Donor Monomers Research Articles

Biradical Initiation in Photoinitiated Copolymerization of Styrene and Maleic Anhydride

AbstractPoly(styrene‐co‐maleic anhydride) (SMAnh) is a copolymer system that is well known for its alternating tendency, which has been thoroughly investigated by many research groups over the decades and is widely used in industry. Investigations have focused almost entirely on thermally initiated systems. However, very few investigations have been conducted on light‐initiated radical copolymerization. In this study, the photoinitiated copolymerization of styrene and maleic anhydride is investigated without the use of an external radical source, such as the classical 2,2‐azobis(2‐methylpropionitrile) (AIBN), benzoyl peroxide (BPO), or any photoinitiators. The initiation of the polymerization is instead found to take place through an excited state biradical generated in situ from a photoexcited charge‐transfer complex (CTC) comprising the donor (styrene) and acceptor (maleic anhydride) monomers. The formation of the complex is found to be solvent dependent. Excitation of the complex results in copolymerization of monomers to afford high‐molecular‐weight (>105 g·mol−1) alternating copolymers.

Interpenetrating Polymer Network Capturing FRET-Sensitive Polymers Available for an Enzyme Assay.

Fluorogenic glycomonomers have been used for biological evaluations, and water-soluble and Förster resonance energy transfer (FRET)-sensitive glycopolymers have also been reported. A FRET-sensitive polymer was conveniently prepared from a fluorogenic donor monomer and a fluorogenic acceptor monomer by means of simple radical polymerization in high yield. Continuous fluorospectroscopic monitoring of the polymer in the presence of an enzyme was performed, and the results showed the possible application of the FRET-sensitive glycopolymer for practical use. In addition to the use of aqueous solution phase, the water-soluble and FRET-sensitive glycopolymer was completely captured into an interpenetrating polymer network (IPN) by means of radical polymerization with a combination of acrylamide and bis-acrylamide as used for the cross-linking reagent system. The IPN including the FRET-sensitive glycopolymer was allowed to react with amylases in an aqueous buffer solution at 37 °C, and the enzymatic reaction was continuously and conveniently monitored by means of fluorometric spectroscopy.

Simple Functionalization of a Donor Monomer to Enhance Charge Transfer in Porous Polymer Networks for Photocatalytic Hydrogen Evolution.

Porous polymer networks (PPNs) are promising candidates as photocatalysts for hydrogen production. Constructing a donor-acceptor structure is known to be an effective approach for improving photocatalytic activity. However, the process of how a functional group of a monomer can ensure photoexcited charges transfer and improve the hydrogen evolution rate (HER) has not yet been studied on the molecular level. Herein, we design and synthesize two kinds of triazatruxene (TAT)-based PPNs: TATR-PPN with a hexyl (R) group and TAT-PPN without the hexyl group, to understand the relationship between the presence of the functional group and charge transfer. The hexyl group on the TAT unit was found to ensure the transfer of photoexcited electrons from a donor unit to an acceptor unit and endowed the TATR-PPN with stable hydrogen production.

Simple Functionalization of a Donor Monomer to Enhance Charge Transfer in Porous Polymer Networks for Photocatalytic Hydrogen Evolution

AbstractPorous polymer networks (PPNs) are promising candidates as photocatalysts for hydrogen production. Constructing a donor‐acceptor structure is known to be an effective approach for improving photocatalytic activity. However, the process of how a functional group of a monomer can ensure photoexcited charges transfer and improve the hydrogen evolution rate (HER) has not yet been studied on the molecular level. Herein, we design and synthesize two kinds of triazatruxene (TAT)‐based PPNs: TATR‐PPN with a hexyl (R) group and TAT‐PPN without the hexyl group, to understand the relationship between the presence of the functional group and charge transfer. The hexyl group on the TAT unit was found to ensure the transfer of photoexcited electrons from a donor unit to an acceptor unit and endowed the TATR‐PPN with stable hydrogen production.

