Synthesis of spherical shape borate-based bioactive glass powders prepared by ultrasonic spray pyrolysis

Spherical shape borate-based bioactive glass powders with fine size were directly prepared by high temperature spray pyrolysis. The powders prepared at temperatures between 1200 and 1400 °C had mixed phase with small amounts of fine crystal and an amorphous rich phase. Glass powders with amorphous phase were prepared at a temperature of 1500 °C. The mean size of the glass powders prepared by spray pyrolysis was 0.76 μm. The glass powders prepared at a temperature of 1200 °C had two distinct exothermic peaks (T_c1 and T_c2) at temperatures of 588 and 695 °C indicating crystallization. The glass transition temperature (T_g) of the powders prepared at a temperature of 1200 °C was 480 °C. Phase-separated crystalline phases with spherical shape were observed from the surface of the pellet sintered at a temperature of 550 °C. Crystallization of the pellet was completely occurred at temperatures of 750 and 800 °C. The pellets sintered at temperatures below 700 °C had single crystalline phase of CaNa₃B₅O₁₀. The pellet sintered at a temperature of 800 °C had two crystalline phases of CaNa₃B₅O₁₀ and CaB₂O₄.     

NMR determination of crystallinity for poly(?-l-lysine)

Crystallinity of poly(?-l-lysine) (?-PL) was discussed by analyzing the differences in the ¹H spin-spin relaxation times (T₂^H), the ¹³C spin-lattice relaxation times (T₁^C), and the ¹³C NMR signal shapes between the crystalline and the non-crystalline phases. The observed ¹H relaxation curve (free induction decay followed by solid-echo method) showed the sum of Gaussian and exponential decays. Similarly, the observed ¹³C relaxation curves obtained from the Torchia method were double-exponential. The ¹³C NMR spectrum of ?-PL was divided into the narrow and the broad lines by utilizing the intrinsic differences in the ¹H spin-lattice relaxation times in the rotating-frame between them, which are attributed to the crystalline and the non-crystalline phases, respectively. Even though the crystallinity is obtained from the identical NMR measurements, the estimated values are different with each other. The crystallinity estimated from the T₂^H differences was 75.8 ± 0.1% at 333 K and 60.7 ± 0.4% at 353 K. From the T₁^C differences, the value was estimated to be 62 ± 11%. Furthermore, the value estimated from the NMR signal separation was 54 ± 5%. In this study we have explained these discrepancies by the difference in susceptibility among the experiments for the inter-phase, which exists in-between the crystalline and the amorphous phases. Furthermore, the estimated crystallinity was ascertained by the X-ray diffraction experiment.     

Phase transitions of lignin-based polycaprolactones and their polyurethane derivatives

Alcoholysis and kraft lignin-based polycaprolactones (LigPCL) were synthesized by the polymerization of ε-caprolactone which was initiated by the hydroxyl (OH) group in lignin. LigPCL-based polyurethanes were also prepared from LigPCL. The caprolactone (CL)/OH ratio of the CAPCLs was changed from 1 to 25 mol mol⁻¹. Thermal properties of the LigPCL and LigPCL-based polyurethane (PU) sheets were studied by differential scanning calorimetry (DSC). Glass transition temperature (T_g), heat capacity difference at T_g (ΔC_p) cold crystallization temperature (T_cc) and melting temperature (T_m), were determined by DSC. The main chain motion of lignin is observed in the whole CL/OH ratio. When CL/OH ratio exceeds 5 mol mol⁻¹ in the LigPCL samples and 10 mol mol⁻¹ in the LigPCL-based PU samples, the crystalline region which is organized by the PCL chain association is observed. It was found that PCL chain association is controlled by both chain length and chemical cross linking.     

High-performance polypropylene film prepared from reactor powders having different characteristics

Ultra-high molecular weight isotactic polypropylene (UHMW-iPP) reactor powders have been successfully ultra drawn below melting temperature (T_m) by a combination of calendar rolling and tensile drawing techniques. Two UHMW-iPP reactor powders having different MWs were synthesized by using the same Ziegler-Natta catalyst system at 70 °C in hexane. The resultant tensile properties increased with increasing draw ratio, due to orientation-crystallization during tensile draw, which was indicated by DSC and WAXD measurements. The film drawn under optimum conditions exhibited the maximum tensile modulus of ∼25 GPa, independent of sample MW, corresponding to 70% of the ultimate modulus of iPP crystal. However, the higher maximum tensile strength of ∼1.0 GPa was achieved for the reactor powder having the higher MW, which is three times as high as those of commercial high-strength iPP tapes. Such a fact that high performances have been achieved by processing from reactor powder state below T_m implies that crystallization with less entanglement occurs during polymerization. When drawability and resultant properties were compared among different iPP reactor powders prepared under different conditions, it was clarified that they were predominantly affected by not only MW but also by the reactor powder morphology, especially surface smoothness.     

