Poly(spirobifluorene)s and their derivatives with three primary colors are promising for application in efficient and stable polymer light‐emitting diodes (PLEDs). Here, a novel approach is reported to tune the emission colors of blue‐light‐emitting poly(spirobifluorene)s through a charge‐transfer mechanism from the side chain to the main chain. By using the electron‐rich 2,3,6,7‐tetra‐octyloxyfluorene unit as the side chain and incorporating the electron‐deficient dibenzothiophene‐S,S‐dioxide ( SO ) unit into the main chain, a series of polyspirobifluorene derivatives are successfully developed. They all display efficient green photoluminescence and electroluminescence. The observed green emission can be ascribed to both intramolecular and intermolecular charge transfer from the pendant 2,3,6,7‐tetra‐octyloxyfluorene unit to the SO unit in the main chain. Single‐layer PLEDs of these polymers reveal a maximum luminance efficiency of 1.99 cd A?1 and a maximum power efficiency of 1.30 lm W?1 with Commission Internationale de L'Eclairage coordinates of (0.37, 0.54).
Melting and reorganization of conformationally disordered crystals (α′‐phase) of poly(l ‐lactic acid) (PLLA) are analyzed as a function of the rate of heating in a wide range between about 10?1 and 103 K s?1. It is found for the first time that the reorganization of conformationally disordered α′‐crystals into stable α‐crystals can be suppressed by fast heating. Heating of α′‐crystals of PLLA at a constant rate, faster than 30 K s?1, leads to its complete melting between 150 and 160 °C and suppression of formation of α‐crystals on continuation of heating. Non‐isothermal reorganization of α′‐crystals into α‐crystals only occurs when heating at a rate slower than 30 K s?1. It is evidenced that isothermal reorganization of α′‐crystals into α‐crystals at 150–160 °C proceeds via melting followed by recrystallization rather than a solid–solid phase transition.
Herein, high performance solution‐processed non‐fullerene organic solar cells employing a medium band gap conjugated polymer (PBDTTS‐TTffBT) and a bay‐linked perylene bisimide derivative (di‐PBI) as an electron donor and acceptor, respectively, have been demonstrated. Owing to the complementary absorption range and well‐matched energy levels, PBDTTS‐TTffBT and di‐PBI have great potential for constructing high‐performance non‐fullerene organic solar cells. The facile control of blend film morphology by careful choice of a processing solvent achieves a promising power conversion efficiency of the device up to 6.51% with high open‐circuit voltage (0.92 V), short circuit current density (10.89 mA cm?2), and a fill factor (0.65). Furthermore, the blend film exhibits high thermal stability, retaining >80% of its initial efficiency at 100 °C up to 120 min. This work demonstrates that the medium band gap is a promising candidate as a donor material for constructing high‐performance non‐fullerene organic solar cells.
Polyacrylonitrile (PAN) with high molecular weight and low dispersity is successfully synthesized by visible‐light‐induced metal‐free radical polymerization at room temperature. This polymerization technique uses organic dye Eosin Y as photocatalyst and benzenediazonium tetrafluoroborates as initiator. Gel permeation chromatography‐multiangle laser light scattering shows the absolute molar weight of the PAN more than 1.50 × 105 g mol−1 with a polydispersity index < 1.3 while MALDI‐TOF MS and 19F NMR spectroscopy indicate the F‐chain‐end process. The first‐order kinetic behavior, molecular weight distributions shifting, and “ON/OFF” experiment results suggest this reaction may follow the atom‐transfer‐like radical polymerization mechanism. In addition, this new approach allows for the efficient synthesis of well‐defined random copolymers.
A low molecular weight hydrazide compound, tetramethylenedicarboxylic di (2‐hydroxybenzohydrazide) (TMBH), greatly improves the crystallization rate and crystallinity of poly(l ‐lactide) (PLLA). The nucleating efficiency of TMBH on the crystallization of PLLA exhibits obvious concentration dependence, which increases first and then decreases slightly with the increase of TMBH loading, reaching a maximum at 0.3 wt%. Time‐resolved Fourier transform infrared spectroscopy spectra indicate that the formation of skeletal conformational ordering structure of PLLA has been accelerated in the presence of TMBH, which can act as efficient precursors speeding up both the nucleation of PLLA on TMBH surface and the formation of intrachain 103 helix structure. The possible hydrogen bonding interaction between the ? OH or ? NH groups in TMBH and the ? C?O groups in PLLA backbones is supposed to be an important factor, which promotes the migration of PLLA chains to TMBH crystallites and the emergence of interchain interactions as well as the conformational ordering.
