Low Bandgap Semiconducting Copolymer Nanoparticles by Suzuki Cross‐Coupling Polymerization in Alcoholic Dispersed Media

The synthesis and formulation of organic semiconductors for the emerging technology of organic electronics requires the use of preparative methods and solvents being environment friendly. Today most of the active layer materials for the organic photovoltaic devices and modules are using chlorinated solvents, which are toxic and hazardous. In this work, the synthesis of poly[N‐9′‐heptadecanyl‐2,7‐carbazole‐alt‐5,5‐(4,7‐di‐2‐thienyl‐2′,1′,3′‐benzothiadiazole] (PCDTBT) in propan‐1‐ol is presented as the dispersant continuous phase in the presence of poly(vinylpyrrolidone) used as stabilizer. Suzuki–Miyaura polycondensation of 9‐(9‐heptadecanyl)‐9H‐carbazole‐2,7‐diboronic acid bis(pinacol) ester and 4,7‐bis(2‐bromo‐5‐thienyl)‐2,1,3‐benzothiadiazole in alcohol dispersion yields colloidally stable nanoparticles of PCDTBT with particles size of 330–1300 nm, depending on the stabilizer concentration. Other reaction parameters are also discussed such as the amount of base or Pd catalyst.

     

Single‐Step Microwave‐Mediated Synthesis of Oxazoles and Thiazoles from 3‐Oxetanone: A Synthetic and Computational Study

The direct microwave‐mediated condensation between 3‐oxetanone and primary amides and thioamides has delivered moderate to good yields of (hydroxymethyl)oxazoles and (hydroxymethyl)thiazoles. The reactions use a sustainable solvent and only require short reaction times. These are highly competitive methods for the construction of two classes of valuable heteroarenes, which bear a useful locus for further elaboration. Electronic structure calculations have shown that the order of events involves chalcogen atom attack at sp³ carbon and alkyl–oxygen cleavage. The critical role of acid catalysis was shown clearly, and the importance of acid strength was demonstrated. The calculated barriers were also fully consistent with the observed order of thioamide and amide reactivity. Spontaneous ring opening involves a modest degree of C? O cleavage, moderating the extent of strain relief. On the acid‐catalysed pathway, C? O cleavage is less extensive still, but proton transfer to the nucleofuge is well advanced with the carboxylic acid catalysts, and essentially complete with methanesulfonic acid.     

Balanced Ambipolar Poly(diketopyrrolopyrrole‐alt‐tetrafluorobenzene) Semiconducting Polymers Synthesized via Direct Arylation Polymerization

The synthesis of an ambipolar π‐conjugated copolymer consisting of alternating diketopyrrolopyrrole and tetrafluorobenzene via direct arylation polymerization (DAP) is reported. Two different combinations of monomers are investigated under various catalytic conditions for DAP. The target polymer obtained under an optimized catalytic condition shows minimal structural defects, a number‐average molecular weight of 33.2 kDa, and balanced electron and hole mobility of 1 × 10⁻² cm² V⁻¹ S⁻¹ in the organic field‐effect transistors fabricated and tested under ambient conditions.

     

Highly Crystalline and Semiconducting Imine‐Based Two‐Dimensional Polymers Enabled by Interfacial Synthesis

Single‐layer and multi‐layer 2D polyimine films have been achieved through interfacial synthesis methods. However, it remains a great challenge to achieve the maximum degree of crystallinity in the 2D polyimines, which largely limits the long‐range transport properties. Here we employ a surfactant‐monolayer‐assisted interfacial synthesis (SMAIS) method for the successful preparation of porphyrin and triazine containing polyimine‐based 2D polymer (PI‐2DP) films with square and hexagonal lattices, respectively. The synthetic PI‐2DP films are featured with polycrystalline multilayers with tunable thickness from 6 to 200 nm and large crystalline domains (100–150 nm in size). Intrigued by high crystallinity and the presence of electroactive porphyrin moieties, the optoelectronic properties of PI‐2DP are investigated by time‐resolved terahertz spectroscopy. Typically, the porphyrin‐based PI‐2DP 1 film exhibits a p‐type semiconductor behavior with a band gap of 1.38 eV and hole mobility as high as 0.01 cm² V^?1 s^?1, superior to the previously reported polyimine based materials.     

Tuneable Transient Thermogels Mediated by a pH‐ and Redox‐Regulated Supramolecular Polymerization

A multistimuli‐responsive transient supramolecular polymerization of β‐sheet‐encoded dendritic peptide monomers in water is presented. The amphiphiles, which contain glutamic acid and methionine, undergo a glucose oxidase catalyzed, glucose‐fueled transient hydrogelation in response to an interplay of pH and oxidation stimuli, promoted by the production of reactive oxygen species (ROS). Adjusting the enzyme and glucose concentration allows tuning of the assembly and the disassembly rates of the supramolecular polymers, which dictate the stiffness and transient stability of the hydrogels. The incorporation of triethylene glycol chains introduces thermoresponsive properties to the materials. We further show that repair enzymes are able to reverse the oxidative damage in the methionine‐based thioether side chains. Since ROS play an important role in signal transduction cascades, our strategy offers great potential for applications of these dynamic biomaterials in redox microenvironments.     

