A biogeographically mixed late Guadalupian (late Middle Permian) brachiopod fauna from an exotic limestone block at Xiukang in Lhaze county, Tibet

A total of 17 brachiopod species belonging to 15 genera are recorded from a limestone block of about 3×4 km2 in the Indus–Tsangbo suture zone at Xiukang in Lhaze County of Tibet. The brachiopod fauna generally indicates a Late Guadalupian age (late Wordian–Capitanian, late Middle Permian) based on its association with the Timorites-bearing ammonoid fauna and the presence of the brachiopod Urushtenoidea crenulata. Palaeobiogeographically, the fauna exhibits transitional/mixed characters between the warm-water Cathaysian and cold to temperate Gondwanan faunas and may have developed on a carbonate build-up or seamount on the oceanic crust.

Improving the color yield of ink-jet printing on cationized cotton

This study examines the performance of digital ink-jet printing on cationized cotton treated with polyepichlorohydrin-dimethylamine (PECH-amine). The results show that the color yield of ink-jet printing with reactive inks on cationic modified cotton is much greater than that on untreated cotton. The effect on the increase of color yield by cationic modification is greater than that by preparation with alkali, urea, and thickener. The reason for this is that introducing positively charged sites increases dye uptake and dye fixation on cationized cotton. The results also show that cationic modification with PECH-amine decreases the rub fastness but increases the wash fastness of the treated cotton.

Selective hydrogen bonding and hierarchical nanostructures in poly(hydroxyether of bisphenol A)/poly(ε-caprolactone)-block-poly(2-vinyl pyridine) blends

The phase behavior, hydrogen bonding interactions and morphology of poly(hydroxyether of bisphenol A) (phenoxy) and poly(var epsilon-caprolactone)-block-poly(2-vinyl pyridine) (PCL-b-P2VP) were investigated using differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) spectroscopy, optical microscopy and atomic force microscopy (AFM). In this A-b-B/C type block copolymer/homopolymer system, both P2VP and PCL blocks have favorable intermolecular interaction towards phenoxy via hydrogen bonding. However, the hydrogen bonding between P2VP and phenoxy is significantly stronger than that between PCL and phenoxy. Selective hydrogen bonding between phenoxy/P2VP pair at lower phenoxy contents and co-existence of two competitive hydrogen bonding interactions between phenoxy/P2VP and phenoxy/PCL pairs at higher phenoxy contents were observed in the blends. This leads to the formation of a variety of composition dependent nanostructures including wormlike, hierarchical and core–shell morphologies. The blends became homogeneous at 95 wt% phenoxy where both blocks of the PCL-b-P2VP were miscible with phenoxy due to hydrogen bonding. In the end, a model was proposed to explain the microphase morphology of blends based on the experimental results obtained. The swelling of the PCL-b-P2VP block copolymer by phenoxy due to selective hydrogen bonding causes formation of different microphases
--Session data-->

Nanostructures and nanoporosity in thermoset epoxy blends with an amphiphilic polyisoprene-block-poly(4-vinyl pyridine) reactive diblock copolymer

Nanostructured thermoset blends were prepared based on a bisphenol A-type epoxy resin and an amphiphilic reactive diblock copolymer, namely polyisoprene-block-poly(4-vinyl pyridine) (PI-P4VP). Infrared spectra revealed that the P4VP block of the diblock copolymer reacted with the epoxy monomer. However, the non-reactive hydrophobic PI block of the diblock copolymer formed a separate microphase on the nanoscale. Ozone treatment was used to create nanoporosity in nanostructured epoxy/PI-P4VP blends via selective removal of the PI microphase and lead to nanoporous epoxy thermosets; disordered nanopores with the average diameter of about 60 nm were uniformly distributed in the blend with 50 wt% PI-P4VP. Multi-scale phase separation with a distinctly different morphology was observed at the air/sample interface due to the interfacial effects, whereas only uniform microphase separated morphology at the nanoscale was found in the bulk of the blend.

Self-assembled complexes of poly(4-vinylphenol) and poly(ε-caprolactone)-block-poly(2-vinylpyridine) via competitive hydrogen bonding