A new block‐co‐polymer based on poly(arylene ether sulfone) and nitrile‐functionalized poly(phenylene oxide) is prepared via polycondensation. Upon swelling with Li triflate dispersed in succinonitrile, a polymer electrolyte suitable for application in secondary Li ion batteries is obtained, which at temperatures above 313 K exhibits conductivities of 10?4–10?3 S cm?1. The presence of distinct coordination modes of the Li ions (not discernible from inspection of 7Li chemical shifts) is revealed based on a dynamic contrast identified from a distribution of transverse relaxation times. Three relaxation components reflecting polymer‐bound, partially and fully solvated Li ion species are identified on the basis of Carr–Purcell–Meiboom–Gill NMR data after inverse Laplace transformation and multiexponential relaxation analysis toolkit analysis thus highlighting the versatility of the applied methods.
A two‐step synthesis of high‐molecular‐weight and bio‐based poly(butylene succinate) (PBS) from succinic anhydride and butane‐1,4‐diol is established, in which the first step is a 12 h atmospheric polycondensation at 95 °C in the presence of succinic acid. The subsequent polymerization, catalyzed by Novozym 435 suspended in toluene, yields PBS with a molecular weight above 73 000 g mol?1. The recovered lipase catalyst appears to give similar performance after six cycles. The versatility of this atmospheric synthetic route to PBS copolymers is validated through the syntheses of poly(butylene succinate‐co‐butylene malate) (PBSM), poly(butylene succinate‐co‐butylene fumarate) (PBSF), and poly(butylene succinate‐co‐butylene terephthalate) (PBST), in which succinic acid is replaced by corresponding di‐acids as monomers.
The preparation of stimuli‐responsive aminomethyl functionalized poly(p‐xylylene) coatings by chemical vapor deposition polymerization is reported. Modification of the paracyclophane precursor with ionizable aminomethyl groups leads to polymer coatings with pH‐responsive swelling properties. The swelling behavior is monitored in situ using spectroscopic ellipsometry and additional streaming potential measurements are performed. With decreasing pH‐value, the coating becomes increasingly charged and reversibly swells to several times its dry thickness. The swelling ratio is sensitive to the ionic strength of the solution. By using a mixture of unfunctionalized and functionalized precursors in the chemical vapor deposition process, the number of charges in the polymer layer can be tuned and with it the swelling ratio of the coating. As a proof‐of‐concept for possible applications, a commercial paper filter is coated. This results in a pH‐dependent wetting behavior and pH‐dependent transport through the capillaries of the paper.
A set of copolyesters (PHTxGluxy) with compositions ranging between 90/10 and 50/50 in addition to the parent homopolyesters poly(hexamethylene terephthalate) (PHT) and PHGlux, are prepared by the melt polycondensation of 1,6‐hexanediol (HD) with mixtures of dimethyl terephthalate (DMT) and dimethyl 2,4:3,5‐di‐O‐methylene‐d ‐glucarate (Glux). The copolyesters have in the 35 000–45 000 g mol?1 range, their microstructure is random, and they start to decompose at a temperature well above 300 °C. Crystallinity of PHT is repressed by copolymerization so that copolyesters containing more than 20% of sugar‐based units are essentially amorphous. On the contrary, PHTxGluxy displays a Tg that increases monotonically with composition from 16 °C in PHT up to 73 °C in PHGlux. Compared with PHT, the copolyesters show an accentuated susceptibility to hydrolysis and are sensitive to the action of lipases upon incubation under physiological conditions. The degradability of PHTxGluxy increases with the content in Glux units.
The search for new polymers from renewable origin is a sparkling field in polymer chemistry, especially those having promising properties, for example, in terms of their thermal performance. In this vein, in this study, an original renewable 2,5‐furandicarboxylic acid‐based cycloaliphatic homopolyester, poly(1,4‐cyclohexylene 2,5‐furandicarboxylate) (PCdF), is synthesized from dimethyl‐2,5‐furandicarboxylate and 1,4‐cyclohexanediol. Poly(1,4‐cyclohexanedimethylene 2,5‐furandicarboxylate) is also prepared for comparison purposes, since it is the direct renewable substitute of poly(1,4‐cyclohexanedimethylene terephthalate) and they are structurally related. The resulting homopolyesters are characterized in detail by using attenuated total reflectance Fourier transform infrared, 1H, 13C and 2D NMR, X‐ray and elemental analysis, and thermal properties are assessed by thermogravimetric analysis, differential scanning calorimetry, and dynamic mechanical thermal analysis. PCdF shows to have a semicrystalline character, exhibiting an extremely high glass transition temperature around 175 °C. Moreover, this polyester also shows to be a high thermally stable material with a degradation temperature of 380.0 °C.
