Preparation And Properties Of Novel Polyacrylamide Hydrogel

Polyacrylamide(PAM)hydrogels with a variety of special functions have been attracted great attention due to their wide application prospects in many areas including drug delivery,tissue engineering,materials separation,industry and agriculture,petrochemical,and so on.However,conventional chemical cross-linking polyacrylamide hydrogels always show lower mechanical properties and are lack of functional groups,which limits the scope of their application to some great extent.Therefore,the preparation and functionalization of PAM based hydrogel with new structures have always been hot topics.Considering the fact that the traditional PAM hydrogels have low strength and are easily destroyed during their application,we have designed and prepared three kinds of high-strength PAM-based hydrogels with different crosslinking mechanisms,i.e.thermo-sensitive self-repairing polyacrylamide hydrogels,in-situ thermal crosslinked polyacrylamide hydrogel,and "living" polymer nanoparticles reinforced polyacrylamide hydrogel,and investigated their mechanical properties.The main content of the research work can be divided into the following three parts:1.One-step synthesis of thermosensitive self-healable PAM hydrogels by the emulsion copolymerization.First,vinyl comonomer 5-acetylaminopentyl acrylate(AAPA)was synthesized,which is easy to form hydrogen bonds.At room temperature,AAPA,dodecyl methacrylate(DM)and acrylamide(AM)were initiated by ammonium persulfate(APS)and N,N,N,N'-tetramethylethylenediamine(TEMED)in the sodium dodecyl sulfate(SDS)solution to form self-healable polyacrylamide hydrogel.The hydrogel with a storage modulus as high as 400 Pa.The hydrophobic segments undergo phase separation driven by hydrophobic association to form a controlled physical crosslinking point,when the temperature increases to 70 ?,a gel-sol transition of the prepared hydrogels will occur.Furthermore,the broken hydrogels can be automatically healed into a body within 2-min's contact and the strength of the healed hydrogels is as high as 95%or more of the original strength.2.Preparation of in-situ-thermal-crosslinked PAM hydrogels.Poly(acrylamide-co-y-methacryloxypropyltrimethoxysilane)(P(AM-co-MPS))was synthesized through free radical polymerization with AM and MPS in tetrahydrofuran.The P(AM-co-MPS)easily dissolved in water and formed a low viscosity polymer aqueous solution.When the concentration of P(AM-co-MPS)is more than 10 wt%,and the content of MPS in the copolymer is higher than 19 wt%,the solution can transform into a stable chemical crosslinking gel spontaneously at 50?70?.The storage modulus of the gel can reach as high as 7500 Pa.3.Synthesis of "li?ving" polymer nanoparticles reinforced PAM hydrogels.Amphiphilic poly(acrylic acid)-b-polystyrene(PAA-b-PS)copolymer was synthesized via reversible addition-fragmentation chain transfer(RAFT)polymerization in methanol.The PAA-b-PS copolymer will self-assemble into vesicles during the water dialysis.Then,after ethylene glycol dimethacrylate(EGDMA)swelled into the hydrophobic microdomain of the vesicles,its copolymerization with AM monomer in water phase was initiated to obtain the hydrogel crosslinked with uniformly distributed PAA-b-PS nanoparticles.The effects of the content of AM,EGDMA and nanoparticle on the hydrogel strength were studied.The results show that the polymer nanoparticle enhanced hydrogel exhibits excellent mechanical properties with the maximum compressive and tensile strength of 7 MPa and 2 MPa respectively,as well as good fatigue resistance.