Computational analysis and experimental verification of donor–acceptor behaviour of berberine, and its co-oligomers and co-polymers with ethylenedıoxythıophene

The donor–acceptor (D-A) type of conjugated polymers has emerged as the paradigm of the third generation of electronically conducting polymers demonstrating improved infrared activity and intrinsic electronic conductivity. Judicious selection of donor (D) and acceptor (A) monomers for copolymerization can further fine-tune these properties. Notably, for such refinement, natural compounds provide many conjugated molecules with various functional groups. Berberine cation (Ber+) found in Coscinium fenestratum has extensive conjugation and contains both an electron deficient isoquinolium A moiety and electron-rich D-type methylenedioxy and methoxy groups. The incorporation of natural products in electronic materials is a novel area of research which opens a wide scope for future electronic and optoelectronic devices. Investigation of their fundamental properties via computer simulations is therefore important. In this study, quantum chemical calculations are performed using density functional theory (DFT) to investigate the electronic and optical properties of oligomers of Ber+ and 3,4-ethylenedioxythiophene (EDOT) and to explore the possibilities for homo-polymerization of Ber+ and its copolymerization with EDOT. It has been revealed that homo-polymerization is not favoured but copolymerization with EDOT is possible. As such, Ber+ was copolymerized with EDOT and the copolymers formed by electro-polymerization are extensively characterised and the D-A behaviour of the copolymers verified. Furthermore, the theoretical predictions have been compared with the experimental data.

Rapeseed oil as feedstock for the polymeric materials via Michael addition reaction

Rapeseed oil was used to synthesize a Michael donor to obtain polymeric materials after nucleophilic polymerization via Michael reaction. Four different bio-polyols as precursors for the Michael donor monomer synthesis were synthesized from epoxidized rapeseed oil using an oxirane ring-opening reaction. Various alcohols such as methanol, butane-1,4-diol, 2,2′-oxydi(ethan-1-ol), and 2-ethyl-2-(hydroxymethyl)propane-1,3-diol were used to obtain bio-polyols with different OH group functionality. The transesterification reaction between the synthesised bio-polyol hydroxyl groups and tert-butyl acetoacetate ester introduced acetoacetate functional groups into their structure. The acid value, hydroxyl value, viscosity and moisture content of the synthesized polyols and corresponding acetoacetates were analyzed. Size-exclusion chromatography and Fourier transform infrared spectroscopy were used to study the chemical structure of polyols and acetoacetates. From developed acetoacetates and commercially available trimethylolpropane triacrylate, bio-based polymers were obtained via carbon-Michael reaction. The different chemical structures and functionalities of the synthesized bio-based monomers allowed for the development of polymer formulations with diverse cross-linking densities. The structural, physical and thermal properties of the developed polymers were analyzed using solid-state NMR, differential scanning calorimetry, dynamic mechanical analysis and thermal gravimetric analysis testing apparatus.

Design and synthesis of novel D-A copolymers based on fused thienothiophene for efficient broad absorption electrochromism

Developing conjugated polymers with broad spectrum modulation is highly desirable in electrochromic field. Herein, three novel polymers based on fused thienothiophene derivative (tris(thienothiophene) (TTT) or indacenodithieno[3,2-b]thiophene (IDTT)) and two acceptors (5,8-bis(4-(2-butyloctyl)thiophen-2-yl)-dithieno[3′,2':3,4; 2″,3'':5,6]benzo[1,2-c][1,2,5]thiadiazole (TBT) and 2,1,3-Benzothiadiazole (BT)) are synthesized via direct arylation polymerization (DArP). The neutral copolymers exhibit visibly broadband absorption due to the combination of the π-π* transition and intramolecular charge transfer absorption, which can be tuned by the feed ratio of the donor and acceptor monomers. As a result, the copolymer synthesized by IDTT, TBT and BT with a feed ratio of 3/2/1 presents a black color in the neutral state and high transparency in the oxidized state, which gives an average optical contrast of 34% in the visible band (400 nm–700nm), good stability and high coloration efficiency (370 cm2/C). Additionally, an electrochromic device with excellent electrochromic performance is fabricated based on the synthesized polymers. All of these confirm the synthesized polymers are attractive candidates for broad absorption electrochromism.

