New Carbazole‐Based Hyperbranched Conjugated Polymer with Good Hole‐Transporting Properties

A copper‐catalyzed Ullmann C–N coupling reaction was used for the preparation of a new carbazole‐based HPU in good yield with a high molecular weight through a facile “AB₂ + A₂ + B₂”‐type approach. The HPU exhibited good solubility, high thermal stability with a T_g of 196 °C, as well as a suitable HOMO level for good hole injection and transporting properties. A two‐layer OLED device, using HPU as hole‐transporting layer (HTL) and Alq₃ as the light‐emitting layer, was fabricated to investigate the hole‐transporting properties of HPU. The luminance efficiency reached 1.14 cd · A^?1 at the maximum current density of 1 240 mA · cm^?2, while the maximum luminance efficiency was 1.65 cd · A^?1, indicating the high morphological and thermal stability of HPU.

     

Flower‐Like Multicompartment Micelles with Janus‐Core Self‐Assembled from Fluorocarbon‐Terminated Pluronics

Multicompartment micelles (MCMs), whose cores have at least two compartments, show potential applications in various areas, but the synthesis of polymers for preparing MCMs is usually tedious and time‐consuming. In this work, two well‐defined telechelic fluorocarbon‐terminated triblock copolymers, F₈‐PEO₁₀₀‐PPO₆₅‐PEO₁₀₀‐F₈ (F₈‐F127‐F₈) and F₈‐PEO₁₃₂‐PPO₅₀‐PEO₁₃₂‐F₈ (F₈‐F108‐F₈), are synthesized via a single‐step coupling reaction of Pluronics F127 or F108 with perfluoro‐1‐octanesulfonyl fluoride and characterized by Fourier‐transform infrared and NMR spectroscopies, as well as gel permeation chromatography and surface tensiometry. Both of these fluorocarbon‐terminated Pluronics can self‐assemble into spherical MCMs with Janus‐core in aqueous solution, as evidenced by transmission electron microscopy imaging. Since the lipophilic block (PPO) and fluorophilic segments (F₈) are separated by the hydrophilic blocks (PEO), these fluorocarbon‐terminated Pluronics will loop to give rise to flower‐like MCMs, and the calculations based on thermodynamics and dynamics support the formation of such unique aggregates. A “pre‐self‐assembly” mechanism is proposed to explain the formation process of flower‐like MCMs with Janus‐core prepared by these telechelic fluorocarbon‐terminated triblock copolymers.     

2D Self‐Assembly of an Amido‐Ended Hydrophilic Hyperbranched Polyester by Copper Ion Induction

The self‐assembly of an amido‐ended hydrophilic hyperbranched polyester (HTDA‐2) into ordered, compact, 2D, tree‐like structures with a diameter of over 500 μm and a trunk‐width of about 3–5 μm by the induction effect of cupric ions is presented. Influencing factors on the morphology of the self‐assemblies, including temperature, time, solvents, concentration, and humidity, investigated by polarizing optical microscopy (POM) and scanning electron microscopy (SEM), are discussed. The self‐assembly mechanism is analyzed by X‐ray photoelectron spectroscopy (XPS), X‐ray diffraction (XRD), SEM, and Fourier transform IR (FTIR) spectroscopy. A dimension (D_f) of about 1.50 for the perfect fractal behavior and the crystal behavior of the self‐assemblies are determined.

     

Backbone‐Thermoresponsive Hyperbranched Polyglycerol by Random Copolymerization of Glycidol and 3‐Methyl‐3‐(hydroxymethyl)oxetane

The hyperbranched polyglycerol analog, hyperbranched poly[glycerol‐co‐3‐methyl‐3‐(hydroxymethyl)oxetane] [HP(G‐co‐M)], was synthesized in one‐step by random copolymerization of glycidol and 3‐methyl‐3‐(hydroxymethyl)oxetane (MHO). The obtained polymer exhibited a thermoresponsive behavior in an aqueous solution, and the corresponding lower critical solution temperature (LCST) could be readily adjusted by changing the feed ratio of glycidol to MHO. The MTT assay against COS‐7 cells demonstrated that HP(G‐co‐M) had low cytotoxicity. Moreover, the existence of numerous hydroxyl terminals of HP(G‐co‐M) facilitated their further modification and functionalization. All of these characteristics suggest that this novel backbone‐thermoresponsive hyperbranched polyglycerol is a promising functional material for biomedical applications.

