Anisotropic magnetically active elastomers based on polydimethylsiloxane and magnetic particles of different chemical natures, shapes, and sizes have been synthesized. A comparative analysis of their mechanical properties (elastic modulus, strength, and elongation at break) has been performed depending on the mutual orientation of the internal structure, formed by magnetic filler particles during the synthesis of the composite in a magnetic field, and the direction of the external mechanical force applied to stretch the samples. The anisotropy of mechanical properties is most pronounced in composites based on anisometric particles, needle-like and plate-like. The highest values of anisotropy coefficient of elastic modulus are observed in the composite containing plate-like iron microparticles; for this composite, the ratio of the elastic moduli in the directions parallel and perpendicular to the internal structure reaches a value of five. The use of magnetic filler and its orientation by means of magnetic field is an effective method for creating polymer composites with anisotropy of mechanical properties.

Синтезированы анизотропные магнитоактивные эластомеры на основе полидиметилсилоксана и магнитных частиц разной химической природы, формы и размера. Проведен сравнительный анализ их механических свойств (модуля упругости, прочности и удлинения при разрыве) в зависимости от взаимной ориентации внутренней структуры, формируемой частицами магнитного наполнителя при синтезе композита в магнитном поле, и направления внешней механической силы при растяжении образцов. Анизотропия механических свойств наиболее ярко проявляется в композитах на основе анизометричных частиц – игольчатых и пластинчатых. Наибольшие значения коэффициента анизотропии упругости наблюдаются у композита, содержащего пластинчатые микрочастицы железа, для него отношение модулей упругости в параллельном и перпендикулярном внутренней структуре направлениях достигает пяти. Использование магнитного наполнителя и его ориентирование при помощи магнитного поля является эффективным методом создания полимерных композитов с анизотропией механических свойств.

The development of conjugated polymers with wide absorption spectra is imperative to achieve high efficiency in polymer solar cells (PSCs), since most of these polymers usually absorb only a limited range of the solar spectrum. Random terpolymers consisting of three blocks (one electron-donor and two electron-acceptor blocks) are promising p-type polymers for PSCs, because the inclusion of a third block in the polymer macromolecules provides a synergistic effect of physical properties, such as absorption capacity, charge transfer, HOMO/LUMO energy levels, and photovoltaic characteristics. In this regard, we have developed and synthesized random terpolymers consisting of two different chromophores (DPP and BFCTP) with complementary absorption spectra as co-acceptor blocks in conjugated donor–acceptor (D–A) copolymers. Random copolymers exhibit both broad absorption and low HOMO levels favoring short-circuit current and idle voltage in PSCs. It is expected that new terpolymers consisting of one electron-donor unit and two electron-acceptor moieties will make a significant contribution to the development of highly efficient PSCs. It is expected that new ternary copolymers consisting of one electron-donor unit and two electron-acceptor fragments will make a significant contribution to the development of high-performance PSСs.

Three D–A conjugated copolymers based on the same 8,10‐dihydro‐9H‐bisthieno[2′,3′:7.8;3″,2″:5.6]naphtho[2,3‐d]imidazol‐9‐one (DTNIA) acceptor unit and different donor units, i.e., 2‐dodecylbenzo[1,2‐b:3,4‐b′:6,5‐b″]trithiophene (3TB) (P1), 5,6‐dioctylnaphtho[2,1‐b:3,4‐b′]dithiophene (DTN) (P2), and 4,5‐diundecylbenzo[2,1‐b:3,4‐b′]dithiophene (DTB) (P3), are formulated and synthesized. All the copolymers exhibit deep highest occupied molecular energy levels of −5.43, −5.50, and −5.51 eV for P1, P2, and P3, respectively, and show an optical bandgap of 2.18, 2.12, and 2.11 eV, for P1, P2, and P3, respectively. These copolymers are used as donors for the construction of polymer solar cells combining ITIC‐m as an electron acceptor. The optimized polymer solar cells based on P1:ITIC‐m, P2:ITIC‐m, and P3:ITIC‐m realize overall power conversion efficiency of ≈9.62%, 12.84%, and 11.80%, respectively. The greater value of open circuit voltage for P2 and P3 relative to P1 may be due to the deeper highest occupied molecular orbital energy level of P2 and P3 as compared to P1. The highest power conversion efficiency for the P2‐based polymer solar cells may be originated from the denser π–π stacking distance and relatively improved crystallinity, which are advantageous for balanced charge transport, resulting in a comparatively high fill factor and short circuit current.

