Electron‐acceptor units, combined with bithiophene substituted with flexible chains end‐functionalized with cross‐linkable moieties, provide soluble donor‐acceptor‐donor (DAD) π‐conjugated oligomer‐type molecules with cross‐linking ability and broad absorption in the visible spectrum. A study on the cross‐linking conditions of the new oligomers to yield insoluble polymer networks is presented, including conditions for obtaining polymer films over poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate‐covered substrates. The combination of the DAD molecular design and cross‐linking functionality opens prospects for applications in solution‐processed small‐molecule solar cells with morphologically‐stable organic layers.
The synthesis of high‐aspect‐ratio (AR) CdSe (NRs) nanorods and their ordered assembly over large areas are reported. Long‐range ordering of hexagonal arrays of high‐AR NRs is achieved by a combination of controlled solvent evaporation and the use of an applied electric field. Vertically oriented assemblies of CdSe NRs functionalized with oligo‐ and polythiophene are also obtained. Aligned and oriented polythiophene CdSe NRs have potential applications in organic–inorganic hybrid bulk‐heterojunction photovoltaic devices.
Using linear side chains for conjugated polymers is hindered by their limited solubility in common organic solvents, creating problems during purification and processing, whereas branched alkyl chains generally preclude interchain interdigitation because their bulkiness usually hinders interchain interactions. To compensate the adverse effects from each side chain, it is shown that replacing commonly employed 2‐ethylhexyl (2EH) solubilizing groups with branched 5‐ethylnonyl (5EN) chains not only improves solution processability to PCDT‐BT polymer, but also induces an advantageous change in polymer self‐assembly and backbone orientation in thin films that correlates with an increase in transistor performance.
Polystyrene (PS) film containing 1,4‐bisbenzil is efficiently crosslinked in two steps. In the first step, visible light (λ > 400 nm) causes molecular oxygen to insert between two carbonyl groups of one of the 1,2‐dicarbonyl groups. The peroxide is subsequently decomposed by absorption of another photon, forming acyloxy radicals, which add to the aromatic ring of the PS chain. The remaining 1,2‐dicarbonyl group is then photoperoxidized to form PS with pendant benzoyl peroxide moieties. In the second step, pendant benzoyl peroxide groups are decomposed thermally to form acyloxy macroradicals responsible for the crosslinking. Crosslinking proceeds simultaneously with degradation. Finally, the gel content in the film may exceed 80 wt%.
Water uptake is measured for ≈100 nm and ≈60 μm thick quaternized comb‐shaped poly(2,6‐dimethyl‐1,4‐phenylene oxide) (QA‐PPO) polymers with 0, 6, 10, and 16 carbon alkyl side chains to probe the influence of thin film confinement. The thin film modulus is measured to probe the effect of side chain length on the thin film modulus and the ensuing water uptake. Increasing the alkyl side chain length results in increased modulus, decreased swelling strain, and decreased water uptake due to the lengthening of the n‐alkyl side chains. Confinement effects on the comb‐shaped QA‐PPO water uptake are expressed through increased water uptake in the thin film compared to the bulk membrane. The thin films also exhibit a different water sorption mechanism consistent with two types of water compared to the bulk membranes that exhibit a single type of water sorption.
Nonionic aliphatic polymers containing ester and sulfonyl moieties, [poly(ester‐sulfones)s] were found to undergo anode‐selective electrophoresis under electrophoretic deposition conditions. Herein are reported the syntheses of unsaturated nonionic polyesters containing sulfide linkages and double bonds on the polymer backbone via acyclic diene metathesis polymerization using a Grubbs' catalyst. Subsequent oxone oxidation was carried out, affording the corresponding poly(ester‐sulfone), followed by electrophoretic deposition of the unsaturated poly(ester‐sulfone) onto stainless steel. Subsequent UV‐irradiation cured the deposited film, improving the peeling strength of the coating.
A narrow‐bandgap conjugated polymer, PFDTBTzQ‐2OC1, is prepared by alternating [1,2,3]triazolo[4,5‐g]quinoxaline and 9,9‐didodecyl‐fluorene. With a bandgap of 1.63 eV, this polymer has wide absorption ranging from 300–760 nm in film. Bulk heterojunction solar cells fabricated by blending PFDTBTzQ‐2OC1 with [6,6]‐phenyl‐C71‐butyric acid methyl ester exhibit a maximum power conversion efficiency of 1.31%, with a short‐circuit current density of 1.98 mA cm–2, an open‐circuit voltage of 0.74 V, and a fill factor of 0.47.
