Investigation On The Stimulus-responsiveness And Molecular Recognition Of Multifunctional Polymer ?-CD-PNIPAM

In recent years,with the rapid development of polymer science,various new multifunctional materials have been continuously designed and synthesized.Combined the unique properties of supramolecular chemistry and sensitive materials,sensitive supramolecular polymers have broad application prospects in drug release,molecular recognition and separation systems.In this paper,the stimulus-responsiveness and molecular recognition of multifunctional polymer ?-CD-PNIPAM were emphatically studied.It is expected to provide theoretical basis for further application research.It mainly includes the following three chapters:(1)Introduction.The structural characteristics,performance characteristics and applications of the supramolecular body ?-CD and the sensitive material PNIPAM were mainly summarized in this chapter.The research situation of intermolecular interactions was briefly introduces.Combined existing problems and recent research dynamics,the significance and main contents of this research were proposed.(2)Preparation and investigation on the stimulus-responsiveness of ?-CD-PNIPAM.?-CD-PNIPAM was prepared by combination of atom transfer radical polymerization and click chemistry according to the literature,its chemical structure was determined by FT-IR and 1H NMR.Then the temperature and solvent double response characteristics of ?-CD-PNIPAM were studied by 1H NMR,DLS,ATR,SEM/AFM and so on.The results showed that the introduction of ?-CD increased the LCST and weakens the temperature sensitivity of PNIPAM.The chemical shift of proton absorption peaks of ?-CD-PNIPAM were increased with the increase of temperature,and the particle sizes exhibited decreases-increases-decreases trend.In water-methanol and water-tetrahydrofuran systems,the LCST of ?-CD-PNIPAM decreased first,then increased until disappearance with the increase of organic solvent volume ratio.The hydrodynamic radius first decreased and then increased.When volume ratio of THF was 30 % or CH3 OH was 35 %.the LCST and hydrodynamic radius were reduced to a minimum of 15 °C,128.7 nm and 24 °C,87.7 nm respectively.When the proportion of THF was 55 % or CH3 OH was 50 %,the phase separation behavior vanished.In conclusion,changing temperature and solvent polarity could change the surface hydrophilicity and molecular aggregation behavior of ?-CD-PNIPAM.(3)Investigation on the interaction between ?-CD-PNIPAM and small molecules.Temperature controlled liquid-liquid extraction method and paper chromatography was used to observe the phase transfer behavior and chromatographic retention behavior of dye molecules on ?-CD-PNIPAM.Then the fluorescent compounds nile red and p-nitrophenol were used as probe molecules and the interaction mode of ?-CD-PNIPAM with probe molecules at different temperatures was explored by UV?FL?DLS?ITC and TEM methods.The results showed that,when temperature is higher than the LCST of ?-CD-PNIPAM,the retention time of dye molecules was longer and in cooperation with the induction of non-polar solvents,the dye molecules can be extracted from the aqueous phase to the two-phase interface.The fluorescence probe experiment showed that the fluorescence emission spectra of nile red moved towards the short-wave direction and fluorescence intensity increased with the increase of temperature.Study on interaction between ?-CD-PNIPAM and PNP showed that,when temperature is below and above the LCST of ?-CD-PNIPAM/PNP,its binding constants to PNP are 1.78×102 M-1 and 9.06 × 105 M-1 respectively.In conclusion,the interaction between ?-CD-PNIPAM and probe molecules could be enhanced with temperature increased.The interaction strength could be injusted by changing temperature and solvent polarity.Based on the phase transition property and molecular recognition of ?-CD-PNIPAM,its application as temperature-controlled supramolecular liquid-liquid microextraction(TC-SM-LLME)adsorbent material to extract organic pollutants in water was proposed.