Application of Poly(3‐hexylthiophene) Functionalized with an Anchoring Group in Dye‐sensitized Solar Cells

A series of three poly(3‐hexylthiophene) functionalized either with a cyanoacetic acid (CA) or a rhodanine‐3‐acetic acid anchoring groups were synthesized and characterized. The TiO₂ based dye‐sensitized solar cells have been fabricated and performances were tested. We show that shorter chain length (15 thiophene units) linked to CA binding group gives good performances as J_sc, V_oc, FF and η(%) were 6.93(mA · cm⁻²), 0.65(V), 0.67 and 3.02%, respectively. A maximum IPCE of ≈50% at 500 nm was recorded with a liquid electrolyte, under AM 1.5 simulated solar irradiance.

     

A Density Functional Theory Study of Secondary Reactions in n‐Butyl Acrylate Free Radical Polymerization

In this work, secondary reactions involved in the free radical polymerization of butyl acrylate are investigated using quantum chemistry. First, various backbiting reactions are studied by adopting a simplified molecular model suitable for treating long polymer chains. The predicted reaction kinetics suggest the possibility of a radical migration along the poly(butyl acrylate) (PBA) chain as a consequence of subsequent j:j + 4 hydrogen abstractions, which are characterized by a low activation energy. Moreover, branching propagation and β‐scission reactions originating from mid‐chain radicals are investigated using a complete PBA model composed of five monomer units. The reaction kinetics involving short‐branch radicals are also examined, and a novel backbiting step leading to the formation of short branches is proposed.

     

A Highly Selective,Colorimetric, and Fluorometric Multisignaling Chemosensor for Hg2+ Based on Poly(p‐phenyleneethynylene) Containing Benzo[2,1,3]thiadiazole

A novel colorimetric and fluorometric chemosensor for Hg²⁺ detection based on poly(p‐phenyleneethynylene) (PPE) containing benzo[2,1,3]thiadiazole (BDT) has been developed. A highly Hg²⁺‐selective fluorescence quenching property in conjunction with a visible colorimetric change from yellow to violet can be observed, which indicates that PPE‐BDT can serve as a sensitive ‘naked‐eye’ indicator for Hg²⁺.

     

Evidence of Branching in Poly(butyl acrylate) Produced in Pulsed‐Laser Polymerization Experiments

Branched poly(butyl acrylate) was obtained from pulsed‐laser polymerizations carried out in bulk and in solution between −16 and 60 °C. The predominantly short branches are formed by backbiting. The Arrhenius temperature dependence of the backbiting rate is calculated, and the activation energy of this process was found to be remarkably higher than that of propagation. Branching thus increases with temperature leading to broader SEC traces and difficulties in the accurate determination of k_p.

Arrhenius plot of k_fp2 versus 1/T determined experimentally.     

Frozen‐In Magnetic Order in Uniaxial Magnetic Gels: Preparation and Physical Properties

We describe the preparation and characterization of uniaxial magnetic gels. Fibril formation of the embedded magnetic particles generates easily detectable magnetic and optical anisotropies. A finite magnetization is frozen‐in and leads to a ferromagnetic‐like response in small homogeneous external magnetic fields. We present, for the first time, frequency dependent measurements of the shear modulus G′. Despite their optical and magnetic anisotropy, the gels are mechanically isotropic.

The time‐dependent G′ for a ferrogel in the parallel orientation in a homogeneous field of 200 mT.     

Novel Photoactive Polymeric Multilayer Films Formed via Electrostatic Self‐Assembly

Summary: We demonstrate a novel approach for constructing photoactive multilayer films in which the aggregation of fluorescing molecules is effectively eliminated. In the films formed via a layer‐by‐layer electrostatic self‐assembly technique, the core‐shell amphiphilic copolymer, poly[(sodium 4‐styrenesulfonate)‐block‐vinylnaphthalene], was deposited. The isolated cores served as nanosized host sites for photoactive guest molecules (pyrene, perylene). The efficient energy transfer between polymeric chromophores and perylene molecules was observed.