     

Water‐Induced Transitions from Ellipsoidal Micelles to Chain‐Like Nanostructures Self‐Assembled by the Coil‐Rod‐Coil Block Copolymer Based on Hydrogen‐Bonding Urea Groups

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.

     

Ultrasound‐Induced Disruption of Amphiphilic Block Copolymer Micelles

Ultrasound‐induced disruption of PEO‐b‐PTHPMA, PEO‐b‐PIBMA, PEO‐b‐PTHFEMA, and PEO‐b‐PMMA block copolymer micelles in aqueous solution was investigated. Fluorescence change of loaded NR, DLS, IR, AFM, and SEM show that those micelles could be disrupted differently by 1.1 MHz high‐intensity focused ultrasound beams. The micelles of PEO‐b‐PIBMA and PEO‐b‐PTHPMA appear to be more sensitive to ultrasound irradiation, resulting in a more severe micellar disruption, and IR spectra show evidence of ultrasound‐induced chemical reactions, most likely hydrolysis. PEO‐b‐PMMA appear to resist HIFU irradiation better, and IR analysis found no evidence of chemical reactions. This study provides new evidence for the prospect of ultrasound‐responsive BCP micelles for controlled delivery applications.

     

High Refractive Index Hyperbranched Polymers Prepared by Two Naphthalene‐Bearing Monomers via Thiol‐Yne Reaction

High refractive index (HRI) materials play an important role in optic‐electronic devices. In this study, two compounds with high content of naphthalene groups, 1,5‐dithiolnaphthalene and 1,3,5‐tris(naphthalyl–ethylnyl) benzene, are selected as “A₂” and “B₃” monomers, respectively to prepare hyperbranched HRI polymers. Metal‐free radical‐initiated “A₂ + B₃” thiol‐yne polyaddition is conducted successfully at different monomer molar ratios even for those sterically demanding molecules being able to adjust the molar mass as well as RI. Polymers with refractive index up to 1.79 at 589.7 nm are obtained, which are among the highest RI values so far reported for pure polymer‐based materials. The high RI, based on the high molar refraction of naphthalene group, metal‐free and easy one‐pot synthesis, high transparency in the visible area, good thermal stability, good solubility, and easy processability into thin films, make these polymers excellent candidates for optic‐electronic applications.

     

Synthesis of Hyperbranched Polymers via Metal‐Free ATRP in Solution and Microemulsion

Atom transfer radical polymerization (ATRP), as one of the most successful controlled radical polymerization techniques, has been broadly used by polymer chemists and nonspecialists for synthesis of various functional materials, although the use of copper as traditional catalyst often results in undesired color or properties. The first homopolymerization of an initiable monomer, that is, inimer, is reported via metal‐free ATRP using 10‐phenylphenothiazine (Ph‐PTH) as photocatalyst in both solution and microemulsion media. Although polymerizations of inimers in both media can be carried out, only the microemulsion polymerization of methacrylate‐based inimer 1 effectively confines the random bimolecular reaction within each segregated latex and produces hyperbranched polymers with high molecular weight and low polydispersity. Several experimental parameters in the microemulsion polymerization of inimer 1 are subsequently studied, including the Ph‐PTH amount, the solids content of microemulsion, and the light source of irradiation. The results not only provide an effective method to tune the structure and molecular weights of hyperbranched polymers in confined‐space polymerization, but also expand the toolbox of using metal‐free ATRP method for synthesizing highly branched polymers in controlled manner.     

