Fabrication And Investigation Of Self-healing Polymers Based On H-Bonding And Conductive Coating With Repeatedly Healable Superhydrophobicity

Self-healing is a capability of automatically healing the damage,which can be widely observed in life entities.Inspired by this,with the aim to enhance mechanical properties,safety and extend lifetime of polymer materials,self-healing polymer materials have attracted intensive concern all over the world.In the last decades,varieties of self-healing polymer materials based on different healing mechanism have been developed.There are materials based on damage-triggered healing process with hollow fibers,microcapsules or three-dimension microvascular networks inside,using planted healing agent to realize the crack healing.These self-healing processes are defined as extrinsic healings.And intrinsic healing is another type of healing process,which utilizes dynamic covalent bonds or non-covalent bonds(i.e.,H bonding,π-π conjugation,coordinative bonds,host-guest chemistry)inside the polymer matrix.The self-healing polymer materials include plastic,thermoplastic elastomer,gel,hydrogel,coating and so on.They are prepared through reasonable structure design and suitable fabrication.So far,studies of self-healing materials focus on intrinsic self-healing materials,and are developing towards multiple functionalities.And it comes up to the request that the self-healing materials are capable to be practically applied in some fields.In this thesis we aim to prepare self-healing polymer materials with different functions via suitable structure design,to reveal the relationship between structure and properties.And we also combine superhydrophobicity with self-healing capability in one conductive coating,paving a new avenue for designing and preparing of multi-functional self-healing materials.First of all,we employed a multiple H-bonding group ureidopyrimidinone-based monomer,MAUPy,designed and synthesized self-healing adhesive materials with biocompatibility.They were obtained via copolymerization of MAUPy with water-soluble high polar monomers containing different length side chains.The structure,Tg and rheological properties of the polymers were investigated,indicating the modulation of side chain on the polymer properties.Due to the dimerization of UPy group via H-bonding,the prepared polymer films showed self-healing ability at ambient temperatures.It was found that the polymer PHEA-UPy,with relatively highest Tg(above r.t.),can only self-heal the crack with assistance of humidity.And the other polymers PPEG360-UPyand PPEG500-UPy could completely heal the cracks within 1 h.These differences can be attributed to the different chain mobility.We investigated the surface free energy and the adhesion strength of the polymers though contact angle method and tension test,respectively.The results showed that the polymers possessed high surface energy and high adhesion strength.Combining with the biocompatibility nature of PEG unit,the prepared self-healing polymers have potential to be applied as wound healing agents in the field of biomedical materials.Then we also designed and prepared hydrogels with self-healing capability at ambient temperature.They were fabricated via copolymerization of UPy-based monomer AUPy with hydrophobic monomers BA and EHA,and hydrophilic monomers HEA and PEGMA under different component and molar ratio design.1H NMR,FTIR and TGA were employed to investigate the structures and thermo properties of hydrogels.Then the effects of crosslinking degree and side chain on the water absorption ability of hydrogels were investigated.SEM was utilized to analyze the porous morphology of inside network of the hydrogels.It was found that the combination of relative long side chain hydrophobic and hydrophilic monomers could give rise to hydrogels with high water absorbing capability.The self-healing tests showed the cut pieces of hydrogels could reattach rapidly at room temperature due to the multiple H-bonding of UPy groups.The in vitro cytotoxicity-test and cell adhesion test were also carried out.The hydrogels showed good biocompatibility with comparative survival rate of cells higher than 90%,and excellent anti-cell adhesion property due to the biocompatibility and low cell adhesion nature of PEG units.We also prepared novel H-bondings based self-healing polymeric materials.H-bonding group containing monomers were synthesized firstly via modifications of N-(2-hydroxyethyl)acrylamide and 2-isocyanatoethyl methacrylate(IEMA).They are AAEA,AAEPC,BCAEMA and EOEUEMA.Then polymers PAAEA and PAAEPCwere prepared via free radical polymerization,with a relatively wide PDI.Polymers PBCAEMA and PEOEUEMA were obtained via ATRP method,with a relativley narrow PDI.The H-bonding interactions between the polymers were confirmed via FTIR.The effect of types and numbers of H-bonds and the main chain flexibility on the polymer characters were investigated through DSC and rheological analysis.The self-healing abilities were also studied at room temperature.The results showed that PAAEPC film can spontaneously heal the cracks without any trigger.Furthermore,the healing process of PAAEPC film was repeatable.The PBCAEMA film needs more than 6 h to heal the crack under a relative humidity of 45%,while the PEOEUEMA film can‘t achieve self-healing.The differences of self-healing ability at r.t.can be contributed to the combination of flexible macromolecular main chain and sufficient H-bonding groups at the side chains.We also fabricated a conductive coating with self-healing superhydrophobicity.It was prepared by chemical vapor deposition of a fluoroalkylsilane(POTS)onto a PEDOT film,which was obtained by electrochemical deposition of monomer 3,4-ethylenedioxythiophene.Scanning electronic microscope is utilized to study the effect of deposition electric quantity(Qd,m C/cm2)on the thickness and morphology of the PEDOT films.It is found that with the increasing of Qd,the thickness increased rapidly,and the film morphology changed into micro-nano binary porous structure due to the deposition of cauliflower-like polymer cluster when Qd is higher than 100.And the porous structure is particularly crucial for the adsorption and retention of POTS.After being etched with O2 plasma,the PEDOT coating showed different self-healing ability.The coating with Qd=200 m C/cm2 was found to exhibit best self-healing ability,which can experience repeating O2 plasma-etching/healing process for at most 9 times.And it showed a water contact angle of 156 o and a small sliding angle of 6.7o after six etching/healing cycles.The healing process was found to be accelerated by humidity.The coating also exhibited good superhydrophobicity recovering ability after being corroded by strong acid solution at p H 1 or strong base solution at p H 14 for 3 h.After element study via EDS and XPS,it was demonstrated that amount of POTS was stored inside the porous coating.Therefore we came up with a proper mechanism for the self-healing superhydrophobicity of the conductive PEDOT coating.