Langmuir–Blodgett Films of Amphiphilic Thieno[3,4-c]pyrrole-4,6-dione-Based Alternating Copolymers

Fluorescence Study of the Interaction between Hydrophobically Modified Polymers and Charged Particles in Aqueous Media

The interaction of hydrophobically randomly modified and end-modified poly(2-(acrylamido)-2-methylpropanesulfonate)s (PAMPSs) with nonionic and positively and negatively charged surfactants was studied with the fluorescence spectroscopic technique of labeled pyrene. The results indicated that the randomly modified PAMPS bound to the nonionic and positively charged surfactants and that the disruption of intrapolymer micelles formed by the polymer occurred. In contrast, end-modified PAMPS was bound to the surfactants without the disruption of multipolymer aggregates formed by the polymer in a comparably low concentration range of surfactants. The conformation of the polymer-surfactant complex was confirmed to depend on the position of the hydrophobic group in the polymer chains. In the case of negatively charged surfactant, the complex formation between the polymers and the surfactants was significantly restricted due to the electrostatic repulsion of anionic sites of the polymer chains and the negatively charged surfactants.

Langmuir and Langmuir-Blodgett Films of Poly[(9,9-dioctylfluorene)-co-(3-hexylthiophene)] for Immobilization of Phytase: Possible Application as a Phytic Acid Sensor

In this work, the copolymer poly[(9,9-dioctylfluorene)-co-(3-hexylthiophene)] was employed as a matrix for immobilizing phytase, aiming at the detection of phytic acid. The copolymer was spread on the air-water interface forming Langmuir monolayers and phytase adsorbed from the aqueous subphase. The interactions between the copolymer and the enzyme components were investigated with surface pressure and surface potential-area isotherms, Brewster angle microscopy, and polarization modulation infrared reflection-absorption spectroscopy (PM-IRRAS). The enzyme could be incorporated in the monolayers from the aqueous subphase, expanding the copolymer films and maintaining its secondary structure. The polymeric films presented a morphological heterogeneous pattern at the air-water interface because of the ability of their chains to fold and entangle, causing inherent defects in the organization as well as unbalanced lateral distribution at the air-water interface because of the formation of aggregates. The interfacial films were transferred to solid supports as Langmuir-Blodgett films and characterized by PM-IRRAS and scanning electronic microscopy, which showed not only the co-transfer of the enzyme but also the maintenance of their heterogeneous morphological pattern. The enzymatic activity of the blended film was analyzed by UV-vis spectroscopy and allowed the estimation of the value of the Michaelis constant (13.08 mM), demonstrating the feasibility of the system to selectively detect phytic acid for biosensing purposes.

Preparation and High Photocurrent Generation Enhancement of Self-Assembled Layered Double Hydroxide-Based Composite Dye Films

Understanding photocurrent conversion of layered double hydroxide (LDH) materials will be a key step in the future application of these materials to light-capturing molecular devices. In the present study, ultrathin nickel-iron layered double hydroxide/dye (NF-LDH/dye) Langmuir-Blodgett (LB) semiconductor films were prepared using an LB device and deposited on an indium tin oxide (ITO) substrate as a photoanode. The photoelectric conversion efficiency of the prepared LB semiconductor film materials was tested. A comparative experiment was performed to effectively explore the photoelectric conversion performances of the LB semiconductor film materials. Specifically, the NF-LDH cast film electrode, the dye cast film electrode, and an ultrathin composite LB film electrode were used as typical samples to explore photoelectric conversion performances. The electrochemical workstation was used to study the photocurrent density, linear scanning voltammetry curve, and electrochemical impedance spectroscopy of LB film electrodes with different layers. The results show that the film electrode cast by LDH alone or dye alone produces weak photocurrent. The photoelectric conversion efficiency of the LB film electrode is enhanced due to the different dyes' molecular structures and/or aggregations on the surface of LDH with various morphological patterns. The combined NF-LDH/dye composite LB film photoelectrode can generate a photocurrent that is 2-5 times stronger than the raw material, and the stable use efficiency is more than 92%. Present obtained composite LB films demonstrated a uniform morphology and good photoelectric conversion ability. This work provides a useful reference for the field of LDH semiconductor optoelectronic devices and solar cells.

