Cross‐Linked Conjugated Polymers for Achieving Patterned Three‐Color and Blue Polymer Light‐Emitting Diodes with Multi‐Layer Structures

Reactions between the ethylene groups in the backbone of conjugated polymers under UV illumination and heat treatment result in the cross‐linking of the main polymer chains. The cross‐linking leads to two simultaneous results in the polymer: excellent solvent resistance and increased bandgap. Using this reaction, three‐color polymer light‐emitting diodes (PLEDs) with a multi‐layer structure can be easily realized by a dry photo‐pattern in an active‐gas‐free environment. Multi‐layer blue devices with dramatically enhanced efficiency can also be achieved conveniently.

     

Highly Thermal Stable Main‐Chain Nonlinear Optical Polyimide Based on Two‐Dimensional Carbazole Chromophores

Summary: A new NLO‐active lambda‐shaped main‐chain polyimide that comprises a two‐dimensional carbazole chromophore was synthesized. This polyimide exhibits high thermal and temporal stability. It can endure temperatures of up to 240 °C for a transient time and maintain a large SH signal at 100 °C for a long time because embedding the two‐dimensional chromophores into the polymer backbone effectively suppresses the randomization of the oriented dipole at high temperatures.

     

Supramolecular Assembly of Gold Nanoparticles Mediated by Polypseudorotaxane with Thiolated β‐Cyclodextrin

Summary: A water‐soluble gold nanoparticle aggregate 2 was prepared by chloroauric acid and a polypseudorotaxane 1 of mono‐6‐thio‐β‐cyclodextrin with poly(propylene glycol) bis(2‐aminopropyl ether) ( ≈ 2 000) in the presence of sodium borohydride in N,N‐dimethylformamide (DMF) solution. The investigative results indicated that the gold nanoparticle aggregate 2 might act as an efficient DNA‐cleavage reagent.

A typical TEM image of gold nanoparticle aggregate 2 .     

Ultra‐Fast RAFT‐HDA Click Conjugation: An Efficient Route to High Molecular Weight Block Copolymers

The use of the reversible addition fragmentation chain transfer—hetero Diels–Alder (RAFT‐HDA) click reaction for the modular construction of block copolymers is extended to the generation of high molecular weight materials. Cyclopentadienyl end‐functionalized polystyrene (PS‐Cp) prepared via both atom transfer radical polymerization (ATRP) and the RAFT process are conjugated to poly(isobornyl acrylate) (PiBoA) (also prepared via RAFT polymerization) to achieve well‐defined block copolymers with molecular weights ranging from 34 000 to over 100 000 g · mol⁻¹ and with small polydispersities (PDI < 1.2). The conjugation reactions proceeded in a very rapid fashion (less than 10 min in the majority of cases) under ambient conditions of temperature and atmosphere. The present study demonstrates—for the first time—that RAFT‐HDA click chemistry can provide access to high molecular weight block copolymers in a simple and straight‐forward fashion.

     

Synthesis and Characterization of β‐Cyclodextrin Based Functional Monomers and its Copolymers with N‐isopropylacrylamide

Two novel monovinyl β‐cyclodextrin (β‐CD) monomers are synthesized. Their chemical compositions are characterized by means of element analysis, NMR and FT‐IR spectroscopy. The results show that the synthesis techniques used are convenient and efficient. Using N‐isopropylacrylamide as a comonomer, two novel linear copolymers can also be synthesized.

Synthesis route of monovinyl β‐CD monomers.     

Synthesis and Characterization of a Block Copolymer Containing Regioregular Poly(3‐hexylthiophene) and Poly(γ‐benzyl‐L‐glutamate)

Poly(3‐hexylthiophene)‐b‐poly(γ‐benzyl‐L ‐glutamate) (P3HT‐b‐PBLG) rod–rod diblock copolymer was synthesized by a ring‐opening polymerization of γ‐benzyl‐L ‐glutamate‐N‐carboxyanhydride using a benzylamine‐terminated regioregular P3HT macroinitiator. The opto‐electronic properties of the diblock copolymer have been investigated. The P3HT precursor and the P3HT‐b‐PBLG have similar UV–Vis spectra both in solution and solid state, indicating that the presence of PBLG block does not decrease the effective conjugation length of the semiconducting polythiophene segment. The copolymer displays solvatochromic behavior in THF/water mixtures. The morphology of the diblock copolymer depends upon the solvent used for film casting and annealing results in morphological changes for both films deposited from chloroform and trichlorobenzene.

