Study On Preparation And Properties Of Ferrocene-based Redox Responsive Hydrogel

Stimuli-responsive hydrogels are a kind of high water containing smart materials.They are widely used in many areas such as biomaterial engineering,drug controlled release and so on.Stimuli-responsive hydrogel can undergo a series of changes with external stimuli like temperature,light,pH and redox.Human body is a complex system in which chemical environment changes with time and place.The most common chemical environment changes which can be utilized are pH and oxidation potential.Redox stimuli responsive hydrogels are a kind of relatively new materials which have not been investigated too much.In this thesis,3 kinds of ferrocene(Fc)and ?-cyclodextrin(?-CD)modified hydrogels were synthesized,all of which showed redox responsive property.In the first part we prepared Fc/?-CD based redox responsive injectable hydrogel.Poly(acrylic acid)(PAA)modified with ?-CD and Fc respectively were synthesized,and characterized by 1H-NMR.Then these two kinds of polymers were mixed in boric acid/KCl/NaOH buffer to form 3-D hydrogel network.By applying redox stimuli to destroy and reconstruct Fc/?-CD inclusion complex,we investigated the role of Fc/?-CD in constructing hydrogel network.We also investigated the influence of polymer structure like side chain length,substitution degree and mass concentration on hydrogel property.In the second part we synthesized Fc/?-CD modified nanogel which has potential application in drug controlled delivery.First Fc and ?-CD modified monomer(Fc-AAm and ?-CD-AAm)were synthesized and characterized with 1H-NMR.By inverse emulsion polymerization,acrylamide(AAm),Fc-AAm and ?-CD-AAm and a chemical crosslinker methylene-bis-acrylamide(MBA)were copolymerized to form nanogel with different substituted degree.We also synthesized nanogels without Fc/?-CD and with only ?-CD.By dynamic light scattering(DLS)and scanning electron microscope(SEM),we found that PAM-Fc/?-CD nanogel expanded obviously after oxidation.To investigate the application of this nanogel,we loaded 1-pyrenemethanamine hydrochloride(PyMA)into ?-CD cavity after oxidation of Fc moiety.Then we investigated the release behavior of PyMA with steady-state fluorescence spectrum.With the stimuli of reductant glutathione(GSH),PyMA underwent release at high speed,compared to those that no Fc+ was reduced.In order to make the synthesizing progress more simple,and make up for the shortage of single stimulus responsive drug-controlled release,we synthesized Fc/?-CD modified poly(N-isopropyl acrylamide)nanogel by using precipitation polymerization and characterized it with FTIR.We used DLS and SEM to observe the diameter change of nanogel before and after oxidation,and investigated the shrinking behavior of different nanogel with temperature rising.We found that the lower critical solution temperature(LCST)of the synthesized nanogel changed with Fc/?-CD substituted degree and the oxidation state of Fc moiety.We also investigated PyMA release behavior of different nanogel at different situation.We found that the release rate went up with GSH concentration but not with temperature rising.The release rate of PyMA from PNIPAM-Fc/?-CD nanogel with 4%Fc/?-CD at about 37 ? showed higher release rate than that at 25 ? and 45 ?.