Study On The Influence Of Microenvironment To The Properties Of Hydrophobic Association Hydrogels

Hydrophobic association hydrogel is a type of physical crosslinked hydrogel,whose crosslinking points are hydrophobic associated microdomains.Because of the hydrophobic interaction is dynamically reversible,hydrophobic associated hydrogels have many exceptional properties such as higher mechanical strength,self-healing and secondary processing properties which are not available from conventional chemica lcrosslinking gels.As a result,hydrophobic association hydrogels have become very popular to researchers.And they have played an important role in our daily life,such as oilfield mining,sewage purification,paint and biomedical.When people are concentrating on the application of hydrophobic associat ion hydrogels,the basic theoretical research progresses slowly.Some new hydrogels do not have systematic theory to support their properties and behavior,thus it is difficult to predict and build according to our needs.For example,the same kind of hydrogels properties and behavior are related to the influence of environment to network structure.Therefore,this paper focuses on the influence of the microenvironment to the hydrophobic association hydrogels properties,exploring the influencing factors and mechanisms,studding and discussing the internal structures and properties of the gels.We selected acrylamide(AM)as hydrophilic monomer,acylphenol polyoxymethyle ne(10)ether acrylate(OP10-AC)as hydrophobic monomer,dodecyl Sodium sulfate(SDS)as surfactant,and used micellar copolymerization to prepared the required hydrophobic association hydrogel.Changing the microenvironment of the gels,we explored the corresponding changes of the gels.Firstly,five groups of hydrogels which have different SDS content were chosen,inorganic salt NaCl was added into the synthesis system to change gel microenvironment,and the mechanical properties and swelling behavior of the gel were studied respectively.Through tensile test,the parameters of the breaking strength and modulus can represent the mechanical properties of the gel.The result showed that the trend of fracture strength and the turning point with the increase of NaCl and SDS molar ratio are roughly the same,"M" type,although the SDS content of the gels were different.Then we used Mooney-Rivlin theory to analyze the microstructure of the gel.The results showed that the addition of NaCl would make the crosslinking density of the gel decrease,and the more NaCl,the greater decreased.In the experiment of swel ing behavior,we found that the swel ing ratio and lifetime are related to the structure of hydrogels.Combining with the result of the second chapter,we could find that swel ing ratio and speed are in the inverse proportional relationship to the crosslinking density.And when the swel ing medium contains NaCl,there are two effects on the swel ing behavior of the gel: one is salting out,which can strengthen the intensity of hydrophobic association.The other is osmotic pressure,which can prevent the gel from further water absorption.These two effects cause the gel have lower swel ing degrees and longer gel life.In addition,we used the solution containing SDS to swell the gel and obtained the effect of SDS on the swel ing behavior of the gel.We got the results which had two points.On one hand,as the surfactant,SDS can promote the disassociation of crosslinking point.On the other hand,as a kind of sulfonate,it can lead to the osmotic pressure to the hydrogel,the swel ing ratio will decrease with the increase of SDS concentration.In conclusion,the influence of mechanical properties and swelling behavior in the hydrophobic association hydrogel system caused by the change of microenvironme nt about inorganic salt NaCl and surfactant SDS were studied in detail.We have had a deeper understanding of its internal structure and cross-linking.The properties and behaviors of hydrogels in macroscopic conditions are attribute to the microscopic network structure.This paper builds theoretical foundations to properties and swelling behavior of polyoxymethylene ether acrylate hydrophobic associated hydrogels in microenvironment,provides methods to project and build hydrogels,and lays a solid foundation for extend application and opening up prospects.