Influence of Composition of Amphiphilic Double-Crystalline P3HT-b-PEG Block Copolymers on Structure Formation in Aqueous Solution

Advances in the Use of Conducting Polymers for Healthcare Monitoring

Conducting polymers (CPs) are an innovative class of materials recognized for their high flexibility and biocompatibility, making them an ideal choice for health monitoring applications that require flexibility. They are active in their design. Advances in fabrication technology allow the incorporation of CPs at various levels, by combining diverse CPs monomers with metal particles, 2D materials, carbon nanomaterials, and copolymers through the process of polymerization and mixing. This method produces materials with unique physicochemical properties and is highly customizable. In particular, the development of CPs with expanded surface area and high conductivity has significantly improved the performance of the sensors, providing high sensitivity and flexibility and expanding the range of available options. However, due to the morphological diversity of new materials and thus the variety of characteristics that can be synthesized by combining CPs and other types of functionalities, choosing the right combination for a sensor application is difficult but becomes important. This review focuses on classifying the role of CP and highlights recent advances in sensor design, especially in the field of healthcare monitoring. It also synthesizes the sensing mechanisms and evaluates the performance of CPs on electrochemical surfaces and in the sensor design. Furthermore, the applications that can be revolutionized by CPs will be discussed in detail.

What is the significance of the chloroform stabilizer C5H10 and its association with MeOH in concentration-dependent polymeric solutions?

The understanding of excitonic transitions associated with polymeric aggregates is fundamental, as such transitions have implications on coherence lengths, coherence numbers and inter- and intra-chain binding parameters. In this context, the investigation of efficient solvents and other ways to control polymer aggregate formation is key for their consolidation as materials for new technologies. In this manuscript, we use Poly(3-hexothiophene) (P3HT) as a probe to investigate the significance of amylene (C5H10) and its association with methanol (MeOH) in both pure and C5H10-stabilized chloroform (CHCl3)-based polymeric solutions. Using the intensity ratio between the first and second vibronic transitions of the P3HT H-aggregates formed, values for their exciton bandwidths and interchain interactions are obtained and correlated with the presence of C5H10 and MeOH as agents determining the CHCl3 quality.

Charge-Transfer-Induced Self-Assembly of Doped Conjugated Block Copolymer Nanofibers

Here, we report charge-transfer-driven self-assembly of conjugated block copolymers (BCP) into highly doped conjugated polymer nanofibers. The ground-state integer charge transfer (ICT) between a BCP composed of poly(3-hexylthiophene) and poly(ethylene oxide) (P3HT-b-PEO) and electron-deficient 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ) induced spontaneous self-assembly of the donor and the acceptor into well-defined one-dimensional nanofibers. The presence of the PEO block plays an important role for the self-assembly by providing a polar environment that can stabilize nanoscale charge transfer (CT) assemblies. The doped nanofibers were responsive to various external stimuli such as heat, chemical, and light and exhibited efficient photothermal properties in the near-IR region. The CT-driven BCP self-assembly reported here provides a new platform for the fabrication of highly doped semiconductor nanostructures.

One-Dimensional Helical Nanostructures from the Hierarchical Self-Assembly of an Achiral "Rod-Coil" Alternating Copolymer

The self-assembly of alternating copolymers (ACPs) has attracted considerable interest due to their unique alternating nature. However, compared with block copolymers, their self-assembly behavior has remained much less explored and their reported self-assembled structures are limited. Here, we report the formation of supramolecular helical structures by the self-assembly of an achiral rod-coil alternating copolymer, poly(quarter(3-hexylthiophene)-alt-poly(ethylene glycol)) (P(Q3HT-alt-PEG)). The copolymer exhibited an interesting hierarchical self-assembly process, driven by the π-π stacking of the Q3HT segments and the solvophobic interaction of the alkyl chains in tetrahydrofuran (THF)-isopropanol (iPrOH) mixed solvents. The copolymer first self-assembled into thin nanobelts with a uniform size, then grew to helical nanoribbons and eventually twisted into helical nanowires with an average diameter of 25 ± 9 nm and a mean pitch of 80 ± 10 nm. Dissipative particle dynamics (DPD) simulation supported the formation course of the helical nanowires. Furthermore, the addition of (S)-ethyl lactate and (R)-ethyl lactate in the self-assembly of P(Q3HT-alt-PEG) resulted in the formation of left-handed and right-handed chiral nanowires, respectively, demonstrating the tunability of the chirality of the helical wires. This study expands the library of ordered self-assembled structures of ACPs, and also brings a new strategy and mechanism to construct helical supramolecular structures. This article is protected by copyright. All rights reserved.