     

Electro‐active Polymer Actuator Based on Sulfonated Polyimide with Highly Conductive Silver Electrodes Via Self‐metallization

We report here a facile synthesis of high performance electro‐active polymer actuator based on a sulfonated polyimide with well‐defined silver electrodes via self‐metallization. The proposed method greatly reduces fabrication time and cost, and obviates a cation exchange process required in the fabrication of ionic polymer‐metal composite actuators. Also, the self‐metallized silver electrodes exhibit outstanding metal‐polymer adhesion with high conductivity, resulting in substantially larger tip displacements compared with Nafion‐based actuators.

     

In situ Synthesis of Magnetic Iron Oxide Nanoparticles in Thermally Responsive Alginate‐Poly(N‐isopropylacrylamide) Semi‐Interpenetrating Polymer Networks

A novel semi‐interpenetrating polymer network based on alginate and poly(N‐isopropylacrylamide) (PNiPAAm) has been synthesized that shows response to temperature and magnetic fields. Highly homogeneous porous hydrogels are obtained by copolymerizing N‐isopropylacrylamide and bis‐acrylamide in the presence of an aqueous alginate solution. The synthesis of magnetic iron oxides by in‐situ oxidation of iron cations coordinated to the alginate network results in a hydrogel with an enhanced deswelling rate with respect to pure PNiPAAm.

     

Ordered Honeycomb‐Structured Films from Dendronized PMA‐b‐PEO Rod‐Coil Block Copolymers

Summary: Fabrication of honeycomb‐patterned films from amphiphilic dendronized block copolymer (PEO₁₁₃‐b‐PDMA₈₂) by ‘on‐solid surface spreading’ and ‘on‐water spreading’ method is reported. Highly ordered honeycomb films with quasi‐horizontally paralleled double‐layered structure can be fabricated by the on‐solid surface spreading method. This work raises the possibility that such structures can be formed in amphiphilic dendronized block copolymers and extends the family of source materials.

     

Chain Transfer and Efficiency of End‐Group Introduction in Free Radical Polymerization of Methyl Methacrylate in the Presence of Poly(methyl methacrylate) Macromonomer

Summary: Experimental and modeling studies of addition–fragmentation chain transfer (AFCT) during radical polymerization of methyl methacrylate in the presence of poly(methyl methacrylate) macromonomer with 2‐carbomethoxy‐2‐propenyl ω‐ends (PMMA‐CO₂Me) at 60 °C are reported. The results revealed that AFCT involving PMMA‐CO₂Me formed in situ during methyl methacrylate polymerization has a negligible effect on the molecular weight distribution.

     

Sensing Diffraction Gratings of Antigen‐Responsive Hydrogel for Human Immunoglobulin‐G Detection

Sensing diffraction gratings of antigen‐responsive hydrogel were developed for human immunoglobulin‐G (H‐IgG) detection. The IgG‐sensing gratings were fabricated by soft lithographic duplication of photoinduced surface relief gratings on azo polymer films to the hydrogel surfaces. The quantitative detection of H‐IgG was achieved by detecting modulation of the diffraction efficiency when the gratings were exposed to antigen solutions. The gratings showed high sensitivity and specificity for the H‐IgG detection. The detection could be performed at a reasonably fast rate with good reusability. In the process, no fluorophore labeling or additional signal enhancement was required.

     

Formation of Silica/Poly(p‐dioxanone) Microspheres by Surface‐Initiated Polymerization

A polymeric film of a biodegradable poly(p‐dioxanone) was grown from 490 nm silica particles by monolayer formation via self‐assembly of hydroxy‐terminated triethoxysilane and subsequent surface‐initiated ring‐opening polymerization of p‐dioxanone. The resulting silica/poly(p‐dioxanone) hybrid particles were characterized by means of ¹H NMR spectroscopy, IR spectroscopy, thermogravimetric analysis, field‐emission scanning electron microscopy, and energy‐dispersive X‐ray spectroscopy.

     

Gels at Extremely Low Weight Fractions Formed by Irreversible Self‐Assembly of Proteins

Food‐grade biomaterials, like β‐lactoglobulin, bovine serum albumin, and ovalbumin, can assemble into fibrils. Using the irreversible fibril formation for β‐lactoglobulin, gels can be formed even at protein concentrations of 0.07%. These fibrillar mesostructures form new structuring materials for food and pharmaceutical applications.

TEM micrograph of β‐lg at pH 2, after heating at 80 °C for 10 h and then the pH was adjusted to pH 8.     

Ethylene and Ethylene/Propylene Polymerization Behavior of Bis(phenoxy‐imine) Zr and Hf Complexes with Perfluorophenyl Substituents

The catalytic properties of bis(phenoxy‐imine) Zr and Hf complexes incorporating perfluorophenyl groups with methylaluminoxane were investigated. The fluorinated complexes produced far higher‐molecular‐weight polyethylenes and ethylene/propylene copolymers with increased activities compared with the non‐fluorinated congeners. Moreover, the fluorinated complexes displayed a higher incorporation ability for propylene.