Co γ-irradiation-initiated RAFT polymerization of VAc at room temperature

In this work, the reversible addition-fragmentation chain transfer (RAFT) polymerization of vinyl acetate (VAc) was successfully performed at room temperature using ⁶⁰Co γ-irradiation as the initiation source. Under the dose rate of 10 Gy/min irradiation, the polymerization proceeded smoothly and converted approximately 90% of the monomer within 7 h. The molecular weight distribution (M_w/M_n) remained narrow (M_w/M_n < 1.35) up to 90% conversion. Compared to AIBN-initiated RAFT polymerization at 60 °C, ⁶⁰Co γ-irradiation-initiated RAFT polymerization is a technique that can better control the molecular weight, especially at high conversion. The ¹H NMR spectra and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry confirmed that most of the chain ends of poly(VAc) (PVAc) from γ-irradiated RAFT polymerization were living and can be reactivated for chain-extension reactions. The microstructures of PVAc from ⁶⁰Co γ-irradiated RAFT polymerization (almost head-to-tail addition) and AIBN-initiated RAFT polymerization (5% tail-to-tail addition) were different, as revealed by the ¹³C NMR spectra. For the first time, ⁶⁰Co γ-irradiation was used as an initiation source for RAFT polymerization of VAc at room temperature.     

Wool powders used as sorbents to remove Co ions from aqueous solution

The Co²⁺ sorption of two wool powders was investigated using its radioisotope ⁵⁷Co (T_1/2 = 271.8 days and γ = 122.1 and 136.5 keV) as a tracer. The effects of the type of buffer, the pH value, the contact time and the initial concentration of Co²⁺ on the sorption behaviour of wool powders were studied. The Co²⁺ releasing ability of wool powders and the re-use of wool powders to sorb Co²⁺ were also examined. The optimum sorption of Co²⁺ by the powders occurred at pH 8 in phosphate buffer and pH 10 in ammonium sulphate buffer. Fourier-transform infrared spectroscopy (FTIR) was used to study the changes in chemical structure of the wool after exposure to both buffer solutions. Compared to the untreated wool fibre, the fine wool powders showed rapid sorption rates and high sorption capacities for Co²⁺. Co²⁺ ions were recovered after exposing the Co²⁺ loaded wool to HCl (0.1 M) and buffer at pH 3 (glycine/sodium chloride). After releasing Co²⁺ ions from wool powders, the efficiency of wool powders re-used to sorb Co²⁺ was 80% of that of the fresh wool powders. It is concluded from this study that wool powder can be used as an efficient sorbent to remove and release Co²⁺ from solution.     

Synthesis of nanocrystalline ytterbium-doped yttria by citrate-gel combustion method and fabrication of ceramic materials

Nanosized ytterbium doped yttria powders were prepared by citrate-gel combustion techniques. As-synthesized precursor and calcined powders were characterized for their crystalline structure, particle size and morphologies. Nanocrystalline Yb³⁺:Y₂O₃ powders with pure cubic yttria crystal structure were obtained by calcination of as-prepared precursors at 1100 °C for 3 h. Powders obtained were well dispersed with an average particle size of 60 nm. By using the obtained powders, nearly full dense Yb³⁺:Y₂O₃ ceramics were produced by vacuum sintering at 1800 °C for 12 h. The emission spectrum of the sintered ceramics under the excitation wavelength of 905 nm illustrates that there are three fluorescence peaks locating at 976 nm, 1030 nm and 1075 nm respectively, all corresponding to the ²F_5/2 → ²F_7/2 transitions of ytterbium ion.     

