Construction And Performance Of Functional Materials Based On Cellulose Acetoacetate

With the wide sources,green,renewable and biodegradable nature,cellulose has obtained widespread concern.It had a wide range of applications in the area of traditional textile industry,architectural coatings,paper and high-tech materials.Now,as sustainable development has become a consensus,the research of cellulose-based functional materials has attracted increasing attention.Cellulose is a linear polymer composed of dehydrated?-glucopyranose units.There is a large number of hydroxyl groups in its molecular structure that could be used as chemical active sites for modification or construction of functional cellulose derivatives.As an active site,the reactivity of the hydroxyl groups mainly depended on nucleophilicity,which limited the types of incoming groups to a certain extent.As a cellulose ester derivative,cellulose acetoacetate(CAA) had a?-dicarbonyl structure with diverse chemical reactivity on its side chain.Specifically,its carbonyl group could be used as an electrophilic group to react with nucleophilic groups such as the amino groups.The active methylene group could be deprotonated under alkaline conditions to form the corresponding carbanion with nucleophilic reactivity.Besides,the?-dicarbonyl groups could participate in a series of multicomponent reactions.Compared with cellulose,CAA with the specific degree of substitution(DS) had good solubility in water or other solvents,and was more suitable for constructing functional materials.Therefore,CAA was a key intermediate to design diversified cellulose functional materials.In this thesis,cellulose was dissolved in the ionic liquid solution and reacted with tert-butyl acetoacetate(t-BAA) to obtain CAA with a controllable DS.As the raw material,CAA was applied to prepare a series of cellulose functional materials through the enamine reaction.In order to achieve functionalization of CAA,cellulose molecular derivation,amphiphilic properties of macromolecules,and three-dimensional network construction were used as the strategy to design CAA-related functional materials.In addition,the heterogeneous reaction was carried out to modify the surface of cellulose related materials with the acetoacetate groups such as cotton fabrics without destroying the original structure.Meanwhile,the function of the acetoacetate-modified surface could be realized by post-modification.The main research contents and conclusions of this thesis were as follows:(1)The Biginelli multicomponent reaction has been used as a model method to efficiently synthesise a library of cellulose derivatives based on CAA.Various cellulose derivatives containing 3,4-dihydropyrimidin-2(1H)-ones(DHPM)with different functional groups(carboxyl,methoxyl,and nitro)were prepared.The entire reaction process was traced using Fourier transform infrared spectroscopy(FTIR),¹H NMR.The results demonstrate that more than 80% of the acetoacetyl groups were converted within four hours.Additionally,all the cellulose derivatives were confirmed to have favourable thermostability and good solubility in selected solvents.Furthermore,polymers(in this case,poly(ethylene glycol) monomethyl ether (mPEG)) could also be anchored to the cellulose backbone via this facile modular approach.Therefore,the Biginelli multicomponent reaction offers a straightforward method for diverse and large-scale cellulose derivatization.These results are expected to prompt broader study of this multicomponent reaction in interdisciplinary fields.(2)CAA served as reactive natural polymer emulsifier to stabilize thyme oil-in-water(O/W) emulsions.Hydroxypropyl chitosan(HPCS) was added to the continuous phase in emulsions to achieve the organo-hydrogel via the enamine bonds under mild conditions.The thyme@CAA emulsion with different loadings of the inner phase(up to 50%) displayed uniform droplets distribution(3-5?m) and favorable stability.The organo-hydrogel was systematically analyzed by FTIR,optical microscope,rheology analyses.The emulsion droplets evenly dispersed in the three-dimensional network.The modulus of organo-hydrogels depended on the viscosity of precursor emulsions and the crosslinking density.The resulting organo-hydrogel displayed favorable antibacterial activity against E.coli and S.aureus.CAA,as the reactive emulsifier and crosslinking agent,was a promising alternative candidate to fabricate a series of organo-hydrogel.(3)A readily modifiable cellulose sponge was prepared from CAA crosslinked with cellulose nanofiber(CNF) by aminopropyltriethoxysilane(APTES).Facile post-modification with primary amino containing modifiers such as octadecyl amine(ODA),cysteine(CYS),and L-glutamic acid(GLU) could be achieved demonstrating the easiness of anchoring broad selection of functional groups to the surface of the sponge.The formation of the enamine anchor points was also shown to be reversible.Therefore,the resulting sponges could serve as a versatile precursor to a broad spectrum of multifunctional porous materials paving a new way for constructing smart sponges through post-modification.(4)Besides,the acetoacetyl group was directly anchored on the surface of cotton fabric(Cotton-acac) via heterogeneous transesterification.This surface modification strategy was systematically characterized by FTIR,solid-state ¹³C nuclear magnetic resonance spectroscopy,X-ray diffraction,and thermogravimetric analysis,which confirmed it was a mild and efficient process.Besides,Cotton-acac was used as the versatile intermediate post-modified with gentamicin(Gen) and ODA molecules to impart cotton fabric dual functions with hydrophobic and antibacterial properties.The resulting cotton fabric showed dual and outstanding hydrophobic and antibacterial performance against E.coli and S.aureus,with the bactericidal rates of over 99.99% and the water contact angle of 145° even after 10 cycles of standard washing.Therefore,the heterogeneous modification provided a benign and versatile method for regulating the interfacial properties of the cellulosic materials,with the possibility of post modification for various applications through the acetoacetyl chemistry.