Anionic Polysaccharides as Templates for the Synthesis of Conducting Polyaniline and as Structural Matrix for Conducting Biocomposites

A green chemoenzymatic pathway for the synthesis of conducting polyaniline (PANI) composites is presented. Laccase‐catalyzed polymerization in combination with anionic polysaccharides is used to produce polysaccharide/PANI composites, which can be processed into flexible films or coated onto cellulose surfaces. Different polysaccharide templates are assessed, including κ‐carrageenan, native spruce O‐acetyl galactoglucomannan (GGM), and TEMPO‐oxidized cellulose and GGM. The resulted conducting biocomposites derived from natural materials provide a broad range of potential applications, such as in biosensors, electronic devices, and tissue engineering.

     

Poly(4‐vinylpyridine) Nanocrosslinked by Polyhedral Oligomeric Silsesquioxane

Summary: Octa(propylglycidyl ether) polyhedral oligomeric silsesquioxane (OpePOSS) was used as the crosslinking agent to prepare the nanocrosslinked poly(4‐vinylpyridine) (P4VP) with POSS content up to 55.2 wt.‐%. The formation of the crosslinked structure is ascribed to the macromolecular reaction between pyridine rings of P4VP and epoxide groups of OpePOSS. The POSS‐crosslinked P4VP displayed enhanced glass transition temperatures (T_gs) and an improved thermal stability in terms of the results of thermal analysis.

Crosslinking of poly(4‐vinylpyridine) with octa(propylglycidyl ether) polyhedral oligomeric silsesquioxane.     

Amphiphilic Hybrid π‐Conjugated Polymers Containing Polyhedral Oligomeric Silsesquioxanes

Amphiphilic hybrid π‐conjugated polymers that have polyhedral oligomeric silsesquioxanes on their side chains have been successfully synthesized by the Sonogashira–Hagihara polycondensation reaction. The obtained polymers were studied with ultraviolet‐visible absorption and photoluminescence spectra. In these polymers, the π‐conjugation length was extended along the poly(p‐phenylene‐ethynylene) backbone. Furthermore, the content of the POSS substituents can influence the aggregation behavior of the polymers and subsequent luminescent properties.

     

Calculation of CLD Using Population Balance Equations of Generating Functions: Linear and Non‐Linear Ideal Controlled Radical Polymerization

Population balance equations in terms of generating functions (GF) are used to predict chain length distributions (CLD) of linear and non‐linear ideal controlled radical polymerization (CRP) systems. It is here shown that under simplified conditions analytical solutions for the CLD can be found and moreover the fundamental CLD derived by H. Tobita in 2006 is a limiting case of the more general solutions here presented. In order to deal with more complex CRP systems, solutions based upon the numerical inversion of GF are presented. These studies are also extended to the non‐linear CRP of vinyl/divinyl monomers where multimodal CLDs are predicted to occur.

     

Ultra Rapid Approaches to Mild Macromolecular Conjugation

In light of the increasing demand for ultra rapid and mild conjugation chemistries for use in macromolecular chemistry, the present Feature Article provides a critical overview of the very latest developments in this field. The principal aim, therefore, is the provision of a quick selection guide to aid in the formulation of a design strategy for novel functional materials and to provide recommendations for future developments in the chemistries discussed.

     

Synthesis of POSS‐Functionalized Polyisobutylene via Direct Initiation

POSS‐functionalized polyisobutylenes (PIBs) were synthesized by carbocationic polymerization using an epoxy‐POSS/TiCl₄ initiating system in hexane/methyl chloride (60:40 v/v) solvent mixture at −80 °C. ¹H NMR spectroscopy verified the incorporation of one epoxy‐POSS per polymer chain. Light scattering and TEM analysis demonstrated the formation of 50–100 nm sized aggregates and micron‐sized clusters.

     

Polyhedral Oligomeric Silsesquioxane Containing Copolymers for Negative‐Type Photoresists

Summary: A series of methacrylate copolymers containing polyhedral oligomeric silsesquioxane (POSS) was synthesized from the free radical copolymerization of methacrylic acid, methyl methacrylate, and isobutyl propylmethacryl polyhedral oligosilsesquioxanes, and then were modified with glycidyl methacrylate to serve as negative‐type photoresists. The UV/Vis spectroscopy reveals that the incorporation of POSS moiety into the copolymer results in a slight decrease in transparency from 99 to 92.5% (at wavelength = 365 nm). The photosensitivity in terms of resist sensitivity (D), contrast (γ), and photopolymerization rate are significantly increased with increase in the POSS content. In addition, the induction time is reduced from 0.520 to 0.515 min after incorporating the POSS unit based on photo‐DSC analyses. These observed results can be rationalized as due to hydrogen bonding interactions between siloxane and hydroxyl groups in copolymers which tend to attract the methacrylate double bonds surrounding POSS units to crosslink, thereby enhancing the photopolymerization rate and sensitivity. We further evaluate the lithographic property of a photoresist under a collimated exposure.

Compact double bonds zone induced via hydrogen bonding.     

