EQCM analysis of the insertion phenomena in a n-doped poly-alkyl-terthiophene with regioregular pattern of substitution

In the present work, we have undertaken the study of the n-doping process in poly-3,3′′- didodecyl-2,2′:5′,2′′-terthiophene (poly-33′′-DDTT) employing the electrochemical quartz crystal microbalance (EQCM). The present study aims at understanding how cathodic charge in n-doped poly-33′′-DDTT is compensated. For this purpose, the in situ analysis of the variations of the polymeric mass has been considered. Poly-33′′-DDTT was obtained as a thin coating onto a metallic substrate via the anodic coupling of the corresponding monomer 3,3′′-didodecyl-2,2′:5′,2′′-terthiophene (33′′-DDTT). When subjected to electrochemical n-doping in the polarization interval -2.5 ≤ Eappl ≤ 0 V vs. Ag/Ag+, the films of poly-33′′-DDTT varied their mass according to a mechanism of cations insertion during n-doping and cations extraction during polymer neutralization. In fact, the electrochemical doping of polythiophenes requires the accompanying exchange of charged species to maintain the electroneutrality within the structure of the polymer in all states of polarization. At the end of a full electrochemical cycle (consisting of the n-doping and the successive neutralization of poly-33′′-DDTT), the polymer retains a fraction of the mass acquired during n-doping, thus manifesting the phenomena of mass trapping. The combined analysis of electrochemical and microgravimetric data suggests that poly-33′′-DDTT in the n-doped state undergoes (or electrocatalyzes) uncontrolled electrochemical reactions that are not accompanied by mass variations

In Situ Measurement of the Conductance of Regioregular Poly-3 ',4 '-didodecyl-2,2 ':5 ',2 ''-terthiophene during Potentiodynamic Growth

This work reports a study of regioregular poly-3 ',4 '-didodecyl-2,2 ':5 ',2 ''-terthiophene (poly-3 ' 4 '-DDTT) deposited electrochemically onto a double-band electrode for the in situ measurement of the electrical conductance. The electrodeposition of poly-3 ' 4 '-DDTT was conducted in the potentiodynamic mode within the applied potential interval 0 <= E (appl) <= 0.9 V vs Ag/Ag+ employing an electrolyte that contained the terthiophenic monomer 3 ' 4 '-DDTT (the starting redox species). These electrochemical conditions warrant the oxidation of 3 ' 4 '-DDTT (initiation step) and prevent the oxidative degradation of the polymerization product(s). Through the adoption of conformal mapping we could calculate the electrical conductivity of the electrodeposited polymer thanks to the observation of a linear variation of conductance with the consumed charge of polymerization. The use of conformal mapping has allowed also the determination of the volume yield for the poly-3 ' 4 '-DDTT under consideration. The electrical conductivity of poly-3 ' 4 '-DDTT depended nonlinearly on the scan rate of electrodeposition and varied in the broad range 12 - 34 S cm(-1). The variability of poly-3 ' 4 '-DDTT conductivity depended on the nature of the electrodeposit which, in turn, depended on the rate of oxidative coupling (determined by the electrical current) and on the rate of precipitation (determined by the conditions of saturation in proximity of the double-band electrode)

Methacrylic polymers bearing side-chain permanent dipole azobenzene chromophores spaced from the main chain by chiral moieties, 3 a Synthesis and chiroptical properties of the homopolymer of (R)-3-methacryloyloxy-1-(4'-nitro-4-azobenzene)- pyrrolidine and of copolymers with the enantiomeric monomer (S)-3-methacryloyloxy-1-(4'-nitro-4-azobenzene)- pyrrolidine

Abstract The optically active photochromic homopolymer deriving from radical polymerization of the monomer (R)-3-methacryloyloxy-1-(4'-nitro-4-azobenzene)- pyrrolidine, containing a chiral group of one prevailing configuration interposed between the methacrylic moiety and the photochromic azoaromatic chromophore, has been synthesized and characterized. Copolymers with the enantiomeric monomer (S)-3-methacryloyloxy-1-(4'-nitro-4-azobenzene)pyrrolidine have also been prepared in order to evaluate the effect on the overall optical activity of side chain chiral groups of opposite configuration in various ratios. The spectroscopic and chiroptical properties in solution of the polymeric derivatives have been assessed

