Design,Preparation And Properties Of Ethyl Cellulose-Based Shape Memory And Self-healing Polymers

Recently,with the increasing concern on the environment issues and the depletion of fossil oils,the utilization of renewable biomass resources to prepare the sustainable functional polymers is attracting tremendous attention.The forestry-based nature resource as the most abundant biomass resources have the advantage of environment friendly,abundant,renewable,low cost,etc.And those biomass resource also have the problems of large differences in sources,complex structure and difficult to use at the same time,which leading to the advantages of biomass resources cannot be fully exerted.So,it is very meaningful to achieve the high value utilization of biomass resource by chemical modification,efficient transformation and recombination to prepare the functional materials.In this paper,we utilized the unique spatial topology of ethyl cellulose,and modified by chemical method.And then efficient recombination with fatty acid,furfural and rosin to prepare four kinds of cellulose-based shape memory and self-healing smart materials with brush,single crosslinking network,semi-interpenetrating network and dual-cure network,respectively.Two kinds of ethyl cellulose shape memory thermoplastic elastomer with semi-block side chain architecture and random side chain architecture were prepared by grafting LMA and THFMA copolymers from cellulose backbone via“grafting from”ATRP through utilizing the sequential monomer addition and one-pot monomer addition approach.DSC analysis indicated the thermoplastic elastomer with semi-block side chain architecture had two distinct thermal transitions at-35 ~oC and 40.4 ~oC,respectively.And the thermoplastic elastomer with random side chain architecture only had one thermal transition at 16.8 ~oC,which indicated the thermoplastic elastomer with semi-block side chain architecture exists phase separation.And the phase separation structure was also confirmed by TEM and SAXS.Mechanical property showed two kinds of shape memory polymers exhibited obviously thermoplastic elastomer property,and the thermoplastic elastomer with semi-block side chain architecture showed better mechanical strength due to the presence of phase separation.Dual-shape memory study showed two kinds of thermoplastic elastomer had excellent shape memory property,and the thermoplastic elastomer with semi-block side chain architecture exhibited faster shape recovery speed and higher shape recovery ratio,and the shape recovery ratio was 95.1%.In addition,due to the thermoplastic elastomer with semi-block side chain architecture had two thermal transition,these thermoplastic elastomer exhibited excellent triple shape memory property,which made these full bio-based shape memory thermoplastic elastomer have important potential application in biomedicine and intelligent circuits.To overcome the pollution of metal copper catalyst during traditional ATRP process,the?-bromophenylacetate was utilized to modify the ethyl cellulose,and prepared ethyl cellulose macroinitiator EC-B-Br.And a series of cellulose graft copolymers with random side chain architecture(lauryl methacrylate(LMA)-co-furfuryl methacrylate(FMA))were synthesized by“grafting from”metal-free ATRP using PTH as catalyst.Then,the modified epoxidized soybean oil bearing 6-maleimidohexanoic group as a crosslinker,and a class of ethyl cellulose shape memory and self-healing thermoset elastomer with single crosslinking network were prepared via Diels-Alder reaction between maleimidohexanoic group and furfural of FMA in cellulose graft copolymers.The polymerization kinetic study showed the metal-free ATRP polymerization process followed the first order kinetic,and the Br chain-end functionality also showed high fidelity.Mechanical property study showed that the mechanical strength of DA crosslinked thermoset elastomer was increased 166%due to the inreasing of chain entanglement density after DA reaction.And the flexibility and elastic properties of the DA crosslinked thermoset elastomer was greatly improved due to the internal plasticizing effect of ESOM,and the elastic recovery values was above 90%at 140%strain.Shape memory study showed the DA crosslinked thermoset elastomer exhibited fast response thermal triggered shape memory performance,and the shape fixed ratio was 99.4%,the shape recovery ratio was 96.2%.Based on the thermal reversibility of DA reaction,these elastomers exhibited excellent self-healing and recyclability.And at same time,those cellulose graft copolymers also showed strong polymerization-induced luminous effect,and the maximum emission wavelength was red-shifted from 438 nm to 478 nm after DA reaction.In addition,these thermoset elastomers had application in self-healing strain sensor and wearable sensing devices after compounding with carbon nanotubes.Ethyl cellulose-based macromonomers(ECM)was prepared by utilizing the methacrylic anhydride to modify the ethyl cellulose,and acted as crosslinker.Then,a class of shape memory and self-healing elastomers with semi-interpenetrating network were prepared by one step bulk radical polymerization of ECM,LMA and THFMA.Compared with control group which removing linear polymer,we concluded that the linear copolymers played an role in internal plasticization which could improve the elastic property of the elastomer.Mechanical property study showed the mechanical strength of elastomer was increased from 1.16 MPa to 3.08 MPa with the increasing of ECM and THFMA content.The cycle tensile test indicated these elastomers exhibited excellent elastic behavior,and the elastic recovery values were all above90%at the strain of 250%.These elastomers also exhibited excellent multiple shape memory performance toward temperature,water,THF and methanol.Moreover,with the assistance of shape memory effect,these elastomers exhibited excellent self-healing property,and the repairing efficiency of strain was 81.2%,the repairing efficiency of stress was 55.4%.It should be noticed that the presence of linear polymers could great enhance the self-healing performance.A novel 3D print photosensitive resin solution was prepared using ECM and HDI as crosslinker,and rosin-based monomer(DAGMA)and HEA bearing double bond and hydroxyl as monomer.Then a series of ethyl cellulose shape memory and repairable thermosets with dual-cure network were prepared by UV/thermal dual cure 3D printing.Thermal mechanical study showed the storage modulus of thermosets were increased with the increasing of thermal treatment time,and the tan?curves showed obviously shoulder peak,indicating the phase separation structure were appeared in thermosets,which was further confirmed by TEM.Mechanical property study showed the formation of dual-cure network could significantly improve the toughness and mechanical strength of the thermoset,and the mechanical strength was increased from 1.6 MPa to 18.8 MPa after thermal treatment.In addition,the mechanical strength was increased from 1.04 MPa to 22.8 MPa with the increasing of DAGMA content from0 wt%to 30 wt%.Shape memory study showed the thsemoset had excellent thermal triggered shape memory property,and the shape fixed ratio up to 100%.The repairability study showed these thermosets had excellent repairability,and the repair efficiency of mechanical strength was95.2%,and elongation repair rate was 86.2%.Specially,these 3D printing thermosets also exhibited strong aggregation-induced emission(AIE)originating from the unique moiety of rosin.In addition,these 3D printing thermosets could be degraded in Na OH aqueous solution and in-situ achieved a range of flexible conductive hydrogels,which made these thermosets have important application in the fields of flexible conductive materials and sensors.