Synthesis Of Thermo-responsive Polymers With A Linear Transition Behavior And Their Applications

Intelligent responsive polymers,also known as stimuli-responsive polymers,have been broadly investigated and applied in daily lives,such as chemical sensing,drug delivery,and so on.It may respond to various types of stimuli such as pH,temperature,ionic strength,light,electric and magnetic fields.They can adapt to the environmental changes by adjusting its physicochemical properties and/or structural conformation.The control of temperature can be easily achieved.Thus the investigations and applications of thermo-responsive polymers are attracted more and more attentions recently.A huge number of applications in the fields of the smart textiles,drug delivery systems,temperature-sensitive sensors are risingIn the present investigation,different types of thermo-responsive microgels with a linear transition behavior were synthesized by monomers with different number of ethoxy groups in the side chain.The effect of monomer dosage on the particle size and linear transition behavior of microgels was studied.The responsiveness and transition behavior of microgels in solution and film were systematically studied.Based on this special property,linear control of moisture permeability and anti-adhesion of bacteria in a broad temperature region realized by cross-linking thermo-responsive microgels onto cotton fabrics.Besides that,a polymer-based,printable,simple-prepared infrared detector was realized by spin-coating microgels containing Au nano rods(AuNRs)onto Si substrate.At the same time,the thin film with linear transition behavior was also prepared by spin-coating di-block copolymers containing two thermo-responsive blocks onto the Si substrate.Based on this special transition behavior,the flexible infrared detectors on PET film were preliminarily studied.The main tasks as follows:(1)2-(2-methoxyethoxy)ethyl 2-methyacrylate(MEO2MA),poly(ethylene glycol)methyl ether methacrylate(OEGMA300),and terminal hydroxyl group Poly(ethylene glycol)methacrylate(EGMA)were used as monomers.P(MEO2MA-co-OEGMA300-co-EGMA)microgels with hydrophilicity and linear transition behavior in a wide temperature range(20-70?)were prepared by free radical precipitation polymerization.The results show that the microgel has a spherical and uniform structure.After cross-linking the P(MEO2MA-co-OEGMA300-co-EGMA)microgels onto cotton fabric,the surface and void of the fibers were covered with a dense microgels layer.The cross-linked cotton fabric has a linear control of moisture permeability and anti-adhesion of bacteria in a broad temperature region.Comparing to the original cotton fabrics,the softness and whiteness of the cross-linked cotton fabrics are not significantly changed.The washing fastness measurements confirms that the stability of the cross-linked microgels is good as well.(2)The application of thermo-responsive microgels in infrared detector was studied as well.P(MEO2MA-co-OEGMA300-co-AA)microgels with a linear transition behavior were synthesized by free radical precipitation polymerization.It indicates that the microgels has a linear change of DH between 10 and 55?.From SEM images,the microgels also have a spherical and uniform structure.After the microgels were mixed with Au nano rods(AuNRs)solution,films were prepared by spin-coating.The white light interferometry was used to investigate the hydration and transition behaviors of the microgels film in a saturated water vapor environment.The film thickness showed a linear shrinkage upon heating.When the film is exposed to 850 nm infrared radiation,a linear correlation between the film thickness(resistance)and the applied infrared power density was observed.The films possessed a good reversibility and fast response.In addition.there is no prominent change of the film morphology before and after the resistance measurements,indicating the films were stable(3)In order to further explore the application of thermo-responsive polymer in flexible detectors,the di-block copolymer P(MEO2MA-b-OEGMA300)was synthesized by RAFT polymerization.The hydration and transition behaviors of the spin-coated P(MEO2MA-b-OEGMA300)film were investigated by white light interferometry.Upon heating,the film thickness showed a linear shrinkage.Based on the linear transition behavior,P(MEO2MA-b-OEGMA300)and AuNRs solution were mixed.Instead of Si substrate,flexible PET film was used as the substrate to prepared the infrared detector.By further adding nano-silver wires into the solution containing P(MEO2MA-b-OEGMA300)and AuNRs,the conductivity and uniformity of the films were improved.