Side-Chain Multifunctional Photoresponsive Polymeric Materials

The contribute reviews the recent literature concerning the state-of-the-art of the research on amorphous polymeric derivatives bearing side-chain photoactive moieties such as the azo-aromatic and the carbazole chromophore as functional groups, in addition to the presence of structural or chemical features suitable to also provide the macromolecules of chiral properties

Part 21: Copolymers with methyl methacrylate

AbstractOptically active photochromic copolymers, deriving from methyl methacrylate (MMA) and the methacrylic ester of (S)-3-hydroxypyrrolidine linked through the nitrogen atom to the highly conjugated photochromic 4'-(β-cyano-β- (methylsulfonyl)vinyl)-4-azobenzene moiety, have been prepared and characterized with the aim to evaluate the effect on their chiro-optical and thermal properties exerted by the insertion of inactive MMA groups along the main chain. The results indicate that these properties are still remarkable at a content of photochromic units as low as 26 mol-%

Photoluminescence and electroluminescence of mono- and dialkyl-substituted soluble polythiophenes

AbstractWe report a comparison between optical properties (photoluminescence and UV-Vis absorption) and electroluminescence in a series of soluble polyalkylthiophenes with the aim of better understanding the role of different structural parameters, viz. length of side chains and introduction of unsubstituted thiophenes and their position in the backbone, on the electro-optical properties. The potential of these polymers as material for an active film in a single layer light emitting diode is evaluated

Synthesis by oxidative polymerization of optically active, regioregular polythiophene from quinquethiophene monomer bearing chiral and n-dodecyl groups as substituents

AbstractThe synthesis and characterization of an optically active quinquethiophene monomer 3,3""-didodecyl-4',3"'-di[(S)-(+)-2-methylbutyl]- 2,2':5',2":5",2"':5"',2""-quinquethiophene [(S)-(+)-DDDMBQT], bearing at the C-β positions of thiophene rings both linear C12 alkyl chain and chiral, enantiomerically pure, alkyl group is described. The polymerization of [(S)-(+)-DDDMBQT] by oxidative mechanism has been optimized in terms of yield of soluble polymer with high molecular weight.The obtained polymeric derivative displays enhanced conjugation extension with respect to similar poly(3-alkylthiophene)s reported in the literature and optical activity in the spectral region related to the chromophore absorptions when in the microaggregate state, indicative of the presence of supramolecular chiral conformations

Synthesis and Photovoltaic Properties of Regioregular Head-to-Head Substituted Thiophene Hexadecamers

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Poly(3-hexylthiophene) Nanoparticles Containing Thiophene-S,S-dioxide: Tuning of Dimensions, Optical and Redox Properties, and Charge Separation under Illumination

We describe the preparation of poly(3-hexylthiophene-S,S-dioxide) nanoparticles using Rozen's reagent, HOF·CH3CN, either on poly(3-hexylthiophene) (P3HT) or on preformed P3HT nanoparticles (P3HT-NPs). In the latter case, core-shell nanoparticles (P3HT@PTDO-NPs) are formed, as confirmed by X-ray photoelectron spectroscopy measurements, indicating the presence of oxygen on the outer shell. The different preparation modalities lead to a fine-tuning of the chemical-physical properties of the nanoparticles. We show that absorption and photoluminescence features, electrochemical properties, size, and stability of colloidal solutions can be finely modulated by controlling the amount of oxygen present. Atomic force microscopy measurements on the nanoparticles obtained by a nanoprecipitation method from preoxidized P3HT (PTDO-NPs) display spherical morphology and dimensions down to 5 nm. Finally, Kelvin probe measurements show that the coexistence of p- and n-type charge carriers in all types of oxygenated nanoparticles makes them capable of generating and separating charge under illumination. Furthermore, in core-shell nanoparticles, the nanosegregation of the two materials, in different regions of the nanoparticles, allows a more efficient charge separation