Nanostructured complexes were prepared from poly(ε-caprolactone)-block-poly(2-vinylpyridine) (PCL-b-P2VP) and poly(4-vinylphenol) (PVPh) in tetrahydrofuran (THF). The phase behavior, specific interactions, and morphology were investigated using differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) spectroscopy, optical microscopy, atomic force microscopy (AFM), transmission electron microscopy (TEM), and small-angle X-ray scattering (SAXS). In this A-b-B/C type block copolymer/homopolymer system, both blocks of the PCL-b-P2VP block copolymer have favorable intermolecular interaction toward PVPh via hydrogen bonding, but the interaction between P2VP block and PVPh is significantly stronger than that between PCL block and PVPh. It was found that the disparity in competitive intermolecular interactions, specifically PVPh and P2VP block interact strongly whereas PVPh and PCL block interact weakly, leads to the formation of a variety of nanostructures depending on PVPh concentration. Spherical micelles of 30−40 nm in diameter were obtained in the complex with 10 wt % PVPh, followed by wormlike micelles with size in the order of 40−50 nm in the complexes with 30−60 wt % PVPh. At low PVPh concentrations, PCL interacts weakly with PVPh, whereas in the complexes containing more than 20 wt % PVPh, the PCL block began to interact considerably with PVPh, leading to the formation of composition-dependent nanostructures. The complex becomes homogeneous with PVPh content beyond 60 wt %, since a sufficient amount of PVPh is available to form hydrogen bonds with both PCL and P2VP. Finally, a model was proposed to explain the self-assembly and microphase morphology of these complexes based on the experimental results obtained. The competitive hydrogen-bonding interactions cause the self-assembly and formation of different microphase morphologies.

Nanostructure and hydrogen bonding in interpolyelectrolyte complexes of poly(ε-caprolactone)-block-poly(2-vinyl pyridine) and poly(acrylic acid)

Nanostructured poly(ε-caprolactone)-block-poly(2-vinyl pyridine) (PCL-b-P2VP)/poly(acrylic acid) (PAA) interpolyelectrolyte complexes (IPECs) were prepared by casting from THF/ethanol solution. The morphological behaviour of this amphiphilic block copolymer/polyelectrolyte complexes with respect to the composition was investigated in a solvent mixture. The phase behaviour, specific interactions and morphology were investigated using differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) spectroscopy, optical microscopy (OM), dynamic light scattering (DLS) and atomic force microscopy (AFM). Micelle formation occurred due to the aggregation of hydrogen bonded P2VP block and polyelectrolyte (PAA) from non-interacted PCL blocks. It was observed that the hydrodynamic diameter (D_h) of the micelles in solution decreased with increasing PAA content up to 40 wt%. After 50 wt% PAA content, D_h again increased. The micelle formation in PCL-b-P2VP/PAA IPECs was due to the strong intermolecular hydrogen bonding between PAA homopolymer units and P2VP blocks of the block copolymer. The penetration of PAA homopolymers into the shell of the PCL-b-P2VP block copolymer micelles resulted in the folding of the P2VP chains, which in turn reduced the hydrodynamic size of the micelles. After the saturation of the shell with PAA homopolymers, the size of the micelles increased due to the absorption of added PAA onto the surface of the micelles.

Competitive hydrogen bonding and self-assembly in Poly(2-vinyl pyridine)-block-Poly(methyl methacrylate)/ Poly(hydroxyether of bisphenol A) blends

Blends of poly(2-vinyl pyridine)-block-poly(methyl methacrylate) (P2VP-b-PMMA) and poly(hydroxyether of bisphenol A) (phenoxy) were prepared by solvent casting from chloroform solution. The specific interactions, phase behavior and nanostructure morphologies of these blends were investigated by Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), dynamic light scattering (DLS), atomic force microscopy (AFM), and transmission electron microscopy (TEM). In this block copolymer/homopolymer blend system, it is established that competitive hydrogen bonding exists as both blocks of the P2VP-b-PMMA are capable of forming intermolecular hydrogen bonds with phenoxy. It was observed that the interaction between phenoxy and P2VP is stronger than that between phenoxy and PMMA. This imbalance in the intermolecular interactions and the repulsions between the two blocks of the diblock copolymer lead to a variety of phase morphologies. At low phenoxy concentration, spherical micelles are observed. As the concentration increases, PMMA begins to interact with phenoxy, leading to the changes of morphology from spherical to wormlike micelles and finally forms a homogenous system. A model is proposed to describe the self-assembled nanostructures of the P2VP-b-PMMA/phenoxy blends, and the competitive hydrogen bonding is responsible for the morphological changes.

Self-assembled monolayers into the 21st century : recent advances and applications

The modification of an interface on a molecular level with more than one molecular ‘building block' is essentially an example of the ‘bottom–up' fabrication principle of nanotechnology. The fabrication of such integrated molecular systems in electrochemistry has seen rapid progress in recent years via the development of sensing interfaces fabricated using self-assembled monolayers (SAMs). This review outlines recent advances and applications of self-assembled monolayers for modifying electrodes with an emphasis on the development of integrated molecular systems. First, some basic issues regarding fabricating integrated molecular systems, such as the role of the surface topography of the electrode and patterning surfaces, are discussed. Subsequently an overview of recent developments in pH, inorganic and bio sensing involving the use of SAMs is given. Finally emerging trends in using molecular building blocks in the fabrication of integrated molecular systems, such as nanotubes, dendrimers and nanoparticles, are reviewed.