The effect of temperature on water sorption by gels based on the copolymers of N -isopropylacrylamide with sodium p -styrene sulfonate containing 1, 3, and 5 mol % of charged monomer units is studied in aqueous media in the presence of salt (NaCl, KCl) or urea. It is shown that the incubation of gels in salt solutions leads to compression of the gels. With increasing temperature, the collapse of gels is observed in all studied media. The difference in the gel collapse temperature in water and salt solution increases with an increase in the fraction of charged units in the polymer gel network and in the salt concentration in the solution. With a return temperature decrease and gel decollapse, the mass of all gels in salt solutions (0.5–5.0 wt %) is completely restored. The incubation of gels in aqueous solutions of urea (0.5–5.0 wt %) has practically no effect on water sorption by gels before the collapse and the collapse temperature. However, the degree of swelling of polyelectrolyte gels during decollapse caused by a temperature decrease is much lower than the initial value, in contrast to the completely reversible swelling of the poly( N -isopropylacrylamide) gel under similar conditions.

Two donor–acceptor (D–A) conjugated polymers designed on same 8,10-bis(2-octyldodecyl)-8,10-dihydro-9H-bisthieno[2′,3′:7,8;3″,2″:5,6]naphtho[2,3- d]imidazole-9-one donor and dissimilar acceptor uni...

The dielectric properties of electrochromic composite material based on poly[4,4’-(1,4-phenylene)bis(2,6-diphenylpyridinium)triflate] (PV) and multi-wall carbon nanotubes (MWCNTs) have been studied. Negative permittivity was registered at low frequencies of the alternating electric field ( $$10^{-1}{-}10^{3}$$ Hz) in the PV/MWCNT nanocomposites of different composition. The frequency of transition from negative to positive permittivity, as well as the values of conductivity, increased in the case of application of direct-current (dc) voltage. The physical mechanism responsible for the unusual properties appears to be related to the delocalized charges located at the multiple insulator–conductor interfaces.

Electrochromic behavior of poly(amine-amide) with pendant N-phenylcarbazole and triphenylamine units (A1) and its composites with multiwalled carbon nanotubes (MWCNTs) were investigated. Cyclic voltammetry showed four separate redox processes with oxidation peaks at E-ox1 = 720 mV, E-ox2 = 1070 mV, E-ox3 = 1295 mV and E-ox4 = 1730 mV vs Ag/Ag+. The first two reactions are reversible and spectroelectrochemical analysis demonstrated color changes. A1 exhibits a colorless initial state, a green radical cation state, and a blue dication state. The polymer exhibits a good stability during the electrochromic tests in the range of -400 to 1100 mV with minimal loss of the transmittance during 30 cycles. The potential increasing above 1100 mV induces the third and fourth redox reactions and results to coloring film to deep blue. However, these redox processes are chemically and electrochemically irreversible. Detailed calorimetric study and FTIR-spectra analysis of polymer before and after electrochemical measurements show change of the macromolecular structure induced by the redox processes at potentials above 1100 mV. The introduction of MWCNTs in the polymer films improves the kinetics of switching between the A1 color states while a slight decrease in the optical contrast. The FTIR spectroscopy, TG and DSC results of A1/MWCNT composites (in the range of the studied component composition) before and after electrochemical tests practically coincide with the data for pristine polymer and indicate a change in the polymer structure in the third and fourth redox reactions. Thus, the introduction of MWCNTs leads to an improvement in electrochromic characteristics during reversible redox reactions, but does not affect the destructive processes induced by the third and fourth oxidative reactions.

The overall power conversion efficiency of the polymer solar cell based on P13 (DPP/BTQx ratio is 1/1) showed the highest value of 9.20% with a Voc of 0.86 V, Jsc of 15.74 mA cm−2, and FF of 0.68.

This study is focused on two electrochromic poly(pyridinium triflate)s. They are aromatic rigid-rod polymer PV1 and PV12 containing alkyl linkages. Electrochromic behavior of both polymers was comparatively investigated by employing a three-electrode cell and «smart windows» prototypes. The electrochromic properties of polymer films were examined by electrochemical and spectroelectrochemical methods. Polymers with π-conjugate and non-conjugate structure demonstrate reversible redox process accompanied by a reversible color change both in three-electrode cell and electrochromic device (ECD). In general, introduction of the non-conjugated spacers to the PV12 backbone structure leads to deterioration in the optical contrast and switching time in comparison with π-conjugated PV1. The same effect was also detected for ECD. The reason behind this is thought to be a complication of electron transport in the system due to non-conjugated PV12 backbone structure.