Disulfide‐Containing Hyperbranched Polyethylenimine Derivatives via Click Chemistry for Nonviral Gene Delivery

Reducible disulfide‐containing hyperbranched PEI‐SS‐HP was synthesized via click chemistry and evaluated as nonviral gene carrier. The structure of the polymers was confirmed by ¹H NMR and FTIR. It was shown that the PEI‐SS‐HP was able to bind plasmid DNA to positively charged nanoparticles. The reduction sensitivity of the PEI‐SS‐HP was confirmed by gel retardation assay in the presence of DTT mimicking an intracellular reductive environment. In vitro experiments revealed that the reducible PEI‐SS‐HP not only had much lower cytotoxicity, but also posed superior transfection activity as compared to non‐degradable 25‐kDa PEI. The results indicate that a reducibly degradable PEI‐SS‐HP can be a promising gene vector.

     

pH‐Responsive Micelles Based on Amphiphilic Block Copolymers Bearing Ortho Ester Pendants as Potential Drug Carriers

Amphiphilic block copolymers (PEG‐b‐PEYM) bearing acid‐labile ortho ester pendant chains were synthesized by atom transfer radical polymerization, and the effect of chain‐length of the ortho‐ester‐bearing PEYM block on micelle properties was investigated. The length of the PEYM block affected the critical micelle concentration and pH‐dependent average particle size but not the kinetics of side‐chain hydrolysis. A hydrophobic dye, Nile red, was loaded in the micelles. Both the loading content and the size of the loaded micelles were influenced by the length of the PEYM block, whereas the release kinetics of Nile red was not. Provided that these acid‐labile micelles are completely cell compatible, they are potentially useful bio‐responsive nanocarriers for enhancing the efficacy of hydrophobic drugs.

     

Block Copolymer Micelles with an Intermediate Star‐/Flower‐Like Structure Studied by 1H NMR Relaxometry

¹H NMR relaxation is used to study the self‐assembly of a double thermoresponsive diblock copolymer in dilute aqueous solution. Above the first transition temperature, at which aggregation into micellar structures is observed, the trimethylsilyl (TMS)‐labeled end group attached to the shell‐forming block shows a biphasic T₂ relaxation. The slow contribution reflects the TMS groups located at the periphery of the hydrophilic shell, in agreement with a star‐like micelle. The fast T₂ contribution corresponds to the TMS groups, which fold back toward the hydrophobic core, reflecting a flower‐like micelle. These results confirm the formation of block copolymer micelles of an intermediate nature (i.e., of partial flower‐like and star‐like character), in which a part of the TMS end groups folds back to the core due to hydrophobic interactions.

     

Hydrophilicity Tunable Hyperbranched Polymers by Visible Light Induced Self‐Condensing Vinyl Polymerization

A facile and efficient route for synthesizing hydrophilicity tunable hyperbranched polymers is described. The method is based on the visible light induced self‐condensing vinyl copolymerization of tert‐butyl acrylate (tBA) and 2‐(2‐bromoisobutryloxy)ethyl methacrylate (BIBEM) as monomer and inimer, respectively, in the presence of dimanganese decacarbonyl (Mn₂(CO)₁₀). Subsequently, the hydrophlicity of the resulting hydrophobic hyperbranched polymers is tuned by hydrolysis of the tert‐butyl ester moieties of the copolymer. The effect of inimer concentration and irradiation time on the branching density and hydrophilicity is evaluated. The precursor and hydrolyzed hyperbranched polymers are characterized by ¹H NMR, GPC, FT‐IR, and contact angle measurements.     

Tannic Acid‐Inspired Star‐Like Macromolecules via Temporally Controlled Multi‐Step Potential Electrolysis

Inspired by tea stains, a plant polyphenolic‐based macroinitiator is prepared for the first time by partial modification of tannic acid (TA) with 2‐bromoisobutyryl bromide. In accordance with the “grafting from” methodology, a naturally occurring star‐like polymer with a polar gallotannin core and a hydrophobic poly(n‐butyl acrylate) side arms is synthesized via a simplified electrochemically mediated ATRP (seATRP), utilizing multiple‐step potential electrolysis. To investigate the kinetics of the electrochemical catalytic process triggered by reduction of Cu(II) or Fe(III) catalytic complex in the presence of the multifunctional initiator, cyclic voltammetry measurements are conducted. The naturally derived tannin macromolecule shows narrow MWDs (? = 1.57). Moreover, solvolysis of the star polymer to cleave the side arms and characterize them indicates that all chains grow to the same length (homopolymers with M_w/M_n <1.17), which confirms the well‐controlled seATRP. The structure of the obtained TA‐based systems is characterized microscopically (AFM) and spectroscopically (¹H NMR, FT‐IR). Atomic force microscopy measurements precisely determine the diameters of the obtained star polymers (19.7 ± 3.3 nm). These new star polymers may find biomedical applications as drug delivery systems and antifouling or antimicrobial coatings.     

