The application of selenol‐X chemistry in nucleophilic substitution and Se‐Michael addition reactions for polymer chain end modification is presented. Selenol‐labeled polystyrene can easily react with alkyl halides, methyl methacrylate, methyl acrylate, pentafluorostyrene, etc. The mild conditions make it attractive for the synthesis of macromonomers. The resulting polymers are analyzed and characterized by UV, size‐exclusion chromatography (SEC), NMR, and matrix assisted laser desorption/ionization time of flight mass spectroscopy.
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%.
A new synthetic strategy is developed for the synthesis of polyphosphazene bearing stable nitroxide radicals as a pendant group. The resulting material is investigated as a cathode‐active material for rechargeable lithium–ion batteries that performs 80 mAh g−1 capacities at a C/2 current density over 50 cycles. Thus, the inorganic–organic hybrid system can be proposed as an alternative cathode‐active material with improved performance.
Hydrogel as a carrier for drug delivery system has been developed, but it is hard to change the load and release of drugs through a simple way. Herein, the authors report a novel pH‐sensitive supramolecular binary hydrogel based on Phe‐Gly derivative gelator (LPPG) and 4,4′‐dipyridine disulfide (DPDS). Fourier transform infrared spectroscopy, circular dichroism, and 1H NMR confirm that the driving force for the coassembly process is intermolecular hydrogen bonds. The composite hydrogel can improve the dye adsorption capacity relative to LPPG hydrogel. Moreover, the controllable absorption of the dyes is studied by varying the pH and concentration of dye solutions. LPPG‐DPDS hydrogel can also release of entrapped dyes at physiological pH. The two‐component hydrogel should be a promising system for controllable drug delivery.
Desorption of thiol‐based self‐assembled monolayers on gold surfaces makes surface‐initiated atom transfer radical polymerization (SI‐ATRP) challenging and results in reduced density “grafted from” polymer film. In this work, in situ attenuated total reflectance‐Fourier transform infrared (ATR‐FTIR) spectroscopy shows that copper‐based catalysts typically used in SI‐ATRP cause substantial desorption of bound thiol‐based initiator films from gold surfaces. Other reaction conditions factors such as low temperature, presence of radicals, and solvents selection have relatively minor effects in comparison. Indeed, the desorption of initiator films is reduced from more than 80% to about 45% when CuCl catalyst is used for the ATRP of styrene instead of CuBr catalyst. However, the polymerization rate is significantly slower in this case.
Reverse iodine transfer polymerization (RITP) of 1,1,2,2‐tetrahydroperfluorodecyl acrylate (FDA) is successfully performed in supercritical carbon dioxide (scCO2) at 70 °C under a CO2 pressure of 300 bar. PolyFDA (PFDA) of increasing molecular weights (from 10 000 to 100 000 g mol?1) is synthesized with good agreement between theoretical, 1H NMR spectroscopy and and size exclusion chromatography/refractive index/right‐angle laser‐light scattering/differential viscometer (SEC/RI/RALLS/DV)‐estimated molecular weights (). Furthermore, the increase of goes with a decrease of the dispersity of the polymers (? from 2.06 to 1.33), which is consistent with a controlled radical polymerization (CRP). Lastly, the structure of final PFDA and therefore the RITP process are confirmed by matrix‐assisted laser desorption ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS) analyses.
Flame‐retardant polypropylene (PP)/carbon nanotubes (CNTs) nanocomposites influenced by surface functionalization and surfactant molecular weights are studied. 3‐Aminopropyl‐triethoxysilane (APTES) is utilized to modify the CNTs (f‐CNTs), and maleic‐anhydride‐grafted PP (MAPP) with two molecular weights ( of 800 and 8000 g mol?1) is used to further improve the dispersion of f‐CNTs in the PP matrix. Thermal gravimetric analysis (TGA) and microscale combustion calorimetry (MCC) reveal that the molecular weight of MAPP directly affects the thermal stability and flammability of PP/f‐CNTs PNCs: both MAPP polymers ( of 800 and 8000 g mol?1) increase the thermal stability of PP; however, the heat release rate of PP/f‐CNTs is reduced in the presence of MAPP ( of 800 g mol?1) and increased in the presence of MAPP ( of 8000 g mol?1). MAPP ( of 800 g mol?1) also results in a lower viscosity of the PP/f‐CNTs PNCs compared with pure PP.