ABSTRACTA series of novel donor–acceptor (D–A) random conjugated terpolymers P2‐P4 along with the homopolymers P1 (BDT‐DPP) and P5 (BDT‐BTDQ) were designed and synthesized by copolymerizing a benzo[1,2‐b:4,5‐b]dithiophene (BDT) donor with an electron‐deficient diketopyrrolo[3,4‐c]pyrrole (DPP) unit and a benzothiadiazolo[3,4‐e]quinoxaline (BTDQ) moieties of different electron‐withdrawing strengths, and the resultant terpolymers showed broad absorption profile ranging from 300 to 1200 nm. The HOMO levels of the polymers were adjusted from −5.23 to −5.11 eV, and the optical bandgaps were controlled from 1.32 to 1.13 eV by changing the molar ratio of DPP and BTDQ acceptors. These terpolymers were used as a donor along with PC71BM as an acceptor for the creation of polymer solar cells, and the performance was optimized via variable the donor to acceptor ratio and solvent vapor annealing. The polymer solar cells made from the random terpolymer P3 showed the highest overall power conversion efficiency of (9.27%), which is higher than that for the corresponding homo‐polymers counterparts, that is, P1 (7.27%) and P5 (7.68%). The results demonstrate that the designing of random D‐A1‐D‐A2 terpolymers may be the best approach for efficient polymer solar cells. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1478–1485

Two new fused quinoxaline-containing monomers—2,3-bis(9-(2-decyltetradecyl)-9H-carbazol-3-yl)dithieno[3,2-f:2'3'-h]quinoxaline (М1) and 2,5-di(nonadecan-3-yl)bis[1,3]thiazolo[4,5-a:5',4'-c]bisthieno[3,2-h:2',3'-j]phenazine (М2)—have been synthesized in high yields of 88 and 83% as promising building blocks of D-A polymers for photovoltaic applications. The optical bandgaps, found from the absorption edge, are 2.79 and 2.88 eV, respectively. The HOMO/LUMO energies of М1 and М2 are–5.83/–2.96 and–5.83/–2.98 eV, respectively. Both monomers have low-lying HOMO levels, which is favorable for a high open-circuit voltage and a high stability in air in the development of PSCs. The E g ec values of monomers М1 and М2 are 2.87 and 2.85 eV and are consistent well with the optical bandgap (2.79 and 2.88 eV, respectively).

Electrochromic properties of two poly(pyridinium) salts (PV1 and PV2 with additional methyl substituent) in different supporting electrolytes were investigated. KCl, NaCl, LiCl and KBr supporting electrolytes were used to analyze the ions transfer due to ions size variation. The electrochromic properties of polymer films were examined by electrochemical and spectroelectrochemical methods. Both polymers demonstrate reversible redox process in all studied supporting electrolytes. In general, replacement of K+ ions by Li+ or Na+ ions leads to deterioration in the optical contrast and coloring time in contrast to bleaching time which is improved for both studied polymers. The reason behind this is thought to be an increasing cation size obstructing the cation transport in redox reactions. Comparing the relative changes in polymer electrochromic characteristics by the electrolyte replacement is less significant for PV2 films. The replacement of supporting electrolyte anions has practically no effect on the electrochromic properties of both polymers.

New derivatives of bis[1,3]thiazolo[4,5-f:5',4'-h]thieno[3,4-b]quinoxaline containing the fused thiadiazoloquinoxaline moiety have been prepared. Monomer M1 shows strong light absorption within 600–800 nm due to intramolecular charge transfer. The optical bandgap E g opt determined from the absorption edge in a film is 1.44 eV. The HOMO and LUMO levels are–5.44 and–3.12 eV, respectively. The new structural fragment has a rather low frontier molecular orbital energies and a small bandgap; therefore, it is a promising building block for the synthesis of polymers for organic electronics.

The influence of different salts and pH on the stability of the aqueous dispersion of multiwalled carbon nanotubes (MWCNTs) non-covalently modified by thermosensitive poly(N-vinylcaprolactam) (PVCL) was studied. The PVCL/MWCNT dispersion was prepared by adding MWCNTs into aqueous PVCL solution with the subsequent ultrasonication and centrifugation. The morphology of MWCNTs and MWCNT/PVCL composites was characterized by TEM. The aggregation temperatures of the MWCNT/PVCL dispersion and the lower critical solution temperature (LCST) of PVCL aqueous solution were determined for different salt types and concentrations as well as pH in the temperature range between 20 and 60 °C. Specific ion effect on LCST of PVCL was analyzed in terms of the Hofmeister series. In the presence of kosmotropes, both the MWCNT/PVCL dispersion aggregation temperature and the LCST of PVCL are well consistent with the Hofmeister series of ions. However, opposite trends were observed for LCST of PVCL and the MWCNT/PVCL dispersion aggregation temperature when adding chaotropic anions. The dynamic light scattering (DLS) technique was used to study the PVCL aggregation kinetics at a temperature above the LCST at different pH values. These results demonstrate that specific thermoresponsive properties of the MWCNT/PVCL dispersion at pH < 3 correlate with the behavior of the individual PVCL macromolecules in acid media above the LCST.