Facile synthesis of water-dispersible poly(3-hexylthiophene) nanoparticles with high yield and excellent colloidal stability

There has been growing interest in water-processable conjugated polymers for biocompatible devices. However, some broadly used conjugated polymers like poly(3-hexylthiophene) (P3HT) are hydrophobic and they cannot be processed in water. We herein report a facile yet highly efficient assembly method to prepare water-dispersible pyridine-containing P3HT (Py-P3HT) nanoparticles (NPs) with a high yield (>80%) and a fine size below 100 nm. It is based on the fast nanoprecipitation of Py-P3HT stabilized by hydrophilic poly(acrylic acid) (PAA). Py-P3HT can form spherical NPs at a concentration up to 0.2 mg/mL with a diameter of ∼75 nm at a very low concentration of PAA, e.g., 0.01-0.1 mg/mL, as surface ligands. Those negatively charged Py-P3HT NPs can bind with metal cations and further support the growth of noble metal NPs like Ag and Au. Our self-assembly methodology potentially opens new doors to process and directly use hydrophobic conjugated polymers in a much broader context.

Disorder in P3HT Nanoparticles Probed by Optical Spectroscopy on P3HT-b-PEG Micelles

We employ photoluminescence (PL) spectroscopy on individual nanoscale aggregates of the conjugated polymer poly(3-hexylthiophene), P3HT, at room temperature (RT) and at low temperature (LT) (1.5 K), to unravel different levels of structural and electronic disorder within P3HT nanoparticles. The aggregates are prepared by self-assembly of the block copolymer P3HT-block-poly(ethylene glycol) (P3HT-b-PEG) into micelles, with the P3HT aggregates constituting the micelles' core. Irrespective of temperature, we find from the intensity ratio between the 0-1 and 0-0 peaks in the PL spectra that the P3HT aggregates are of H-type nature, as expected from π-stacked conjugated thiophene backbones. Moreover, the distributions of the PL peak ratios demonstrate a large variation of disorder between micelles (inter-aggregate disorder) and within individual aggregates (intra-aggregate disorder). Upon cooling from RT to LT, the PL spectra red-shift by 550 cm^-1, and the energy of the (effective) carbon-bond stretch mode is reduced by 100 cm^-1. These spectral changes indicate that the P3HT backbone in the P3HT-b-PEG copolymer does not fully planarize before aggregation at RT and that upon cooling, partial planarization occurs. This intra-chain torsional disorder is ultimately responsible for the intra- and inter-aggregate disorder. These findings are supported by temperature-dependent absorption spectra on thin P3HT films. The interplay between intra-chain, intra-aggregate, and inter-aggregate disorder is key for the bulk photophysical properties of nanoparticles based on conjugated polymers, for example, in hierarchical (super-) structures. Ultimately, these properties determine the usefulness of such structures in hybrid organic-inorganic materials, for example, in (bio-)sensing and optoelectronics applications.

Crystallization Control of N,N'-Dioctyl Perylene Diimide by Amphiphilic Block Copolymers Containing poly(3-Hexylthiophene) and Polyethylene Glycol

The preparation of micron- to nanometer-sized functional materials with well-defined shapes and packing is a key process to their applications. There are many ways to control the crystal growth of organic semiconductors. Adding polymer additives has been proven a robust strategy to optimize semiconductor crystal structure and the corresponding optoelectronic properties. We have found that poly(3-hexylthiophene) (P3HT) can effectively regulate the crystallization behavior of N,N'-dioctyl perylene diimide (C8PDI). In this study, we combined P3HT and polyethylene glycol (PEG) to amphiphilic block copolymers and studied the crystallization modification effect of these block copolymers. It is found that the crystallization modification effect of the block copolymers is retained and gradually enhanced with P3HT content. The length of C8PDI crystals were well controlled from 2 to 0.4 μm, and the width from 210 to 35 nm. On the other hand, due to the water solubility of PEG block, crystalline PEG-b-P3HT/C8PDI micelles in water were successfully prepared, and this water phase colloid could be stable for more than 2 weeks, which provides a new way to prepare pollution-free aqueous organic semiconductor inks for printing electronic devices.

Dispersible Conjugated Polymer Nanoparticles as Biointerface Materials for Label-Free Bacteria Detection

Fast and efficient identification of bacterial pathogens in water and biological fluids is an important issue in medical, food safety, and public health concerns that requires low-cost and efficient sensing strategies. Impedimetric sensors are promising tools for monitoring bacteria detection because of their reliability and ease-of-use. We herein report a study on new biointerface-based amphiphilic poly(3-hexylthiophene)-b-poly(3-triethylene-glycol-thiophene), P3HT-b-P3TEGT, for label-free impedimetric detection of Escherichia coli (E. coli). This biointerface is fabricated by the self-assembly of P3HT-b-P3TEGT into core-shell nanoparticles, which was further decorated with mannose, leading to an easy-to-use solution-processable nanoparticle material for biosensing. The hydrophilic block P3TEGT promotes antifouling and prevents nonspecific interactions, while improving the ionic and electronic transport properties, thus enhancing the electrochemical-sensing capability in aqueous solution. Self-assembly and micelle formation of P3HT-b-P3TEGT were analyzed by 2D-NMR, Fourier transform infrared, dynamic light scattering, contact angle, and microscopy characterizations. Detection of E. coli was characterized and evaluated using electrochemical impedance spectroscopy and optical and scanning electron microscopy techniques. The sensing layer based on the mannose-functionalized P3HT-b-P3TEGT nanoparticles demonstrates targeting ability toward E. coli pili protein with a detection range from 10³ to 10⁷ cfu/mL, and its selectivity was studied with Gram(+) bacteria. Application to real samples was performed by detection of bacteria in tap and the Nile water. The approach developed here shows that water/alcohol-processable-functionalized conjugated polymer nanoparticles are suitable for use as electrode materials, which have potential application in fabrication of a low-cost, label-free impedimetric biosensor for the detection of bacteria in water.

