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We have prepared a series of platinum complexes with a rodlike ligand and smectic (Sm) liquid crystals (LCs) to demonstrate polarized phosphorescence. The ligands for the Pt complexes “12F2PPyO8” [2-(4′-dodecyl-5′,6′-difluorophenyl)-5-octyloxypyridinato-N,C2′] and “12F2PPyO12” [2-(4′-dodecyl-5′,6′-difluorophenyl)-5-dodecyloxypyridinato-N,C2′] with long alkyl and alkoxy chains exhibited the Smectic A (SmA) phase, however no liquid crystallinity was evident in Pt complexes with LC ligands. The host LCs 1-(4-butyl-2,3-difluoro-phenyl)-4-(trans-4-pentylcyclohexyl)benzene (4F2PPCH5) and 2-(2,3-difluoro-4-hexylphenyl)-6-octyloxynaphthalene (6F2PNaO8) with long flexible chains showed wide SmA phase temperature ranges. Pt complex/Sm LC mixtures were oriented on rubbed polyimide substrates or by applying a magnetic field. The orientation coefficients of the magneto-oriented samples were recorded to be over 0.6 in the Sm LC temperature range. The oriented samples exhibited polarized optical emissions assigned to the monomer and excimer states, which were perpendicular to the orientation direction. This indicates that the transition dipole moment of the Pt complex is oriented from the ligand to the Pt atom. Pt complexes with rodlike ligands with long alkyl and alkoxy chains and host Sm LC with such chains are much more likely to obtain high order parameters and generate highly polarized optical emissions. In the mixtures, the polarization ratios of the monomer and excimer in the SmA phase were estimated to be approximately 2.5–2.9 and 4.6–5.4, respectively.

The influence of temperature during reactive extrusion of poly(L-lactide) (PLLA) on the molecular architecture and crystallization behavior was investigated for OO-(t-butyl) O-(2-ethylhexyl) peroxycarbonate-modified polymer. The long chain–branched PLLA (LCB-PLLA) content and its structure in the resulting slightly crosslinked PLLA (χ-PLLA) containing linear and LCB-PLLA were characterized by both analyses, size exclusion chromatography equipped with multiangle laser light scattering and rheological measurements. A reduction of LCB-PLLA content in χ-PLLA and an increase of number of branches in LCB-PLLA were found with increasing the extrusion temperature. An increase of extrusion temperature induces different process in the polymer: decrease of the lifetime of peroxide, increase of the radical concentration due to rapid peroxide decomposition rate, and increase of the chain diffusion to the amorphous phase. Among these indices, the lifetime of peroxide is a good index for crosslinking behavior of PLLA during extrusion. As for the isothermal crystallization behavior from the melt, the Avrami crystallization rate constant of χ-PLLA increases as an increase of LCB-PLLA content in χ-PLLA. This implies that LCB-PLLA acts as a nucleating agent for PLLA. Furthermore, regime analysis and the free energy of nucleus of χ-PLLA were investigated using Hoffman–Lauritzen theory. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Electrically conducting samples of polyaniline (PANI) were prepared by doping with dodecylbenzene sulfonic acid (DBSA) using a thermal doping method without the application of shear. Besides characterizing the samples using optical microscopy, SEM, UV-vis-NIR, the degree of doping and the electrical conductivity were also measured. The pure PANI powder consisted of aggregates of PANI particles and was non-conducting. In the shear-free thermal doping of the PANI/DBSA mixture, the original aggregates were progressively broken up into smaller pieces with increasing temperature while maintaining the original primary particle shape and size and which were dispersed rather uniformly in the DBSA matrix. The electrical conductivity of doped PANI increased with increasing doping temperature. This increase strongly mirrored the increase in the levels of DBSA directly associated with PANI and suggested that the increasing levels of PANI doping were directly responsible for the increase in electrical conductivity as a function of the doping temperature. Despite the absence of the absorption peak at around 800 nm, the sample absorbed strongly in the near-infrared. Moreover, PANI/DBSA samples possessing a higher ratio of absorbance at 2600 nm to that at 800 nm showed higher electrical conductivity. These results suggest that shear-free thermal doping provides a simple route to controlling the morphology of the mixture by enabling the disintegration of the micron scale aggregates present in the as-purchased PANI. This in turn can be used to control the degree of doping of the PANI and consequently the conductivity of the sample. Copyright © 2011 John Wiley & Sons, Ltd.

Polycarbonate (PC)/vapor-grown carbon fiber (VGCF) composite was prepated through melt compounding. It was unexpectedly found from differential scanning calorimetry (DSC) and wide angle X-ray diffraction (WAXD) that the crystallization of PC was substantially accelerated in the presence of the ordered graphite surface of VGCF. To make an aligned structure of PC crystallization together with the orientation of VGCF, a magnetic field of 2.4 T was applied to the composite under several temperature profiles. The WAXD pattern revealed that not only dispersed VGCF but also matrix PC orystallization was magnetically aligned through the optimization of processes. The evidence for PC crystallization by VGCF with and without magnetic force is described.

