Atomic force microscopy (AFM), small angle X-ray scattering (SAXS), temperature modulated differential scanning calorimetry (TMDSC), variable heating rate DSC, an independent rapid heating rate method for melting points, and cyclic mechanical testing were used to study semicrystalline thermoplastic elastomeric polypropylenes (ELPPs) and related semicrystalline polyolefins including ethylene copolymers. Low crystallinity (ca., 9 and 15%) ELPP samples were studied by AFM in the nonoriented and melt-oriented states. AFM images taken as a function of time after quenching of a melt-drawn and highly nucleated film resolved details of secondary crystallization involving lateral growth on the ordered row-nucleated structures. For nonoriented films, isothermal melt crystallization at high temperatures (110 °C) led to similar features for the two ELPPs. The dominant crystalline morphology studied by AFM consisted of small (several nm in width) granular crystallites organized into immature but large spherulites spanning tens of microns. A striking cross-hatch morphology was detected in regions of the surface in 110 °C crystallized samples, which is contrasted with melt-drawn films where row nucleated structures dominated the morphology in the film under no external stress. AFM was also used to monitor the morphological changes that occurred as the films were stretched at 25 °C. Break-down of lamellae was observed, resulting in oriented narrow fibrils. Cyclic stress-strain curves showed the expected result where lower crystallinity ELPPs had higher recoverable levels of set after both 100 and 500% elongation. TMDSC was used to resolve the broad melting and recrystallization regions in these low to medium crystallinity ELPP systems, and to contrast the results with ethylene copolymers. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011

The crystal morphological properties of segmented poly(ether ester aramide) elastomers with aromatic hard-segment amide units of uniform length were studied. Four samples with hard-segment fractions ranging from 3.4 to 9 wt % were studied by tapping atomic force microscopy (AFM). For one sample, both solution and melt-processed surfaces were examined, and similar crystal morphologies were found. The semicrystalline morphologies of these polymers had some similarities to other low-hard-segment segmented elastomers. The very thin needlelike or ribbonlike crystallites at the surface had a high aspect ratio for all the samples. The main difference observed for the different compositions was a decrease in the surface area density of ribbons with a decrease in the hard-segment fraction. One sample was chosen for in situ AFM studies during film extension. The details of the crystallite orientation and breakup were studied in increments up to 700% elongation (8 X stretch ratio) and after relaxation. (C) 2004 Wiley Periodicals, Inc.

Temperature modulated differential scanning calorimetry (TMDSC), variable heating rate DSC, and tapping atomic force microscopy (AFM) were used to study semi-crystalline liquid crystalline polymers (LCPs). Main chain LCPs included a random copolyester (Vectra® A950) and an azomethine alternating copolymer. For the azomethine LCP the TMDSC non-reversing signal detected broad exothermic transitions associated with melting and recrystallization as the slow DSC heating scan induced surprisingly large morphological changes. Non-isothermally crystallized Vectra® and some isothermally crystallized samples at lower temperatures exhibited different levels of DSC scan induced crystal reorganization. Such crystal metastability was also studied by variable heating rate DSC and an independent technique for estimating the melting point at very rapid heating rates. The TMDSC characterization of the scan induced crystal perfection in Vectra® was substantially different than for the other polymers studied. In most cases even though crystal perfection was occurring, no clear exotherm was detected in the non-reversing signal. High temperature annealing for long times resulted in degrees of crystal perfection which could be studied by DSC with minimal scan induced reorganization. High resolution tapping AFM was used to elucidate details of crystal morphology for mechanically oriented and non-oriented Vectra® before and after annealing. Structures resembling lamellae were found to be oriented perpendicular to the chain direction in the oriented Vectra®. In the non-oriented film broad and sometimes curved ‘lamellae’ were detected. They were about 1000nm long and between 20 and 35nm wide, with the width increasing slightly as a function of increased annealing time at 260°C melt crystallization conditions. Substructure of the lamellae in both oriented and non-oriented Vectra® consisted of smaller stacked crystallites which are detected by AFM studies of these surfaces.

New AFM methods were applied to resolve the morphology of the ionic domains in poly(ethylene-co-methacrylic acid) copolymers. Using standard tapping AFM techniques with a precision in the lateral dimensions on the order of a nanometer, the crystalline lamellar structure and overall morphology consisting of stacks of ethylene-rich lamellae separated by sometimes broad noncrystalline regions were characterized. By operating the AFM under special low oscillation amplitude conditions where tip-ionic cluster interactions could be induced to dominate the phase signal, it was shown that this method could be used to uniquely resolve ionic-rich regions and individual ionic domains. The individual domains were found to be on the order of 2 nm in diameter. Small-angle X-ray scattering (SAXS) characterization was used to confirm some aspects of the morphology and to contrast the different levels of resolution of the two techniques for both lamellar crystals and ionic domains. By sequential images taken under different tapping AFM conditions, the "softer" amorphous regions were found to be the richest in ionic domains. Lamellar morphology and perfection were found to be controlled by mobility in the melt which depends on acid level, neutralization level, and counterion type in the different ionomers studied. The crystalline domains in the metal neutralized ionomers were compared to the unneutralized "acid" form of the ionomer. Data for the acid form verified that no ionic domains exist in this material.