Amphiphilic polymers are synthesized from various biobased compounds involving telomerization of glycerin‐derived acrylate monomers with mercaptan‐modified fatty acids. The effects of the chemical structure of the saturated or unsaturated hydrophobic block are investigated. Dynamic and static light scattering measurements, transmission electronic microscopy, and atomic force microscopy observations show that these copolymers are capable of self‐assembling into nanosized spherical particles in aqueous solution, made from compound micelles. The critical micellar concentration of these polymers is in the range of 10–60 mg L?1 determined by fluorescence. These biobased polymers could have applications in various industrial fields, such as cosmetics and agrochemicals.
The study reports the fabrication of a free‐standing reactive macroinitiator thin film via simple layer‐by‐layer assembly and dissolution of the sacrificial layer. The resulting macroinitiator thin film can be postfunctionalized by grafting polymer brush from it. Since the thin film is free from any substrate, bifacial functionalization can be done on the free‐standing film. This approach is expected to significantly increase the functionality of free‐standing polymer brush for most applications like catalysis and sensor because of the increase in functional group density per area.
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 novel poly(phenylene ethynylene) containing 2‐thiohydantoin [poly( 1 )] is synthesized. The addition of F? quenches the fluorescence, while the fluorescence of the solution only changes slightly upon addition of other anions, indicating the sensing ability of poly( 1 ) toward F?. The addition of Ag+ quenches the fluorescence of the polymer, whereas the addition of other metal ions results in only slight changes to the fluorescence. Compared with its small‐molecule counterpart, the Stern–Volmer quenching constants of poly( 1 ) toward F? and Ag+ are 165 and 105 times greater, respectively. This result indicates the amplified quenching effect of poly( 1 ).
Interactions between polymer chains and nanoparticles can play a dominant role in composites mechanics, yet the control of such interfacial dynamics is still a significant challenge. This paper reports the effect of pH on cellulose nanofibrils (CNFs) transient hydrogels network mechanics via interfacial ionic cross‐linking bonds. For this purpose, carboxylated CNFs are incorporated with amine groups terminated 8‐arm poly(ethylene glycol) (PEG‐NH2) to assemble the first noncovalent network via reversible ionic interactions at the CNF surfaces, where the end‐group acrylate modified linear difunctional PEG forms the second lightly covalent cross‐linked network. The viscoelastic properties of the supramolecular gels are examined as a function of pH, and the unique transient mechanics resulting from CNF‐PEG complexation structures show that the processing from acidic‐to‐alkaline pH change leads to the gel cross‐links transition from covalent type to covalent–noncovalent hybrid one. This finding offers an alternative way to tune CNF gels mechanical reinforcement and sheds light on the pH dependence of network architectural changes.
A simple and environmentally friendly method for the preparation of composite cathode materials from cost‐effective waste‐product elemental sulfur and sustainable, nonhazardous vegetable oils is presented. High sulfur contents of up to 80 wt% are achieved. Scanning electron microscopy reveals that the composite materials consist of micrometer sized sulfur particles which are embedded in a crosslinked polymeric network. The polymeric network formed upon copolymerization of the fatty acid residues and elemental sulfur is similar to factice. For the first time factice‐like sulfur containing composites are utilized successfully as the active cathode material in Li–S batteries. Upon employment, high initial specific capacities up to 880 mAh g−1, good capacity retention abilities (63% after 100 cycles) as well as high coulombic efficiencies are achieved, suggesting reasonable suppression of polysulfide diffusion as a consequence of the embedment.
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).
Dendrigraft poly(l ‐lysine) (DGL) polyelectrolytes, obtained by iterative polycondensation of N‐trifluoroacetyl‐l ‐lysine‐N‐carboxyanhydride, constitute very promising candidates in many biomedical applications. In order to get a better understanding of their structure–property relationships in these applications, their absolute average molecular weights have to be accurately measured. Size‐exclusion chromatography coupled to a multi‐angle laser‐light‐scattering detector (SEC‐MALLS) is known to be the most appropriate analytical tool. These measurements require the determination of the refractive index increment, dn/dc, of these highly branched polycationic macromolecules in aqueous solution. This optical property has to be measured in the same aqueous conditions as SEC‐MALLS eluents. Consequently, data are determined and discussed as a function of different aqueous SEC‐MALLS eluents, as well as different counter‐ions of the many ammonium groups of DGL (generation 3, DGL‐3, used as a model herein). The resulting number‐average molecular weights, , are found to be very dissimilar when the measured dn/dc values are directly considered. In contrast, very close values are obtained (average = 18 700, standard error of 1110 g mol?1) with a low coefficient of variation for such data (ca. 6% for six analyses), when the dn/dc are corrected by the exact lysine amount (measured by the total Kjeldahl nitrogen method).