The temperature‐dependent swelling behavior of poly(N‐isopropylacrylamide) and tripeptide Gly–Gly–His (GGH)/poly(NIPAAm) conjugate hydrogel coatings are investigated using a quartz crystal microbalance with dissipation (QCM‐D) while in contact with NaCl, ZnCl2, NiCl2, and CuCl2 solutions. To fabricate the tripeptide conjugated gels, precursor gels of poly(NIPAAm‐co‐3‐aminopropylmethacrylamide[3.5 mol%]) are synthesized via free‐radical polymerization. The metal‐binding tripeptide, GGH, is subsequently synthesized in the gel via a Merrifield solid‐phase peptide synthesis (SPPS) technique, in which the amino group of the copolymer gel provides a functional site to support peptide synthesis. It is found that the logarithm of the transition temperature of the tripeptide GGH/poly(NIPAAm) conjugate hydrogel is proportional to the ionic strength, showing two distinct regions at low and high ionic strengths for the divalent ions. In the low‐ionic‐strength regime, the salting out constants are 0.08, 0.07, and 0.06 M?1 for Cu2+, Ni2+, and Zn2+, respectively, which follows the known trend for binding of ions to GGH. In the high‐ionic‐strength region, when the metal‐ion binding sites in the tripeptide conjugate hydrogel are saturated, the salting out constants are similar to the salting out constants associated with pure poly(NIPAAm).
Two carbazole derivatives with terpyridine units attached to the 3,6‐positions are synthesized, 1 with a hydrogen at the 9‐position and 2 bearing a dodecyl chain there, to evaluate the influence of H‐bonds on their self‐assembly behavior with metal ions. The unalkylated derivative 1 assembles with zinc ions to form a single product identified by NMR, electrospray ionisation mass spectrometry (ESI‐MS), and X‐ray photoelectron spectroscopy (XPS) as a pentametric metallocycle ( Zn‐1 ), whereas 2 forms a mixture of two assemblies ( Zn‐2 ). The pentamer Zn‐1 shows tunable dual emission in the blue and green regions by varying the solvent and excitation wavelength, and molecular packing studies by powder X‐ray diffractometry (XRD), transmission electron microscopy (TEM), polarising optical microscopy (POM), and atomic force microscopy (AFM) reveals a high propensity to form ordered layers. A fluorescence quenching experiment of electron‐rich Zn‐1 with C60 shows a high association constant of Ksv = 3.2 × 105m ?1, suggesting effective charge transfer between Zn‐1 and C60 molecules.
A novel spacer‐free liquid crystalline polyrotaxane (LCPR) is synthesized by directly grafting 4‐phenylazobenzoyl chloride onto the hydroxyl of threaded α‐cyclodextrin (α‐CD) as the side‐chain. It is found that LCPR can form nematic LC phase above 180 °C or under the concentration of 5–0.2 wt% in dimethyl sulfoxide (DMSO) solution. The mechanisms of formation of thermotropic and lyotropic LC phase are proposed, respectively, which show the mobility of both threaded α‐CDs and substituted azo‐mesogens is responsible for the formation of LC phase. This mechanism is further demonstrated by the formation of crystalline phase under UV radiation, which is characterized by polarizing optical microphotograph and UV measurements.
Poly(N‐isopropylacrylamide‐co‐N‐isopropylmethacrylamide) (poly(NIPAAm‐co‐NIPMAAm)) is synthesized as an attractive thermo‐responsive copolymer by an original procedure. Due to the similar structure of the two co‐monomers, the poly(NIPAAm‐co‐NIPMAAm) copolymer displays a very sharp phase transition, under physiological conditions (phosphate buffer solution at pH = 7.4). The copolymer, showing the 51/49 co‐monomer NIPAAm/NIPMAAm molar ratio, displays a lower critical solution temperature (LCST) close to that of the human body temperature (36.8 °C). The poly(NIPAAm‐co‐NIPMAAm) microgels obtained at the 51:49 co‐monomer ratio displays a volume phase transition temperature (VPTT) slightly smaller than LCST. The deswelling rate of the microgels is very high (k = 0.019 s?1), the shrinkage occurring almost instantaneously, whereas the swelling rate is slightly lower (k = 0.0077 s?1). The microgels are loaded with the model drug dexamethasone and the drug release is investigated at different temperatures, below and above the VPTT. Under thermal cycling operation between 32 and 38 °C, the pulsatile release of dexamethasone is observed.
Novel self‐healing silicone rubbers are prepared by a two‐step procedure: aminopropyl methyl phenyl polysiloxanes is first reacted with salicylaldehyde and then with copper acetate. The reversible nature of the metal–ligand coordination interaction between polysiloxanes with pendent Schiff‐base groups and Cu2+ has endowed silicone rubbers with superior self‐healing properties. As compared with other self‐healing silicone rubbers based on hydrogen bonds or Diels–Alder reaction, this cross‐linked system shows high healing power. The materials are cut into two parts and put together in a mold for 1 h at 30 °C, observing a macroscopic healing and a strength recovery up to 87.0%.
