The Molecular Structure And Supramolecular Structure Design Of The Microgel-reinforced Hydrogels

Hydrogels,which consist of chemically or physically crosslinked macromolecular aggregations,have the ability to keep its three-dimensional network even absorbing a large amount of water.Hydrogels exhibit swelling-shrinking response to a number of environmental stimuli,which greatly increase their extensive uses in the flexible materials,medical devices,aerospace aviation areas.Microgels are hydrogel particles in colloidal form,which are used to reinforce the hydrogels to obtain high performance materials.In this paper,we introduce the supramolecular interactions between the microgels and hydrogels,and then study the influences of the supramolecular interactions,such as chain entanglements,hydrogen bonds,ionic crosslinking,and so on,on the mechanical performance of the Carbopol composited hydrogels.It is evident that a wide range of hydrogels with improved mechanical strength and shape memory properties have been prepared based on the supramolecular interactions.Morever,the ferrocene group modified microgels are also prepared,which provide a better fundamental understanding of redox and electrical responsive hydrogels.The research results are as follows:1.A pentaerythritol-crosslinked poly(acrylicacid)(PAAc)microgel,named as Carbopol,is composited with poly(acrylic amide)(PAAm)hydrogel.The toughness of the hydrogel is improved significantly by constructing an interpenetrating network of Carbopol and PAAm.Chain entanglements within the composited hydrogel result in a strain-hardening phenomenon and an efficient stress transferring from the PAAm matrix to the sacrificing network of Carbopol.Hydrogen bonds between PAAc and PAAm can be formed in acidic environment,which function as reversible sacrificing bonds and further improve the stretchability of the hydrogel.2.The above prepared hydrogels are soaked in the Fe3+solutions to obtain the high strength shape memory hydrogels.The introduction of the ferric ions endow the hydrogel additional physical crosslinks which can act as sacrificing bonds to dissipate energy for enhancing the mechanical properties.The complexation of Fe3+ with carboxyl groups renders the hydrogels with the capability of shape memory.Through an interpenetrating network and a single network structure analysis,the interpenetrating network topological structure is more helpful to form the interchain ionic crosslinking,resulting in the high mechanical properties and shape memory function.3.Redox-responsive microgels modified the Ferrocenecarboxylic acid(FCA)groups have been synthesized via emulsion polymerization with N-isopropylacrylamide(NIPAM)and Allylamine(AA)as comonomers.The resultant microgels are characterized by 1H NMR spectrum and UV-Vis absorption spectrum to prove the existence of ferrocene group.The electrical responsive behavior of the microgels is investigated by the electrochemical measurement.The dynamic light scattering is used to study the particle sizes of the microgels.The results show that,under chemical and electrical stimuli,the microgels modified ferrocene groups can change the interactions among the segments of polymer,leading to the change of particle size.What's more,the microgels loaded anti-cancer drug 5-FU can change the drug release rate due to the swelling-shrinking of the microgels under the electrical stimuli.In this essay,we have constructed composited hydrogels with high mechanical strength and novel functions by introducing supramolecluar interactions into the microgel fillers and the hydrogel matrix.The metal-ligand supramolecular interactions endow the hydrogels more excellent mechanical properties and shape memory functions.The redox-responsive microgels are obtained through adding the redox groups,which perform the smart response to external chemical and electrical stimuli.This kinds of hydrogels have potential applications in the biological medicine areas.