Defined Poly[styrene‐block‐(ferrocenylmethyl methacrylate)] Diblock Copolymers via Living Anionic Polymerization

Ferrocenylmethyl methacrylate (FMMA) is one of the very few metallocene‐based monomers that are promising candidates for truly living anionic polymerization. Nevertheless, FMMA homopolymers with a narrow polydispersity, or block copolymerization studies that result in satisfying blocking efficiencies, are unknown so far. Here we describe a procedure that leads to highly regular FMMA‐based polymers for the first time, characterized by polydispersity indices (PDI) of less that 1.05 and very high blocking efficiencies (>95%) in sequential copolymerization with styrene. Some of the obtained poly[styrene‐block‐(ferrocenylmethyl methacrylate)]s show unusual microphase morphologies, presumably the consequence of high T_gs causing ‘frustrated’ non‐equilibrium states.

     

Polyelectrolyte Multilayer Microspheres as Carriers for Bienzyme System: Preparation and Characterization

Summary: Polyelectrolyte multilayer microspheres were prepared by alternating adsorption of dextran sulfate and protamine on melamine formaldehyde cores followed by the partial decomposition of the core. Peroxidase and glucose oxidase were immobilized in the prepared microspheres. Retention of enzymatic activity of the peroxidase/glucose oxidase system incorporated into the microspheres was demonstrated. Applicability of the bienzyme system immobilized in the microspheres for kinetic glucose assay was shown.

SEM image of the polyelectrolyte multilayer microsphere.     

Synthesis of Nanosized (<20 nm) Polymer Particles by Radical Polymerization in Miniemulsion Employing in situ Surfactant Formation

A novel method for synthesis of ultrafine polymeric nanoparticles of diameters less than 20 nm has been developed. The method is based on miniemulsion polymerization exploiting combination of the in situ surfactant generation approach (whereby the surfactant is formed at the oil–water interface by reaction between an organic acid and a base) and ultrasonication. Conventional radical polymerization and nitroxide‐mediated radical polymerization of styrene have been conducted in miniemulsion using oleic acid/potassium hydroxide, demonstrating that particles with diameters less than 20 nm can be obtained by this approach at surfactant contents much lower than traditionally required in microemulsion polymerizations.

     

Hybrid Nanocomposite Films from Mono‐ and Multi‐Functional POSS Copolyacrylates in Miniemulsion

Summary: The synthesis of aqueous dispersions of hybrid acrylic copolymer particles with either a monofunctional or a multifunctional polyhedral oligomeric silsesquioxane methacrylate comonomer has been performed by free radical heterophase polymerization. The miniemulsion process gives stable latexes, whereas the less controlled emulsion route results in colloidal instability of the products. The thermal and mechanical properties of the nanocomposite latex films have been preliminarily investigated.

The nanocomposite latex particles based on hybrid copolyacrylates with highly dispersed POSS cages.     

Formation of o‐Phenylenediamine Oligomers and their Self‐Assembly into One‐Dimensional Structures in Aqueous Medium

Summary: Uniform one‐dimensional (1D) structures of o‐phenylenediamine (oPD) oligomers are obtained by direct mix of AgNO₃ and oPD aqueous solutions at room temperature. The formation of the 1D structures involves two stages: (1) oxidation of oPD by AgNO₃, yielding individual oPD oligomers; and (2) self‐assembly of the oligomers, forming the 1D structures. Upon decreasing medium pH, the 1D structures can break‐apart to form individual oligomers, or vice versa. It is also found that both the concentration and molar ratio of reactants can influence the morphology of the structures thus formed.

Schematic illustration of the formation mechanism of 1D structures from oPD and AgNO₃, and energy‐dispersed spectrum of the precipitate.     

Opto‐Mechanical Effect in Photoactive Nematic Side‐Chain Liquid‐Crystalline Elastomers

The mechanical behaviour of monodomain nematic side‐chain liquid‐crystalline elastomers containing azoderivatives as pendant groups or crosslinkers has been studied under UV irradiation and in the darkness at different temperatures. From the evaluation of the opto‐mechanical experiments, the mechanical efficiency, kinetic rates, activation energies and the isomerization mechanism of the azocompounds in the liquid‐crystalline matrix could be determined, as well as the effect of the chemical constitution of the azobenzene derivatives and their role in the elastomeric network.

     

Horseradish Peroxidase as a Catalyst for Atom Transfer Radical Polymerization

The hemoprotein horseradish peroxidase (HRP) catalyzes the polymerization of N‐isopropylacrylamide with an alkyl bromide initiator under conditions of activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP) in the absence of any peroxide. This is a novel activity of HRP, which we propose to name ATRPase activity. Bromine‐terminated polymers with polydispersity indices (PDIs) as low as 1.44 are obtained. The polymerization follows first order kinetics, but the evolution of molecular weight and the PDI upon increasing conversion deviate from the results expected for an ATRP mechanism. Conversion, and PDI depend on the pH and on the concentration of the reducing agent, sodium ascorbate. HRP is stable during the polymerization and does not unfold or form conjugates.

     

Supercritical Carbon Dioxide‐Treated Electrospun Poly(vinylidene fluoride) Nanofibrous Membranes: Morphology,Structures and Properties as an Ionic‐Liquid Host

A reverse‐barrier technique is used to enable the treatment of electrospun poly(vinylidene fluoride) nanofibrous membranes with supercritical carbon dioxide. The treatment induces the formation of nanopores and extended‐chain β crystallites of small lateral dimensions in the nanofibers. It also creates interfiber junctions, resulting in a remarkable improvement in mechanical properties of the membranes. The treated membranes are able to retain their shape very well after loading with an ionic liquid (IL). The ionic conductivity of the IL‐loaded membrane is very close to that of the neat IL.