Three novel dithieno[3,2‐b:2′,3′‐d]thiophene‐based low‐bandgap polymers are synthesized by a Suzuki–Miyaura coupling reaction or by direct arylation polycondensation. The polymers present a high molecular weight (26–32 kDa) and narrow polydiversity (1.3–1.7). With a highest occupied molecular orbital (HOMO) energy level around ?5.20 eV, these polymers exhibit a narrow bandgap of 1.75–1.87 eV. All the polymers display strong absorption in the range of 350–700 nm. Bulk‐heterojunction (BHJ) solar cells are further fabricated by blending the as‐prepared polymer with (6,6)‐phenyl‐C61‐butyric acid methyl ester (PC61BM) at different weight ratios. The best devices contribute a power conversion efficiency (PCE) of 0.73% under AM 1.5 (100 mW cm?2).
In this paper, the acid–base bifunctional microporous organic nanotube networks (MONNs–SO3H–NH2) are successfully prepared by combination of hyper‐crosslinking core–shell bottlebrush copolymers and a postfunctionalization strategy. Based on the large surface area, good multiporosity interconnectivity, and robust organic frameworks, the acid–base bifunctional MONNs catalyst shows a high catalytic activity and excellent reusability for one‐pot cascade reactions.
Alternating copolymers of an oligopeptide (N3‐GVGV‐N3, where G: glycine; V: valine) and an oligothiophene (5,5′‐bis(ethynyl)‐3,3'‐dioctyltetrathiophene) are prepared by click chemistry. The experimental results discover that these copolymers exhibit strong molecular‐weight‐dependent self‐assembly behaviors. The copolymer P1 with the lowest weight‐average molecular weight ( = 7400 g mol?1), assembles into well‐ordered fibrous nanostructures. P3 ( = 16 980 g mol?1) assembles into nanoballs. P2, which has the medium between P1 and P3, ( = 14 800 g mol?1), exhibits more‐complicated self‐assembly behaviors, more like a transition state between the other two. All of the results suggest the self‐assembly ability of these oligopeptide segments might be the major reason for the nano‐structure evolution.
mPEG‐aldehydes and activated mPEG‐carboxylic acids on which the polymer and the reactive functional group are separated by aliphatic chains of different lengths, are well known reagents of widespread application in PEGylation technology. The syntheses of these functional polymers are not easy and usually the preparation of each of these compounds requires a very specific set of reagents and experimental conditions. In fact, a general method for their preparation is, still nowadays, unavailable. In this work a simple synthetic method is developed for preparation of mPEG‐aldehydes and carboxylic acids with excellent yields. The key step of the method involves a substitution reaction of mPEG‐mesylate with mono‐alkoxides of symmetrical diols to afford hydroxyl‐terminated polymers, which are converted to the aldehydes and acids by mild oxidation reactions.
Inspired by using the condensed tannins as coinitiator and crosslinker to prepare stretchable hydrogel (TIC‐gel) and by tannins' ability to prepare tannins‐reduced graphene oxide (TGO) at 80 °C, this paper designs a simple and effective method with a thermal treatment process for the mixture of tannin and graphene oxide (GO) to prepare super extensible TGO composite TIC‐gel (TGO‐gel). After the thermal treatment process, graphene oxide is reduced by tannin and its surface becomes orderly which leads to strong π–π stacking interaction between tannins and graphene sheets. By this way, the interaction between graphene sheets and polymer chains is improved. As a result, these composite hydrogels have high tensile strength (0.5–1.2 MPa) and extremely high elongations (3100–4800%) which are much higher than those of GO composites TIC‐gel (TA/GO‐gel) without thermal‐treated process and those of normal graphene composite hydrogel.
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