Search

Solid‐state cross‐polarization magic angle spinning (CPMAS) 13C NMR is employed to examine the morphological factors that contribute to the enhanced hole mobility observed in poly(3‐hexylthiophene) (P3HT) by the introduction of electrically inert poly(styrene) (PSt). Chain mobilities of crystalline and amorphous phases in the P3HT domain are evaluated utilizing T1C (13C spin‐lattice relaxation time in the laboratory frame). The crystallinity of P3HT component is estimated based on the spectral editing method through T1ρH (1H spin‐lattice relaxation time in the rotating frame) filtered CPMAS. Moreover, the miscibility of P3HT crystalline and P3HT amorphous domains is estimated. These results suggest the formation of the rigid amorphous (short‐range ordered amorphous) in a block copolymer (P3HT‐block‐PSt). An increase in the proportion of the crystallite and proximate presence of each crystallite in a blend sample of P3HT with PSt (P3HT‐blend‐PSt) are also indicated. Enhanced mobility is attributed to the larger portion of rigid amorphous domain for P3HT‐block‐PSt, and to higher crystalline content for P3HT‐blend‐PSt. [ABSTRACT FROM AUTHOR]

Poly(9,9-di-n-octylfluorene) (PFO) is a promising material for polymer light-emitting diodes (PLEDs) due to its advantageous properties. To enhance its electron transporting capabilities, diblock polymers were synthesized by attaching polystyrene (PSt) chains of varying lengths to one end of the PFO molecule. In a comparative study with PFO homopolymer, the diblock polymers maintained similar thermal properties, absorption spectra, and photoluminescent stability, while exhibiting slightly deeper lowest unoccupied molecular orbital (LUMO) levels and higher crystallinity. Notably, diblock polymers with shorter polystyrene blocks demonstrated higher electron mobility than the PFO homopolymer and diblock polymers with excessively long polystyrene blocks. These findings suggest that the optimal chain length of the polystyrene block is crucial for maximizing electron mobility, thus offering valuable insights for designing high-performance PLED materials. [ABSTRACT FROM AUTHOR]

This study reports the synthesis of a flexible light‐emitting polymer film by casting the solution formed by blending poly[2‐methoxy‐5‐((2‐ethylhexyl)oxy)‐1,4‐phenylenevinylene] (MEH‐PPV) with poly(styrene‐co‐butadiene‐co‐styrene) (SBS). Scanning force microscopy (SFM) and differential scanning calorimetry (DSC) confirm that MEH‐PPV molecules are selectively positioned in the polystyrene (PS) domain of the fabricated film. As MEH‐PPV molecules are dissolved in the PS phase without aggregation, the photoluminescence (PL) spectrum of the MEH‐PPV/SBS film exhibits a nanometer‐scale bicontinuous luminescent domain with low aggregation quenching. Furthermore, the MEH‐PPV/SBS film exhibits typical elastomeric characteristics (with linear elasticity, a plateau, and densification regions in its stress–strain curves), and its tensile properties are comparable to those of neat SBS films. As MEH‐PPV molecules are almost absent in the polybutadiene (PB) phase (which influences the bulk‐film elastic properties), the concentration of MEH‐PPV shows very little effect on the elastic properties of the composite film. [ABSTRACT FROM AUTHOR]

The characterization and gas permeation properties of ultraviolet (UV)-cured fluorine-containing telechelic polyimide membranes and end-capped with a crosslinker with acryloyl groups were investigated. Membrane formation property was improved by the addition of crosslinker by using UV irradiation. The densities of UV-cured membranes were almost similar to each other, and high gel fraction was shown on the UV-cured membranes. This result suggests that the crosslinker promotes crosslink reaction at the polymer chain ends and does not induce appreciable membrane densification. Furthermore, the gas permeability of the UV-cured membranes was higher than that of the membrane without the crosslinker. The higher gas permeability is due to the new crosslink structure formed at the polymer chain ends, which was promoted by the crosslinker after UV irradiation, but did not induce appreciable membrane densification. The use of a BEI crosslinker in the telechelic polyimide membranes promoted the crosslink reaction and increased the [H.sub.2] selectivity because H2 permeability was not sensibly affected by the crosslink reaction. POLYM. ENG. SCI., 54:1089-1099, 2014. © 2013 Society of Plastics Engineers, INTRODUCTION Fluorine-containing polyimides have been widely used as adhesives, electronic components, and gas separation membranes because of their greater thermal stability and mechanical strength, lower dielectric constant, and higher gas [...]

