Design,preparation And Properties Of Novel Self-healing Polymer Hydrogels

Due to their excellent biocompatibility and other unique properties such as tissue-like elasticity,polymer hydrogels can be used as biomaterials.However,unlike natural hydrogel-like biological tissues with elasticity and toughness,classic hydrogels prepared in a conventional way are often brittle and exhibit very poor mechanical performance,thereby limiting their potential applications as biomaterials.In recent years,many efforts have been made to develop novel hydrogels with excellent mechanical properties.Unfortunately,these hydrogels behave similar to classic hydrogels in response to damage.Definitely,it has great theoretical significance and broad application prospects to design and fabricate novel hydrogels possessing both self-healing and excellent mechanical properties.Base on summarizing and analyzing the literature on high strength polymer hydrogels and self-healing polymer hydrogels,we propose the research subjects about building novel polymer hydrogels with excellent mechanical and self-healing properties used of reversible non-covalent interactions.The interactions exist ubiquitously in living systems.The monomer containing 2-ureido-4-pyrimidone(UPy)unit which can form quadruple AADD-DDAA hydrogen-bond array,zwitterionic sulfobetaine monomer,some specific functional macromonomer and prepolymer were desgined and prepared by the organic synthetic method,the design principle of structrue and property of macromolecular and the preparation method of polymer hydrogels.Three polyurethane(PU)hydrogels,one chemical-physical double network polymer hydrogel based on both the stearyl thacrylate micelles(C18)and self-assemble nanoparticles of hydrophilic PU macromonomer and two zwitterionic sulfobetaine nanocomposite hydrogel based on inorganic nanoparticles for crosslinker were prepared,respectively.The structures,physical and mechanical properties and self-healing behavior of the polymer hydrogels were characterized.The effect of polymer composition,structure and different non-covalent interactions on the three-dimensional structure,self-healing behavior and physical and mechanical properties of the polymer hydrogels were studied.The contribution of different self-healing mechanism to mechanical and self-healing properties of the polymer hydrogels were analyzed.The novel self-healing polymer hydrogels with novel structure and excellent performance are designed and prepared and have not beenreported.The preparation method of the polymer hydrogels has certain characteristics.The main contents and results of the work are as following:1.UPy-PU-UPy type and PU-UPy-PU type supramolecular polyurethane hydrogels were designed and fabricated from a prepolymer system based on polyethylene glycol(PEG),isophorone diisocyanate(IPDI)and 2-amino-4-oxo-6-methyl pyrimidine(MIC)or2-amino-4-oxo-5-(2-hydroxyethyl ethyl)-6-methyl pyrimidine(HMIC),respectively.The fabricated supramolecular polyurethane hydrogels can complete the self-healing within 1 h at ambient temperature without the need for any stimulus.In addition,they have excellent strength and toughness.The tensile strength of UPy-PU-UPy type and PU-UPy-PU type supramolecular polyurethane hydrogels are 71 kPa and 133 kPa,and their elongation at break are 1367 % and 1527 %,respectively.2.A novel class of polyurethane(PU)hydrogels with intermolecular quadruple hydrogen-bonding interactions were fabricated by the UV initiated polymerization of PU-PEGMA with SCMHBMA bearing the 2-ureido-4-pyrimidone(UPy)unit.These hydrogels based on reversible multiple hydrogen bonding exhibit rapid and outstanding self-healing ability.The corresponding PU hydrogels self-healed for 10 min possess a slightly lower tensile stress at the same strain level than the original PU hydrogels,but their tensile strength still lies in the range from 107.5 to 331.0 kPa,corresponding to 80.2 ~ 86.6 % of the tensile strength of the original PU hydrogels.More than 60 % of the self-healing process can be achieved within 5 min,thereby exhibiting their outstanding self-healing ability.The tensile strength of the original PU hydrogels containing 3.0 to 10.0 wt % SCMHBMA is in the range from 134.0 to 382.0 kPa and their elongation at break exceeds 1800 %.At high compressive strain level of 90 %,the original PU hydrogels containing 3.0 to 10.0 wt % SCMHBMA can reach their maximum compression stresses ranging from 3.1 to 4.5 MPa without the occurrence of compression fractures.3.We developed a novel two different mixed multifunctional cross-linking copolymerization method to prepare self-healing,highly stretchable and resilient hydrogels.The polymerization is based on the UV initiated free-radical copolymerization of water soluble acrylamide,2-hydroxyethyl methacrylate end-capped urethane ether prepolymer(PU-HEMA)which can self-assemble into nanoparticles acting as multifunctional cross-linkers,and C18 micelles asphysical multifunctional cross-linkers.The fabricated CPDN hydrogels can complete the self-healing within 30 min at ambient temperature without the need for any stimulus.The tensile strength of the original hydrogels containing 0.05 g to 0.3 g PU-HEMA is in the range from 25.0 to 156.0 kPa,and their elongation at break decreace from 3100 % to 1400 %.In addition,CPDN hydrogel samples showed excellent resilient,and their tensile strength can be quickly restored to its original level.The second hysteresis loop is similar size to the first hysteresis loop.4.The novel zwitterionic sulfobetaine nanocomposite hydrogels were successfully fabricated by the UV initiated polymerization of zwitterionic sulfobetaine monomer(DMAPMAPS)with HEMA monomer.The tensile strength of the nanocomposite hydrogels containing 3.0 %to 7.0 % clay is in range from 67.0 kPa to 168.0 kPa,their elongation at break from 600 % to2300 %.The self-healing ratio of hydrogel is from 85 % to 98 % within 10 h.thereby exhibiting outstanding self-healing ability.The results showed that EWC decreases with increasing clay content,but increased with increasing DMAPMAPS monomer content.5.The zwitterionic sulfobetaine nanocomoposite hydrogels were successfully fabricated by the thermal initiated polymerization of zwitterionic sulfobetaine monomer(DMAPAAPS)with N,N-dimethyl-allylamine(DMAA)monomer.The corresponding hydrogels self-healed for 10 h possess corresponding to 71 ~ 95 % of the tensile strength of the original PU hydrogels.The results showed that the tensile strength of the nanocomoposite hydrogels increased with increasing clay content.However,elongation at break decreased with increasing clay content.Elongation at break increased at first and then declined with increasing DMAPAAPS content.Elongation at break is from 1900 % to 2300 %.In addition,the obtained nanocomposite hydrogels with a temperature responsive,they are transparent at room temperature.At temperature below UCST,the hydrogels become turbid.