Structural and spectroscopic properties of Nd:Y2Si2O7 phosphors

Phosphors of α-Y₂Si₂O₇ doped with Nd³⁺ ions were prepared using the sol–gel technique. Nano-sized crystalline phosphor powders were obtained by annealing the dried gels at 960 °C. The crystallization properties of the phosphor powders were determined from their XRD patterns. The α-Y₂Si₂O₇ phase was the only phase observed in all compositions. As the amount of amorphous SiO₂ in the composition was increased, the crystalline sizes and the widths of the size distribution curves were found to decrease from 17.8 nm to 10.6 nm and from 15.6 nm to 12.2 nm, respectively. The spectroscopic properties of the powders were studied by measuring the luminescence and the decay patterns of the ⁴F_3/2→ ⁴I_9/2 and ⁴F_3/2→ ⁴I_11/2 transitions between 50 K and 310 K. No appreciable effect of the crystallite sizes on the average lifetime of the ⁴F_3/2 level was observed at temperatures below 100 K. The effect of temperature, however, becomes relevant above 100 K as the size of α-Y₂Si₂O₇ nano-crystal becomes smaller.     

Influence of precursor Bi/Fe ion concentration on hydrothermal synthesis of BiFeO3 crystallites

In this study we investigated the effect of precursor Bi³⁺/Fe³⁺ ion concentration on the hydrothermal synthesis of BiFeO₃ crystallites. It is demonstrated that the phase-purity and morphology of the products is highly dependent on the metal ion concentration. Phase-pure BiFeO₃ crystals can be prepared at the Bi³⁺/Fe³⁺ ion concentration ranging from 0.025 to 0.0625 M. The samples prepared at n(Bi³⁺/Fe³⁺)=0.025, 0.0375, 0.05, and 0.0625 M, are composed, respectively, of cuboid-like particles (100–200 nm), regular spherical agglomerates (30–40 μm) made up of irregular grains with size about several hundred nanometers, irregular flower-like clusters formed from irregular grains of several hundred nanometers in size, and octahedron-shaped particles (500–600 nm). These samples have a similar bandgap energy of 2.20 eV and exhibit a typical antiferromagnetic behavior at room temperature.     

Glass transition behavior and dynamic fragility in polylactides containing mobile and rigid amorphous fractions

The segmental dynamics of polylactide chains covering the T_g − 30 °C to T_g + 30 °C range was studied in absence and presence of a crystalline phase by dynamic mechanical analysis (DMA) using the framework provided by the WLF theory and the Angell's dynamic fragility concept. An appropriate selection of stereoisomers combined with a thermal conditioning strategy to promote crystallization (above T_g) or relaxation of chains (below T_g) was revealed as an efficient method to tune the ratio of the rigid and mobile amorphous phases in polylactides. A single bulklike mobile amorphous phase was taken for poly(d,l-lactide) (PDLLA). In turn three phases, comprising a mobile amorphous fraction (MAF, X_MA), a rigid amorphous fraction (RAF, X_RA) and a crystalline fraction (X_c) were determined in poly(l-lactide) (PLLA) by modulated differential scanning calorimetry (MDSC) according to a three-phase model. The analysis of results confirms that crystallinity and RAF not only elevate the T_g and the breadth of the glass transition region but also yields an increase in dynamic fragility parameter (m) which entails the existence of a smaller length-scale of cooperativity of polylactide chains in confined environments. Consequently it is proposed that crystallinity is acting in polymeric systems as a topological constraint that, preventing longer range dynamics, provides a faster segmental dynamics by the temperature dependence of relaxation times according to the strong-fragile scheme.     

Network structures and dynamics of dry and swollen poly(acrylate)s. Characterization of high- and low-frequency motions as revealed by suppressed or recovered intensities (SRI) analysis of C NMR

