Insoluble porous conjugated polymer films via phase separation and photo‐crosslinking for the trace detection of 2,4‐dinitrotoluene

A novel conjugated polymer film with microscale/submicroscale porous morphology fabricated from crosslinked poly(fluorene‐co‐carbazole) (PFC1) was developed for the detection of 2,4‐dinitrotoluene (DNT). The fluorescent conjugated polymer PFC1 with pendant photo‐crosslinkable coumarin groups was synthesized by Suzuki coupling polymerization. Taking advantage of the phase separation of PFC1/polystyrene (PS) blends in the film and the solvent‐resistant network, porous structured films were prepared by removal of PS. Films with porous morphologies exhibited marked responsive sensitivity to trace DNT vapor due to the unique porous structure favoring the diffusion of and association with DNT molecules. The formation of a crosslinked network by dimerization of the coumarin moieties may be beneficial for isolating the polymeric backbones, thus to some extent preventing chain aggregation. This facile fabrication method enabled the crosslinked porous films to be efficient fluorescence chemosensors towards the detection of trace amounts of DNT vapor.© 2012 Society of Chemical Industry     

Nanofabrication with metallopolymers ‐ recent developments and future perspectives

Synthetic polymers containing metals and metal centers have experienced rapid growth in the last two decades. Metal‐containing polymers have an unprecedented role to play in modern high‐tech applications including nanomanufacturing, sensing, separation and catalysis. Advancement in synthetic strategies for macromolecules has enabled the synthesis of novel, exotic and use‐inspired metallopolymers. Using state‐of‐the‐art design strategies, it is now possible to perform targeted synthesis of macromolecules with varied complexity that contain a range of metal centers either in the backbone or in the side chains of the organic moiety. The presence of an inorganic element (metals and metal centers) in organic moieties has led to a number of new physicochemical properties while implementing novel functionality to the polymer matrix. This review covers nanotechnology influenced by distinctive features of metal‐containing macromolecular systems, particularly in developing flexible, functional materials. © 2013 Society of Chemical Industry     

Molecular design and density functional theory investigation of novel low‐band‐gap copolymers between quinoid acceptors and aromatic donors

The structures and electronic properties of furo[3,4‐b]pyridine‐based alternating donor and acceptor conjugated oligomers, in which furan and pyrrole are used as donors, and their periodic polymers were investigated using density functional theory at the B3LYP/6‐31G(d) level. The bond lengths, bond length alternation, bond critical point (BCP) properties, nucleus‐independent chemical shift (NICS) and Wiberg bond index (WBI) were analyzed and correlated with conduction properties. The changes of bond length, BCP properties, NICS and WBI all show that the degree of conjugation increases with main chain extension. The changes of NICS also show that the conjugation is stronger in the central section than in the outer section. Hydrogen bonding interactions and nitrogen atom substitution in the acceptors play very important roles in the geometries, electronic structures and energy gaps. The theoretical results suggest that pyrrole‐based polymers are good candidates for conducting materials, compared with furan‐based polymers. With an increase of nitrogen atom substitution in the acceptors in these polymers, the intermolecular charge transfers along the polymeric axes are enhanced, and the bond length alternations and HOMO–LUMO energy gap for these polymers are decreased. The results suggest that the six polymers studied all have lower energy gaps (in the range 0.81–1.26 eV), which indicate that these proposed polymers are good candidates for n‐doping conductive materials, especially poly(7‐(furan‐2‐yl)furo[3,4‐e][1,2,4]triazine) and poly(7‐(1H‐pyrrol‐2‐yl)furo[3,4‐e][1,2,4]triazine). Copyright © 2011 Society of Chemical Industry     

Effects of mechanical force on crystalline structure of electrospun poly(1‐butene) membranes

Fibrous poly(1‐butene) membranes were prepared from solutions using mixed solvents via electrospinning. The electrospun fibrous poly(1‐butene) membranes were stretched at elongations of 8, 16 and 24%, respectively. Scanning electron microscopy and stress–strain analysis showed that the deformation was elastic at an elongation of 8%, while plastic deformation occurred above 16%. The crystalline transformation induced by mechanical stretching was investigated using wide‐angle X‐ray diffraction. The poly(1‐butene) membrane stretched at 24% exhibited decreased diffraction intensity at 2θ = 11.8° and 18.3°, corresponding to the (200) and (213) crystalline reflections, indicating that crystalline transformation from metastable form II to either stable form I or I′ occurred due to mechanical stretching. Copyright © 2011 Society of Chemical Industry     

