Synthesis, Self-Assembly And Properties Of Polymer Nano-Materials

It is well-known that those well-defined polymers,such as dendrimers, block copolymers, and hyperbranched polymers,will aggregate to form polymer nanomaterials with an ordered structure, uniform size and unique morphology by means of self-assembly, which is based on non-covalent driving forces including electrostatic interaction, hydrogen bond,tc-tc interaction,and hydrophilic-hydrophobic forces,etc. In addition,inorganic nanoparticles and organic polymers can be self-assembled into ordered inorganic-organic hybrid nanomaterials under the driving of the above-mentioned inter-molecular forces. The size and microstructure of the polymeric nanomaterials can be well controlled by self-assembly while special functionalities are endowed as well,which makes the polymeric nanomaterials be potentially applied in new materials, electronics,photonics and biomedical areas.In this paper, an ultra-long, one-dimensional nanoribbon has been prepared via self-assembly by using carbon dots(C-dots) and oligomers as building blocks. It is found that the nanoribbon is conductive, and showing multi-colored fluorescence. The subsequently prepared Ag-(PS-PSS)/C-dots nanobelt exhibits an outstanding surface-enhanced Raman scattering(SERS) effect. In addition, an amphiphilic copolymer with a targeting molecule triphenylphosphine(-TPP) has been synthesized by using reversible addition fragmentation chain transfer(RAFT) polymerization method. And then a kind of biomacromolecule,bovine serum albumin(BSA), was linked to the copolymer by bio-conjugation. The obtained copolymer-BSA conjugates self-assembled into spherical nanomicelles in aqueous solution, which showed mitochondria-targeting property in HeLa cells.The main works can be summarized as follows:1. Formation of ultra-long noribbons by self-assembly of C-dots and oligomers First,using konjac flour as a starting material,a kind of fluorescent C-dotshas been prepared by pyrolysis method. Second, the oligomer of styrene and4-styrenesulfonalte(PS-PSS) was synthesized by radical polymerization in a mixture of ethanol and water(4/1,v/v). Upon the addition of C-dots into the solution, ultra-long(>100 μm) nanoribbons with a well-ordered structure and an average thickness about 80 ?120 nm have formed, which was based on self-assembly of positively charged C-dots and anionic oligomers(PS-PSS) in the ethanol/water solution. Moreover, the thickness of nanoribbons would increase with prolonging the self-assembly time,together with the change in the nanoribbon morphology. The microstructure, components and fluorescent property of the nanoribbon has been characterized by employing transmission electron microscopy(TEM),scanning electron microscopy(SEM), atomic force microscopy(AFM),MALDI-TOF mass spectrum, nuclear magnetic resonance(NMR) spectroscopy, ultraviolet-visible(UV-vis) absorption and photoluminescence(PL) spectrum. The results indicate that the architecture of the nanoribbon is built on C-dots and PS-PSS oligomer blocks,which combine into a repeating unit and then each units self-assembled into an ordered ID inorganic-organic hybrid nanostructure. The obtained hybrid(PS-PSS)/C-dots nanoribbons show a multi-colored fluorescence and an electrical conductivity of3.368 S/m.2. Preparation of Ag-(PS-PSS)/C-dots nanobelt as a sensitive SERS substrateThe hybrid Ag-(PS-PSS)/C-dots nanobelts(NBs) have been prepared by decorating Ag nanoparticles(NPs) on surface of the ultra-long, semiconducting(PS-PSS)/C-dots nanoribbons(NRs) via an electroless plating method. The as-prepared Ag-(PS-PSS)/C-dots NB has been demonstrated to be an excellent substrate for surface-enhanced Raman scattering(SERS) with a detection limit of10-14 M and an enhancement factor of 3.35 x 10~8 while using rhodamine 6G as probe molecules. Moreover, we have investigated the application of Ag-(PS-PSS)/C-dots NBs as SERS substrate for detection of coumarins. Further, the Ag-(PS-PSS)/C-<iots NB could be used as a sacrificial template to form a novel kind of hollow porous Agnmiotubes(NTs) by simply removing the inner NR in tetrahydrofuran. However,the obtained Ag NTs show a weaker SERS effect compared to that of the Ag-(PS-PSS)/C-dots NBs,which indicates that the inner organic /C-dots NR plays an essential role in SERS property of the Ag-(PS-PSS)/C-dots NBs. The possible reasons are as follows:(1) the organic(PS-PSS)/C-dots NR acts as a dielectric support for Ag NPs to enhance the surface plasmon resonance(SPR) at the Ag-NR interface;(2) their large surface area are favorable for creating more "hot-spots";(3) the embedded sp2-hybridized C-dots in NR can adsorb more aromatic R6 G molecules via ti-tc interaction,which also drives R6 G molecules approaching to the "hot-spots", thus enhancing the SERS signals.3. Synthesis, self-assembly of mitochondria-targeting polymer nanocarriers First,a kind of amphiphilic block copolymer with an ending group of-TPP has been synthesized by RAFT polymerization, a typical synthesis procedure ia as follows;using azobisisobutyronitrile(AIBN) as an initiator and dithioester as a chain transfer agent, a copolymer of a temperature-sensitive monomer- diethylene glycol monomethyl ether methacrylate(DEGMA) and a fluorescent monomer4-(2-acryloyloxyethylainino)- 7- nitro_ 2,1,3- benzoxadiazole(NBDAE) has been synthesized, and then a block copolymer with an ending group of-COOH was produced by RAFT polymerization when the reaction system was added with a hydrophilic monomer N,N- dimethylacrylamide(DMA). Second,the obtained amphiphilic block copolymer TPP-PDMA-6-P(DEGMA-co-NBDA￡) was linked to a biomacromolecule(BSA) by bio-conjugation. Finally, the polymer-BSA bioconjugates self-assembled into spherical nanomicelles in an aqueous solution. The nanoraicelles are fluorescent, less toxic and relatively stable in solution, moreover, the post-treatment of dyeing or staining is not required. Further,by means of laser scanning confocal microscopy, it was seen that the polymeric nanomicelles were uptaken by HeLa cells and enriched around the mitochondria membranes, which means the as-synthesized polymeric nanomicelles can be potential mitochondria-targeting nanocarriers applied in targeted drug delivery system for treatment of mitochondrial dysftinction-related diseases.