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The solution behavior of poly(butylene terephthalate) (PBT) copolyesters with dilinoleic monomer units (dilinoleic diol (LD) / dilinoleic diacid (LA)) is studied to understand the processing behavior from melt. NMR investigations show that the short‐chain branches are characterized by a distribution of different alkyl chain lengths, where n‐butyl (C4) and longer chains have the largest content (>55 mol%). High‐temperature size exclusion chromatography with threefold detection (multi‐angle light‐scattering, refractive index, and viscosity detector) in 1,2,4‐trichlorobenzene is performed to determine molar masses, hydrodynamic radii, viscosity radii, and Kuhn–Mark–Houwink–Sakurada (KMHS) exponents α in dependence of the molar amount of short‐chain branched comonomers. Low concentrations of dilinoleic comonomers in PBT copolyesters improve the solubility of the copolyesters significantly. Higher amounts cause contraction of the polymer coils as illustrated by smaller hydrodynamic radii as well as lower KMHS exponents. The α values decrease with increasing amount of short‐chain branched comonomer except for very low concentrations. The solution behavior of LA and LD copolyesters with a higher aliphatic content shows different trends of the influence of short‐chain branches on the melt behavior, which reflects the influence of intramolecular versus intermolecular entanglements in solution and in melt. [ABSTRACT FROM AUTHOR]

Two readers offer suggestions for ways to increase iron in toddlers other than by supplement: healthier food, and breastfeeding. [ABSTRACT FROM AUTHOR]

Ethylene vinyl acetate copolymer (EVA) is the most commonly used embedding material in crystalline silicon photovoltaics. It is responsible for fixing module components, electrical isolation and protecting cells against mechanical and environmental stresses. The degradation of EVA during weathering can cause adhesion loss, the so called delamination, and yellowing of the foil, resulting in a drop of module efficiency. In order to improve the long-term stability, several stabilizers including UV-absorber, hindered amine light stabilizer and phosphite are added to the polymer. However, the exact influence of the different stabilizers on failure mechanisms has not yet been identified in detail. Therefore, different EVA foils containing variable additive formulations were exposed to artificial UV-irradiation at 50 °C. As a result, delayed EVA degradation could be observed depending on stabilizers added. On the other hand, some of the tested additives were found to be involved in delamination and yellowing processes. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the interactions between poly(propylene imine) (PPI) dendrimers and 2′-/3′-O-(N′-methylanthraniloyl)-ATP (Mant-ATP). Mant-ATP was used as a model molecule. Purine and pyrimidine nucleoside analogues are antimetabolites commonly used in therapy for cancer. Drug molecules can complex with dendrimers in two ways: therapeutic agents may be attached in dendrimer interior or bind to functional groups on the surface. Drugs attached to nanoparticles are characterized by improved solubility, pharmacokinetics and stability. Here, we have used poly(propylene imine) dendrimers of the 4th and 5th generations (PPI G4 and PPI G5) with primary amino surface groups partially modified with maltose (PPI-m) or without modification (PPI). We assessed the efficiency of complex formation in relation to dendrimer generation, pH of solution and the type of dendrimer used. A double fluorimetric titration method was used to estimate the binding constant ( K) and the number of binding centers per molecule of the binding agent ( n). [ABSTRACT FROM AUTHOR]

Abstract: Partially ethoxysilyl-modified hyperbranched aliphatic–aromatic polyesters (HBPs) were effectively used as toughening as well as multi-site coupling agents in the preparation of organic–inorganic UV-thermal dual-cured epoxy/TEOS coatings. Through chain transfer reaction of the phenolic terminal units of the HBPs effective incorporation in the epoxy resin is achieved in the photo-initiated cationic polymerization whereas the ethoxysilane groups allow effective formation of a strongly interconnected inorganic–organics network during the in-situ sol-gel process with TEOS by binding the organic to the inorganic phase. Under those conditions, the addition of the inorganic precursor to the epoxy/HPB (20 wt%) system induced an increase of the storage modulus and more important, an improvement of the viscoelastic properties by extending the performance of the elastic modulus to higher temperatures. Thus, highly transparent hybrid coatings with enhanced thermal-mechanical and surface hardness properties resulted by the use of the partially ethoxysilyl-modified HBPs as multifunctional coupling agents. [Copyright &y& Elsevier]

Organic and inorganic salts of the hexacyano-[3]-radialene anion-radical are readily available and thermally stable compounds (up to ∼180 °C). The tetrabutylammonium salt exhibits an extremely high solubility in a range of solvents (＞300 mg l−1 in CHCl3) and acts as an efficient p-dopant for poly(3-hexylthiophene) to provide composite films with a conductivity above 2 S cm−1. [ABSTRACT FROM AUTHOR]