One‐Step Approach for the Preparation of Organic‐Inorganic Janus‐Like Particles by Alkalization of Polystyrene‐block‐Poly(2‐vinylpyridine)/FeCl3 Complex Micelles

A novel approach to organic‐inorganic Janus‐like particles based on the alkalization process of polystyrene‐block‐poly(2‐vinylpyridine) (PS‐b‐P2VP) micelles containing FeCl₃ precursors in the P2VP cores in toluene is presented. It is found that by addition of a small amount of NaOH solution to a solution of the spherical PS‐b‐P2VP/FeCl₃ micelles, organic‐inorganic Janus‐like particles with a produced α‐FeOOH domain on one side and PS‐b‐P2VP block copolymers on the other can be prepared. The Janus‐like nanoparticles obtained by this facile approach may have potential application in biomedical areas.     

Fiber‐Like Micelles from the Crystallization‐Driven Self‐Assembly of Poly(3‐heptylselenophene)‐block‐Polystyrene

The crystallization‐driven self‐assembly (CDSA) of crystalline‐coil polyselenophene diblock copolymers represents a facile approach to nanofibers with distinct optoelectronic properties relative to those of their polythiophene analogs. The synthesis of an asymmetric diblock copolymer with a crystallizable, π‐conjugated poly(3‐heptylselenophene) (P3C7Se) block and an amorphous polystyrene (PS) coblock is described. CDSA was performed in solvents selective for the PS block. Based on transmission electron microscopy (TEM) analysis, P3C7Se₁₈‐b‐PS₁₂₅ formed very long (up to 5 μm), highly aggregated nanofibers in n‐butyl acetate (nBuOAc) whereas shorter (ca. 500 nm) micelles of low polydispersity were obtained in cyclohexane. The micelle core widths in both solvents determined from TEM analysis (≈ 8 nm) were commensurate with fully‐extended P3C7Se₁₈ chains (estimated length = 7.1 nm). Atomic force microscopy (AFM) analysis provided characterization of the micelle cross‐section including the PS corona (overall micelle width ≈ 60 nm). The crystallinity of the micelle cores was probed by UV–vis and photoluminescence (PL) spectroscopy and wide‐angle X‐ray scattering (WAXS).     

New Thermo‐Sensitive Graft Copolymers Based on a Poly(N‐isopropylacrylamide) Backbone and Functional Polyoxazoline Grafts with Random and Diblock Structure

New thermo‐sensitive functionalized graft copolymers characterized by a poly(N‐isopropylacrylamide) backbone and grafts containing 2‐ethyl‐2‐oxazoline and 2‐(2‐methoxycarbonylethyl)‐2‐oxazoline units were synthesized. The conformation transition temperatures of the graft copolymers could be modified by variation of the molar composition in the side chain, by different side chain structure (random distribution of both oxazolines vs. diblock structure) and by hydrolysis of the methylester to the acid form. Graft copolymers with long functional oxazoline side chains allowed the stabilization of aggregates above the phase transition temperature of the backbone until the LCST of the side chain. The temperature window allowing for the formation of stable aggregates was widened with acid functions in the corona.