We recorded temperature-dependent high-resolution ¹³C NMR spectra of dry and swollen poly(acrylate)s [poly(2-methoxyethyl acrylate) (PMEA), poly(2-hydroxyethyl methacrylate) (PHEMA), and poly(tetrahydrofurfuryl acrylate) (PTHFA)] by dipolar decoupled-magic angle spinning (DD-MAS) and cross-polarization-magic angle spinning (CP-MAS) methods, to gain insight into their network structures and dynamics. Suppressed or recovered intensities (SRI) analysis of ¹³C CP-MAS and DD-MAS NMR was successfully utilized, to reveal portions of dry and swollen polymers which undergo fast and slow motions with fluctuation frequencies in the order of 10⁸ Hz and 10⁴-10⁵ Hz, respectively. Fast isotropic motions with frequency higher than 10⁸ Hz at ambient temperature were located to the portions in which ¹³C CP-MAS NMR signals of swollen PMEA were selectively suppressed. In contrast, low-frequency motion was identified to the portions in which ¹³C DD-MAS (and CP-MAS) signals are most suppressed at the characteristic suppression temperature(s) T_s. Network of PMEA gels (containing 7 wt% of water) turns out to be formed by partial association of backbones only, as manifested from their T_s gradient at lowered temperature, whereas networks of PHEMA (containing 40 wt% of water) and PTHFA (9 wt% of water) gels are tightly formed through mutual inter-chain associations of both backbones and side-chains, as viewed from the raised T_s values for both near at ambient temperature. It is also interesting to note that flexibility of gel network (PMEA > PTHFA > PHEMA) characterized by the suppression temperature T_s (PMEA < PTHFA < PHEMA) is well related with a characteristic parameter for biocompatibility such as the production of TAT (thrombin-antithrombin III complex) as a marker of activation of the coagulation system.     

Lamella reorientation in thin films of a symmetric poly(l-lactic acid)-block-polystyrene upon crystallization at different temperatures

The thin films of a symmetric crystalline-coil diblock copolymer of poly(l-lactic acid) and polystyrene (PLLA-b-PS) formed lamellae parallel to the substrate surface in melt. When annealed at temperatures well above the glass transition temperature of PLLA block (T_g^PLLA), the PLLA chains started to crystallize, leading to reorientation of lamellae. Such reorientation behavior exhibited dependence on the correlation between the crystallization temperature (T_c), the glass transition temperature of PS (T_g^PS), the peak melting point of PLLA crystals (T_m^PLLA), and the end melting point of PLLA crystals (T_m,end^PLLA). When annealed at (T_c=) 80 °C (T_c < T_g^PS < T_ODT, order-disorder transition temperature), 123 °C (T_g^PS < T_c < T_m^PLLA < T_ODT), 165 °C (T_g^PS < T_m^PLLA < T_c < T_m,end^PLLA < T_ODT), the parallel lamellae became perpendicular to the substrate surface, exclusively starting at the edge of surface relief patterns. Meanwhile, the corresponding lamellar spacing was significantly enhanced. The PLLA crystallization between PS layers was hypothesized to account for the lamella reorientation during annealing. The crystallization, chain conformation, and possible chain folding mechanisms were discussed, based on detailed analysis of the lamellar structure before and after crystallization.     

Detection of N-methyladenosine in urine samples by electrochemiluminescence using a heated ITO electrode

A sensitive and rapid electrochemiluminescence (ECL) method for the detection of N⁶-Methyladenosine (m6A) in urine samples on a heated indium-tin-oxide (ITO) electrode is presented. The ECL intensity of Tris(2,2′-bipyridyl) dichlororuthenium(II)hexahydrate (Ru(bpy)₃²⁺) can be enhanced by the presence of m6A. Experimental results showed that the change of ECL intensities (ΔI) of the Ru(bpy)₃²⁺ between before and after addition of m6A was affected by the working electrode surface temperature (T_e); the highest ΔI occurred at 31 °C. Under optimum conditions, the ΔI had a linear relationship with the m6A concentration in the range of 1.9 × 10⁻⁹-3.9 × 10⁻⁶ mol/L and a detection limit of 7.7 × 10⁻¹⁰ mol/L (S/N = 3) at T_e = 31 °C. The recovery of m6A standards added to urine samples verified the accuracy of the proposed method.     

Chemometric solid-state C NMR analysis of morphology and dynamics in irradiated crosslinked polyolefin cable insulation

The relative concentrations and carbon spin-lattice relaxation constants (T_1,C) of the amorphous, intermediate, and crystalline phases of unaged crosslinked polyolefin cable insulation (ultimate elongation, e=310%), ⁶⁰Co γ-irradiated (e=22%), and irradiated+annealed (e=220%) samples were determined by chemometric analyses of directly polarized solid-state ¹³C NMR spectra. The T_1,C relaxation curves of the intermediate and amorphous components were found to be mono-exponential. The intermediate component contains 23±5% of the CH₂ segments in the unaged sample and has an T_1,C relaxation constant of 1.4±0.3 s. γ-Irradiation caused a slight decrease in the amount of intermediate component to 19±5% and an increase of the relaxation constant to 1.8±0.3 s. The subsequent annealing of the irradiated sample resulted in an additional increase of the relaxation constant to 2.1 s and a slight loss of crystallinity. The amorphous T_1,C relaxation constants were found to be identical in all three samples and have a value of 0.38±0.03 s. At ambient temperature, the crystalline phase was found to relax via chain diffusion from the intermediate component. The rate of helical jumps was twice as fast in the irradiated and irradiated+annealed samples compared with the unaged material.     

