Impact of doping on the mechanical properties of conjugated polymers

Conjugated Polymer-Photosensitizers for Cancer Photodynamic Therapy and Their Multimodal Treatment Strategies

Conjugated polymers (CPs) have emerged as promising candidates for photodynamic therapy (PDT) in cancer treatment due to their high fluorescence quantum yield, excellent photostability, and remarkable reactive oxygen species (ROS) generation capability. This review systematically summarizes molecular design strategies to augment CP photosensitivity efficiency, including: (1) constructing donor-acceptor (D-A) alternating structures, (2) incorporating aggregation-induced emission (AIE) moieties, (3) employing heavy-atom effects, and (4) designing hyperbranched architectures. In addition, considering the limitations of monotherapy like tumor heterogeneity, we will further discuss the synergistic treatment strategies of CP-mediated PDT in combination with other therapeutic modalities, including photothermal therapy (PTT)-PDT, immunotherapy-PDT, chemotherapy-PDT, Chemiluminescence (CL)-PDT, diagnostic technology-PDT, and chemodynamic therapy (CDT)-PDT. These multimodal approaches leverage complementary mechanisms to achieve enhanced tumor eradication efficacy.

Recent Trends in the Development of Green Analytical Sample Preparation Methods Using Advanced Materials

Recent concern about the impact of environmental preservation and the health of living beings has opened new avenues for scientific research. In this context, contemporary analytical chemistry has been marked by the development of green analytical methodologies, which aim to reduce the use of toxic reagents and minimize the environmental impact of analytical processes. Progress in this area involves the optimization of sample preparation techniques and the use of new functional materials, which contribute to a more sustainable and efficient analysis. Among these methodologies, miniaturized sample preparation techniques stand out, as they use smaller volumes of solvents and offer high sensitivity and selectivity. The use of advanced materials, such as molecularly imprinted polymers, MOFs, and conductive polymers, has driven innovation in analytical procedures regarding complex matrices, including environmental, food, and biological samples. These materials offer high selectivity and stability, improving efficiency in the extraction and detection of specific analytes. This review explores the integration of sustainable and green methodologies. It critically highlights applications and evaluates them using the Analytical Greenness Metric for Sample Preparation, based on publications from the past 6 years.

Precisely Prepared Hierarchical Micelles of Polyfluorene-block-Polythiophene-block-Poly(phenyl isocyanide) via Crystallization-Driven Self-Assembly

The precise preparation of hierarchical micelles is a fundamental challenge in modern materials science and chemistry. Herein, poly(di-n-hexylfluorene)-block-poly(3-tetraethylene glycol thiophene) (poly(1m-b-2n)) diblock copolymers and polyfluorene-block-polythiophene-block-poly(phenyl isocyanide) triblock copolymers were synthesized using a one-pot process via the sequential addition of corresponding monomers using a Ni(II) complex as a single catalyst for living/controlled polymerization. The crystallization-driven self-assembly of amphiphilic conjugated poly(1m-b-2n) led to the formation of nanofibers with controlled lengths and narrow dispersity. The block copolymers exhibited white, yellow, and red emissions in different self-assembly states. By using uniform poly(1m-b-2n) nanofibers as seeds, introducing the polyfluorene-block-polythiophene-block-poly(phenyl isocyanide) triblock polymer as a unimer in the seed growth process, and adjusting the structure of the poly(phenyl isocyanide) block and the polarity of self-assembly solvent, A-B-A triblock micelles, multiarm branched micelles, and raft micelles were prepared.

Controlling Ion Uptake in Carboxylated Mixed Conductors

Organic mixed ionic-electronic conductors (OMIECs) have garnered significant attention due to their capacity to transport both ions and electrons, making them ideal for applications in energy storage, neuromorphics, and bioelectronics. However, charge compensation mechanisms during the polymer redox process remain poorly understood, and are often oversimplified as single-ion injection with little attention to counterion effects. To advance understanding and design strategies toward next-generation OMIEC systems, a series of p-channel carboxylated mixed conductors is investigated. Varying side-chain functionality, distinctive swelling character is uncovered during electrochemical doping/dedoping with model chao-/kosmotropic electrolytes. Carboxylic acid functionalized polymers demonstrate strong deswelling and mass reduction during doping, indicating cation expulsion, while ethoxycarbonyl counterparts exhibit prominent mass increase, pointing to an anion-driven doping mechanism. By employing operando grazing incidence X-ray fluorescence (GIXRF), it is revealed that the carboxyl functionalized polymer engages in robust cation interaction, whereas ester functionalization shifts the mechanism towards no cation involvement. It is demonstrated that cations are pivotal in mitigating swelling by counterbalancing anions, enabling efficient anion uptake without compromising performance. These findings underscore the transformative influence of functionality-driven factors and side-chain chemistry in governing ion dynamics and conduction, providing new frameworks for designing OMIECs with enhanced performance and reduced swelling.