Poly(2‐(3‐butenyl)‐2‐oxazoline)s (PBOX) with glucose‐S‐butyl (Glc) and perfluoroalkyl‐S‐butyl (F) side chains (three samples: Glc/F = 100/0, 0/100, and 88/12) are synthesized by ring‐opening polymerization of 2‐butenyl‐2‐oxazoline and thiol‐ene click photochemistry, and their thermal properties are analyzed by direct‐pyrolysis mass spectrometry. Significant changes in the thermal stability and thermal‐degradation products are observed depending on the structure of the side chain. The thermal degradation of PBOX‐Glc and PBOX‐F homopolymers starts with loss of side chains at relatively low temperatures and successive cleavage along the side and main chains follows. The stability of the glucose units of the PBOX‐Glc/F copolymer is significantly increased by the presence of perfluoroalkyl groups, attributable to OH···F hydrogen bonding interactions during pyrolysis.
Size exclusion chromatography coupled with light scattering (SEC/MALS), dynamic light scattering (DLS), steady‐state and time‐resolved fluorescence, as well as molecular dynamics (MD) simulations are used to study the behavior of several poly(ethylene glycol) (PEG)/α‐cyclodextrins (αCDs) polyrotaxanes (PRs) in solution. The number of CD units in any of the PRs studied is always smaller than that required to saturate the PEG chains. These PRs seem to aggregate in dimethyl sulfoxide (DMSO) solution. The presence of hairpins in the non‐saturated PRs contributes to diminishing their expected large dimensions. Intra‐ and intermolecular interactions and forces responsible for hairpins and aggregation are investigated.
Postfunctionalization is a key tool for the elaboration of hydrophobic surfaces. For that purpose, the elaboration of surfaces suitable for the Huisgen reaction allows for functionalization with various hydrophobic side chains. Here the synthesis of azido or alkyne monomers is reported to prepare platform surfaces suitable for click chemistry. The surface hydrophobicity and morphology are investigated. Superhydrophobic and parahydrophobic properties are obtained depending on the starting monomer and the molecule used for the postfunctionalization.
The inner walls of thin glass capillaries are coated with a reactive precursor coating that can be converted into different temperature‐ and light‐responsive coatings. The switching range of wettability can be determined by measuring the meniscus height of water inside these capillaries at different temperatures and upon UV‐light irradiation. In comparison with the sessile drop measurement, very accurate equilibrium contact angles are obtained by this method.
Comb‐like copolymers based on a polyolefin backbone of poly(10‐undecene‐1‐ol) (PUol) with poly(ε‐caprolactone) (PCL) side chains are synthesized in two steps. After synthesis of PUol by metallocene‐catalyzed polymerization, the side‐chain hydroxyl functionalities of this polar polyolefin are used as an initiator for the ring‐opening polymerization (ROP) of ε‐caprolactone (CL). In this context, copolymers with different lengths of PCL grafts are prepared. The chemical structure and the composition of the synthesized copolymers are characterized by 1H and 13C NMR spectroscopy. It is shown that the hydroxyl end groups of PUol act effectively as initiating sites for the CL ROP. Size‐exclusion chromatography (SEC) measurements confirm the absence of non‐attached PCL and the expected increase in molar mass after grafting. The thermal and decomposition behaviors are investigated by DSC and thermogravimetric analysis (TGA). The effect of the length of the PCL grafts on the crystallization behavior of the comb‐like copolymers is investigated by DSC and wide‐angle X‐ray scattering (WAXS).
Polysulfone‐based membranes with excellent chemical resistance and a wet thickness up to 200 μm are obtained via UV curing of unmodified polymers after careful tuning of the photoinitiating system and the crosslinker structure. Combinations of photoinitiator and crosslinker are studied in depth, followed by a characterization of the formed macromolecular structure. The performance of the resulting membranes is then evaluated through long‐term immersion in solvents. Classical depth‐curing acyl phosphine oxide‐based photoinitiators in combination with a pentaacrylate crosslinker are found to be the optimal system.