     

Photocatalytic Suzuki–Miyaura Coupling Reactions over Palladium Anchored on 8‐Hydroxyquinoline‐Based Polymers

Through a one‐pot Friedel–Crafts polymerization method, a series of 8‐hydroxyquinoline‐based polymers with excellent light capturing ability is synthesized to support palladium for light‐driven Suzuki–Miyaura reactions (SMRs). The results of X‐ray powder diffractometer and transmission electron microscopy analyses suggest that the 8‐hydroxyquinoline‐based polymers are amorphous in structure and irregular in morphology. According to the data of thermogravimetric analysis and Brunauer‐Emmett‐Teller gas absorption, they are thermally stable up to 340 °C and are large in specific surface area. With palladium anchored securely on the 8‐hydroxyquinoline units of the polymer skeleton, the obtained photocatalysts exhibit excellent activity and reusability in SMRs under blue‐light irradiation.     

Synthesis and Self‐Assembly of o‐Nitrobenzyl‐Based Amphiphilic Hybrid Polymer with Light and pH Dual Response

In this paper, novel light‐responsive polyhedral oligomeric silsesquioxane (POSS) end‐capped poly(o‐nitrobenzyl methacrylate) (POSS–PNBMA) are synthesized by the combination of atom transfer radical polymerization (ATRP) and click chemistry. After subsequent partial photocleavage of PNBMA yielding poly(methacrylic acid) (PMAA), pH‐ and light‐responsive random copolymer of POSS–P(NBMA‐co‐MAA) is obtained. The o‐nitrobenzyl‐based amphiphilic hybrid polymer can self‐assemble into spherical micelles in aqueous solution. Hydrophobic POSS and PNBMA segments aggregate into the inner core, and the hydrophilic PMAA chains tend to stretch from the core. The micellar morphology can be tuned by pH changes and UV irradiation. Light irradiation leads to the transformation of P(NBMA‐co‐MAA) into PMAA and to the reorganization of the assemblies, causing the release of encapsulated guest molecule Nile Red into water. This dual‐responsive polymer has a broad potential use in targeted drug delivery.

     

Studies on the Synthesis and Conductivity of a Novel Reactive Ladder‐Like Poly(β‐cyanoethylsilsesquioxane) and Poly[(β‐cyanoethylsilsesquioxane)‐co‐(β‐methylsilsesquioxane)]

Two novel reactive poly(β‐cyanoethylsilsesquioxane) ( CN‐T ) and poly[(β‐cyanoethylsilsesquioxane)‐co‐(β‐methylsilsesquioxane)] ( CN‐Me‐T ) have been synthesized successfully for the first time via stepwise coupling polymerization (SCP). A variety of characterization methods including FTIR, ¹H NMR, ²⁹Si NMR, X‐ray diffraction (XRD), differential scanning calorimetry (DSC) and vapor pressure osmometry (VPO) were combined to demonstrate that the structures of the title polymers possess ordered ladder‐like structures. As expected, the ionic conductivity of these polymers mixed homogeneously with lithium perchlorate reached 10^?6 S · cm^?1 at room temperature and obviously increased with the raise of temperature.

     

Synthesis and Solution Self‐Assembly of Polyisoprene‐block‐poly(ferrocenylmethylsilane): A Diblock Copolymer with an Atactic but Semicrystalline Core‐Forming Metalloblock

Polyisoprene‐block‐poly(ferrocenylmethylsilane) (PI‐b‐PFMS) copolymers, containing the atactic but semicrystalline PFMS block, have been prepared by sequential anionic polymerization of isoprene and methyl[1]silaferrocenophane. The reaction to form the metalloblock is not living in nature, but still enabled three block copolymers to be prepared (PI₃₅‐b‐PFMS₅, PI₂₀₀‐b‐PFMS₁₀, and PI₂₄₇‐b‐PFMS₂₃) with relative narrow molar mass distributions (polydispersity < 1.3). The self‐assembly of all three materials was studied in PI selective n‐alkanes and found to afford lenticular platelets, tapered cylindrical micelles, and regular cylinders, as the length of the PFMS block increased. PI₂₀₀‐b‐PFMS₁₀ micelles could be increased in length by self‐seeding a sample of short micelles at temperatures of 90 °C and above; however, this process also resulted in an increase in width. Addition of a solution of PI₂₄₇‐b‐PFMS₂₃ copolymer to preformed seed micelles also resulted in an increase in length, although growth is not linearly related to the amount of copolymer added beyond ≈600 nm.