The effects of miscibility and blend ratio on uniaxial elongational viscosity of polymer blends were studied by preparing miscible and immiscible samples at the same composition by using poly(methyl methacrylate) (PMMA) and poly(acrylonitrile-co-styrene) (AS). Miscible polymer blend samples for the elongational viscosity measurement were prepared by using three steps: solvent blends, cast film, and hot press. A phase diagram of blend samples was made by visual observation of cloudiness. Immiscible blend samples were prepared by maintaining the prepared miscible samples at 200°C, which is higher than cloud points using a LCST (lower critical solution temperature) phase diagram. The phase structure of immiscible blends was observed by an optical microscope. The elongational viscosity of all samples was measured at 145°C, which is lower than the cloud-point temperature at all blend ratios. The elongational viscosity of PMMA and AS was similar to each other. The strain-hardening property of miscible blends in the elongational viscosity was only slightly influenced by the blend ratio, and this was also the case with immiscible blends. The strain-hardening property was only slightly influenced, whether it was miscible or immiscible at each blend ratio. Polydispersity in molecular weight for blend samples was not changed by GPC (gel permeation chromatography) analysis. Almost no change in the polydispersity of the molecular weight for blends and the similarity of elongational viscosity between PMMA and AS resulted in little influence of the blend ratio and miscibility on the strain-hardening property. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 757–766, 1999

Uniaxial elongational viscosity of low density polyethylene (LDPE) that was filled with glass bead, glass flake, talc, or glass fiber was measured. The effect of various inorganic fillers on the strain-hardening property in elongational viscosity was investigated. The strain-hardening property of LDPE became weaker by the addition of fillers in the order of glass bead, glass flake, and talc. Glass fiber filled LDPE showed a strain-softening property. The smaller the particle and the larger the aspect ratio, the weaker the strain-hardening property. Their causes were analyzed from the two terms, i.e., the relaxation spectrum and the damping function, by Bernstein-Kearsley-Zapas (BKZ) model. By the incorporation of fillers, the relaxation modules became larger, and the damping function became stronger in the order of glass bead, glass flake, talc, and glass fiber. Recoverable strain was also measured to understand weaker strain-hardening properties. The degree of recovery became smaller by the addition of fillers. It was found that the smaller the particles and the larger the aspect ratio, the smaller the degree of recovery. It was concluded that weaker strain-hardening properties of LDPE composite than that of LDPE are caused by stronger damping function and smaller degree of recovery.

The effect of miscibility on elongational viscosity of polymer blends was investigated in homogeneous, miscible, and immiscible states by the blend of 1.5 wt % of ultrahigh-molecular-weight (UHMW) polymer. The matrix polymer was either poly(methyl methacrylate) (PMMA), or poly(acrylonitrile-co-styrene) (AS) that has a comparable elongational viscosity value. The homogeneous blend consisted of 98.5 wt % of PMMA and 1.5 wt % of UHMW–PMMA. The miscible blend was composed of AS and UHMW–PMMA at the same ratio. The immiscible blend was a combination of AS and UHMW–polystyrene (PS) at the same ratio. The strain-hardening behavior of the different blends were compared with that of pure PMMA. It was demonstrated that 1.5 wt % of UHMW induces a strong strain-hardening property in the homogeneous and miscible blends but was hardly changed in the immiscible blend. The optical microscope observation of the immiscible blend suggested that the UHMW domains were stretched, but that the degree of domain deformation was less than a given elongational strain. It was concluded that the strain-hardening property is strongly affected by the miscibility of UHMW chain and matrix. The strong strain-hardening property is caused by the deformation of the UHMW polymer. UHMW chains are stretched when they are entangled with surrounding polymers. However, UHMW chains in an immiscible state are not so deformed because of viscosity difference and no entanglements between domain and matrix. A smaller degree of UHMW chain deformation in immiscible state results in weaker strain-hardening property. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 961–969, 1999

The influence of random and block copolymerized structures on the uniaxial elongational viscosity was investigated. The investigated random copolymers were poly(ethylene-random-ethyl methacrylate) with comb-branched structure and poly(styrene-random-acrylonitrile) with linear structure. The studied block copolymers were poly(styrene-block-ethylenebutylene-block-styrene) with linear structure. The elongational viscosities of random copolymers showed strain-hardening properties. The strain-hardening property was influenced little by comonomer contents and depended on whether copolymers had linear or branched structures. In contrast, the elongational viscosities of block copolymers gave strain-softening properties. The strain-softening property was not affected by strain rates and block comonomer ratios. The causes of strain-hardening and -softening properties are discussed from relaxation spectrum and damping function based on the Bernstein–Kearsley–Zapas model. The damping functions of linear and branched random copolymers agreed with those of linear and branched homopolymers, respectively. On the other hand, linear block copolymers exhibited stronger damping than linear homopolymers. It was concluded that strain-hardening and -softening properties in the elongational viscosity of random and block copolymerized structures are correlated with their damping functions. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 69: 1765–1774, 1998

Effects of block copolymerized structure on nonlinear stress properties under elongational and shear deformation were investigated. Samples used in this study were poly(styrene-block-butadiene-block-styrene) (SBS, weight rate of S/B = 40/60) and polystyrene (PS) as a reference. Tensile stress–strain and shear stress relaxation properties were measured at the molten state. SBS showed high elasticity after reaching the yield point under elongational deformation at room temperature. PS melt showed substantial tensile stress increase after the yield point as strain rates increased. However, SBS melt did not exhibit noticeable tensile stress rise at higher elongation, and this property was almost independent of strain rates. Stress relaxation experiments revealed that the damping function of SBS melt was more strain-softening than that of PS melt. The results suggested that the block copolymerized structure decreases melt elasticity under elongational and shear deformation. A transmission electron micrograph indicated that the lack of melt elasticity in SBS melt is caused by orientation of the lamellar structure toward the stretched direction during deformation. © 1995 John Wiley & Sons, Inc.