Nanosized Shape‐Changing Colloids from Liquid Crystalline Elastomers

A method to prepare shape‐changing nanospheres from liquid crystalline elastomers is reported. The nanosized colloids are prepared by a miniemulsion process. During this process, colloids are prepared from a liquid crystalline (LC) main‐chain polyester and subsequently crosslinked into a nanometer‐sized LC elastomer. The ability of these LC elastomers to change their shape at the phase transition temperature from the smectic A to the isotropic phase was detected by temperature‐dependent transmission electron microscopy. The phase transition‐induced shape change leads to strongly shape anisotropic nanosized elastomer particles.

     

A Glassy Bending‐Mode Polymeric Actuator Which Deforms in Response to Solvent Polarity

Summary: We investigate a series of glassy polymer actuators which are found to bend rapidly and reversibly in response to changes in the solvent environment. The actuators are based on hydrogen‐bonded liquid crystal networks, and bending motion is created using director profiles engineered to take advantage of the network swelling anisotropy. Strongly polar solvents easily swell the network, forcing bending in one direction, while the less polar solvents extract water to force bending in the opposite direction.

Shape variation of twisted configuration liquid crystal polymer films in acetone and water.     

Facile Fabrication of Functional Polypyrrole Nanotubes via a Reactive Self‐Degraded Template

Summary: Polypyrrole nanotubes with high electric conductivity and azo function have been fabricated in high yield via an in‐situ polymerization. During the process fibrillar complex of FeCl₃ and methyl orange (MO), acting as a reactive self‐degraded template, directed the growth of polypyrrole on its surface and promoted the assembly into hollow nanotubular structures.

TEM image of uncompleted PPy nanotubes synthesized in MO solutions after reaction for 40 min.     

Single‐Chain‐Particles of Poly(N‐isopropylacrylamide)

Spherical single‐chain‐particles of poly(N‐isopropylacrylamide) were prepared in aqueous solution above the lower critical solution temperature upon the addition of sodium dodecyl sulfate. The size of the single‐chain‐particles was investigated by means of transmission electron microscopy and viscosity measurements of the corresponding solutions, indicating the absence of inter‐chain entanglements among the single‐chain‐particles.

Schematic of the preparation of PNIPAM single‐chain‐globules in solution.     

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.

     

Red Ionic Water‐Soluble Imidazolium‐Containing Polydiacetylene

Synthesis of a water‐soluble polydiacetylene has been achieved by topochemical polymerization in the solid state of the bis(N‐methylimidazolium)diacetylene monomer. Structural characterization for the monomer by X‐ray diffraction and NMR spectroscopy supports a photopolymerization initiated at the surface. Characterization of the polymer (NMR, UV and Raman spectroscopy, and dynamic light scattering) is given along with a molecular modelling interpretation of the polymerization in the solid state.

     

A Novel Route for Fabricating Metal‐Polymer Composite Nanoparticles with Phase‐Separated Structures

Au nanoparticles (NPs) and polymer composite particles with phase‐separation structures were prepared based on phase separation structures. Au NPs were successfully synthesized in amphiphilic block‐copolymer micelles, and then composite particles were formed by a simple solvent evaporation process from Au NPs and polymer solution. The phase separated structures (Janus and Core‐shell) were controlled by changing the combination of polymers having differing hydrophobicity.

     

1,1‐Diphenyl Ethylene‐Mediated Radical Polymerisation: A General Non‐Metal‐Based Technique For The Synthesis Of Precise Core Cross‐Linked Star Polymers

This communication details the successful synthesis of low polydispersity core cross‐linked star (CCS) polymers via DPE‐mediated polymerisation. We demonstrate the ability to produce poly(methyl methacrylate) and poly(acrylonitrile) CCS polymers that are currently inaccessible via the two most common non‐metal‐based controlled radical polymerisation techniques (NMP and RAFT polymerisations).

     

Aromatic Ring‐Fused Carborane‐Based Luminescent π‐Conjugated Polymers

A series of π‐conjugated polymers linked by benzocarborane (1,2‐(buta‐1′,3′‐diene‐1′,4′‐diyl)‐1,2‐dicarbadodecaborane) were synthesized via Sonogashira–Hagihara polycondensation reaction. The opened molecular structure of diiodo monomer containing benzocarborane resulted in fast polymerization and high molecular weights. The obtained polymers were fully characterized by ¹H, ¹³C, and ¹¹B NMR spectroscopies. UV‐vis absorption and photoluminescence studies revealed the acceptor‐profile of benzocarborane. Unlike the polymers linked by o‐carborane, these polymers exhibited strong luminescence in the solution state, presumably because the inductive effect of carborane is dominant, rather than cage‐π interactions.

     

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.