Combustion properties and transference behavior of ultrafine microencapsulated ammonium polyphosphate in ramie fabric‐reinforced poly(L‐lactic acid) biocomposites

Flame‐retardant biocomposites have attracted much attention in past decades. They can provide many advantages, such as total biodegradability and their abundant renewable sources. In the work reported, biocomposites based on poly(L ‐lactic acid) (PLLA), ramie fabric (FAB) and microencapsulated ammonium polyphosphate (MCAPP) were synthesized via hot press molding using the powder‐stacking procedure. The effects of transference behavior of the flame retardant on sustaining flame retardancy of the biocomposites were investigated. Thermogravimetric analysis shows that the improved flame retardancy is due to an increased char residue at high temperature. Field emission scanning electron microscopy images and wide‐angle X‐ray diffraction data were used to investigate the hydrolysis reaction and transference behavior of ammonium polyphosphate in the biocomposites. UL‐94 testing and limiting oxygen index measurements show that the PLLA/FAB/MCAPP biocomposites retain their flame retardancy even after 21 days in UV‐irradiation hydrothermal aging tests. The good sustained flame retardancy of the PLLA/FAB/MCAPP biocomposites is attributed to the docking interactions and good distribution of MCAPP in the biocomposites. Copyright © 2010 Society of Chemical Industry     

Odor Significance of the Volatiles Formed During Deep-Frying With Palm Olein

Palm olein is currently considered to be one of the best options for deep-frying, but as with any other edible oil, during frying, deteriorative reactions produce off-flavor compounds that reduce the oil sensory quality. This study assessed the odor significance of the volatiles formed during 136 h of deep-frying a chicken product in palm olein, aiming to identify potential markers of the oil sensory quality during frying. The volatiles were isolated by solid phase microextraction, and identified by GC–MS. Trained judges assessed the odor intensity and quality of the volatiles formed during frying, evaluating the GC effluents through a GC–olfactometry technique called OSME. Two hundred and eight volatiles were detected by GC/MS in the palm olein after 136 h frying. Of these, heptanal, t-2-heptenal, decanal and t-2-undecenal were identified as potential markers of the sensory quality of palm olein during frying. Hexanal, pentanal and pentane, usually associated with lipid oxidation, showed no odor impact in the GC effluents, and were thus proven not to be good markers of the sensory quality of palm olein when used for a long frying period.     

Potenzial des IR Micro‐Imaging zur In‐situ‐Untersuchung chemischer Reaktionen in nanoporösen Katalysatoren

The in‐situ study of chemical reactions is an intensively studied research topic. A suitable method for this investigation is the IR micro‐imaging technique, which allows to record space‐ and time‐resolved IR spectra. The preparation of a suitable model system with a 3D pore system for the in‐situ recording of concentration profiles using IR micro‐imaging is described, enabling the space‐ and time‐resolved monitoring of catalytic reactions in nanoporous catalysts for the first time. The model system consists of a nanoporous glass monolith with gas‐tight sealed outer surface, therefore, enabling the recording of concentration profiles of cyclohexane and cyclohexane‐benzene mixtures as a function of time.     

Increased Prostaglandin Response to Oxytocin in Ewes Fed a Diet High in Omega-6 Polyunsaturated Fatty Acids

Diets high in omega-6 polyunsaturated fatty acids (n-6) are associated with increased prostaglandin F_2α (PGF_2α) synthesis in cattle, however, the specific effects on the potential prostaglandin response to an oxytocin challenge in sheep have not been reported. The aim of the current study was to determine whether oxytocin-stimulated PGF_2α was significantly increased when ewes were fed a diet high in n-6 compared with a control diet low in n-6. Merino x Border Leicester ewes (n = 30) received one of two dietary treatments, either high in n-6 (70 % oat grain) or low in n-6 (control diet, 100 % cereal/legume silage). Ewes consumed the diets for 44 days prior to two consecutive oxytocin challenges. Plasma n-6 and PGF_2α metabolite (PGFM) concentrations following oxytocin challenge were greater (P < 0.05) when ewes were fed a diet high in n-6 compared with the control diet. A higher availability of n-6 may have lead to an increased in vivo synthesis of PGF_2α, however, further research is required to determine the exact mechanisms involved.