Polymethacrylate Functionalized Polypyrrole Network Films on Indium Tin Oxide: Electropolymerization of a Precursor Polymer and Comonomer

The electropolymerization and deposition of conjugated polypyrrole network films on planar indium tin oxide electrode surfaces is described. The precursor polymer, a polymethacrylate functionalized with pyrrole, PPHMA2, was synthesized and then electropolymerized on ITO substrates. The possibility of inter- and intramolecular polymerization resulted in a cross-linked conjugated network microstructure. The pyrrole group was chosen because of its good electropolymerizablity and organic semiconductor characteristics. To induce greater electropolymerizability toward linear polypyrrole units and control of surface morphology, PPHMA2 was copolymerized with pyrrole monomer at various composition (feed) ratios. The spectroscopic, morphological, and composition properties of the films were characterized by FT-IR spectroscopy, atomic force microscopy, and X-ray photoelectron spectroscopy, respectively. Interesting trends were observed on structure−property relationships with respect to film composition

Polymethacrylate Functionalized Polypyrrole Network Films on Indium Tin Oxide: Electropolymerization of a Precursor Polymer and Comonomer

The electropolymerization and deposition of conjugated polypyrrole network films on planar indium tin oxide electrode surfaces is described. The precursor polymer, a polymethacrylate functionalized with pyrrole, PPHMA2, was synthesized and then electropolymerized on ITO substrates. The possibility of inter- and intramolecular polymerization resulted in a cross-linked conjugated network microstructure. The pyrrole group was chosen because of its good electropolymerizablity and organic semiconductor characteristics. To induce greater electropolymerizability toward linear polypyrrole units and control of surface morphology, PPHMA2 was copolymerized with pyrrole monomer at various composition (feed) ratios. The spectroscopic, morphological, and composition properties of the films were characterized by FT-IR spectroscopy, atomic force microscopy, and X-ray photoelectron spectroscopy, respectively. Interesting trends were observed on structure−property relationships with respect to film composition

Atomistic and Coarse-Grained Molecular Dynamics Simulation of a Cross-Linked Sulfonated Poly(1,3-cyclohexadiene)-Based Proton Exchange Membrane

Atomistic and coarse-grained (CG) molecular dynamics (MD) simulations were conducted for a cross-linked and sulfonated poly­(1,3-cyclohexadiene) (xsPCHD) hydrated membrane with λ­(H₂O/HSO₃) = 10 and 20. From the atomistic level simulation results, nonbonded pair correlation functions (PCFs) of water–water, water–H₃O⁺ ion, H₃O⁺–H₃O⁺, polymer–water, and polymer–H₃O⁺ ion pairs were obtained and studied. The water self-diffusivity and H₃O⁺ vehicular self-diffusivity were also obtained. Membrane structure was further studied at CG level using a multiscale modeling procedure. Nonbonded PCFs of polymer–polymer pairs were obtained from atomistic simulation of hydrated membrane with λ = 10 and 20. Two sets of CG nonbonded potentials were then parametrized to the PCFs using the iterative Boltzmann inversion (IBI) method. The CGMD simulations of xsPCHD chains using potentials from above method satisfactorily reproduced the polymer–polymer PCFs from atomistic MD simulation of hydrated membrane system at each hydration level. The transferability of above two set of CG potentials was further tested through CGMD simulation of hydrated membrane at an intermediate hydration level (λ = 15). Limited transferability was observed, presumably due to the use of an implicit solvent. Using an analytical theory, proton conductivity was calculated and compared with that from experimental measurement under similar conditions. Good agreement was obtained using inputs from both atomistic and CG simulation. This study provides a molecular level understanding of relationship between membrane structure and water and H₃O⁺ ion transport in the xsPCHD membrane

Nanostructured Ultrathin Films of Alternating Sexithiophenes and Electropolymerizable Polycarbazole Precursor Layers Investigated by Electrochemical Surface Plasmon Resonance (EC-SPR) Spectroscopy

Nanostructured ultrathin films of linear and dendrimeric cationic sexithiophenes, 6TNL and 6TND, respectively, alternated with anionic polycarbazole precursor, poly(2-(N-carbazolyl) ethyl methacrylate-co-methacrylic acid) or PCEMMA32, were successfully fabricated using the layer-by-layer self-assembly deposition technique. The two electro-optically active oligomers exhibited distinct optical properties and aggregation behavior in solution and films as studied by UV−vis and fluorescence spectroscopy. The stepwise increase of the 6TNL/PCEMMA32 and 6TND/PCEMMA32 layers was confirmed by UV−vis spectroscopy and in situ surface plasmon resonance (SPR) spectroscopy. The intralayer electrochemical polymerization and cross-linking behavior of the carbazole functionalized PCEMMA32 layers were then investigated using cyclic voltammetry (CV) and electrochemical surface plasmon resonance (EC-SPR) spectroscopy. The increase in current with each cycle confirmed intralayer cross-linking followed by the doping−dedoping process within these films. The two types of films differed with respect to dielectric constant and thickness changes before and after electropolymerization, indicating the influence of the oligothiophene layers. This demonstrated for the first time the preparation of highly ordered organic semiconductors alternated with in situ electropolymerizable layers in ultrathin films

Ruthenium(II)-Cored Polythiophene Dendrimers

We report the synthesis and characterization of ruthenium(II)-cored polythiophene dendrimers. Four new redox-active ruthenium(II) pyridine oligothiophene dendritic complexes that fluoresce in the near-infrared region have been synthesized, and their absorption spectra, fluorescence properties, and redox behavior have been investigated. The dendritic ligands phen3T and phen7T containing 1,10-phenanthroline as chelating sites and two oligothiophene dendrons (3T6COMe and 7T6COMe) have been synthesized and employed. The metal–polythiophene dendrimers investigated here are [Ru(bpy)2(phen3T)]2+, [Ru(bpy)2(phen7T)]2+, [Ru(phen3T)3]2+, and [Ru(phen7T)3]2+. Upon addition of acid, the charge transfer absorption bands of free dendritic ligands are significantly red-shifted and the fluorescence is greatly quenched. The Ru(II) polythiophene dendrimers exhibit very strong metal-to-ligand charge transfer (MLCT) absorption and enhanced absorption in the UV region and can be regarded as better light-harvesting species. The MLCT emission is extraordinarily red-shifted (∼165 nm) because of their planar excited states. The core of the dendrimers shows an electrochemical behavior typical of encapsulated metal electroactive units

Assembly and Characterization of Well-Defined High-Molecular-Weight Poly(<i>p</i>-phenylene) Polymer Brushes

The assembly and characterization of well-defined, end-tethered poly(p-phenylene) (PPP) brushes having high molecular weight, low polydispersity and high 1,4-stereoregularity are presented. The PPP brushes are formed using a precursor route that relies on either self-assembly or spin coating of high molecular weight (degrees of polymerizations 54, 146, and 238) end-functionalized poly(1,3-cyclohexadiene) (PCHD) chains from benzene solutions onto silicon or quartz substrates, followed by aromatization of the end-attached PCHD chains on the surface. The approach allows the thickness (grafting density) of the brushes to be easily varied. The dry brushes before and after aromatization are characterized by ellipsometry, atomic force microscopy, grazing angle attenuated total reflectance Fourier transform infrared spectroscopy, and UV-Vis spectroscopy. The properties of the PPP brushes are compared with those of films made using oligo-paraphenylenes and with ab initio density functional theory simulations of optical properties. Our results suggest conversion to fully aromatized, end-tethered PPP polymer brushes having effective conjugation lengths of 5 phenyl units