Facile synthesis of cross-linked patchy fluorescent conjugated polymer nanoparticles by click reactions

        V?ala ?rahimova, Seyma Ekiz, ?lem Gezici and D?? Tuncel

                Polym. Chem., 2011, 2, 2818-2824 
               

Cross-linked, patchy fluorescent conjugated polymer nanoparticles were prepared eithervia 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.

White-Emitting Conjugated Polymer Nanoparticles with Cross-Linked Shell for Mechanical Stability and Controllable Photometric Properties in Color-Conversion LED Applications" Eun-Ju Park, Talha Erdem, Vusala Ibrahimova, Sedat Nizamoglu, Hilmi V. Demir,* and Donus Tuncel*

                                                       Figure 1. Cartoon representation of the conjugated polymer nanoparticle preparation.

We report on the synthesis and characterization of water-dispersible, mechanically stable conjugated polymer nanoparticles (CPNs) in shelled architecture with tunable emission and controllable photometric properties via cross-linking. Using a reprecipitation method, whiteemitting polymer nanoparticles are prepared in different sizes by varying the concentration of polymer; the emission kinetics are tuned by controlling the shell formation. For this purpose, polyfluorene derivatives containing azide groups are selected that can be decomposed under UV light to generate very reactive species, which opportunely facilitate the inter- and intra-cross-linking of polymer chains to form shells. Nanoparticles before and after UV treatment are characterized by various techniques. Their size and morphologies are determined by using dynamic light scattering (DLS) measurements and imaging techniques including scanning electron microscopy (SEM) and atomic force microscopy (AFM). For optical characterization, UV
vis and steady-state and timeresolved fluorescent spectroscopies are performed. Solid-state behaviors of these CPNs are also investigated by forming films through drop-casting. Moreover, the photometric calculations are also performed for films and dispersions to determine the color quality. A device has been constructed to show proof-of-principle white light generation from these nanoparticles. Additionally, mechanical stability studies are performed and demonstrated that these nanoparticles are indeed mechanically stable by removing the solvent after cross-linking using a freeze-dryer and redispersing in water and THF. Optical and imaging data confirm that the redispersed particles preserve their shapes and sizes after cross-linking.

SCAN 2010 event is designed to be composed of a 2-day research workshop that will be held between September 30th and October 2nd 2010 followed by a one-day excursion on Oct 3. This workshop will be followed by a 3 day mini-school (between Oct 4-Oct 6) which will include 2-hr lectures from invited speakers to deliver talks to graduate students and faculty members who would like to acquire in depth knowledge about a specific subject covered during the workshop.

October 6, 201

The Effect of Cucurbit[n]uril on the Solubility, Morphology, and the Photophysical Properties of Nonionic Conjugated Polymers in an Aqueous Medium" DONUS TUNCEL, MUGE ARTAR, SALTUK BUGRA HANAY

The effects of cucurbit[n]uril on the dissolution and the photophysical properties of nonionic conjugated polymers in water are described. For this purpose, a fluorine-based polymer,namely, poly[9,9-bis{6(N,N-dimethylamino)hexyl}fluoreneco- 2,5-thienylene (PFT) was synthesized and characterized by spectroscopic techniques including 1D and 2D NMR, UVVvis, fluorescent spectroscopy, and matrix-assisted laser desorption mass spectrometry (MALDI-MS). For the first time, it was demonstrated that a nonionic conjugated polymer can be made soluble in water through an inclusion complex formation with CB8. The structure of the complex was elucidated by NMR experiments including 1H and selective 1D-NOESY. This complex emits green and is highly fluorescent with fluorescent quantum yield of 35%. In contrast, CB6 or water-soluble CB7 although they are chemically identical to CB8 do not have any effect on the dissolution and photophysical properties of PFT. By preparing a protonated version of PFT, the optical properties of PFT in methanol, protonated PFT and PFT@CB8 in water have been studied and compared. It was also observed that the morphology of the polymer PFT was affected by the presence of CB8. Thus CB8-assisted self-assembly of polymer chains leads to vesicles formation; these structures were characterized by DLS, AFM, SEM, and TEM fluorescent optical microscopy VC 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4894-4899, 2010