DFT and TD-DFT study of Optical and Electronic Properties of new donor–acceptor–donor (D–A–D′) monomers for polymer solar cells

AbstractThe Density Functional Theory (DFT) and time-dependent-DFT method with Becke’s three-parameter Lee-Yang–Parr functional approach at a basis set of 6-311G was used to analyze the ground state and excited state properties of newly designed donor–acceptor–donor (D–A–D′) donor molecules based on triphenylamine and carbazole as donor units and benzothiadiazole and its derivatives as acceptor units to make a total of nine potential monomers. The energies associated with highest occupied molecular orbital, lowest occupied molecular orbital, energy gap (Eg), electron excitation (Eopt), exciton binding (Eb) and open-circuit voltage (Voc) were calculated, and the simulated absorption spectra in both gas and chlorobenzene solvent were plotted. The outcomes of replacing the acceptor building unit and substituting the donor units to tailor the optoelectronic properties of the designed monomers were discussed. The monomer molecules A7, A8 and A9 are suitable for [6,6]-phenyl-C61-butyric acid methyl ester because of their small Eg, Eopt, Eb and, more importantly, large Voc values. Suggesting changing the acceptor unit and substituting the donor units of the D–A–D′ seem to be an excellent approach to tailoring the optoelectronic properties of the molecules.

Synthesis of donor and acceptor monomers for conjugated polymers in organic optoelectronic applications

Introduction: In today's life, conductive polymers play an increasingly important role, and it is very important to research and find materials with new properties and the ability to improve the performance of devices. The synthesis of monomer units as donor-acceptor structural units in conducting polymers is extremely important. Methods: In this research, the process of synthesizing these potential monomer structural units with high efficiency has been described, including three main units, (4-hexyl-phenyl)(10H-phenoxazin-10-yl)methanone (HP-POzM) (58%, yield), 4,8-bis(hexyloxy)benzo[1,2-b:4,5-b']dithiophene (BHBDT) (90%, yield) and 5-(2-ethylhexyl)-4H-thieno[3,4-c]pyrrole-4,6(5H)-dione (EHTPD) (95%, yield). Results: The successful synthesis of monomers was demonstrated by qualitative analytical measurements of 1H NMR and TLC monitor. In addition, it is an overview of the direction that scientists are aiming for these monomer units, as D-A units in conductive polymers, applied in current fields and development orientation in the future.

Sequence-selective duplex formation and template effect in recognition-encoded oligoanilines.

A new family of duplex-forming recognition encoded oligomers, capable of sequence selective duplex formation and template directed synthesis, was developed. Monomers equipped with both amine and aldehyde groups were functionalized with 2-trifluoromethylphenol or phosphine oxide as H-bond recognition units. Duplex formation and assembly properties of homo- and hetero-oligomers were studied by 19F and 1H NMR experiments in chloroform. The designed backbone prevents the undesired 1,2-folding allowing sequence-selective duplex formation, and the stability of the antiparallel duplex is 3-fold higher than the parallel arrangement. Dynamic combinatorial chemistry was exploited for the templated synthesis of complementary oligomers, showing that an aniline dimer can template the formation of the complementary imine. The key role of the H-bond recognition confers to the system the ability to discriminate a mutated donor monomer incapable of H-bonding. Sequence selective duplex formation combined with the template effect makes this system an attractive target for further studies.

