Palladium-mediated surface-initiated Kumada catalyst transfer polycondensation is used to generate poly(3-methyl thiophene) films with controlled thickness up to 100 nm. The palladium initiator density is measured using cyclic voltammetry and a ferrocene-capping agent, where the surface density is found to be 55% (1.1 × 10(14) molecules per cm(2)). UV-Vis spectroscopy and AFM show increased aggregation in palladium-initiated films due to the higher grafting density of palladium initiators on the surface. The anisotropy of the P3MT films is determined using polarized UV-Vis spectroscopy, which indicates a degree of orientation perpendicular to the substrate. Evidence that palladium can maintain π-complexation even at elevated temperatures, is also shown through the exclusive intramolecular coupling of both a phenyl and thiophene-based magnesium bromide with different dihaloarenes.
In this work, we have investigated a quaternary ammonium compound that exhibits excellent antimicrobial activity and can be permanently grafted to substrates containing C−H bonds to form a durable polymeric film within 1 min. The compound consists of a biocidal component, dodecyl-alkylated quaternary ammonium, and a benzophenone moiety that, under mild UV irradiation, generates a densely cross-linked network and covalently attaches to a variety of substrates, including plastics, fabrics, and alkyl-modified glass surfaces. The surface attachment is 1 order of magnitude faster than that of previously reported benzophenone-associated cross-linkers, due to the electronwithdrawing effect of quaternary ammonium on the benzophenone chromophore. The modified surfaces are nonleaching and exhibit contact-killing and highly effective antimicrobial activity against Staphylococcus aureus (Gram-positive) and Escherichia coli (Gram-negative) using cell count and live/dead staining methods. The charged ammonium group also promotes photoreaction efficiency with respect to network robustness, leading to a thin film that can sustain high shear forces and abrasion when compared to commercially available silanebased quaternary ammonium compounds. The biocidal activity is also retained after exposure to mechanical stress and abrasion.
In this work, uniform poly(3-methylthiophene) (P3MT) films are fabricated on indium-tin oxide (ITO) surfaces using surface-initiated Kumada catalyst-transfer polycondensation (SI-KCTP) from surface-bound arylnickel(II) bromide initiators. The P3MT interfacial layer is covalently bound to the ITO surface, thereby preventing possible delamination during the processing of additional layers. These surface-bound P3MT layers successfully serve as the hole-transport layer for solution-processed bulk heterojunction polymer solar cells. Efficiencies greater than 5% have been achieved on devices based on doped thin P3MT interfacial layers. Moreover, because of the excellent stability of the covalently immobilized P3MT on ITO substrates, devices based on reused P3MT/ITO substrates extracted from old devices exhibit efficiencies similar to those of the original devices.
The kinetic isotope effect (KIE) is used to experimentally elucidate the first irreversible step in oxidative addition reactions of a zerovalent nickel catalyst to a set of haloarene substrates. Halogenated o-methylbenzene, dimethoxybenzene, and thiophene derivatives undergo intramolecular oxidative addition through irreversible π-complexation. Density functional theory computations at the B3LYP-D3/TZ2P-LANL2TZ(f)-LANL08d level predict η(2)-bound π-complexes are generally stable relative to a solvated catalyst plus free substrate and that ring-walking of the Ni(0) catalyst and intramolecular oxidative addition are facile in these intermediates.
Post-polymerization modification is a simple and effective method to add complex functionality to a polymeric interface. A wide variety of click reactions have been utilized as a means of postpolymerization functionalization on surface-bound polymers to tune interfacial properties, such as friction, wettability, and adhesion. Patterning surfaces with spatial control of chemical functionality has also been obtained through orthogonal or sequential click reactions. This review highlights the progress in post-polymerization modification of polymers covalently attached to a surface, focusing on the design of functional interfaces in terms of the various reactive functional groups.
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