Monodisperse oligomers

Soapless seeded emulsion copolymerization has been proposed as an alternative method for the preparation of uniform copolymer microspheres in the submicron-size range [115-117]. In this process, a small part of the total monomer-comonomer mixture is added into the water phase to start the copolymerization with a lower monomer phase-water ratio relative to the conventional direct process to prevent the coagulation and monodispersity defects. The functional comonomer concentration in the monomer-comonomer mixture is also kept below 10% (by mole). The water phase including the initiator is kept at the polymerization temperature during and after the addition of initial monomer mixture. The nucleation takes place by the precipitation of copolymer macromolecules, and initially formed copolymer nuclei collide and form larger particles. After particle formation with the initial lower organic phase-water ratio, an oligomer initiated in the continuous phase is... 

The authors developed two general methodologies for the synthesis of these monodisperse, defined oligomers. They can be built up stepwise, e. g. via additon of organometallic species to cyclohexan-1,4-dione, followed by aromatization to the oligoarylene (e.g. for 21). 

The thiophene ring is a common building block for novel oligomeric and polymeric materials. The synthesis of monodisperse thiophene oligomers continues to be widely studied and the preparation of one class of oligomers, oligothienylenevinylenes <00CEJ1698,... 

R. E. Martin, F. Diederich, Linear Monodisperse ji-Conjugated Oligomers Model Compounds for Polymers and More , Angew. Chem. Int. Ed. Engl. 1999, 38, 1350-1377. 

Monodisperse analogs of such ir-electron systems, PPV oligomers (molecular glasses) were studied by Bazan and coworkers [217]. The films prepared from 192 by solution casting showed completely amorphous structure due to a tetrahedral structure of the molecule and OLEDs ITO/PVK/192/Al-emitted green light with an efficiency up to 0.22 cd/A (Chart 2.42). 

Y Geng, ACA Chen, JJ Ou, SH Chen, K Klubek, KM Vaeth, and CW Tang, Monodisperse glassy-nematic conjugated oligomers with chemically tunable polarized light emission, Chem. Mater., 15 4352-4360, 2003. 

Wagner et al. used the reaction procedure shown in Fig. 4.2.5, and variations thereof, to yield the monodisperse oligoethoxylate monomethyl ether oligomers (n = 3-9). The trisiloxanes were then produced by hydrosilylation as in step b of Fig. 4.2.4 [72]. Distillation procedures were used to purify the intermediates and resulting trisiloxane alkylethoxylate products, and structural characterisation was performed by GC-MS and NMR. Purities for the n = 3-9 oligomers of 99, > 99, 99, 97.5, 96, 95 and 90%, respectively, as determined by GC-MS, were reported. 

Martin RE, Diederich F Angew Chem Int Ed (1999) 38 1350-1377 Linear monodisperse n-conjugated oligomers model compounds for polymers and more... 

Fig. 9. Phase transition temperatures Tc, T, and Tk of monodisperse oligomers as function of the degree of polymerization r ( phase transformation crystalline to isotropic)...

Supramolecular self-assembly has recently been extensively investigated as a tool to create nanostructured or hierarchically structured optoelectronically active materials from monodisperse, conjugated oligomers because such n-conjugated organic materials are interesting candidates for the fabrication of organic... 

Iightowler, S. and Hird, M. (2005) Monodisperse aromatic oligomers of defined structure and large size through selective and sequential Suzuki palladium-catalyzed crosscoupling reactions. Chemistry of Materials A Publication of the American Chemical Society, 27, 5538 -9. 

Because of the complex mechanism of these reactions, not yet sufficiently understood, directed synthesis of single monodisperse oligomers by endcapping polymerization of bis-deprotected acetylenes is not yet very effi-... 

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