Monodisperse Styrene-Maleic Anhydride-Isoprene Terpolymer Microspheres with Tunable Crosslinking Density Prepared by Self-Stabilized Precipitation Polymerization

Synthesis and industrial production of functional monodisperse microspheres still face enormous challenges like precise size control and process simplification. Herein, a strategy to prepare monodisperse styrene-maleic anhydride-isoprene terpolymer microspheres via self-stabilized precipitation polymerization was reported. The prepared microspheres with different isoprene proportions have uniform particle sizes (623–1156 nm) and narrow size distributions. The structure analysis showed that the copolymerization proceeded in an alternating way between the electron donor (styrene and isoprene) and electron acceptor (maleic anhydride) monomer, and isoprene was incorporated into the polymer chain through 1, 4 addition. The gel fraction of microspheres varies from 0 to 99% along with an increasing isoprene feeding ratio. The Diels–Alder (D–A) reaction between maleic anhydride and isoprene can be effectively inhibited by increasing the amount of initiator or decreasing the polymerization temperature. The resultant uniform microspheres contain reactive anhydride groups and unsaturated C═C bonds derived from isoprene, which can be used to covalently attach functional moieties and have great potential in fields of adsorption and separation, drug delivery, biodetection, and enzyme immobilization.

3D‐Printable Shape‐Memory Polymers Based on Halogen Bond Interactions

AbstractThe supramolecular halogen bonding (XB) is utilized for the first time for the preparation of shape‐memory polymers. For this purpose, an iodotriazole‐based bidentate XB donor featuring a methacrylamide is synthesized. Free radical polymerization of the XB donor monomer together with butyl methacrylate, triethylene glycole dimethacrylate, and methacrylic acid results in covalently cross‐linked polymer networks bearing both, halogen bond acceptors and donors, in their side chains. While the reversible halogen bond interactions can act as switching unit, the required stable phase of the shape‐memory polymers is formed by covalent cross‐links. The successful formation of the supramolecular cross‐links is proven via Fourier‐transform Raman spectroscopy. Furthermore, the thermal properties are investigated via differential scanning calorimetry and thermo gravimetric analysis. Thermo‐mechanical analysis reveals excellent shape‐memory abilities with fixity rates above 95% and recovery rates up to 99%. Moreover, it is possible to 3D‐print this kind of material exhibiting the ability to recover its shape within a few seconds at 130 °C.

One-Pot Synthesis of Fully Conjugated Amphiphilic Block Copolymers Using Asymmetrically Functionalized Push–Pull Monomers

Developing a fully conjugated block copolymer with a specific molecular weight and block ratio is crucial for understanding the impact of the bulk heterojunction morphology on device performance in organic photovoltaic devices. Herein, we have revealed a strategy to synthesize fully conjugated amphiphilic diblock copolymers in one pot by combining Suzuki and Stille pseudoliving polymerizations. Our strategy was to synthesize asymmetrically functionalized push–pull monomers as precursors for the synthesis of the donor polymer poly[4,8-bis(5-(2-ethylhexyl)-4-hexylthiophene-2-yl)-benzo[1,2-b:4,5b′]dithiophenebenzo [c][1,2,5]thiadiazole] p(BDT-BT) and the acceptor polymer poly[N,N′-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5′-(2,2′-bithiophene) p(NDI-TT). The acceptor monomer (M1) was synthesized with tributyltin and triflate functionalities, whereas the donor monomer (M2) was prepared with MIDA boronate and bromide groups. These heterobifunctional acceptor and donor monomers were suitable for Stille and Suzuki polymerizations, respectively. Initially, TfOPh-p(NDI-TT) was synthesized by pseudoliving Stille polymerization with a single triflate (OTf) end group and specific molecular weight. Subsequently, TfOPh-p(NDI-TT) was used as a macroinitiator to grow an amphiphilic diblock copolymer (BCP1) via a grafting-into approach, where the donor polymer block was grown using pseudoliving Suzuki polymerization. Lastly, one-pot synthesis of the amphiphilic diblock copolymer (BCP2) was established using optimized conditions developed for stepwise block copolymer synthesis.