     

A Comprehensive Kinetic Model of Free‐Radical‐Mediated Interfacial Polymerization

A mathematical model describing interfacial radical polymerization‐based film formation on hydrogels is elucidated. A glucose oxidase‐mediated multistage initiation reaction is used to accomplish interfacial film formation. A polymer concentration‐dependent diffusion coefficient is used to reflect the changing mass transport conditions as the film develops. Model predictions of the film thickness as a function of the species concentrations agree well with experiments. The model predicts that the degree of initiation reaction delocalization with the enzyme‐mediated initiation system is significantly higher than an enzyme‐independent system, thus affecting the film growth rate and structure. The mass transport properties of the film and its adhesion to the underlying substrate are also investigated.

     

Microwave‐Assisted Ring‐Opening Polymerization of ε‐Caprolactone in the Presence of Ionic Liquid

Summary: Microwave‐assisted ring‐opening polymerization of ε‐caprolactone in the presence of 1‐butyl‐3‐methylimidazolium tetrafluoroborate ionic liquid using zinc oxide as a catalyst is investigated. By adding 30 wt.‐% ionic liquid, poly(ε‐caprolactone) with a weight‐average molar mass of 28 500 g · mol⁻¹ is obtained at 85 W for 30 min. The results indicate that the polymerization could be efficiently enhanced in the presence of ionic liquids under microwave irradiation because ionic liquids can effectively absorb microwave energy.

     

Solvent Resistant Honeycomb Films from Photo‐Crosslinkable Polycinnamate

Microporous films consisting of two‐dimensionally ordered void structures ‐ so‐called honeycomb films ‐ were produced by evaporation of polymer solutions under high humidity. Two types of poly(vinyl cinnamate)s were used: A newly synthesized amphiphilic poly(vinyl cinnamate) and a mixture of a commercial poly(vinyl cinnamate) and an amphiphilic polyion complex. Photo‐crosslinking of the honeycomb structure could be achieved by UV irradiation while completely retaining the film morphology. The crosslinked films showed excellent stability against organic solvents.

     

Fabrication of Metal‐Block‐Copolymer Composite Films by a Palladium‐Catalyzed Electroless Nickel‐Plating Process

Summary: Homogeneous films of PI‐b‐PDMAEMA are prepared on top of silicon (100) substrates. The free film surface shows microdomains of PDMAEMA within a PI matrix. These microdomains act as templates for the highly site‐selective synthesis of metal nanoparticles via palladium‐catalyzed electroless nickel plating. The particle formation is studied by atomic force microscopy in tapping mode and implications for a redox reaction and a nanoparticle growth mechanism on the surface of nanopatterned films are discussed.

Chemical structure of the PI‐b‐PDMAEMA copolymer and AFM phase image of a PI‐b‐PDMAEMA film on Si (100) substrate.     

Influence of Copolymerization on Fragmentation Behavior Using Ziegler‐Natta Catalysts

Summary: A morphological investigation was carried out on different Ziegler‐Natta catalysts during the early stages of propylene homo‐ and propylene‐ethylene copolymerization. For similar polymerization conditions, but dependent on the nature of the catalysts, fragmentation occurs layer‐by‐layer or instantaneously into a large amount of small pieces. However, the incorporation of comonomer ethylene slows down the fragmentation progress. This is believed to be the result of the higher mobility of the just formed propylene‐ethylene copolymer molecules at the active sites.

SEM images of the cross‐sectional morphology of polymer particles from catalyst‐I.     

Effect of Chain‐Length Dependence of Interaction Parameter on Spinodals for Polydisperse Polymer Blends

Summary: The chain‐length dependence of the Flory‐Huggins (FH) interaction parameter is introduced into the FH lattice theory for polydisperse polymer‐blend systems. The spinodals are calculated for the model polymer blends with different chain lengths and distributions. It is found that all the related variables, r_n, r_w, r_z, and chain‐length distribution, have effects on the spinodals for polydisperse polymer blends.

The spinodals at different chain lengths.     

Synthesis and Dispersion Characteristics of Multi‐Walled Carbon Nanotube Composites with Poly(methyl methacrylate) Prepared by In‐Situ Bulk Polymerization

Multi‐walled carbon nanotubes (MWNT) purified by acidic solution were processed with PMMA via an in‐situ polymerization. Experimental evidences indicate the role of radical initiator (AIBN) and MWNT, showing increases of polymerization rate and MWNT diameter. Induced radicals on the MWNT by AIBN were found to trigger the grafting of PMMA. Moreover, the solvent cast film showed a better nanoscopic dispersion of MWNT and possibilities of CNT composites in engineering applications.

Fractured surface of multi‐walled carbon nanotube composite with PMMA prepared by in‐situ bulk polymerization.     

A New Class of Blue‐Emitting Materials for LED Applications: Triarylamine N‐Functionalised 2,7‐Linked Carbazole Polymers

Attachment of triarylamino‐functional groups at the 9‐position of 2,7‐linked carbazole polymers results in blue‐emitting materials with two independent redox processes that were attributed to the triarylamino groups and the polymer backbone, respectively. This new class of blue‐emitting conjugated polymers was prepared via a Suzuki cross‐coupling reaction and showed low turn‐on voltages in electroluminescent devices as a result of their low ionisation potentials. The photophysical, electrochemical and electroluminescent properties of these materials are discussed.