This work presents a study of the optical properties of polyhydrosilanes in relation with their specific chemical structure. For this purpose, poly[methyl(H)silane‐co‐diphenylsilane] copolymers with a different content of methylhydrosilyl‐segments have been investigated. Steady‐state fluorescence analysis and X‐ray photoelectron spectrometry showed that polyhydrosilanes possess a specific emission profile due to the presence of both methylhydrosilyl segments and silicon nanoparticles within the polymeric matrix. Polyhydrosilanes are capable of generating singlet oxygen reactive species at room temperature. This unusual property was investigated by analyzing the morphological changes in biological systems during Hek293 cell cultures growth in the presence of polyhydrosilanes.
New synthetic strategies for thiophene‐nickel(II)porphyrin hybrid molecules are described. Three principles—linear direct, linear spacer and lateral spacer connectivities—were realised and compared with respect to their electrochemical behaviour. Computational investigations by DFT methods confirm experimental data and explain cylic voltammetric oxidations. For the linear direct connectivity, the number of thiophene units per substituted position must be at least two, since the porphyrin core acts as conjugation breaker and hinders the formation of higher oligomers. Alternatively an ethynylene spacer can be introduced to increase conjugation and to optimise the conducting properties. The lateral spacer connection mode proved to be best suited to the electrochemical formation of hybrid compounds.
PIB derivatives such as PIBSAs and the corresponding PIBSIs characterized by different contents of functional groups were prepared. They showed luminescence both in their neat form and in heptane solution when the amount of functional groups per polymer chain was higher than a critical value. This behavior is attributed to aggregation‐induced emission, a phenomenon caused by the aggregation of non‐emissive chromophoric carbonyl groups present on PIB derivatives. AIE was studied in heptane solution as a function of the type (SAs or succinimides) and number of interacting functional groups. The results suggest that fluorescence measurements might be an effective tool to determine the degree of functionalization of PIB derivatives.
For the first time, graphene materials have been conveniently covalently functionalized with polyacetylene through the nitrene chemistry reaction. The resultant functional polyacetylenes became soluble in different organic solvents and were well characterized, thus providing a new approach to prepare graphene‐polymer composite materials.
The effects of binding ligand variation on the externally initiated Ni catalyzed polymerization of P3HT were investigated using a novel methodology allowing facile screening of ligands. P3HT was synthesized with >80% initiator incorporation for both mono‐ and bidentate phosphine ligands. Variation of the initiating aryl group demonstrated vastly superior results for o‐tolyl over p‐tolyl substituents.
The Diels–Alder reaction of furan and maleimide is used to prepare reversibly cross‐linking polymer gels consisting of furan‐bearing polymer chains and bismaleimides. The roles of chain length, stoichiometry, and concentration on gelation kinetics and other properties are evaluated. Additionally, kinetics of the Diels–Alder reactions in the gelling system are compared with the kinetics of small molecule systems. By combining spectroscopic and rheological techniques, a mechanochemical analysis is performed.
Electrohydrodynamic jetting has the ability to capture and translate different phases of evolution in a living sol into materials with grossly different morphologies such as fibres or remarkably, as shown in this work, monodisperse spherical nanoparticles, depending on the sol properties and exposure time to the spray at the point of jetting as demonstrated using a tailor‐made siloxane sol.
The effect of inorganic salt at concentrations typical of a biological environment on the micellar morphology of semicrystalline PCL‐b‐PEO in aqueous solution is investigated. The salt is introduced either by dialysis of a THF solution against an aqueous solution of the salt or by adding it into an aqueous solution containing preformed micelles. The inorganic salt can induce sphere‐to‐rod or sphere‐to‐lamella transformations of the PCL‐b‐PEO micelles in aqueous solution, depending on the length of the PCL block. The inorganic salt induces “salting‐out” of the PEO block, leading to a decrease in the reduced tethering density of the corona in the micelles.
The in situ electrochemical and dielectric film properties of monomer co‐electropolymerization with a CPN precursor was investigated. A polysiloxane/polythiophene precursor was electropolymerized with thiophene monomer at different composition ratios using cyclic voltammetry. This was investigated in situ by EC‐SPR spectroscopy and EC‐SPFELS. The characteristic oscillations corresponded to distinct transitions in film deposition. The resonance coupling of the SPR decreased with higher thiophene monomer content. Increasing the amount of thiophene monomer increased the RMS roughness of the film as observed by AFM, which corresponded to an increase in scattered light intensity with EC‐SPFELS.
The influence of the support architecture (structure and pore size) on the activity of MAO/(nBuCp)2ZrCl2 heterogeneous catalysts in the polymerization of ethylene and 1‐hexene is studied through the characterization of the polymers' microstructure. SBA‐15 silica‐based mesostructured materials are synthesized with different pore sizes and compared with commercial silica. All SBA‐15 supported catalysts lead to higher catalytic activities than amorphous silica and give rise to ethylene/1‐hexene copolymers with bimodal CCD, which suggests that the carrier structure plays an important role not only in the global rate of the process but also in the copolymer composition. The structures and pore sizes of the support show a marked influence on the polymer CCD shape.