Impact of Sequential Chemical Doping on the Thin Film Mechanical Properties of Conjugated Polymers

Conjugated polymer (CP) films with nanometer-scale thickness exhibit unique properties distinct from their bulk counterparts, which is an important consideration for their end application as thin film devices. In the realm of organic electronic devices, enabling high electrical conductance properties of CPs often necessitates doping. However, the impact of doping on intrinsic polymer mechanical properties, such as the elastic modulus, in ultrathin films at device-relevant thicknesses is not well understood and has not been directly measured. In this study, we quantified the effect of doping on the mechanical properties of poly(3-alkylthiophenes) (P3ATs) using pseudofree-standing tensile testing. We observed modulation of the mechanical properties of ultrathin CP films through sequential doping of P3ATs thin films (60-80 nm thick) with the molecular dopant F4TCNQ. Our findings reveal that, despite the ease of doping all P3ATs with F4TCNQ, the resulting changes in mechanical properties are highly dependent on the side-chain lengths of the P3ATs. Specifically, the elastic modulus of rubbery P3ATs with side-chain lengths of six carbons or more (e.g., P3HT and P3OT) increases significantly-by one to two times-upon F4TCNQ doping, while the modulus of the glassy poly(3-butylthiophene-2,5-diyl) (P3BT) remains nearly unchanged. Such a phenomenon is linked to the changes in the glass transition temperature (T g) of the doped film, where the rise of T g results in a large change in the modulus for P3HT samples. However, the P3BT remained in a glassy state before and after doping, exhibiting a minimal change in its mechanical properties. These insights into the mechanical behavior of doped ultrathin CP films are crucial for the design and optimization of flexible electronic devices.

Design Principles for Enhancing Both Carrier Mobility and Stretchability in Polymer Semiconductors via Lewis Acid Doping

With the rise of skin-like electronics, devices are increasingly coming into close contact with the human body, creating a demand for polymer semiconductors (PSCs) that combine stretchability with reliable electrical performance. However, balancing mechanical robustness with high carrier mobility remains a challenge. To address this, tris(pentafluorophenyl)borane (BCF) for Lewis acid doping is proposed to improve charge mobility while enhancing stretchability by increasing structural disorder. Through systematic investigation, several key structural principles have been identified to maximize the effectiveness of BCF doping in stretchable PSCs. Notably, increasing the lamellar stacking distance and reducing crystallinity facilitate the incorporation of BCF into the alkyl side-chain regions, thereby enhancing both mobility and stretchability. Conversely, stronger Lewis base groups in the main chain negatively impact these improvements. These results demonstrate that with a small addition of BCF, a two-fold increase in carrier mobility is achieved while simultaneously enhancing the crack onset strain to 100%. Furthermore, doped PSCs exhibit stable mobility retention under repeated 30% strains over 1000 cycles. This method of decoupling carrier mobility from mechanical properties opens up new avenues in the search for high-mobility stretchable PSCs.

Synergistically Improved Crystallinity and Molecular Doping Ability of Polythiophene-Diketopyrropyrrole Derivatives by m-Trifluoromethylbenzene Containing Side Chains for Improved Thermoelectric Materials

m-Trifluoromethylbenzene (FB) groups have been widely employed in various fields; however, no studies have reported the use of FB in side chains to enhance the carrier mobility and molecular doping of conjugated polymers. In this study, based on density functional theory (DFT) calculations, we discovered that FB groups can effectively bind to [FeCl4]-, the counterion of the p-type dopant FeCl3, thereby increasing doping ability. Consequently, FB groups were incorporated into the side chains of thiophene-diketopyrrolopyrrole-based donor-acceptor (D-A)-conjugated polymers, and a series of random conjugated polymers were synthesized (denoted as PDPPFB-x, where x represents the molar ratio of the FB side chain). The findings revealed that an appropriate number of FB groups can decrease the π-π stacking distances, enhance the films' crystallinity, and consequently improve the charge transfer ability. Furthermore, after doping with FeCl3, the UV-vis-NIR spectra indicated that the doping efficiency was augmented by increasing the molar fraction of the FB side chain. Among these polymers, PDPPFB-10 exhibited the highest conductivity and power factor, which were 2.0 and 1.5 times higher than those of PDPPFB-0, respectively. These results illustrated a straightforward molecular design strategy for enhancing the crystallinity and conductivity of conjugated polymers, thereby expanding the way to optimize their thermoelectric performance.