Design Of Controlled Cyclopolymerization System And Its Study Of Multi-responsive Properties And Sensor Applications

The polymers with the larger rings in the main chain have the special propertiesand applications, especially capturing some small molecules and ions based on thesupramolecular chemistry. The cyclopolymerization, discovered by Butler andco-workers in1949, has been considered as one of the most convenient method forthe preparation of the polymers with cyclic structures in the main chain. However, itstill remains a challenge to construct a cyclopolymerization system forming largerrings （such as crown ether） by using the flexible monomers. At the meantime,poly（ethylene glycol）（PEG） is a well-known thermo-responsive polymer and hasbeen applied for biomedical and pharmaceutical fields. And a great deal of studiesfocused on the crown ether cavities as a side pendant functional group of thepolymers since crown ethers are highly selective in the recognition of specific cations.However, it has not been studied about the responsive properties and sensorapplications of such polymers with crown ether units on the main chain and PEG asthe side chains.This thesis mainly focused on the developing a new controlled cyclopolymerizationprotocol for the common flexible monomers with maleic anhydride. Simultaneously,we also grafted PEG onto the anhydride groups of the copolymer chain andinvestigated the responsiveness of the resulting polymers. These multi-responsiveamphiphilic copolymers can also be used to detect Cu²⁺and Ag⁺as the sensor afterlabeled by the pyrene. The details are as following:Firstly, the cyclopolymerization of distyrenic flexible monomers with maleicanhydride via reversible addition fragmentation chain transfer （RAFT） has beeninvestigated. The reaction proceeded to yield gel-free copolymers soluble in organicsolvents. The kinetic study indicated that the cyclopolymerization proceeded in acontrolled manner. The structures of resulting crown ether cavity-containingcopolymers were characterized by the use of NMR spectroscopy and MALDI-TOFmass spectrometry. Additionally, it was found that the crown ether cavities of thecopolymers exhibited a selective recognition for certain dialkylammonium ions. Secondly, a series of amphiphilic copolymers were synthesized bycyclopolymerization of distyrenic monomers with maleic anhydride followed bygrafting methoxy poly（ethylene glycol） onto the anhydride groups. Theseamphiphilic graft copolymers exhibited multiple responsive toward temperature, pHand selected cations in aqueous solutions. The cloud points （CP） of the graftcopolymers increase with increasing length of the side chains and with increasing pHvalue of solution. The addition of KCl or LiCl to the solutions had a “salting-out”effect, lowering the CPs of the graft copolymers. The addition of NaCl, however,firstly raised the CP due to the complexation of the crown ether with Na+and thenlowered the CP. The light scattering results also confirmed the effect of Na+on theCP.Finally, a series of responsive copolymers （toward temperature and pH） with thecrown ether cavities in the main chain could be obtained by the labeling pyrene andgrafting PEG onto the copolymer of distyrenic monomers with maleic anhydride.These copolymers can act as metal sensors since the crown ether can capture someions and some transition metal ions can quench the fluorescence of pyrene. Thesesensors showed the highly selectivity and sensitivity toward to Cu²⁺or Ag⁺withoutinterference from other metal ions and can be used into the system of Cu²⁺and Ag⁺with the concentration of2-12μM. And the Cu²⁺or Ag⁺detection limit can be downto about1.02or0.75ppm, respectively.In addition, a series of new well-defined nanoparticles containing an organotincore and a polystyrene shell were obtained by cross-linking of n-Bu₂SnO withvarious chain-length amphiphilic copolymers. The structures of the nanoparticleswere studied by the transmission electron microscopy （TEM）, scanning electronmicroscopy （SEM） and X-ray photoelectron spectroscopy （XPS） analysis. Notably,the morphology of the cross-linked copolymer showed individual nanoparticles withregularly spherical shape. And the nanoparticle diameters decreased with increasingnumber of organotin carboxylate units.