Femtosecond laser-induced two-photon polymerization (2PP) of carbon nanofiller doped polymers was utilized to produce electrically conductive microstructures, which are expected to be applicable as microelectronic components or micro-electromechanical systems in sensors. The nanocomposites were processed by compounding an inorganic-organic hybrid material with two different types (short and long) of single walled carbon nanotubes (SWCNTs). Different SWCNT contents were dispersed in the polymer by sonication to adjust the electrical conductivity of the nanocomposites. Low surface resistivity values of ~ 4.6 × 10 5 Ω/sq. could be measured for coated reference films with a thickness of 30 μm having an exceptionally low SWCNT content of 0.01 wt% of the long type of SWCNTs. In contrast, a higher minimum resistivity of 1.5 × 10 6 Ω/sq. was exhibited for composites with a higher content, 2 wt%, of short SWCNTs. The structural quality of the microstructures processed by 2PP was mainly influenced by the dispersion quality of the SWCNTs. To characterize the electrical conductivity, conductive atomic force microscopy was applied for the first time. In microstructures with 0.05 wt% of the long type of SWCNTs, a contact current could be detected over a wide range of the measured area visualizing the electrical conductive CNT network, which has not been reported before. [ABSTRACT FROM AUTHOR]

Poly(ionic liquid)s with alkyl imidazolium moieties in the main chain were synthesized by step growth addition polymerization of the AB monomers 1-(4-chlorobutyl)-1 H -imidazole, 1-(6-chlorohexyl)-1 H -imidazole, and 1-(6-bromohexyl)-1 H -imidazole in the melt. The molar masses of the polymers were controlled by adding 1-butyl-1 H -imidazole as monofunctional chain stopper. The bromine containing monomer polymerized spontaneously at room temperature whereas the chlorine containing monomers were sufficiently stable up to 40 °C. This could be evidenced by DSC measurements which showed a broad exothermal peak above 40 °C caused by the polymerization. MALDI-TOF investigations proved that dissociation of the alkyl imidazolium groups which might disturb the expected directional chain topology (AB-AB-AB…) did not occur. This is an important precondition for the intended cross-linking free grafting reactions of the AB monomers on halide containing polymers without any danger of gelation. Additionally, the results of the MALDI-TOF investigations indicated partial complexation of the polymer with the matrix and structural rearrangements during the measurements which converted the ionic imidazolium moieties into neutral moieties. The thermal behavior of the poly(ionic liquid)s has proved to be dependent on the length of the alkyl linking group between the imidazolium moieties and the type of counter ion. [ABSTRACT FROM AUTHOR]

Electrically conductive films of polymers with low content of multiwalled carbon nanotube (MWCNT) polymers were prepared by multilayer spray coating technology; these films are suitable for application such as electrodes or charge transport layers in sensor systems. Melt mixed polymer/MWCNT composites with varying MWCNT content were first prepared, where the polymer was one of polycarbonate (PC), polymethylmethacrylate (PMMA) or polyvinylidenfluoride (PVDF). For spray coating, these composites were then dissolved in suitable solvents (chloroform or dimethylformamide). To ensure good dispersion of MWCNTs, the solutions were sonicated for a few minutes. Spray coating was carried out on glass and polyethylene terephthalate substrates in a nitrogen-purged glove box. The electrical properties of the spray coated films were evaluated by conducting surface and volume resistivity measurements and by conductive atomic force microscopy. Additional properties – including roughness, thickness and optical transmittance – were studied. Composite films prepared with PC showed low surface resistivity values of 1.3 × 10 5 Ω/sq. at a MWCNT content of 4 wt%. PMMA-based composite films exhibited similar values at a MWCNT content of 3 wt%. The lowest surface resistivity value (6.4 × 10 4 Ω/sq.) and volume resistivity value (5.1 × 10 3 Ω cm) were attained for PVDF/MWCNT composites containing only 2 wt% of MWCNTs; these films also exhibited the lowest roughness values and largest optical transmittance compared to PC- and PMMA-based composites. Electrically conductive films with minimum MWCNT contents between 2 and 4 wt% and a thickness of few microns were successfully produced by the spray coating method, which enables large area coverage and multilayer coatings at a high throughput with low material waste. [ABSTRACT FROM AUTHOR]

Homo- and copolymers of propene and 1-undecene were synthesized by controlled olefin polymerization (quasi-living polymerization) using two bis(phenoxyamine) zirconium complexes as catalysts. The controlled character is demonstrated by an asymptotic growth of molar mass as a function of polymerization time. For the first time, it was possible to synthesize block-like copolymers incorporating long 1-olefins like 1-undecene and propene blocks using the strategy of sequential monomer addition. The obtained copolymers have been characterized in terms of molecular and thermal properties. The copolymer composition was determined by 1 H NMR spectroscopy whereas the quantification of diads by 13 C NMR spectroscopy proves the blocky character of the polymers. SEC results confirm indirectly the formation of block-like copolymers showing monomodal molar mass distribution excluding the formation of two homopolymers. The DSC measurements revealed that the blocky samples show two melting and two crystallization peaks, in contrast to statistical copolymers. These results of DSC and NMR measurements give distinct indication of the blocky type of the copolymer structure. [ABSTRACT FROM AUTHOR]

Organo-modified aluminophosphate with kanemite-like structure was used for the in situ synthesis of polypropylene (PP) nanocomposites performed by metallocene-catalyzed polymerization. The filler exhibits a layered structure with different organic pending groups arranged in the interlayer space. Melt-compounded composites with the same filler were prepared for comparison. X-ray diffraction (XRD) and transmission electron microscopy (TEM) proved exfoliation of the filler in the PP matrix and formation of nanocomposite after in situ synthesis. In contrast, in the melt-composites the filler is agglomerated and only microcomposites are obtained. [ABSTRACT FROM AUTHOR]