Visible light-induced photopolymerization of Deep Eutectic Monomers, based on methacrylic acid and tetrabutylammonium salts with different anion structures

Deep Eutectic Monomers were prepared by dissolution of selected tetrabutylammonium salts serving as hydrogen bond acceptors (HBA) in methacrylic acid (MAA) acting both as hydrogen bond donor (HBD) and vinyl monomer. In this study, we systematically investigate the influence of chloride, nitrate, hydrogensulphate and fluoroborate anions on properties of DEMs and the course of radical photopolymerization. By Combining FTIR, 1H and 13C NMR spectroscopy we found the that degree of coordination of MAA in DEMs by anions follows the order: Cl− > NO3– > HSO4− ≫ BF4−. Moreover, the studies indicated that the strength of hydrogen bonds between HBD and HBA in DEMs is lower than in MAA dimers. Real-time FT-IR spectroscopy studies of photopolymerization of DEMs indicate that the mixtures formed from MAA and tetrabutylammonium fluoroborate show significant lower initial photopolymerization rate in comparison with other investigated DEMs, which polymerize with similar rates.

Vinyl-Fluorene Molecular Wires for Voltage Imaging with Enhanced Sensitivity and Reduced Phototoxicity.

Fluorescent voltage indicators are an attractive alternative for studying the electrical activity of excitable cells; however, the development of indicators that are both highly sensitive and low in toxicity over long-term experiments remains a challenge. Previously, we reported a fluorene-based voltage-sensitive fluorophore that exhibits much lower phototoxicity than previous voltage indicators in cardiomyocyte monolayers, but suffers from low sensitivity to membrane potential changes. Here, we report that the addition of a single vinyl spacer in the fluorene molecular wire scaffold improves the voltage sensitivity 1.5- to 3.5-fold over fluorene-based voltage probes. Furthermore, we demonstrate the improved ability of the new vinyl-fluorene VoltageFluors to monitor action potential kinetics in both mammalian neurons and human-induced pluripotent stem cell-derived cardiomyocytes. Addition of the vinyl spacer between the aniline donor and fluorene monomer results in indicators that are significantly less phototoxic in cardiomyocyte monolayers. These results demonstrate how structural modification to the voltage sensing domain have a large effect on improving the overall properties of molecular wire-based voltage indicators.

Studies on photophysical and electrochemical properties of triphenylamine α, β-unsaturated ketone side-arm PAE CPs

A series of polyaryleneethynylene (PAE) conjugated polymers (CPs) have been synthesized using 1-(4-((2,5-diethynylphenyl)ethynyl)phenyl)-3-(4-(diphenylamino)phenyl)prop-2-en-1-one, 1,4-diiodo-2,5-bis(octyloxy)benzene, 1,4-bis(dodecyloxy)-2,5-diiodobenzene and 2,7-diiodo-9,9′-dioctyl-9H-fluorene with terminal hydrogen presented diethynylene and diiodo–substituted precursor as acceptor and donor monomers. The donor and acceptor (D-A) unit network of CPs developed through the Heck–Sonogashira cross-coupling reaction mechanism. The triphenylamine attached α,β unsaturated ketone of phenylethynylene side-arm PAE CPs was studied for their photophysical and electrochemical behaviors based on the molecular-level electronic properties. From the solution-phase UV–visible (UV–Vis) and Fluorescence (FL) measurements explained the π–π* electronic transition and intramolecular charge transfer (ICT) behavior of the CPs. The shift between UV–Vis maxima and FL maxima are well accounted for calculating the Stokes shift, which supports the evidence for the red shift of PAE CPs, namely NPAEC8-127 nm, NPAEC12-131 nm, and NPAEF8-25 nm. The thin-film UV–Vis absorption spectra and electrochemical measurements ascertain the existence of the optical low band gap (Eg) (NPAEC8-2.57 nm, NPAEC12-2.62 nm, and NPAEF8-2.70 nm) and HOMO–LUMO energy levels of the PAE CPs. Based on data obtained from different studies, it is suggested that the synthesized PAE CPs are suitable for the photovoltaic and sensor applications.