Bio‐based epoxy polymer was prepared from cardanol derivatives, epoxy prepolymer and phenalkamine at room temperature without solvent. Chemical structures of cured epoxy polymers were analyzed by FT‐IR and 1H NMR spectroscopy. The drying, physical, thermal, optical, and mechanical properties of the epoxy polymers were investigated in terms of the composition of epoxy and amine compounds, molecular weight of the epoxy prepolymer, and the effect of post‐curing process. The resultant epoxy polymers showed flexible nature, thermal stability (e.g., thermal decomposition temperature of 300°C). Furthermore, the epoxy polymers possessed the anti‐microbial activity against Escherichia coli and Staphylococcus aureus The molecular weight of the epoxy prepolymer also strongly affected the drying property, suggesting that the drying time can be controlled by the molecular weight of the prepolymer. Thermal treatment of the polymers as post‐curing was effective approach to improve the hardness, thermal stability, and mechanical strength. Hence, this cardanol derivatives‐based novel epoxy polymer can be expected as highly green functional epoxy polymers for coating, film and resin applications. [ABSTRACT FROM AUTHOR]

A novel fluorine-containing telechelic polyimide end-capped with acetylene group which derived from 4,4-(hexafluoroisopropylidene) diphthalic anhydride (6FDA), 3,4-diaminodiphenyl ether (DADE), and 4-(2-phenyle-thynyl) phthalic anhydride (PEPA) was synthesized using polycondensation. The physical and C[O.sub.2] permeation properties of its crosslinked membranes prepared by the cyclotrimerization reaction of the acetylene groups at the polymer chain end using tantalum (V) chloride (Ta[Cl.sub.5]) as a catalyst under thermal treatment was investigated in terms of C[O.sub.2]-induced membrane plasticization. The crosslinked membranes showed a gel content in organic solvent, which was good solvent of noncrosslinked membranes, and improved their thermal stability. Based on the measurement of the high-pressure time dependence on C[O.sub.2] permeation, the crosslinked 6FDA-DADE-PEPA membranes exhibited more resistance to C[O.sub.2]-induced plasticization than noncrosslinked 6FDA-DADE and thermal treated 6FDA-DADE-PEPA. Furthermore, the increase in Ta[Cl.sub.5] content resulted in more resistance to plasticization. The cyclotrimerization reaction of the acetylene groups at the polymer chain ends using a transition metal catalyst under thermal treatment was found to be more effective than conventional thermal treatments for suppressing membrane plasticization without the membrane densification. POLYM. ENG. SCI., 53:1667-1675, 2013. © 2012 Society of Plastics Engineers, INTRODUCTION Global warming is currently one of the most serious environmental problems. Global warming is closely related with increased C[O.sub.2] emissions from large fixed sources, such as power plants as [...]

The relations among polyimide membrane colors, their gas transport and separation properties, and their fluorescence spectra were systematically investigated using fluorine-containing aromatic polyimide, 6FDA TeMPD {[4,4-(hexafluoroisopropyiidene) diphthalic an hydride] [(6FDA)-2,3,5,6-tetramethyM,4-phenylene diamine (TeMPD)]}, which was used in electronic device and gas separation materials. Different molecular ordering structures of 6FDA-TeMPD polyimides were prepared by controlling kinds of casting solvents and dry conditions. This difference was based on the effect of charge transfer (CT) interaction formed by % elec trons of ring structures in polyimide. Membrane color measured using spectrophotometer determined colors as intrinsic parameters without sample collection. The permeability coefficients of oxygen and nitrogen of the 6FDA-TeMPD polyimide membranes were correlated with membrane color index parameters such as. L*, a*, b*, and Δ E*, and fluorescence properties such as maxi mum peak emission wavelength λ max and intensity /max, which reflect molecular ordering affected by CT inter action in polyimide membranes. POLYM. ENG. SCI., 51:2360-2369, 2011. [C] 2011 Society of Plastics Engineers, INTRODUCTION The color of polymer material generally changes accordingly with the change of chemical structure in car-bonyl, ethylene, or azo groups. Change of chemical structure is caused by the degradation [...]