AFM image of a nanostructured polymeric film prepared via a layer‐by‐layer technique and containing photoactive block copolymer poly[(sodium 4‐styrenesulfonate)‐block‐vinylnaphthalene]. Below is the representative height profile taken along the drawn line.     

Collapse of Cylindrical Brushes with 2‐Isopropyloxazoline Side Chains Close to the Phase Boundary

A high‐molar‐mass cylindrical brush polymer with a main chain degree of polymerization of P_w = 1047 is synthesized by free‐radical polymerization of a poly‐2‐isopropyloxazoline macromonomer with P_n = 28. The polymerization is conducted above the lower phase transition temperature of the macromonomer, i.e., in the phase‐separated regime, which provides a sufficiently concentrated macromonomer phase mandatory to obtain high‐molar‐mass cylindrical brushes. Upon heating to the phase transition temperature, the hydrodynamic radius is observed to shrink from 34 to 27 nm. Further increase in temperature resulted in aggregated chains which were observed to coexist with single chains until eventually only aggregates of μm size were detectable.

     

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.

     

Mechanics of Homeotropically Ordered Smectic‐A Elastomers with Global Oblate Chain Conformation

Smectic‐A elastomers combine one‐dimensional translational order of rod‐like segments with the rubber elasticity of a polymer network. In recent years, detailed investigations were carried out on elastomers showing a global prolate chain conformation. In this communication, the first experiments on fluorinated S_A elastomers exhibiting a global oblate chain conformation are presented, where the polymer chains are on average compressed along the layer normal of the lamellar phase structure. The mechanical anisotropy is studied by means of thermoelastic experiments and stress–strain measurements. For the first time, the layer compression modulus B of smectic elastomers is directly measured. B is significantly larger as compared to conventional low molar mass liquid crystals and decreases significantly with increasing local disorder introduced by the isotropic crosslinker.

     

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.     

Self‐Organizing Alignment of Carbon Nanotubes in Thermoplastic Polyurethane

Summary: A simple compounding technique for the fabrication of polymer nanocomposites with single‐walled carbon nanotubes having exceptional alignment and improved mechanical properties is described. The aligned‐nanotube composite was prepared by dissolving single‐walled carbon nanotubes in a solution of thermoplastic polyurethane and tetrahydrofuran. Solvent‐polymer interactions that induce the orientation of soft chain segments during the swelling and moisture curing stage are believed to serve as a driving force for the macroscopic alignment of the carbon nanotubes.

Alignment of single‐walled carbon nanotubes in thermoplastic polyurethane during polar solvent exposure.     

Polymer‐Bound Thiol Groups on Poly(2‐oxazoline)s

A new 2‐oxazoline monomer with a protected thiol group, 2‐[2‐(4‐methoxybenzylsulfanyl)ethyl]‐2‐oxazoline, MOB‐SOx , was synthesized from commercially available compounds. MOB‐SOx and 2‐ethyl‐2‐oxazoline (EtOx) were simultaneously polymerized yielding well defined copolymers with narrow molar mass distributions and target polymer chain length. The copolymerization was initiated by N‐methyl‐2‐methyl‐2‐oxazolinium triflate ( MeOxOTf ). After quantitative deprotection, poly(2‐oxazoline) with pendant thiol groups was obtained. The thiol groups were quantitatively added to the double bond of N‐phenyl‐acrylamide ( PhA ) and benzylmaleimide ( BzM ). Graft copolymers were obtained by reaction of those SH containing polymers with poly(2‐methyl‐2‐oxazoline)s bearing acrylamide ( PMeOx ₁₀ A ) and maleimide ( PMeOx ₁₀ M ) as terminal reactive groups.

     

Polymerization of Vinyl Ethers by (α‐diimine)NiII/Methylaluminoxane Catalysts

Polymerizations of vinyl ethers are carried out with (α‐diimine)nickel(II ) catalysts in the presence of methylaluminoxane. Effects of structural variations of the ligand on the activities of catalysts and polymer microstructure are described. The catalysts prepared by changing the bulkiness of ligand substituents in the ortho aryl position result in no specific trends terms of the yield and molecular weight of polymer. Poly(vinyl ether)s are atactic regardless of the structure of the catalyst used.

