Study On The Molten Construction And Properties Of Biomass-Based Multifunctional Water-Free Ionogels

Biomass refers to the organic non-fossil resources with the renewable feature.It has been regarded as the idea material to replace the non-renewable fossil-derived chemicals for preparing the ionogels,because of the abundance,broad resource,unique physicochemical properties,and designability.However,there are still some challenges needing to be solved for the applications of biomass in the field of the ionogels.（1）The petroleum-derived chemicals（monomers,crosslinkers,initiators）still have dominated the ionogels,while the proportion of the biomass materials is relatively low.（2）The polymerization processes are complicated and time-consuming,which seriously limits the large-scale production of ionogels.（3）The dominant water in the ionogel’s polymer networks is prone to evaporate upon the practical applications,resulting in the function deterioration.（4）It is hard for the most of the ionogels to simultaneously obtain and balance the multiple properties and functions.（5）Achievement of the recyclability and reusability remains a huge challenge.In this thesis,from the perspective of the constitutional dynamic chemistry,the biomass-based anhydrous polymer networks with the different microstructures are designed and constructed using the small biomass molecule lipoic acid（LA）as the main building monomer,by the simple melt polymerizations of the LA or with other biomass materials.Through the regulating the amount and type of the molecular forces in these polymer networks,the target functions are systematically controlled and balanced,leading to the successful fabrications of a series of biomass-based water-free ionogels with the multiple functions,recyclability,and reusability.At the same time,their applications aiming at the soft wearable electronics are also investigated substantively.The main research works of this thesis include the following parts.（1）Small biomass molecule lipoic acid（LA）is used to design and construct the anhydrous polymer networks mediated by the dynamic covalent disulfide bonds,non-covalent hydrogen bonds,and coordination bonds,through a melt polymerization with the acrylic acid（AA）,choline chloride（CCl）,and ferric chloride（Fe Cl₃）.The use of AA successfully inhibits the serious depolymerization of LA polymer chains,thus providing a guarantee for the fabrication of the transparent（85%）,electrical conductivity(0.21×10^-2 S/m),highly stretchable（1100%）,and rehealable（mechanical healing efficiency of 86%,electrical healing efficiency of 96%）biomass-based water-free ionogels（LACF）.Furthermore,the ionogels with the appealing sensitivity can be served as strain sensors to detect and distinguish various human activities.Notably,the ionogels can be fully recycled and reprocessed into the biomass adhesives by a direct heating process,which offers a good adhesive strength on the surfaces of the variety substrates,such as glass,wood,plastic,and so on.（2）The two kinds of the small biomass molecules lipoic acid（LA）and itaconic acid（TA）are served as the building motifs to melt polymerize with the ionic liquid（[Emim][OAc]）and aluminium trichloride（Al Cl₃）.As a result,the anhydrous polymer networks driven by the dynamic disulfide bonds,hydrogen bonds,coordination bonds,and electrostatic interactions are successfully designed and constructed.The introduction of TA not only effectively inhibits the depolymerization of LA polymer chain,but also provides the additional carboxyl groups as the interfacial interaction sites to improve the surface adhesion of the biomass-based water-free ionogels（LTEA）.The resultant ionogels integrate the self-adhesion,high transparency（>90%）,good ionic conductivity(0.37×10^-2 S/m),high elongation（≈800%）,mechanical strength（187.2k Pa）,self-healing abilities,and strain/pressure sensitivities at the same time.Impressively,the LTEA can be fully recycled and reused by the simple heating without the obvious sacrifices of the original functions.Before and after recycling,the ionogels as soft conductors can be assembled into the conformal contact ionic skins to precisely detect and distinguish the joints motions in basketball training,and its response signal waveforms are stable without obvious electronic noises.（3）A biomass-based water-free ionogel（LCBA）with the anhydrous double networks is fabricated by the melt polymerization of the biomass macromolecule hydroxypropyl cellulose（HPC）,acrylic acid（AA）,and ionic liquid（[Bmim]Cl）in the molten liquid of the small biomass molecule lipoic acid（LA）.The HPC can be served as the secondary network to reinforce the mechanical performances of the LCBA by the multiple hydrogen bonding interactions.As a result,the integrated merits of the high mechanical strain（624%）,high mechanical strength（0.56 MPa）,moderate conductivity(7.4×10^-3 S/m),high transparency（84.7%）,healability（100^oC,1 h）,ultraviolet resistance,thermal stability,and full recyclability are realized in the LCBA.Encouraging by these features,a transparent and stretchable triboelectric nanogenerator（L-TENG）is fabricated using the LCBA as the functional electrodes.This nanogenerator can harvest the biomechanical energies and convert them into the electrical outputs.Notably,L-TENG is able to maintain the energy harvesting performance after the highly stretching,high temperature storage,long-term operation,mechanical damage,and even recycling.Notably,the L-TENG can not only work as the green power supply to drive small electronics,but also as self-powered sensors to distinguish the human motions.（4）A novel strategy of adopting the lithium bonds（Li-bonds）as both the depolymerization quencher and dynamic mediator is proposed to melt transform small biomass molecule lipoic acid（LA）and lithium salt（Li TFSI）into the biomass-based water-free ionogels（LLTG）.They feature with the anhydrous networks anchored by multiple dynamic Li-bonds.Meanwhile,the ionogel simultaneously integrates the fast and high-efficiency self-healing ability（3 h,90.3%）as well as the chemical stability,transparency（86.7%）,mechanical strength（224.9 k Pa）,ultrahigh stretchability（1585%）,conductivity(2.14×10^-5 S/m),re-mouldability,strain-sensitivity,recyclability,and degradability.The multi-functions enable LLTGs as the soft strain sensors for the human-computer interaction and the wireless remote sport monitor.Moreover,the recycled LLTG is proved to be an effective conductive filler for making the transparent ionic paper（IP）.The IP can be employed to design the soft transparent triboelectric nanogenerators for harvesting the biomechanical energy,driving the small electronics,and self-powered sensing the multidirectional deformations.