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.
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).
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%.
The self‐assembly and structure formation in binary blends of asymmetric polystyrene‐block‐poly(4‐vinylpyridine) diblock copolymers in different solvent systems and the bulk morphology of the blend films are studied by using dynamic light scattering, small‐angle X‐ray scattering, and transmission electron microscopy. In dilute solutions, the chains of pure diblock copolymers or binary blends of diblock copolymers having similar or different molecular weights remain as unimers, form common micelles in selective solvents or form unimers in coexistence with micelles in slightly selective solvents or solvent mixtures. The blends show mixing of the chemically similar blocks in the blend films and solutions at high concentrations. A single‐phase with common spherical morphology is formed in the blend films similar with the morphology of the individual components in the pure state. The characteristic length scale of the blends depends on the number average molecular weight following the typical scaling behavior of a strongly segregated block copolymer.
Cyclodextrin (CD)‐based host–guest interactions are one of the important supramolecular interactions and have been playing significant role in the design of self‐healing materials due to high selectivity and dynamic equilibrium. However, a deeper understanding of the self‐healing mechanism is still rare, although self‐healing materials based on CD–guest interactions have many advantages. This study provides a first step for the fundamental understanding of the influence factors on self‐healing behavior of materials containing CD–guest complexes. It is found that the healing motifs are CD–guest interactions. Sufficient polymer chains mobility, a small amount of water, and high inclusion constant (K ) of host–guest interactions are also essential to the self‐healing process. The threshold of K value is around 102 M−1.
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.
This paper designs and synthesizes a novel amphiphilic fluorinated block copolymer, composed of oligo ethylene glycol methyl ether methacrylate, 2‐(N ,N‐dimethylamino)ethyl methacrylate, and developing 2‐((2‐methacryloyloxy ethyl) disulfanyl) ethyl 3,5‐bis(trifluoromethyl) benzoate, by reversible addition–fragmentation chain transfer polymerization. This amphiphilic block copolymer can self‐assemble with hydrophobic lanthanide‐based upconversion nanoparticles to form hybrid colloidal nanoclusters. The obtained nanoclusters exhibit not only good water‐dispersibility, high biocompatibility, and strong stability in biological milieu, but excellent pH/redox‐dual‐responsive release in vitro behavior for doxorubicin (DOX). And the DOX‐loaded nanoclusters have much better therapeutic effect than free DOX and can be uptaken by MCF‐7 cells with evident upconversion luminescence signal for intracellular imaging.
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.
Two silane compounds, i.e., ((chloromethyl)phenylethyl)trimethoxysilane (Ph‐Si) and 3‐chloropropyltriethoxysilane (Pr‐Si), are employed as covalent crosslinkers to fabricate high temperature proton exchange membranes based on polybenzimidazole (PBI) in order to better understand the correlation between the structure and the property of the crosslinked membranes. All the crosslinked PBI membranes display longer morphology durability over the neat PBI membrane toward the radical oxidation. The crosslinked membranes with the crosslinker containing a rigid group of phenylene (PBI‐Ph) show superior acid doping level, high conductivity, and excellent mechanical strength simultaneously, comparing to those with the crosslinker having a flexible alkyl chain (PBI‐Pr) and the pristine PBI based membrane. The technical feasibility for using as high temperature proton exchange membranes is demonstrated by the acid doped crosslinked PBI‐Ph membranes via fuel cell tests.
In this study, the self‐assembly of ionic porphyrins and polyelectrolytes in dependence on the polyelectrolyte architecture and molecular mass is investigated systematically. The systems consist of tetravalent anionic meso‐tetrakis(4‐sulfonatophenyl)‐porphyrin (TPPS), which is combined with different positively charged macroions: poly(amidoamine) dendrimer of generation 4, linear polylysine of different molecular masses, poly(diallyldimethylammonium chloride), and a cylindrical poly‐l ‐lysine brush. Light scattering reveals defined supramolecular assemblies with hydrodynamic radii between R H = 30 nm and R H = 180 nm. Further, size and shape of TPPS–polyelectrolyte assemblies are substantially affected by the polyelectrolyte architecture but less by the molecular mass of the polyelectrolyte. ζ‐potential measurements detect an assembly charge corresponding to the excess component that is responsible for the aggregate being stable in solution.
Synthesis of complex macromolecular architectures exhibiting no chain ends such as flower‐like polymers is still of interest in the aim of investigating their physicochemical properties. For this purpose, poly(3,4‐dimethyl maleic imidoethyl acrylate)‐block‐polybutadiene‐block‐poly(3,4‐dimethyl maleic imidoethyl acrylate) triblock copolymer is synthesized in a convergent manner using a combination of living polymerization (anionic polymerization), reversible deactivation radical polymerization, and click chemistry. This copolymer is self‐assembled in a selective solvent (heptane/THF mixture) of the polybutadiene block leading to the formation of flower‐like micelles in thermodynamic equilibrium in dilute solution. These resulting transient architectures are fixed by covalently crosslinking the micelles core by inducing [2+2] cyclodimerization of the 3,4‐dimethyl maleic imidoethyl groups borne by the short solvophobic blocks under UV irradiation. Single flowers are isolated from residual non‐crosslinked chains by semipreparative size exclusion chromatography (SEC) and characterized by 1H NMR, SEC, dynamic light scattering (DLS), and transmission electron microscopy (TEM).