Exploring the Scope of Through-Space Charge-Transfer Thermally Activated Delayed Fluorescence in Acrylic Donor–Acceptor Copolymers

A series of acrylic donor and acceptor monomers were prepared to investigate the effect of electronic and structural changes on the through-space charge-transfer (TSCT) thermally activated delayed ...

Donor−acceptor−donor (D-A-D) structural monomers as donor materials in polymer solar cells: a DFT/TDDFT approach

ABSTRACT Density functional theory (DFT) and time-dependent DFT (TD-DFT) are used to investigate the ground- and excited-state properties of donor-acceptor–donor (D-A-D) monomers based on 3,6-carbazole (CB) combined with various-conjugated benzothiazole derivatives, using B3LYP and the 6–311 G basis set. To create nine D-A-D monomers for this investigation, nine (9) distinct acceptors were inserted at the C3 and C6 positions of carbazole. The impact of various electron-donor groups on structural, electrical, and optoelectronic properties is investigated. Our technique for developing novel donor monomers provides a theoretical framework for further optimizing the photovoltaic device’s electrical, optical, and efficiency features. The HOMO and LUMO energies, bandgap, excited state, exciton binding energy, open-circuit voltage (VOC) and absorption spectra were calculated. Our findings indicate that CB-TDP-CB and CB-SDP-CB monomers have an appropriate electronic structure for polymer solar cells.

Dynamics of Photoinduced Energy Transfer in Fully and Partially Conjugated Polymers Bearing π-Extended Donor and Acceptor Monomers.

The photophysical properties of donor (D)-acceptor (A) polymers were studied by designing two types of polymers, (D-σ-A)n and (D-π-A)n, with non-conjugated alkyl (sp3) and π-conjugated (sp2) linkers using π-extended donor and acceptor monomers that exhibit planar A-D-A structures. The non-conjugated alkyl linker provides structural flexibility to the (D-σ-A)n polymers, while the π-conjugated linker retains the rigid structure of the (D-π-A)n polymers. Photoinduced energy transfer occurs from the large donor to acceptor units in both polymers. However, the photoinduced energy transfer dynamics are found to be dependent on the conformation of the polymers, where the difference is dictated by the types of linkers between the donor and acceptor units. In solution, intramolecular energy transfer is relatively favorable for the (D-σ-A)n polymers with flexible linkers that allow the donor and acceptor units to be proximally located in the polymers. On the other hand, intermolecular (or interchain) energy transfer is dominant in the two polymer films because the π-extended donor and acceptor units in polymers are closely packed. The structural flexibility of the linkers between the donor and acceptor repeating units in the polymers affects the efficiency of energy transfer between the donor and acceptor units and the overall photophysical properties of the polymers.

Phenothiazine derivatives, diketopyrrolopyrrole-based conjugated polymers: synthesis, optical and organic field effect transistor properties

Novel donor–acceptor (D-A) conjugated polymers containing phenothiazine and diketopyrrolopyrrole derivatives were successfully synthesized via direct arylation polymerization using the palladium catalyst system. The C-N coupling reaction was performed for the synthesis of 4-(10H-phenothiazin-10-yl)-N,N-diphenylaniline (PDA) and 10-(pyren-1-yl)-10H-phenothiazine (PYP) as donor monomers. The D-A conjugated polymers synthesized by polymerization of PDA/PY with diketopyrrolopyrrole have been characterized via GPC, 1H NMR, FTIR, XRD, DSC, PL and UV-Vis spectroscopy, and used for fabrication of organic field effect transistors.