA）copolymer was prepared using dopamine methacrylamide（DMA）and hydroxyethyl methacrylate（HEMA）by free radical polymerization.Then,P（HEMA-co-DMA）copolymer was crosslinked with cellulose nanofibril（CNF）to prepare composite adhesive.When CNF content was 0.5 wt%,the maximum adhesion strength of the composite adhesive was increased to 5.50 MPa for iron under dry condition.CNF/P（HEMA-co-DMA）adhesive could enhance its cohesion throughπ-πstacking interaction,hydrogen bonding,and covalent bonding.The electrostatic interaction,hydrogen bonding,and covalent bonding were formed between adhesive and different substrates,endowing to excellent adhesive performance,which has promising applications in electronics and mechanical engineering.To prepare adhesive with wet adhesion,TOCNF-DOPA copolymer was prepared through amidation reaction by grafting DOPA onto TOCNF.Then,Ca Cl₂/TOCNF-DOPA/PAM adhesive hydrogel with wet adhesion strength of 50 k Pa on tissue surface,tensile strength of 95 k Pa,and compression strength of 0.35 MPa was fabricated by free radical polymerization.Finally,antifreezing/antiheating Ca Cl₂/TOCNF-DOPA/PAM adhesive organohydrogel was prepared by immersing hydrogel into glycerol/water aqueous solution.The composite organohydrogel could adhere to tissue surfaces through the catechol group.The hydrogel had high tissue adhesiveness of 50 k Pa,good conductivity of 4.9×10^-4S/cm,stretchability over 700%,and excellent biocompatibility.Animal test showed that the organohydrogel are anti-freezing and anti-heating.The organohydrogel could be used as multifunctional sensing dressings for detecting human signals,which has promising applications in biomedicine and electronics.To improve the water resistance of cellulose-based adhesives,monobasic-grafted cellulose-based catechol-containing adhesive was prepared using atomic transfer radical polymerization（ATRP）by grafting DMA onto cellulose.The peak of-NH appeared in the FTIR and ¹H NMR spectra,showing that monobasic-grafted cellulose-based catechol-containing adhesive was successfully prepared.The initial decomposition temperature was over 145°C and catechol groups enhanced the thermal stability of monobasic-grafted cellulose-based catechol-containing adhesive.The swelling ratio of monobasic-grafted cellulose-based catechol-containing adhesive was about 8.5%,indicating that water has less effect on the adhesive.The maximum adhesion strength was 2.10 MPa under dry condition and 0.16 MPa under wet condition on iron.In addition,NIH 3T3 cells experiment showed that relative cell viability of monobasic-grafted cellulose-based catechol-containing adhesive was over 95%,exhibiting excellent biocompatibility.The adhesive has promising applications in mechanical engineering and electronics.To further prepare adhesive with high strength and good water resistance,binary-grafted cellulose-based catechol-containing adhesive was synthesized by grafting DMA and methyl methacrylate（MMA）onto cellulose using ATRP.The characteristic peaks of amide appeared in FTIR and ¹H NMR spectra,showing that binary-grafted cellulose-based catechol-containing adhesive was successfully prepared.TGA showed that the initial decomposition temperature of binary-grafted cellulose-based catechol-containing adhesive with catechol content of25.4 mol%increased to 230°C.The swelling ratio of adhesive was about9.5%,indicating that the adhesive has good water resistance.Compared to monobasic-grafted cellulose-based catechol-containing adhesive,the maximum adhesion strength of binary-grafted cellulose-based catechol-containing adhesive on iron increased to 3.50 MPa under dry condition and 0.48 MPa under wet condition.The adhesive with strong adhesion strength and water resistance has promising applications in biomedical and electronic fields.