Conformational transitions and aggregations of regioregular polyalkylthiophenes

Diverse conformational transitions and aggregations of regioregular poly (3-alkylthiophene)s (PATs) in different environment have been studied by means of AFM and UV-vis-spectroscopy. In methanol, which is a non-solvent for both alkyl side groups and aromatic backbone at low polymer concentration, PATs chains fold into compact poorly ordered flat structures. At higher polymer concentration PATs molecules undergo 3D aggregation into near spherical particles. In hexane, which is a selective solvent for alkyl side chains, PATs molecules undergo ordered main-chain collapse followed by 1D aggregation. Concentration-independent red shift of λmax and good resolved fine vibronic structure in the electronic absorption spectra indicate that planarization occurs on the single-molecule level.     

Selective Terminal Functionalization of Linear Alkanes**

A two-step sequential strategy involving a biocatalytic dehydrogenation/remote hydrofunctionalization, as a unified and versatile approach to selectively convert linear alkanes into a large array of valuable functionalized aliphatic derivatives is reported. The dehydrogenation is carried out by a mutant strain of a bacteria Rhodococcus and the produced alkenes are subsequently engaged in a remote functionalization through a metal-catalyzed hydrometalation/migration sequence that subsequently react with a large variety of electrophiles. The judicious implementation of this combined biocatalytic and organometallic approach enabled us to develop a high-yielding protocol to site-selectively functionalize unreactive primary C−H bonds.     

Preparation of PA6/nano titanium dioxide (TiO2) composites and their spinnability

In this work, surface modification technique with coupling agents and anchoring polymerization was adopted to tailor the surface properties of nanoscaled titanium dioxide (TiO₂). Ethyl glycol sols with TiO₂ were prepared in order to simulate the dispersibility of differently modified TiO₂ in a molten polyamide 6 (PA6) matrix. The modified TiO₂ were melt compounded with PA6 and composites and fibers were prepared. The average filler diameter of 47 nm (in composites) and 44 nm (in fibers) indicated homogeneous dispersion of TiO₂ in the matrix, whereas unmodified TiO₂ showed agglomerated structures in the PA6 matrix. The mechanical properties of the composite fibers were improved as compared to pure PA6 fibers and composite fibers with unmodified TiO₂.