Design,preparation And Applications Of Biobased Vanillin-derived Functional Polymers Containing Aldehyde Groups

Vanillin is a kind of small molecular derivative from lignin.It inherits the advantages from lignin,in particular benzene-ring structure,while solving the problem that lignin is difficult to be applied directly due to the crosslinking network structure.Hence,the preparation of bio-based aromatic polymers from vanillin to achieve comprehensive utilization of lignin resources has gained wide attention.For preparing functional polymers,dynamic covalent bonds provide a group of powerful building structures.Since aldehyde groups can undergo reversible Schiff base reactions with amino groups under mild conditions,a variety of functional polymers can be prepared based on this Schiff base type reversible covalent bond.The aldehydes currently used include acrolein,glutaraldehyde,and oxidated polysaccharide,and vanillin is expected to work as a new source for bio-based aldehydes.On the other hand,the selection of appropriate polymerization method can realize constructing functional polymers with special morphologies,thereby expanding the application potentials of functional materials.In this work,using vanillin derivative,vanillin methacrylate(VMA)as biobased monomer,a series of aldehyde-containing porous,magnetic hybrid microspheres and monoliths were respectively prepared by suspension polymerization,precipitation polymerization,dispersion polymerization and high internal phase emulsion template polymerization approaches.In the polymers,the functional aldehyde groups provide the materials with further modification potential and adsorption and release abilities;the structural benzene-rings provide the materials with structural rigidity,heat stability and lipophilicity;the porous and spherical morphology facilitate the materials to be used for further applications such as adsorption,desorption and even graft modification.The prepared bio-based functional materials have good application potentials as Schiff base chelating resins,amino scavenging resins,drug carriers,and oil adsorbing resins.Also worthy to be highlighted is that,the prepared biobased materials can taken as a promising platform for further preparing other functional polymers.Preparing high value-added functional materials from biomasses is expected to achieve a win-win situation in both sustainable materials and economy.Also,the development of high value-added downstream lignin-based materials will promote the whole lignocellulosic industry chain progress.The main research contents are as follows:1.The biobased oil-solubility monomer,vanillin methacrylate VMA,was synthesized by reacting vanillin with methacryloyl chloride.Employing suspension polymerization,the biobased aldyhyde-containing microspheres were prepared and further endowed with surface pore structures by controlling the N2 bubbling mode and optimizing the cosolvent.The pore structures of microspheres and the pore-forming process were demonstrated by SEM and mercury intrusion porosimetry measurement.The functional aldehyde groups provide the microspheres with further modification ability;the structural benzene-rings render the microspheres with heat stability;the functional morphology offers varioius opportunies for further utilizing the microspheres.2.Schiff base-type chelating resins were successfully prepared by grafting the suspension polymerization-prepared aldehyde-containing porous microspheres with an amino acid representative,glycine,by Schiff base reaction.The grafting process was qualitatively and quantitatively characterized by FT-IR spectroscopy and ninhydrin colorimetry techniques.The maximum grafting amount of glycine was 4.3 mmol/g,which confirmed that bio-based microspheres can be used as a platform for preparing functional polymers.The heavy metal ion removal ability of the prepared chelate resin was determined by using copper ions as a heavy metal ion model.The maximum adsorption capacity of the chelate resin microspheres to copper ions was 156 mg/g,and the possible adsorption mechanism was the coordination of heavy metal ion by both Schiff base and carboxylic acid structures.The chelating resins are expected to be used as a heavy metal ion adsorbent in water treatment.3.The oleic acid-modified magnetic nanoparticles OA-Fe3O4 NPs were synthesized by chemical co-precipitation method in the presence of oleic acid.Further by a one-pot two-step method,the methacrylate-modified magnetic nanoparticles MethA-Fe3O4 NPs were synthesized by ligand exchange.The sustainable aldehyde-containing magnetic hybird microspheres(ACMMs)were prepared through suspension polymerization,in which MethA-Fe3P4 NPs were used as magnetic supplier.The resulting ACMMs were proved to have remarkable magnetic property(VSM)and adsorption capacity toward paraanisidine,which was employed as a representative of amines.The maximum adsorption was found to be up to 433 mg/g.Also noticeably,the adsorption was realized by forming a reversible Schiff base.Desorption process was performed conveniently,proving that the ACMMs can be easily recycled.The ACMMs demonstrate the potentials to be used as scavenger resins in adsorbing amines.4.Non-crosslinked bio-based aldehyde-containing microspheres(P-UACMs)were prepared by precipitation polymerization,while the crosslinked ones(D-CACMs)were prepared by dispersion polymerization.The regular particle size distribution of the microspheres was characterized by SEM.The drug loading capacity of D-CACMs microspheres was characterized by selecting benzocaine as a drug representative.The drug loading was 190 mg/g under equivalent drug feed.Both physical adsorption and Schiff base type chemical adsorption co-existed in drug loading process.Drug releasing experiments demonstrated the pH sensitivity of releasing process.In detail,.the releasing rate is 100%at pH 2;the equilibrium releasing rate decreases with pH increasing;and in a neutral pH environment,only physically adsorped drugs release,which demonstrate the potentials of D-CACMs to be used as drug controlled release carriers.5.A novel type of biobased,porous,functional material[poly(high internal phase emulsions),polyHIPEs]was prepared from vanillin and laurinol derivatives.Owing to the multilevel pore structures(cell,window,and skeleton pores)and the chemical compositions,the polyHIPEs demonstrate suprahydrophobicity and lipophilicity.The polyHIPEs demonstrate high porosity,low density,and high specific surface area.The polyHIPEs are further explored as an oil adsorbent.The polyHIPEs’advantages,i.e.being derived from biomass and showing high oil-adsorption capacity,instantaneous oil absorption,oil-water separation ability and satisfactory recycling usability,endow them with promising potential as sustainable oil adsorbents.