Structures of complexes 1 – 4 .     

Construction of Large‐Scale Highly Ordered Macroporous Monoliths of π‐Conjugated Polymers

Large scale of well‐ordered macroporous π‐conjugated polymer monoliths have been successfully prepared through a new approach using micrometer‐sized naphthalene crystals as templates. The macroporous monoliths of poly(p‐phenylenevinylene) (PPV) and poly(p‐phenyleneethynylene) (PPE) grew along the unidirectional freezing direction inside the template naphthalene crystals which lead to the formation of controlling morphologies and homogeneous diameters. The polymer monoliths show straight and lamella macroporous structures. The diameters of pores and the thickness of pore walls can be controlled by tuning the freezing temperature.

     

Novel Shape‐Memory Polymer Based on Hydrogen Bonding

Summary: Due to a large difference in storage modulus below and above the glass transition temperature, a novel shape‐memory poly[(methyl methacrylate)‐co‐(N‐vinyl‐2‐pyrrolidone)]/poly(ethylene glycol) semi‐interpenetrating polymer networks structure was synthesized, which is stabilized by hydrogen‐bonding interactions. The recovery ratio of these polymers could reach 99%. In such a system the maximum molecular weight of PEG required for the semi‐IPNs formation reaches 1 000.

Transition from the temporary shape (chem) to the permanent shape (four rods) for a shape‐memory P(MMA‐co‐VP)/PEG1000 semi‐IPNs.     

Patterned Hydrophilization of Nanoporous 1,2‐PB by Thiol‐ene Photochemistry

We present an efficient method for functionalizing the large polymer–air interface of a gyroid nanoporous polymer. The hydrophilicity of nanoporous cross‐linked 1,2‐polybutadiene is tuned by thiol‐ene photo‐grafting of mercaptosuccinic acid or sodium 2‐mercaptoethanesulfonate. The reaction is monitored by FT‐IR, UV–Vis, contact angle, and gravimetry. Overall quantum yields are calculated for the two thiol‐ene “click” reactions in nano‐confinement, neatly revealing their chain‐like nature. Top–down photolithographic patterning is demonstrated, realizing hydrophilic nanoporous “corridors” exclusively hosting water. The presented approach can be relevant for many applications where, e.g., high control and contrast in hydrophilicity, chemical functionality or refractive index are needed.

     

Resilient Amorphous Networks Prepared by Photo‐Crosslinking High‐Molecular‐Weight D,L‐Lactide and Trimethylene Carbonate Macromers: Mechanical Properties and Shape‐Memory Behavior

Tough networks are prepared by photo‐crosslinking high‐molecular‐weight DLLA and TMC macromers. These amorphous networks exhibit tunable thermal and mechanical properties and have excellent shape‐memory features. Variation of the monomer ratio allows adjustment of T_g between approximately ?13 and +51 °C. The elastic moduli at room temperature can be varied between 4.5 and 2730 MPa. The crosslinks allow the networks to return to their original shape after deformation. 60:40 DLLA:TMC networks have T_g values between room temperature and body temperature, with mechanical properties at body temperature close to soft tissues. Several medical devices are prepared from these networks.

     

Comprehensive Triblock Copolymer Analysis by Coupled Thermal Field‐Flow Fractionation‐NMR

Thermal field‐flow fractionation (ThFFF) is used as a novel fractionation technique to investigate the molecular heterogeneity of PB‐b‐PVP‐b‐PtBMA triblock copolymers. Such copolymers cause major problems in liquid chromatography due to very strong polar interactions with the stationary phase. ThFFF separates the copolymers with regard to size and/or chemical composition based on the normal and thermal diffusion coefficients. The separation mechanism in ThFFF and the chemical composition of the separated species is elucidated by online ¹H NMR. Based on the compositional analysis and a calibration of the system with the respective homopolymers, the samples are quantified regarding their molar masses, chemical compositions, and microstructures providing comprehensive information on the complex structure of these block copolymers.

     

Multi‐Morphological Complex Aggregates Formed from Amphiphilic Poly(ethylene oxide)‐block‐Polydimethylsiloxane‐block‐Poly(ethylene oxide) Triblock Copolymers

Summary: Amphiphilic triblock copolymers (PEO_x‐b‐PDMS_y‐b‐PEO_x) with different block lengths were synthesized and multi‐morphological complex crew‐cut, star‐like, and short‐chain aggregates were prepared by self‐assembly of the given copolymers. The morphologies and dimensions of the aggregates can be well controlled by variation of the preparation conditions. TEM, SEM, FFR‐TEM, and LLS studies show the resulting morphologies range from LCMs, unilamellar or multilayer vesicles, LCVs, porous spheres to nanorods.

TEM images of the vesicles formed from PEO‐b‐PDMS‐b‐PEO.