Metal Free Acid‐Mediated Solid‐State Polymerization and Processability of Polymers Based on 3,4‐Alkylenedioxythiophenes

The present article reports metal free acid‐mediated polymerization of 3,4‐alkylenedioxythiophenes in a solvent free medium and processability of insoluble polymers. It also describes structural variants and functional aqueous dispersions based on 3,4‐alkylenedioxythiophenes. Polymers were processed by dispersing the insoluble polymer powders in aqueous media using polymeric aromatic surfactant (polystyrenesulfonate, PSS) and aliphatic surfactant (sodiumdodecylsulfonate, SDS), respectively. The effect of surfactant on particle size, stability, and conductivity of the dispersions was investigated in detail. Polymer particles in SDS‐based dispersions tend to agglomerate which resulted enhanced conductivity of the thin films. Electrochemical studies revealed that the polymers are electroactive in nature and are transparent in oxidized state. The electrochromic contrast between the oxidized and reduced states of the polymers was in the range of 40–46%. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 783–791     

Polyacetylene‐Type Networks Prepared by Coordination Polymerization of Diethynylarenes: New Type of Microporous Organic Polymers

Microporous organic polymers (MOP) of a new type have been synthesised in high yields by a simple coordination polymerization of 1,3‐diethynylbenzene, 1,4‐diethynylbenzene and 4,4′‐diethynylbiphenyl catalysed by [Rh(cod)acac] and [Rh(nbd)acac] complexes. The new MOPs are non‐swellable polyacetylene‐type conjugated networks consisting of ethynylaryl‐substituted polyene main chains that are crosslinked by arylene linkers. Prepared MOP samples have a mole fraction of branching units (by ¹³C CP/MAS NMR) from 0.30 to 0.47 and exhibit the BET (Brunaer‐Emmett‐Teller) surface up to 809 m² g⁻¹ and hydrogen uptake up to 0.69 wt% (77 K, H₂ pressure 750 torr).     

Synthesis and Structure–Property Relationships of Phosphole‐Based π Systems and Their Applications in Organic Solar Cells

Phosphole is a chemically tunable heterole, and its π‐conjugated derivatives are potential candidates for optoelectronic materials. This account describes recent developments in the synthesis and structure–property relationships of π‐conjugated phosphole derivatives made by my research group. Thiophene–phosphole–styrene, phosphole–acetylene–arene, oligophosphole, polyphosphole, areno[c]phosphole, and phosphole–heterole π systems are synthesized using titanacycle‐mediated metathesis and palladium‐catalyzed cross‐coupling reactions. The structural, optical, and electrochemical properties of selected compounds are discussed. Initial results on some applications of thiophene–phosphole copolymers, acenaphtho[c]phospholes, and amine–terthiophene–phosphole donor–π–acceptor dyes in organic solar cells are described. These results give valuable information and guidelines for designing new phosphorus‐containing organic materials for molecular electronics.     

High‐Nitrogen‐Based Pyrotechnics: Perchlorate‐Free Red‐ and Green‐Light Illuminants Based on 5‐Aminotetrazole

Prototype testing of perchlorate‐free hand‐held signal illuminants for the US Army’s M126 A1 red‐star and M195 green‐star parachute illuminants are described. Although previous perchlorate‐free variants for these items have been developed based on high‐nitrogen compounds that are not readily available, the new formulations consist of anhydrous 5‐aminotetrazole as the suitable perchlorate replacement. Compared to the perchlorate‐containing control, the disclosed illuminants exhibited excellent stabilities toward various ignition stimuli and had excellent pyrotechnic performance. The illuminants are important from both military and civil fireworks perspectives, as the perchlorate‐free nature of the illuminants adequately address environmental concerns associated with perchlorate‐containing red‐ and green‐light‐emitting illuminants.     

Mussel‐Inspired Dendritic Polymers as Universal Multifunctional Coatings

A rapid and universal approach for multifunctional material coatings was developed based on a mussel‐inspired dendritic polymer. This new kind of polymer mimics not only the functional groups of mussel foot proteins (mfps) but also their molecular weight and molecular structure. The large number of catechol and amine groups set the basis for heteromultivalent anchoring and crosslinking. The molecular weight reaches 10 kDa, which is similar to the most adhesive mussel foot protein mfp‐5. Also, the dendritic structure exposes its functional groups on the surface like the folded proteins. As a result, a very stable coating can be prepared on virtually any type of material surface within 10 min by a simple dip‐coating method, which is as fast as the formation of mussel byssal threads in nature.     