Step‐growth PEG‐based microgels are produced via three liquid–liquid two‐phase suspension polymerization systems: i) hexane with surfactants Span80/Tween80; ii) mineral oil with surfactant Pluronic F‐68; and iii) surfactant‐free dextran‐rich aqueous solution. Following short vortexing to create monomer droplets, microgels are polymerized by a visible‐light‐initiated thiol‐ene photo‐click reaction using eosin‐Y as the only photoinitiator. The use of hexane as the organic phase and Span‐80/Tween‐80 as the surfactants leads to PEG microgels with entrapped solvent droplets that dissolve rapidly with time. Microgels polymerized in mineral oil with surfactant Pluronic F‐68 contain no entrapped droplets and are more uniform with smaller sizes. Visible‐light‐cured step‐growth thiol‐ene microgels can also be photopolymerized in a surfactant‐free aqueous two‐phase system. The sizes of the microgels formed in aqueous phase are one order of magnitude smaller than those formed in organic solvent. Dual‐layer microgels are also prepared using two‐step thiol‐ene reactions.
A synthesis route to siloxane‐based thermoplastic elastomers (TPE) with functional hard blocks is described. The photophysical functionality is provided by oligothiophenes, namely terthiophene and bithiophene. Polyaddition of isocyanate‐bearing thiophenes and amine‐terminated siloxanes yields polymers incorporating a bisurea structure motive. Phase separation and strong hydrogen bonds provide ordering of the thiophenes, which is shown by wide‐angle X‐ray scattering (WAXS) and X‐ray powder diffraction (XRD). Fluorescence measurements reveal a strong red shift of emission of polymer films compared with polymer solutions, thus confirming the existence of hard block segments with an enhanced π system and higher charge–carrier mobility. Tuning of the optical band gap by different polymer compositions and various post polymerization treatments is demonstrated.
Synthesis of a multiblock copolymer composed of cis‐1,4‐polybutadiene (PBd) segments and poly(3‐buten‐1‐ol) segments is performed via successive hydroboration and oxidation of cis‐1,4/syn‐1,2‐multiblock PBd. The ratio of functionalization can be controlled by changing the amount of the borane reagent. The obtained polymer shows two distinctive glass‐transition temperatures, which correspond to the cis‐1,4‐PBd block and the poly(3‐buten‐1‐ol) block. These thermal properties clearly show that the functionalization of the PBd proceeds keeping the elastic property derived from cis‐1,4 segment.
Synthesis of a novel multifunctional block based on asymmetrically substituted pentaerythritol, succinic acid, and tetraethylene glycol is reported. The proposed reaction conditions allow selective preparation of the product in high overall yield. The block can be used in the assembly of biocompatible polyester‐co‐polyether (PEPE) hyperbranched macromolecules, which allows the product to be considered as a promising intermediate for the development of new biomedical dendrimers. As an example, the use of the “block by block” strategy is employed to obtain a second‐generation dendron. It is shown that the approach is much more efficient than the pathway of step‐by‐step grafting of separate molecular fragments.
A layer‐by‐layer approach is used to anchor small gold nanoparticles onto organic nanotubes resulting from the self‐assembly and polymerization of diacetylene‐containing nitrilotriacetic amphiphiles. The obtained nanotube–gold hybrid is used as a catalyst for the aerobic oxidation of various silanes. With minimal gold loading (0.05 mol%), all substrates are converted into the corresponding silanols with hydrogen gas as the only by‐product. The catalyst operates under mild conditions and can be easily recycled, losing neither activity nor selectivity.
Phospholipids, dendrimers, and polymers are each able to assemble to form vesicles, but each has limitations such as leakiness and multistep syntheses. A new class of versatile amphiphilic block copolymers is reported containing hyperbranched polyglycerol (HPG) and polystyrene (PS) units. These compounds self‐assemble into polymersomes (HPGsomes). Under solvent exchange methods, amphiphilic polystyrene‐HPG diblock (PS‐b‐HPG) structures are self‐assembled and characterized by transmission electron microscopy. The assemblies are robust up to 95 °C in polar, protic solvents, and encapsulate dyes with minimal release. Polymersomes are typically assembled from linear amphiphilic polymers; however, it is shown that combining linear and hyperbranched polymers is a feasible strategy to encapsulation.
Functional hybrid materials with optically active metal‐ligand moieties embedded within a polymer matrix have a great potential in (bio)materials science, including applications in light‐emitting diode devices. Here, a simple strategy is reported to incorporate terpyridine derivatives into the side chains of elastin‐like polymers (ELPs). The further binding of trivalent lanthanide ions with the terpyridine ligands generates an array of photoluminescence ranging from the visible to the near‐infrared regions. As thin films, these ELP‐based optical materials also exhibit distinct morphologies that depend upon the temperature of the aqueous solutions from which the hybrid polymers are spin coated or drop cast.
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