Preparation, characterization and dielectric properties of CaCu3Ti4O12 ceramics

CaCu₃Ti₄O₁₂ nano-sized powders were successfully prepared by sol-gel technique and calcination at 600-900 °C. The thermal decomposition process, phase structures and morphology of synthesized powders were characterized by IR, DSC-TG, XRD, TEM, respectively. It was found that the main weight-loss and decomposition of precursors occurred below 450 °C and the complex perovskite phase appeared when the calcination temperature was higher than 700 °C. Using above synthesized powders as starting materials, CCTO-based ceramics with excellent dielectric properties (?₂₅ = 5.9 × 10⁴, tan δ = 0.06 at 1.0 kHz) were prepared by sintering at 1125 °C. According to the results, a conduction mechanism was proposed to explain the origin of giant dielectric constant in CCTO system.     

Conformation transition and molecular mobility of isolated poly(ethylene oxide) chains confined in urea nanochannels

Inclusion compounds formed from host small molecules and guest polymers have provided a novel platform to study the behavior of isolated polymer chains confined in nanochannels. In this article, the PEO chain conformation in the metastable poly(ethylene oxide) (PEO)-urea inclusion compound (IC) and its transition was characterized via a combination of different analytical methods. Based on the FTIR and Raman spectroscopy results, PEO chains in the metastable tetragonal IC are tentatively assigned to the tgg′ conformation. The structural changes of the metastable tetragonal IC to the stable trigonal form were observed via in situ FTIR and ex situ WAXD. The transformation is a kinetic solid-solid process and can even occur at room temperature. The activation energy of about 222 kJ/mol indicates that the transition occurred via cooperative disruption of several hydrogen bonds. Measurement of the laboratory frame spin-lattice relaxation time T₁ (¹³C) shows that molecular motions of the nanoconfined PEO chains are more intensive than the neat crystalline PEO but weaker than those of the neat amorphous PEO. Second harmonic generation microscopy demonstrates that the trigonal IC exhibits stronger nonlinear optical activity than the tetragonal IC. The intermolecular hydrogen bonding is attributed to the driving force for the transformation of the metastable tetragonal IC into the stable trigonal form.     

Kinetic study of the II-I phase transition of isotactic polybutene-1

Kinetics of the solid-solid II-I phase transition of isotactic polybutene-1 was investigated. The fraction W_I of phase I as a function of time t_tr during the phase transition was measured by X-ray diffraction at various temperatures T_tr. The Avrami indices n of the W_I-t_tr plots are approximately unity for T_tr > 288 K. A bell-shaped temperature dependence of the transition rate V with the maximum transition rate at 285 K was obtained. The V-T_tr curve and the Avrami index n = 1 suggest that the rate-determining process is primary nucleation. The dependence of V on T_tr for T_tr < 283 K is described by the William-Landel-Ferry (WLF) equation, which shows that the glass transition affects the transition rate. The Avrami index decreases to n < 1 for T_tr < 283 K, indicating a broadened distribution of the transition rate caused by the spatial heterogeneity of the amorphous state at low temperatures near the glass transition. Those evidences at low temperature clearly suggest that the solid-solid phase transition is influenced by the mobility of chain folding, tie chains and cilia in the amorphous between the stacks of lamellar crystals.     

