Preparation And Characterization Of Two Environmentally Responsive Polymers

Environmentally responsive polymers,also known as stimulatedresponsive,intelligent polymers,can recognize a small change in the external environment and carried out a rapid response through their own physical and chemical properties’ changes.These "smart"macromolecules have a wide applications in the fields of biomaterials,medicine,materials science and engineering because of their unique characteristics.At the level of macromolecules,the response behavior of polymer segments can be achieved by a variety of changes,including their own hydrophilic/hydrophobic balance,solubility,conformation,degradation,breakage of chemical bond and self-assembly structure with detection behavior.Based on a large number of literature research,two different environmentally responsive polymers were designed and synthesized,and their responsive performance was studied.The main research contents are as follows:(1)Photo-responsive amphiphilic diblock poly(carbonate)s mPEG113-b-PMNCn with pendent o-nitrobenzyl ester group were synthesized through living ring opening polymerization(ROP).In aqueous solution,the copolymers can self-assemble to spherical micelles with a PC core and a PEG shell.The spherical micelles have a average particle size of 150 nm and a critical micelle concentration(CMC)of 0.01 mg/mL.The photocleavage properties of o-nitrobenzyl groups under 365 nm UV irradiationwas measured by UV-vis spectrophotometer,1H NMR,GPC,TEM and DLS.The results showed that the photocatalytic activity of o-nitrobenzene was better under ultraviolet light.The light-controlled release behaviors of payload Nile Red(NR)were further proved by fluorescence spectroscopy.The results showed that the drug could be released completely under UV irradiation after 75 min.MTT assay was used to test the cytotoxicity of polymer micelles.The results showed that the polymer mPEG113-b-PMNCn had good biocompatibility.Therefore,this photo-responsive amphiphilic block polymer is a promising drug delivery carrier material,which can be used in the transport and release of hydrophobic anticancer drugs.(2)Using one-pot method,with D,L-homocysteine thiolactone as raw material,temperature-pH double-responsive polyamides P1 and P2 were synthesized by the way of repeated click reaction of "mercapto-bromine",functionalizing the side chain and polymerizing at the same time.The UV-vis spectrum showed that the polymer P1 had worse pH response in the pH range of 1-14 than polymer P2 and the polymer P2 had a good pH response.The polymer P2 solution was hydrophilic at pH ≤9,when pH ≥9.5,the polymer was hydrophobic,at this point the polymer solution undergoes a obvious phase transition.The test results show that polymer P2 has a good pH response reversibility.It is also known from the light transmittance data that the polymer P2 has a good temperature responsiveness and its LCST decreases with increasing pH,and further study indicates that the polymer P2 has a good temperature response reversibility.This experiment provides a new method for rapid synthesis of intelligent polymer materials,and the intelligent response is well.