     

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.     

Lewis Acid‐Induced N‐Methyleneamines as Initiators in the Synthesis of Secondary Amine‐Terminated Polymers

Summary: The cationic polymerization of poly(tert‐butyl vinyl ether) using N‐methyleneamine equivalents derived from a Lewis acid/1,3,5‐trimethylhexahydro‐1,3,5‐triazine (TMTA) co‐initiating system is reported. The resulting polymers possessed secondary amine functionality at the chain terminus, verified by derivatization with 4‐chloro‐7‐nitrobenzo‐2‐oxa‐1,3‐diazole (NBD‐Cl) and subsequent analysis with GPC‐UV (470 nm) and ¹H NMR.

Use of N‐methyleneamine equivalents lacking aryl substituents to afford amine‐terminated poly(tert‐butyl vinyl ether).     

Alternating Poly(Pt‐salphen)‐(p‐phenyleneethynylene) as Phosphorescent Conjugated Linear‐Rod and Coilable Sensory Materials

Phosphorescent conjugated polymers consisting of alternating p‐phenylene‐ethynylene and ‘para‐’ or ‘meta‐type’ Pt(II)‐salphen luminophore units have been synthesized. Side‐arms bearing different substituents (n‐alkoxy and acetylated‐sugar) have afforded contrasting emission properties that are attributed to the polymer conformation, extent of π‐stacking interactions and differences in chemical structure. Intriguing selectivity in luminescent sensing of metal ions has been observed.

     

Phase Separation and Organisation of Colloidal Spheres Suspended in Sheared Lyotropic Liquid‐Crystalline Polymers

Summary: Organisation behaviours of spherical particles suspended in sheared, lyotropic, liquid‐crystalline polymer solutions have been investigated using polarizing optical microscopy. We find that in a nematic phase the particles phase separate and adopt anisotropic chain‐like structures along the director. An earring defect is observed around a single particle whereas a cross or strings defect between neighbouring particles is found to serve as a repulsive barrier to prevent the particles from contacting each other. A theoretical analysis is presented to explain this new phenomenon.

An optical micrograph of 0.01 wt.‐% glass spheres suspended in a nematic solution of 40 wt.‐% ethyl cellulose in chloroform under an external shear force.     

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.

     

Enzyme‐Catalyzed Preparation of Aliphatic Polythioester by Direct Polycondensation of Diacid Diester and Dithiol

Summary: Aliphatic dithiol‐diacid type polythioesters were first enzymatically prepared by the direct polycondensation of hexane‐1,6‐dithiol and diacid diesters using the immobilized lipase from Candida antarctica (lipase CA). As a typical example, diethyl sebacate and hexane‐1,6‐dithiol were polymerized using lipase CA in bulk in the presence of molecular sieves 4A to produce the corresponding polythioester with an of 10 200 in 90% yield. Both the melting and crystallization temperatures of the produced polythioesters were higher when compared to those of the corresponding polyoxyesters. A higher molecular weight polythioester was produced using lipase in a two‐step procedure, i.e., cyclization with subsequent ring‐opening polymerization.

Preparation of polythioester and melting temperature of various polythioesters and polyoxyesters.     

Efficient Oxygen‐Induced Molar‐Mass Control of Poly(p‐phenylene vinylenes) Synthesized via the Gilch Route

Oxygen is shown to act as an efficient molar‐mass regulating agent in Gilch syntheses of PPV. As a scavenger, it undergoes instantaneous recombination with the initiating diradicals as soon as they appear in the system. Regular polymer formation can only start when all oxygen has been used, proceeding predominantly as chain‐growth polymerization of the p‐quinodimethane monomers. Since all radical species involved in this Gilch process are diradicals, some polyrecombination events occur in parallel. Therefore the initially formed peroxy diradicals are also incorporated into the resulting chains. Later, they break under very mild conditions, thereby causing a systematic decrease of the final molar mass of PPV.