Synthesis And Properties Of Hyperbranched Polymers Containing Ionic Frameworks

Hyperbranched polymers?HBPs?are three-dimensional macromolecules,which contain many cavities formed by the branched chains and functional end groups.Based on the inclusion properties of the cavities,hyperbranched polymers have found broad applications in many fields such as adsorption,separation and biological medicine.Currently,more functional hyperbranched polymers were obtained by modifying their terminal groups,whereas there are few reports on functioned backbones of a hyperbranched polymer.In this dissertation,a series of novel hyperbranched-based polymers containing cationic groups on their backbones were designed and synthesized.Incorporation of cationic groups onto the backbones is to obtain electrostatic interaction with anionic guest molecules when they are included into the cavities of a hyperbranched polymer.Thus,large inclusion capacity and highly selective adsorption of the cations functioned hyperbranched polymer toward anionic guest molecules may be achieved due to the enhanced host-guest binding affinity.It is expected for this type of hyperbranced polymers to have application in some fields such as adsorption,separation and biomedicine.In this thesis,the adsorption capacity and mechanism of these polymers towards anionic dyes and heavy metal ions were studied emphatically.Also,the paper deals with the sustained release of an anionic-type drug from hydrogels with hyperbranched polymer environments.The main contents and results are summarized as follows:?1?A hydrophobic hyperbranched polymeric ionic liquid?hb-PIm⁺PF₆^-?containing imidazolium hexafluorophosphate-based backbones was designed and synthesized for anionic dye removal and selective adsorption.Synthesis procedure of hb-PIm⁺PF₆^-involves:?1?the thiol-ene addition reaction of di-mercapto A₂ monomer with tri-vinyl imidazolium-based B₃monomer afforded the water-soluble hyperbranched polymeric imidazolium clrodie ionic liquid?hb-PIm⁺Cl^-?;?2?hb-PIm⁺PF₆^-was obtained by anion exchange reaction of hb-PIm⁺Cl^-with KPF₆.The effect of synthesis conditions on the structure of hb-PIm⁺Cl^-was studied,and the adsorption properties of hb-PIm⁺PF₆^-towards anionic and cationic dyes were investigated.The results showed that hb-PIm⁺PF₆^-had large adsorption capacities for anionic dyes?e.g.,the maximum adsorption capacity towards Congo red?CR?could reach 2000 mg/g?.In contrast,the adsorption capacity of hb-PIm⁺PF₆^-towards cationic dyes?e.g.methylene blue,methyl violet,etc?was very low under the same conditions.Therefore,hb-PIm⁺PF₆^-can be applied to the separation of a mixed anion/cation dyes system.The adsorption mechanism of hb-PIm⁺PF₆^-towards CR was studied by means of scanning electron microscopy/energy dispersive spectroscopy,transmission electron microscopy and Fourier transform infrared spectroscopy.The adsorption mechanism was also analyzed by adsorption kinetics,adsorption isotherm and adsorption thermodynamics models.The results show that the cooperation between the backbone electrostatic attraction and the cavities inclusion of the hyperbranced polymer for CR binding is the critical factor for its large adsorption capacity and highly selective adsorption.In order to extend the application range of hb-PIm⁺PF₆^-,hb-PIm⁺PF₆^-was combined with polyvinylidene fluoride?PVDF?,which has excellent thermal stability,and oxidation,acid and alkali resistances.hb-PIm⁺PF₆^-/PVDF composite films were prepared for removing anionic-type dyes by filtration method.The results show that,under dynamic condition,hb-PIm⁺PF₆^-/PVDF could remove bromophenol blue?BPB?.The high removal efficiency of the composite film towards BPB is attributed to the presence of the hb-PIm⁺PF₆^-microenvironment.?2?By using an“A₃+B₃”polymerization system,the hyperbranched hydrogel?hbGel-PEG-TTIm⁺Br^-?containing ionic liquid groups at cross-linking sites was designed and synthesized for hexavalent chromium ions?Cr?VI??adsorption.The effects of the monomer concentration on the structure and properties of hbGel-PEG-TTIm⁺Br^-were investigated.The results showed that the imidazolium functional groups and network structure were responsible for the efficient adsorption of Cr?VI?and the moderate mechanical properties.The obtained hbGel-PEG-TTIm⁺Br-5#had a compressive strength of 2.52 MPa at strain 60%,and its maximum adsorption capacity of Cr?VI?could reach 188 mg/g.?3?On the basis of chapter 3,a new amphiphilic A₃ monomer was synthesized by incorporation of polycaprolactone?PCL?segment into the previous A₃-type monomer.Through“A₃+B₃”polymerizationsystem,poly?glycerolethoxylate?–polycaprolactone-poly?imidazolium bromide ionic liquid?hyperbranched hydrogel?hbGel-PEG-PCL-TTIm⁺Br^-?was prepared for the adsorption of anionic-type dyes.The effects of the PEG/PCL ratio of the new A₃ monomer on the structure and properties of resulting hbGel-PEG-PCL-TTIm⁺Br^-hydrogels were investigated.The results showed that the incorporation of the PCL segments could reduce monomer concentration required for gelation without reducing the mechanical properties.It was found that the swelling,mechanical and adsorption properties of the resulting hydrogels depended on the ratio of hydrophilic/hydrophobic polymer chains of the new A₃ monomer.The imidazolium functional groups formed in situ and the proper proportion of PCL hydrophobic chains provided multiple interaction environments for dyes BPB,achieving an efficient adsorption of BPB.The adsorption capacity of hbGel-PEG-PCL-TTIm⁺Br^--8#sample towards BPB was 395 mg/g,and the compressive strength of the gel was 2.42 MPa.The adsorption capacity of hbGel-PEG-PCL-TTIm⁺Br^--9#sample towards BPB was 305 mg/g,and the compressive strength of the gel could reach 5.11 MPa.The selective adsorption of anionic dyes by hbGel-PEG-PCL-TTIm⁺Br^-can also be used for the separation of anionic/cationic dye mixtures.?4?Poly?hydroxyethyl acrylate?hydrogels?PHEA-hb-PAMAM?containing hyperbranched polyamidoamine?hb-PAMAM?environments were designed and synthesized for retarding release of anionic-type drugs.hb-PAMAM with terminal double bonds was synthesized by the Azo-Michaeladditionreactionofpiperazine?A₂monomer?with1,3,5-triacryloylhexahydro-1,3,5-triazine?B₃ monomer?.PHEA-hb-PAMAM was obtained by copolymerization of hb-PAMAM with hydroxyethyl acrylate.The results showed that the electrostatic interaction between salicylic acid?SA?and hb-PAMAM microenvironment of the hydrogel reduced the transport and diffusion of SA molecules in the hydrogel matrix,and as a result,a sustained release pattern of SA was realized.