Preparation Of Stimulus-responsive Phase Transition Hydrogels And Phase Behavior Mechanisms

Because of its unique chemical and physical properties,stimuli-responsive polymers have great potential for application in many fields,such as drug delivery or controlled release,and become highly attractive polymer materials,which are very popular in academia.Although their research has been carried out for decades,it is still important to design novel stimuli-responsive polymer materials,as well as to study the mechanism of phase behavior.the complete phase behavior mechanism can guide people to synthesize the desired stimulus response effect.This paper is based on the design,synthesis of linear amphiphilic copolymers and the addition of third-party monomers to prepare grafted amphiphilic copolymers to test the phase transition behavior of the two polymers in different environments.And a series of stimuli-responsive hydrogels were further prepared from linear amphiphilic copolymers.the relatively complete phase behavior mechanism was summarized by studying the phase transition temperature under various conditions.The following is a brief introduction to the main research contents.First,for the synthesis and phase transition of linear amphiphilic copolymers,we selected hydrophilic polyethylene glycol diglycidyl ether and hydrophobic polypropanediol diglycidyl ether as the main monomers,and ethanolamine as the amine monomer,which was synthesized by one pot condensation.The chemical structure of the polymer was characterized by FT-IR and H-NMR,and its molecular weight was tested by GPC.And then the phase transition transmittance was tested by UV spectrophotometer under different conditions.The experimental results show that the increase of polymer aqueous solution concentration will reduce the phase transition temperature,and the increase of PEGDGE content will increase the transition temperature.And in pH experiments,adding hydrochloric acid to lower the pH value and adding sodium hydroxide to increase pH value will increase the transition temperature.These results can be explained by the coexistence of hydrogen bonds and electrostatic interactions.Finally,in oscillatory phase transition experiments,it is known that the polymer has a stable reversible phase transition.Secondly,in the experiment of preparing amphiphilic graft copolymer,we also chose the hydrophobic polypropanediol diglycidyl ether and amphiphilic polyetheramine,and the third-party monomer ethanolamine was used to regulate the amphiphilicity of the grafted polymer.The micelle size of the grafted polymer was tested and it was found that it had little relationship with the composition of the polymer.Compared with the phase transition behavior of the grafted structure and the linear structure,the grafted amphiphilic polymer has more sensitive phase transition ability.Finally,based on the previously synthesized linear amphiphilic copolymers,we successfully synthesized phase transition hydrogels with multiple stimuli-responsive by adding polyetheramines with three amino-terminal groups as crosslinkers.And the effects of hydrophilic monomer content,pH value,sodium chloride dose and urea dose on phase change behavior were fully discussed.The results show that the phase transition temperature of hydrogel increases with the increase of hydrophilic monomer content,and the addition of hydrochloric acid also increases the transition temperature,which is consistent with the experimental results of linear amphiphilic copolymer.But the phase transition temperature decreased after adding sodium hydroxide.Three main reasons for the phase transition mechanism are summarized by all phase transition behavior experiments,namely hydrophobic interaction,charge effect and hydrogen bond interaction.In addition,we also tested the swelling behavior of hydrogels.The results showed that the swelling ability was weakened at high temperature,and the swelling ability was enhanced by acidic conditions.