A new range of end‐functionalized poly(1,1,2,2‐tetrahydroperfluorodecyl acrylate)s was synthesized by ATRP. Such macromonomers were used as reactive and steric stabilizers for the preparation of original core‐shell polyurethane particles in supercritical carbon dioxide. The nature of the chain end functionality, as well as the molar mass of the reactive stabilizer, were varied in order to investigate the role of such parameters on the properties of the resulting materials. Due to the low surface energy of PFDA combined with the high surface roughness induced by the specific microstructure of particles deposited on a silica plate, PUR materials exhibited super‐hydrophobic behavior with a water CA above 150°.
This contribution describes the influence of short‐chain branching on the temperature dependence of rheological properties of polyethylene (PE) melts in shear. The materials investigated are linear and short‐chain branched, metallocene‐catalyzed PEs of narrow molecular mass distribution. The linear viscoelastic properties are determined by dynamic‐mechanical analysis. Short‐chain branching (SCB) leads to an increase of the flow activation energy. The activation energy was found to increase linearly with rising weight comonomer content.
The room temperature mineralization of thermoplastic starch (TPS) with a high glycerol content and its blends with low‐density polyethylene (LDPE) and polylactic acid (PLA) are examined under controlled degradation conditions. These results are correlated with the morphologies and continuity behavior of the various blend systems. It is found that thermoplastic starch degrades more rapidly than native starch. Lowering the glycerol content in the TPS has virtually no effect on its biodegradation behavior. The only contribution to biodegradation of the TPS blend is from the TPS component. Blending TPS with LDPE and PLA in a co‐continuous morphology at a 50/50 composition provides a significant increase in TPS surface area, which increases the biodegradation rate for the blends as compared to pure TPS. The results indicate a close relationship between morphology, phase continuity, and biodegradation behavior.
A new class of aromatic, hydrazide‐based, zigzag polymer has been synthesized using the Yamazaki polymerization conditions. Hydrophobic, hydrophilic or amphiphilic side chains are introduced to the backbones to tune their solubility in organic solvents of different polarities. The side chains form successive, intramolecular, six‐membered RO···HN hydrogen bonds, which increase the planarity of the backbones. The new shape‐persistent polymers are revealed to self‐assemble into vesicles or fibers to gelate organic solvents of different polarities. The polymeric backbones may be regarded as a conceptual extension of the emerging foldamers, which are usually constructed from oligomeric backbones.
The present work describes, for the first time, the synthesis of spiral nanostructures of conducting polymers by chemical oxidant polymerization using a hydrated surfactant (sodium dodecyl sulfonate (SDSn)) crystallite template. A spiral dislocation structure on the surface of a hydrated SDSn crystallite has been observed and is responsible for the growth of the spiral nanoarchitecture of conducting polymers (polypyrrole, polyaniline). Ammonium peroxydisulfate (APS) has a strong tendency to induce the formation of a spiral dislocation structure of hydrated SDSn crystallites. The mechanism of adsorption of pyrrole or aniline oligomers on the steps of dislocation is proposed for the growth of conducting polymer spirals.
Electrospinning at relatively low polymer concentrations produces polymer particles rather than fibers. To study the relationship between solvent characteristics and particle morphologies, PMMA was electrospun from seven different solvents and PSVPh random copolymers were electrospun from solutions in MEK. High‐speed photography was used to visualize the particle‐formation process. Based on these studies, a qualitative relationship between the solvent properties and the electrospun particle morphologies is discussed. By tailoring the solution properties and electrospinning conditions, particles with different morphologies (porous polygonal particles, solid polygonal particles, hollow spheres, cups etc) can be produced.
P(AN‐GMA) and PGMA fibers coated with monodisperse silver nanoparticles have been prepared by a combination of electrospinning and electroless plating. The morphology of the electrospun fibers remains unchanged after surface hydrazination. Oxidation of hydrazine in an ammoniacal solution of AgNO3 reduces and deposits silver atoms along the fiber surface, which then coalesce to Ag particles. The size of the silver nanoparticles is varied between 20–60 nm. Since the density of the active sites for silver reduction is lower in P(AN‐GMA), a smaller particle size could be obtained. The catalytic activity of the silver nanoparticles has been confirmed.
A novel core/sheath glycosylated polyphosphazene nanofibrous membrane for use in protein recognition is fabricated via coaxial electrospinning process with alkyl polyphosphazene as the sheath and polyacrylonitrile (PAN) as the core, followed by introduction of saccharide residues to the surface of the polyphosphazene nanofibrous membrane using alkyne–azide “click” chemistry. A glucose/protein binding assay effectively demonstrates that this nanofibrous membrane can selectively recognize Con A while showing almost no binding with bovine serum albumin (BSA). Furthermore, the affinity capability of proteins (BSA and Con A) for the glycosylated polyphosphazene surface is investigated quantitatively using a surface plasmon resonance (SPR) technique.
A novel norbornene monomer bearing a thermally curable benzoxazine group is synthesized and polymerized by ROMP using the Grubbs first‐generation ruthenium catalyst. The $\overline {M} _{{\rm w}} $ of the side‐chain benzoxazine functionalized polyoxanorbornene can be up to 87 000 Da with unimodal molecular‐weight distribution and narrow polydispersity between 1.18 and 1.65. Thermally activated ring‐opening polymerization of benzoxazine moieties leads to the formation of highly cross‐linked structures. The effects of molecular weight on the thermal ROP of polybenzoxazine precursors are examined.
