Browsing by Subject "Functional polymers"
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Item Open Access Facile synthesis of cross-linked patchy fluorescent conjugated polymer nanoparticles by click reactions(2011) İbrahimova, V.; Ekiz, S.; Gezici, Ö.; Tuncel, D.Here, we report a novel method to synthesize multifunctional nanoparticles that can be used in biological studies, such as in cell imaging and as a carrier for biomolecules/drugs. The nanoparticles were prepared either via Cu-catalyzed or cucurbit[6]uril (CB6)-catalyzed click reactions between azide groups containing hydrophobic blue, green and yellow emitting fluorene-based conjugated polymers and a hydrophilic diaminodialkyne containing cross-linker. Through the click reaction, not only does the cross-linking confer stability, but it also introduces functional groups, such as triazoles and amines, to the nanoparticles. Moreover, CB6 not only acted as a catalyst to facilitate the copper-free click reaction, but it also allowed us to obtain nanoparticles containing rotaxanes in which the triazole units were encapsulated by CB6 units. TEM images of the nanoparticles also showed that they display very interesting morphologies. Incorporation of hydrophilic functional groups to the hydrophobic conjugated polymers resulted in a distinct phase separation, producing Janus-like or patchy particles.Item Open Access Like-Charge Attraction And Opposite-Charge Decomplexation Between Polymers and DNA Molecules(American Physical Society, 2017) Buyukdagli, S.We scrutinize the effect of polyvalent ions on polymer-DNA interactions. We extend a recently developed test-charge theory [S. Buyukdagli, Phys. Rev. E 94, 042502 (2016)1539-375510.1103/PhysRevE.94.042502] to the case of a stiff polymer interacting with a DNA molecule in an electrolyte mixture. The theory accounts for one-loop level electrostatic correlation effects such as the ionic cloud deformation around the strongly charged DNA molecule as well as image-charge forces induced by the low DNA permittivity. Our model can reproduce and explain various characteristics of the experimental phase diagrams for polymer solutions. First, the addition of polyvalent cations to the electrolyte solution results in the attraction of the negatively charged polymer by the DNA molecule. The glue of the like-charge attraction is the enhanced shielding of the polymer charges by the dense counterion layer at the DNA surface. Second, through the shielding of the DNA-induced electrostatic potential, mono- and polyvalent cations of large concentration both suppress the like-charge attraction. Within the same formalism, we also predict a new opposite-charge repulsion effect between the DNA molecule and a positively charged polymer. In the presence of polyvalent anions such as sulfate or phosphate, their repulsion by the DNA charges leads to the charge screening deficiency of the region around the DNA molecule. This translates into a repulsive force that results in the decomplexation of the polymer from DNA. This opposite-charge repulsion phenomenon can be verified by current experiments and the underlying mechanism can be beneficial to gene therapeutic applications where the control over polymer-DNA interactions is the key factor.Item Open Access Macroscopic photoconductive nanowire arrays(IEEE, 2011) Bayındır, Mehmet; Yaman, Mecit; Özgür, Erol; Aktaş, Ozan; Khudiyev, Tural; Kanık, Mehmet; Deniz, HakanA novel high-throughput fabrication technique to produce polymer embedded functional chalcogenide nanowire arrays is demonstrated. Indefinitely-long selenium nanowire arrays are obtained and their size dependent photoconductivity is investigated. Logarithmic increase in photo-conductance is observed. © 2011 IEEE.Item Open Access Nano-structured organically modified silica thin films for functional surfaces(2011) Bayındır, Mehmet; Yıldırım, Adem; Budunoglu, Hülya; Yaman, Mecit; Deniz, Hakan; Güler, Mustafa O.We report a template-free sol-gel method for preparation of nanoporous ormosil thin films at ambient conditions. The thin films are coated to the surfaces by using colloidal suspensions of ormosil gels. Gels are synthesized by using a trifunctional organosilane monomer, methyltrimethoxysilane (MTMS), with a two-step acid base reaction. We prepared several ormosil thin films on glass, metal, plastic and paper surfaces with different functionalities like superhydrophobic, antireflective, antifogging and ice retarding properties, from gels prepared in different conditions. Also films on flexible substrates exhibits durable surface properties after several bending cycles. In addition, we also demonstrate that these thin films can be used for fluorescent sensing of explosives by doping them with fluorescent dyes.Item Open Access Novel molecular building blocks based on the boradiazaindacene chromophore: applications in fluorescent metallosupramolecular coordination polymers(2009) Bozdemir, Ö. A.; Büyükcakir, O.; Akkaya, E. U.We designed and synthesized novel boradiazaindacene (Bodipy) derivatives that are appropriately functionalized for metal-ion-mediated supramolecular polymerization. Thus, ligands for 2-terpyridyl-, 2,6-terpyridyl-, and bipyridyl-functionalized Bodipy dyes were synthesized through Sonogashira couplings. These fluorescent building blocks are responsive to metal ions in a stoichiometry-dependent manner. Octahedral coordinating metal ions such as Zn II result in polymerization at a stoichiometry corresponding to two terpyridyl ligands to one Zn II ion. However, at increased metal ion concentrations, the dynamic equilibria are re-established in such a way that the monomeric metal complex dominates. The position of equilibria can easily be monitored by 1H NMR and fluorescence spectroscopies. As expected, although open-shell Fe II ions form similar complex structures, these cations quench the fluorescence emission of all four functionalized Bodipy ligands. © 2009 Wiley-VCH Verlag GmbH & Co. KGaA.