Novel nitrogen‐doped graphene nanoribbons (GNR‐Ns) are synthesized by the coupling reaction between a pyrazine (or benzene) derivative and naphthalene followed by cyclodehydrogenation. The amount of nitrogen doping in the GNR‐Ns is controlled by changing the monomer feed ratio of pyrazine to benzene for polymerization. The electron mobility of the GNR‐Ns increases while the hole mobility decreases, as the amount of nitrogen doping in the GNR increases, indicating that the charge‐transport behavior of GNRs is changed from ambipolar to an n‐type semiconductor. The threshold voltage of the GNR‐Ns also shifts from 20 to ?6 V as the amount of nitrogen doping increases.
Poly(phenylene ethynylene)‐alt‐poly(phenylene vinylene)s (PPE‐PPVs) with various thiophene units (thiophene, bithiophene, and 3,4‐ethylenedioxythiophene) at the X position, with the general backbone design (Ph? C?C? X ? C?C? Ph? CH?CH? Ph? CH?CH? ), bearing identical solubilizing side chains at the phenylene rings of the polymers, are synthesized to study the effect of this structural alteration on the properties such as the photophysics, the electrochemical properties, the charge‐carrier mobility, and the morphology of the materials and its impact on their photovoltaic performance. The polymers are obtained in good yields with reasonable molecular weights and show solubility in ordinary organic solvents required for solution‐processing applications. The polymer with a basic thiophene ring at the X positions shows the highest open‐circuit voltage (VOC of 930 mV) and the polymer with a bithiophene unit at the X position shows the highest short‐circuit current density and charge‐carrier mobility, whereas the polymer with 3,4‐ethylenedioxythiophene shows the lowest photovoltaic performance.
A great extent of past work has focused on the development of stimuli‐responsive hydrogels that can primarily achieve a two‐state transition, such as sol‐gel translation. In the current work, a reversible hydrogel with three‐state transition is designed. The three transformations between original, oxidized, and reduced states are achieved via controlling the external stimuli conditions. Hydrogels in their original state possess a weak self‐healing property and negligible fluidity. The oxidized state hydrogel can keep molding, however, losing the self‐healing property. In contrast, the reduced state hydrogels exhibit strong self‐healing property. Moreover, the hydrogel becomes injectable subsequent to dithiothreitol addition. Thereafter, under UV‐light irradiation or NaClO immersion, the hydrogels can be remolded to any desired shapes. These properties provide novel designing strategies and potential applications for smart and reusable materials.
In the context of novel sustainable and structurally significant building blocks for polymer science, the synthetic routes are described to new oligoamide structures based on the terpenoid ketone (?)‐menthone. The basic concept is an oxime formation of this cyclic ketone followed by the Beckmann rearrangement, resulting in the corresponding lactams. These lactams are polymerized under anionic or acid‐catalyzed conditions (ring‐opening polymerization (ROP)) to give alkyl‐substituted and stereocenter containing oligoamide scaffolds that are assumed to be suitable for further copolymerizations and modifications and thus for a wide range of different applications. The regio‐ and the stereochemistry of the formed oximes and lactams as well as their impact on the polymerization behavior is discussed.
Stationary and time‐resolved electron spin resonance spectroscopy measurements are employed to investigate the kinetics of the surface‐initiated reversible addition fragmentation chain transfer (RAFT) polymerization of n‐butyl acrylate from silica nanoparticles using both R‐ and Z‐group‐attached trithiocarbonates as RAFT agents. The obtained kinetic parameters reveal that the addition rate coefficient in the main equilibrium of RAFT graft polymerizations is significantly smaller than the one for comparable RAFT polymerizations in solution phase, as translational diffusion of surface‐attached molecules is limited. In comparison to the R‐group approach, the equilibrium constants of the Z‐group approach are about one to two orders of magnitude smaller due to a stronger shielding of the RAFT moieties.
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.
Herein, a novel coil‐rod‐coil triblock copolymer with the coil blocks composed of poly(ethylene glycol) methyl ether and the rigid midterm block alternatively connected with isophorone diisocyanate and isophorone diamine is developed. The triblock copolymer can self‐assemble into ellipsoidal micelles in 1‐methyl‐2‐pyrrolidinone. After the addition of a second coil‐selective solvent (water) to the micellar solutions, these ellipsoidal micelles can further transform into chain‐like nanostructures. The self‐assembly behavior is highly influenced by the additional order of the solvents, which is considerably due to the impacts of the hydrogen‐bonding urea groups and rigid motifs. The transition of the ellipsoidal micelles to chain‐like nanostructures is governed by the water molar fractions. The sizes of the chain‐like nanostructures increase first and then decrease with the growth of the water molar fractions in the mixed solutions.
High‐temperature thermal gradient interaction chromatography (HT‐TGIC) fractionates polyolefins based on an adsorption–desorption mechanism. Several factors influence the shape and position of HT‐TGIC chromatograms, notably polymer microstructure, analytical conditions, and, to a lesser extent, solvent type. This article investigates the joint influence of chain length and comonomer content of a series of polyethylene and ethylene/1‐octene copolymers having similar 1‐octene fractions (0–13 mol%) and a wide range of molecular weights on HT‐TGIC fractionation. For each series of copolymers having similar 1‐octene fraction, the elution peak temperature decreases exponentially and the profiles become increasingly broader below a critical number average chain length value. The authors use Monte Carlo simulation and Stockmayer distribution to explain the observed behavior, finding that no simple correlation exists between ethylene sequences in the copolymers and peak elution temperature, but that there is strong evidence that axial dispersion is responsible for symmetrical broadening of the HT‐TGIC profiles. The authors also study the HT‐TGIC of binary blends, finding that components with similar 1‐octene contents and dissimilar chain lengths tend to increase co‐adsorption/co‐desorption effects.
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.
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