Bioinspired Actuators Based on Stimuli‐Responsive Polymers

Organisms exhibit strong environmental adaptability by controllably adjusting their morphologies or fast locomotion; thus providing constant inspiration for scientists to develop artificial actuators that not only have diverse and sophisticated shape‐morphing capabilities, but can also further transfer dynamic and reversible shape deformations into macroscopic motion under the following principles: asymmetric friction, the Marangoni effect, and counteracting forces of the surrounding conditions. Among numerous available materials for fabricating bioinspired artificial actuators, stimuli‐responsive polymers are superior in their flexible features and the ability to change their physicochemical properties dynamically under external stimuli, such as temperature, pH, light, and ionic strength. Herein, different mechanisms, working principles, and applications of stimuli‐responsive polymeric actuators are comprehensively introduced. Furthermore, perspectives on existing challenges and future directions of this field are provided.     

Silk‐Inspired β‐Peptide Materials Resist Fouling and the Foreign‐Body Response

The functions of implants like medical devices are often compromised by the host's foreign‐body response (FBR). Herein, we report the development of low‐FBR materials inspired by serine‐rich sericin from silk. Poly‐β‐homoserine (β‐HS) materials consist of the hydrophilic unnatural amino acid β‐homoserine. Self‐assembled monolayers (SAMs) of β‐HS resist adsorption by diverse proteins, as well as adhesion by cells, platelets, and diverse microbes. Experiments lasting up to 3 months revealed that, while implantation with control PEG hydrogels induced obvious inflammatory responses, collagen encapsulation, and macrophage accumulation, these responses were minimal with β‐HS hydrogels. Strikingly, the β‐HS hydrogels induce angiogenesis in implant‐adjacent tissues. Molecular dynamics simulations indicated that the low FBR performance of β‐HS results from what we term “dual hydrogen bonding hydration”, wherein both the backbone amide groups and the sidechain hydroxyl groups of β‐HS undergo hydration.     

Cost‐Effective,High‐Performance Porous‐Organic‐Polymer Conductors Functionalized with Sulfonic Acid Groups by Direct Postsynthetic Substitution

We demonstrate the facile microwave‐assisted synthesis of a porous organic framework 1 and the sulfonated solid ( 1S ) through postsubstitution. Remarkably, the conductivity of 1S showed an approximately 300‐fold enhancement at 30 °C as compared to that of 1 , and reached 7.72×10^?2 S cm^?1 at 80 °C and 90 % relative humidity. The superprotonic conductivity exceeds that observed for any conductive porous organic polymer reported to date. This material, which is cost‐effective and scalable for mass production, also revealed long‐term performance over more than 3 months without conductivity decay.     

Synthesis of Functional Polymers by Post‐Polymerization Modification

Post‐polymerization modification is based on the direct polymerization or copolymerization of monomers bearing chemoselective handles that are inert towards the polymerization conditions but can be quantitatively converted in a subsequent step into a broad range of other functional groups. The success of this method is based on the excellent conversions achievable under mild conditions, the excellent functional‐group tolerance, and the orthogonality of the post‐polymerization modification reactions. This Review surveys different classes of reactive polymer precursors bearing chemoselective handles and discusses issues related to the preparation of these reactive polymers by direct polymerization of appropriately functionalized monomers as well as the post‐polymerization modification of these precursors into functional polymers.     

High‐Nitrogen‐Based Pyrotechnics: Development of Perchlorate‐Free Green‐Light Illuminants for Military and Civilian Applications

The development of perchlorate‐free hand‐held signal illuminants for the US Army’s M195 green star parachute is described. Compared with the perchlorate‐containing control, the optimized perchlorate‐free illuminants were less sensitive toward various ignition stimuli while offering comparable burn times and visible‐light outputs. The results were also important from the perspective of civilian fireworks because the development of perchlorate‐free illuminants remains an important objective of the commercial fireworks industry.     

Hyperbranched Polymers by Type II Photoinitiated Self‐Condensing Vinyl Polymerization

Type II photoinitiated self‐condensing vinyl polymerization for the preparation of hyperbranched polymers is explored using 2‐hydroxyethyl methacrylate (HEMA) or 2‐(dimethylamino)ethyl methacrylate (DMAEMA), and methyl methacrylate as hydrogen donating inimers and comonomer, respectively, in the presence of benzophenone and camphorquinone under UV and visible light. Upon irradiation at the corresponding wavelength, the excited photoinitiator abstracts hydrogen from HEMA or DMAEMA leading to the formation of initiating radicals. Depending on the concentration of inimers, type of the photoinitiator, and irradiation time, hyperbranched polymers with different branching densities and cross‐linked polymers are formed.