Grain boundaries and the influence of the ionophilic-ionophobic balance on Li and F NMR and conductivity in low-dimensional polymer electrolytes with lithium tetrafluoroborate

⁷Li and ¹⁹F NMR linewidths and impedance spectra are reported for low-dimensional CmOn (I):LiBF₄ mixtures. Data for the ionophilic polymer C18O5 is compared with that for the ionophobic C18O1 and the block copolymer C16O1O5(21%) (21 mol% of C16O5). In C18O5:LiBF₄ (1:1) narrow ⁷Li linewidths, which were observed in the liquid crystal phase above the side chain melting temperature (∼50 °C), persist in the crystal down to ca. 0 °C and broaden below −20 °C. However, in C18O1:LiBF₄ (1:0.6) narrow ⁷Li linewidths were also observed down to −20 °C suggesting highly mobile neutral aggregates of salt since this system is non-conductive. In the copolymer C16O1O5(21%):LiBF₄ (1:0.7) the linewidths were even narrower down to −70 °C with weak temperature dependence. In all systems ¹⁹F linewidths were significantly broader than ⁷Li linewidths. The complex plane plots obtained by impedance spectroscopy exhibit characteristic minima identified with ‘grain boundary’ resistance and, following heat treatment, minima with weak temperature dependence identified with ‘internal crystal’ resistance, R_i, and conductivities, σ_i ≥ 10⁻⁴ S cm⁻¹. Four-component mixtures of copolymers CmO1O5 and CmO1O4 with LiBF₄ and ‘salt-bridge’ poly(tetramethylene oxide)-dodecamethylene copolymers gave conductivities of ca. 4 × 10⁻⁴ S cm⁻¹ at 20 °C with weak temperature dependence. A novel carrier-hopping mechanism of lithium transport decoupled from side chain melting in the crystalline state is postulated.      

Fluorescence improvement of Ba1.3Ca0.7SiO4:Eu,Mn phosphors via Dy addition and their color-tunable properties

A series of novel single-phase white phosphors Ba_1.3Ca_0.69−x−ySiO₄:0.01Eu²⁺,xMn²⁺, yDy³⁺ were synthesized by the solid-state method. The excitation spectra of these phosphors exhibit a broad band in the range of 260–410 nm, which can meet the application requirements for near-UV LED chips (excited at 350–410 nm). The emission spectra consist of two broad bands positioned around 455 nm and 596 nm, which are assigned to 5d→4f transition of Eu²⁺, and ⁴T₁→⁶A₁ transition of Mn²⁺, respectively. The luminescence intensity of phosphors enhances obviously by doping Dy³⁺ ions, and the intensity of two bands reaches an optimum when Dy³⁺ amounts to 2 mol%. In addition, thermoluminescence investigation of phosphor was conducted, getting two shallow trap defects with activation energy of 0.43 eV and 0.45 eV, which demonstrates the energy transfer mechanism of Dy–Eu through the process of hole and electron traps. By precisely tuning the Mn²⁺ content, an optimized white light with color rendering index (CRI) of R_a=84.3%, correlated color temperature (CCT) of T_c=8416 K and CIE chromaticity coordinates of (0.2941, 0.2937) is generated. The phosphor could be a potential white phosphors for near-UV light emitting diodes.     

Phase transitions and structural parameters of HIQ-40 liquid crystalline co-polyester

We describe the impact of thermal treatment on the structure and phase transitions of the liquid crystalline aromatic co-polyester, HIQ-40, comprising 40 mol% p-hydroxybenzoic acid (H), 30 mol% isophthalic acid (I), and 30 mol% p-hydroquinone (Q). Simultaneous, real-time wide and small angle X-ray scattering (WAXS, SAXS), differential scanning calorimetry, and optical ellipsometry were used to study initially isotropic, amorphous films of HIQ-40. Films were annealed above the glass transition temperature, T_g, at temperatures, T_a, from 130 to 290 °C. Depending upon T_a, thermal treatment results in formation of regions of nematic order and/or crystalline order in a disordered matrix. As T_a increases, molecular mobility in the amorphous phase increases resulting in a reduction in T_g. Two or three endothermic events are seen in all samples by thermal analysis. The lowest temperature endotherm is associated with melting of crystals formed either at T_a or during the thermal scan. The two higher temperature endotherm features result from transformation of crystal melt-to-nematic, and formation of more mobile nematic domains from constrained liquid, respectively, and are relatively insensitive to T_a.A strong Bragg scattering peak is seen for corresponding to formation of two-phase structure comprising crystals and disordered phase. At higher temperatures, very strong scattered intensity in the SAXS pattern re-emerges, even after all WAXS crystal reflections have disappeared. Results suggest that a two-phase structure, of ordered nematic domains co-existing with less ordered regions, may be forming continuously above the crystal melting point.