In this paper we describe an experimental procedure that can be used to study the photoreduction of metal ions on the surfaces of individual TiO2 particles. The submicrometer-sized particles are isolated on porous membranes, characterized by atomic force microscopy (AFM), removed from the microscope, exposed to AgNO3 solution and light, and reimaged. Photoreduction of Ag+ produces 5−50 nm particles of Ag0 distributed over the surfaces of the TiO2 particle. This procedure allows the spatial distribution of the chemical reactivity of particle surfaces to be mapped at the nanometer scale resolution of the atomic force microscope. Using different excitation wavelengths (366, 400 and ∼600 nm), we demonstrate by AFM that the photoreduction of Ag on single anatase or rutile particles is consistent with the differences in the band gaps of the bulk samples. We also show that the Ag0 particles are not uniformly distributed over the TiO2 crystallite surfaces implying that a closer study of the unreacted particle sur...

The nanophase separated hard segment domains in solvent cast alms of a segmented polyurethane and a segmented polyamide elastomer were imaged in real space using phase and topographical information from tapping-mode AFM techniques. A styrene triblock copolymer was used as a control to demonstrate the contrast mechanisms. For the segmented polyurethane and polyamide elastomers, contrast results from local stiffness variations of hard domains beneath a ca. 1 nm thick soft segment overlayer. Domain sizes and dispersity, shape, orientation, spacing, and uniformity in space are uniquely extracted from these real space AFM data. The ca. 7 nm diameter domains were relatively symmetric and uniformly space filling in the polyurethane. They were lamellar or sheetlike in the segmented polyamide elastomer, with a high aspect ratio and no curvature. There was no obvious correlation of lamellae orientation with macrocrystal aggregate (spherulite) position in the polyamide copolymer, while no such aggregates exist in the polyurethane.

[MnOEP][A] {A=[TCNE](.-) and [C-4(CN)(6)](.-)} have been isolated as extended 1D coordination polymers with trans-mu(2)-[A] bridging ligands with strong {A=[C-4(CN)(6)](.-)} and weak {A=[TCNE](.-)} ferromagnetic coupling as evidenced from the fit of the magnetic susceptibility to the Curie-Weiss law (theta=5.1 and 67.1 K, respectively); the strong behaviour arises from the presence of uniform chains which are not present for the [TCNE](.-) salt.

Cooperative magnetic interactions have been observed in α‐[MnPc][TCNE], which results from the reaction of manganese phthalocyanine with tetracyanoethylene. This is the latest in a series of molecule based materials found to exibit such unusual magnetic behaviour. The α polymorph displays very strong magnetic coupling, while the coupling in β‐[MnPc][TCNE] is much weeker. The IR data suggest that the behaviour of the α polymorph is unlikely to be unique among the metallomacrocyclic electron‐transfer complexes. It is proposed that uniformity of the one0‐dimensional chains in α‐[MnPc][TCNE] and the corresponding lack of uniformity of those in the β polymorph may give rise to the difference in behaviour.

Cooperative magnetic interactions in molecular materials at room temperature are the goal of much interdisciplinary research. The title compound is shown to have a Tc of 18 K and to be of a new structural type which makes it a suitable model for the previously reported, disordered, infusible V(TCNE), which is a room‐temperature magnet. The synthesis and structure of the new material are discussed.

Cooperative magnetic interactions in molecular materials at room temperature are the goal of much interdisciplinary research. The title compound is shown to have a T c of 18 K and to be of a new structural type which makes it a suitable model for the previously reported, disordered, infusible V(TCNE), which is a room‐temperature magnet. The synthesis and structure of the new material are discussed.

${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{6+\mathrm{x}}$ is known to undergo a transition from a magnetic semiconductor to a metallic high-temperature superconductor as the oxygen content is increased from the range 0.0\ensuremath{\le}x\ensuremath{\le}0.5 to 0.5\ensuremath{\le}x\ensuremath{\le}1.0. We report here detailed temperature-dependent magnetic-susceptibility studies for x in the composition range 0.0\ensuremath{\le}x\ensuremath{\le}1.0. For 0.05\ensuremath{\le}x\ensuremath{\le}0.5, the effective moment ${\ensuremath{\mu}}_{\mathrm{eff}}$ decreases with decreasing temperature from 300--160 K, as expected for an antiferromagnet whose N\'eel temperature is above room temperature. Below 160 K, ${\ensuremath{\mu}}_{\mathrm{eff}}$ increases, reaching a maximum at \ensuremath{\sim}40 K then decreases again. The magnitude of this low-temperature peak in ${\ensuremath{\mu}}_{\mathrm{eff}}$ increases with x, reaches a maximum at x=0.35, then decreases toward zero. A Monte Carlo simulation method has been used to model the three-dimensional antiferromagnetic ordering of this system as a function of oxygen composition. The calculation reveals the presence of spin frustration as x increases from 0 to 0.3 in accord with the increasing number of effective moments at low temperatures. Above x=0.3 a new long-range order (corresponding to a doubling of the magnetic unit cell perpendicular to the planes) is predicted to occur in agreement with the observed magnetic susceptibility and recent neutron-diffraction experiments of Kadowaki et al. and Lynn et al. Above x=0.5, relatively few localized moments are observed in the temperature-dependent susceptibility measurement. In the metallic regime the ``Pauli susceptibility'' is observed to increase approximately linearly with oxygen content. This is in accord with decreasing effects of antiferromagnetic correlation with increasing x.