Copolymer electrolytes based on 5‐(methacrylamido)tetrazole (MTet) and vinyl phosphonic acid (VPA) are prepared. The obtained copolymers are analyzed by FTIR, 1H NMR, 13C NMR, and 31P NMR spectroscopy, thermogravimetric analysis (TGA), differantial scanning calorimetry (DSC), energy dispersive X‐ray spectrometry (EDS), elemental analysis (EA), cyclic voltammetry (CV), and impedance spectroscopy. The morphology of the copolymers is characterized by X‐ray diffraction (XRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM). The highest proton conductivity is obtained as 0.01 S/cm at 150 °C and in anhydrous conditions.
Three medium‐bandgap polymers based on a 4,5‐ethylene‐2,7‐dithienyl carbazole as the electron‐donating unit and different 5,6‐dialkoxy‐2,1,3‐benzothiadiazoles as the electron‐accepting units, are synthesized as polymer donors for photovoltaic applications. The three copolymers possess highest occupied molecular oribital (HOMO) levels around ?5.47 eV and medium bandgaps of about 1.94 eV. The solar cells with polymer:[6,6]‐phenyl C71‐butyric acid methyl ester (PC71BM) = 1:4 as the active layer, show an especially high open‐circuit voltage (Voc) of 0.95 V and attain good power conversion efficiency up to 5.91%. The hole mobilities of the active layer films, measured by space‐charge‐limited current (SCLC), are up to 3.5 × 10?4 cm2 V?1 s?1. Given the favorable medium bandgaps, low‐lying HOMO levels, and good hole mobilities, these copolymers are promising candidates for the construction of a highly efficient front cell to harvest the shorter wavelength band of the solar radiation in a tandem solar cell with high Voc.
Triple hydrophilic asymmetric poly(2‐hydroxyethyl acrylate)‐b‐poly(ethylene oxide)‐b‐poly(2‐hydroxyethyl acrylate) (PHEA‐b‐PEO‐b‐PHEA) triblock copolymers are obtained by copper(0) catalyzed reversible deactivation radical polymerization (RDRP). Copper wire catalyzed polymerization of HEA from large PEO (Mn = 35 000 g mol?1) macroinitiator in dimethylsulfoxide or in water fails to reach high monomer conversion in a controlled manner contrary to what is previously published with a shorter PEO macroinitiator. Catalysis by nascent Cu(0) particles generated by disproportionating CuBr in water allows rapid polymerization and high monomer conversion with a rather good control of both dispersity and HEA block length. Model disproportionation experiment shows that HEA influences the disproportionation/comproportionation equilibrium. Larger quantities of HEA lead to higher apparent rate constants and less disproportionation of CuBr which is in agreement with the supplemental activator and reducing agent atom transfer radical polymerization (SARA ATRP) mechanism and not with the single electron transfer–living radical polymerization (SET‐LRP) mechanism.
The radical copolymerization of N‐substituted maleimides containing polymethylene and poly(ethylene oxide) side chains as the N‐substituent groups with isobutene, styrene, and α‐methylstyrene as the electron‐donating monomers is carried out in order to investigate the structure and thermal properties of the resulting comb‐like copolymers. The obtained copolymers show excellent thermal stability and their glass transition temperatures vary depending on the chain length of the introduced N‐substituents. The main‐ and side‐chain motions of the copolymers are investigated by dynamic mechanical analysis at various frequencies over the temperature range of ?150 to 100 °C.
Poly[(R )‐3‐hydroxybutyrate] (P3HB) is a potential candidate for biomaterials due to its biocompatibility and biodegradability. However, P3HB needs to have tunable hydrophobicity, modification through chemical functionalization and the right hydrolytic stability to increase their potential for water‐based biomedical applications such as using them as in situ forming gels for drug delivery. This work focuses on using a copolymer, poly[(R )‐3‐hydroxybutyrate‐co‐4‐hydroxybutyrate] (P3HB4HB) in a thermogelling multiblock system with polypropylene glycol and polyethylene glycol to study the effect of the hydrophobic P3HB4HB on gelation properties, degradation, and drug release rates with reference to P3HB. Thermogels containing P3HB4HB segments show lower critical micellization concentration values in a range from 3 × 10−4 to 1.08 × 10−3 g mL−1 and lower critical gelation concentration values ranging from 2 to 6 wt% than that of gels containing P3HB. Furthermore, gels containing P3HB4HB degrade at a slower rate than the gels containing P3HB. Drug release studies of 5 µg mL−1 of doxorubicin show that gels containing P3HB4HB exhibit sustained release although the release rates are faster than gels containing P3HB. However, this can be modified by varying the concentration of the gels used. Process optimization of purifying the starting material is one important factor before the synthesis of these biomaterials.
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