Modulating Surface Morphology and Thin-Film Transistor Performance of Bi-thieno[3,4-c]pyrrole-4,6-dione-Based Polymer Semiconductor by Altering Preaggregation in Solution

Due to their strong intermolecular interactions, polymer semiconductors aggregate in solution even at elevated temperature. With the aim to study the effect of this kind preaggregation on the order of thin films and further transistor performance, bi-thieno[3,4-c]pyrrole-4,6-dione and fluorinated oligothiophene copolymerized polymer semiconductor P1, which shows strong temperature-dependent aggregation behavior in solution, is synthesized. Its films are deposited through a temperature-controlled dip-coating technique. X-ray diffraction and atomic force microscopy results reveal that the aggregation behavior of P1 in solution affects the microstructures and order of P1 films. The charge transport properties of P1 films are investigated with bottom-gate top-contacted thin-film transistors. The variation of device performance (from 0.014  to 1.03 cm² V^-1 s^-1) demonstrates the importance of optimizing preaggregation degree. The correlation between preaggregation degree and transistor performance of P1 films is explored.

Langmuir-Blodgett Thin Films of Diketopyrrolopyrrole-Based Amphiphiles

We report on two π-conjugated donor-acceptor-donor (D-A-D) molecules of amphiphilic nature, aiming to promote intermolecular ordering and carrier mobility in organic electronic devices. Diketopyrrolopyrrole was selected as the acceptor moiety that was disubstituted with nonpolar and polar functional groups, thereby providing the amphiphilic structures. This structural design resulted in materials with a strong intermolecular order in the solid state, which was confirmed by differential scanning calorimetry and polarized optical microscopy. Langmuir-Blodgett (LB) films of ordered mono- and multilayers were transferred onto glass and silicon substrates, with layer quality, coverage, and intermolecular order controlled by layer compression pressure on the LB trough. Organic field-effect transistors and organic photovoltaics devices with active layers consisting of the amphiphilic conjugated D-A-D-type molecules were constructed to demonstrate that the LB technique is an effective layer-by-layer deposition approach to fabricate self-assembled, ordered thin films.

Air-Liquid Interfacial Self-Assembly of Non-Amphiphilic Poly(3-hexylthiophene) Homopolymers

Here, we demonstrate that the self-assembly of poly(3-hexylthiophene) (P3HT) at the air-water interface can lead to free-standing films of densely packed P3HT nanowires. Interfacial self-assembly on various liquid subphases, such as water, diethylene glycol, and glycerol, indicates that the viscosity of the subphase is an important factor for the formation of well-ordered nanostructures. The thin-film morphology is also sensitive to the concentration of P3HT, its molecular weight (MW), and the presence of oxidative defects. The densely packed nanowire films can be easily transferred to solid substrates for device applications. The ultrathin films of P3HT prepared by the interfacial assembly showed significantly higher hole mobility (∼3.6 × 10^-2 cm²/V s) in a field-effect transistor than comparably thin spin-cast films. This work demonstrates that the air-liquid interfacial assembly is not limited to amphiphilic polymers and can, under optimized conditions, be applied to fabricate ultrathin films of widely used conjugated polymers with controlled morphologies.

Dramatically different charge transport properties of bisthienyl diketopyrrolopyrrole-bithiazole copolymers synthesized via two direct (hetero)arylation polymerization routes

Two diketopyrrolopyrrole-bithiazole copolymers with same building blocks synthesized via direct (hetero)arylation polymerization through different routes show dramatically different charge transport properties.

An electrochemically polymerized and assembled cyclopalladated bi-thiophene imine for catalyzing coupling reactions: a modern strategy to enhance catalytic activity

The catalytic activity and recyclability of thiophene imine as a catalyst for coupling reactions is enhanced using the LB-ECP-SA method.

Synthesis of donor–acceptor conjugated polymers based on benzo[1,2-b:4,5-b′]dithiophene and 2,1,3-benzothiadiazole via direct arylation polycondensation: towards efficient C–H activation in nonpolar solvents

1,2-Dimethylbenzene, as a nonpolar high boiling point solvent, has been discovered to be a superior medium to perform direct-arylation polymerization.