Fabrication And Performance Of Hydrogel Systems Based On Multiple Interactions

Hydrogel is a kind of polymer with a three-dimensional network structure.According to the reported literatures with respect to their preparation and application,there are various kinds of hydrogels which have been widely used.They are divided into physical crosslinking and chemical crosslinking based on their crosslinked structure.Their structures and properties vary with their crosslinking types.Herein,on the basis of previous work,we are focused on the establishment of hydrogel based on multi-crosslinking.In addition,we have explored the crosslinking mechanism and catalysis of these multi-crosslinked hydrogels.The detail is described below:1)Firstly,we have prepared three kinds of hydrogels based on the multiple physical interactions.A supramolecular hydrogel composed of poly[acrylamide-co-2-(dimethylamino)ethyl methacrylate][P(AM-co-DMAEMA)],poly(vinyl alcohol)(PVA)and ?-cyclodextrin(?-CD)was fabricated,in which P(AM-co-DMAEMA)served as the inclusion accepter and PVA-g-?-CD as the inclusion donor.And then,we also prepared hydrogels consisted of P(AM-co-DMAEMA),PVA and un-grafted ?-CD as well as binary hydrogels composed of P(AM-co-DMAEMA)and PVA.We have revealed the influence of multiple physical interaction on the crystallization of PVA through freezing-thawing cryo-treatment on all these hydrogels.Taking advantage of FTIR,2H NOESY,TGA,XRD and rheology measurement,we have investigated the physical interactions between each composition and their influence on the mechanical properties and thermal stability of hydrogels.It can be concluded that there is hydrogen bonding between each pair of PVA,P(AM-co-DMAEMA)and ?-CD.As well,there is host-guest inclusion interaction between ?-CD and P(AM-co-DMAEMA).As a result,the crystallization of PVA has been restrained to a certain extent.All these multiple physical crosslinked hydrogel exhibited excellent mechanical properties.2)We prepared Au nanoparticles with uniform size through HAuCl4 at room temperature while DMAEMA served as a reducing agent.The reaction mechanism and optimal reaction condition were identified through time-dependent UV-vis and 1H NMR.According to the FTIR spectrum and TGA spectrum of AuNPs.it can been seen that there are lots of DMAEMA monomers attached on the surface on AuNPs,thus they can act as a crosslinker in hydrogel.Additionally,we have illustrated the influence of different crosslinking on the structures of hydrogels and polymerizable AuNPs.In consequence,the double-crosslinking hydrogel behaved a higher crosslinking degree with samller pores.Since methyl orange and its product are negative charge,there is a decrease on the catalytic activity of double-crosslinking hydrogel with N,N'-Methylenebisacrylamide(MBAAm)and Ethylene dimethacrylate(EGDMA)as chemical crosslinker.Meanwhile,when the chemical crosslinker is N,N'-bis(acryloyl)cystamine(BACy)covered a disulfide bond which is sensitive to NaBH4,the catalytic activity of double-crosslinking hydrogel stayed stable after several times.Because the crosslinking degree become lower in the process of reduction,which accelerated the diffusion of methyl orange.As a contrast,even after several cycles both two signal-crosslinking hydrogels displayed outstanding catalytic activity for their lower crosslinking degree.