Fluorescent electronic tongue based on soluble conjugated polymeric nanoparticles for the discrimination of heavy metal ions in aqueous solution

A fluorescence sensing array (or fluorescent electronic tongue) based on six sorts of soluble conjugated polymeric nanoparticles (SCPNs) decorated with PEG chains is designed for the rapid identification of heavy metal ions in water.

Effect of Composition and Molecular Structure of Poly(l-lactic acid)/Poly(ethylene oxide) Block Copolymers on Micellar Morphology in Aqueous Solution

The effect of the hydrophobic block length in diblock (PLLA _x- b-PEO₁₁₃, x = 64, 166, 418) and triblock (PLLA _y- b-PEO₉₁- b-PLLA _y, y = 30, 52, 120) copolymers of l-lactic acid and ethylene oxide on the structure of micelles prepared by dialysis was studied by wide- and small-angle X-ray scattering in dilute aqueous solution, dynamic light scattering, transmission electron microscopy, atomic force microscopy, and force spectroscopy. It was found that the size of the crystalline PLLA core is weakly dependent on the PLLA block length. In addition to individual micelles, a number of their micellar clusters were detected with characteristic distance between adjacent micelle cores decreasing with an increase in PLLA block length. This effect was explained by the change in the conformation of PEO chains forming the micellar corona because of their overcrowding. Force spectroscopy experiments also reveal a more stretched conformation of the PEO chains for the block copolymers with a shorter PLLA block. A model describing the structure of the individual micelles and their clusters was proposed.

Exclusive Synthesis of Poly(3-hexylthiophene) with an Ethynyl Group at Only One End for Effective Block Copolymerization

Well-controlled synthesis of ethynyl-functionalized poly(3-hexylthiophene) (P3HT) is crucial for preparation of block copolymers containing the P3HT segment by means of click coupling reaction. A well-known chain end modification method, in which Kumada-Tamao catalyst-transfer polymerization is quenched with ethynylmagnesium chloride, under various conditions is re-examined, but in all cases not only P3HT with an ethynyl group at one end but also P3HT di-ethynylated at both ends is obtained. Accordingly, Sonogashira coupling reaction of P3HT having H/Br ends with trimethylsilylacetylene is tried, followed by removal of the trimethylsilyl group, and it is found that this protocol affords exclusively P3HT with an ethynyl group at one end. This post end-modification method is applied to the synthesis of an amphiphilic diblock copolymer of P3HT and poly(2-ethyl-2-oxazoline) (PEtOx) by means of click reaction between ethynylated P3HT and PEtOx with an azide group at one end, and the product is confirmed to be free from contamination with triblock copolymer. Micellization of this block copolymer is confirmed in tetrahydrofuran (THF)/water and THF/methanol mixtures.

Cu Elimination from Cu-Coordinating Macromolecules

We demonstrate a simple, fast, and efficient process for the elimination of Cu impurities from water-soluble Cu-coordinating macromolecules that are difficult to purify via standard polymer purification techniques. The process is based on the complexation and precipitation of Cu by sodium diethyldithiocarbamate and was investigated for two different compound classes known to coordinate to Cu in aqueous solution. More than 99.9% of the Cu impurity was eliminated, with a remaining level below the detection limit (0.0005 wt %). Further analysis by ¹H NMR, MALDI, ATR-IR, and SEC showed no degradation or side reactions of the polymers induced by the treatment. This process thus compliments the growing toolbox of Cu-catalyzed conjugation techniques as a mild, effective, and scalable tool for the removal of Cu from water-soluble and Cu-coordinating polymers.

Pentafluorobenzene end-group as a versatile handle for para fluoro "click" functionalization of polythiophenes

A convenient method of introducing pentafluorobenzene (PFB) as a single end-group in polythiophene derivatives is reported via in situ quenching of the polymerization. We demonstrate that the PFB-group is a particularly useful end-group due to its ability to undergo fast nucleophilic aromatic substitutions. Using this molecular handle, we are able to quantitatively tether a variety of common nucleophiles to the polythiophene backbone. The mild conditions required for the reaction allows sensitive functional moieties, such as biotin or a cross-linkable trimethoxysilane, to be introduced as end-groups. The high yield enabled the formation of a diblock rod-coil polymer from equimolar reactants under transition metal-free conditions at room temperature. We further demonstrate that water soluble polythiophenes end-capped with PFB can be prepared via the hydrolysis of an ester precursor, and that such polymers are amenable to functionalization under aqueous conditions.

Synthetic approaches towards structurally-defined electrochemically and (photo)redox-active polymer architectures

This review details synthetic strategies leading to structurally-defined electrochemically and (photo)redox-active polymer architectures,e.g.block, graft and end functionalized (co)polymers.