Large area microdomain alignment in a ferroelectric liquid crystalline diblock copolymer (LCBCP) poly(styrene)-block-poly(isoprene-LC), (PS-PILC), incorporating a biphenyl 3-nitro-4-alkoxybenzoate LC mesogenic group and a non-LC block hexagonally packed cylinder microstructure, was successfully accomplished by application of a magnetic field at elevated temperatures. Small-and mediumangle X-ray scattering demonstrated that the PS cylinders in the LC matrix orient over large areas with their long axes perpendicular to the applied magnetic field. Correspondingly, the smectic layers of the LC mesophase in the matrix are also perpendicular to the field as the anchoring of the mesogens at the intermaterial dividing surface (IMDS) between the cylindrical microdomains and the matrix is planar (homogeneous) in this material. A negative diamagnetic anisotropy for the LC mesogens is inferred from the data. A lamellar sample was also studied and found to exhibit no preferred microstructural orientation when subjected to the magnetic field. This result is consistent with the orientational state degeneracy of planar anchoring of mesogens at the flat lamellar IMDS and closely parallels our prior results obtained by orientation of nonferroelectric LCBCPs using oscillatory shear. IntroductionIncreasingly, research on the structure of soft matter has focused not just on the physics of the self-assembly of interesting materials, but on methods to control and direct the formation of the structures themselves, whether by understanding and directly manipulating the physics of self-assembly in the materials 1-4 or simply by empirically searching for useful process conditions. Structure-property-processing relationships in novel and emerging classes of soft materials are, more and more, highlighted by a comprehensive understanding of structure on the micro-and nanoscales.Block copolymers, while not entirely new and unknown materials, still do represent one such class of soft mattersmany demonstrate great promise as materials for application in various macroscopic as well as microscopic technologies, 5 and their performance is often greatly affected by both their rich structure on the micron scale and at the microdomain level. Thus, methods are sought to control and produce globally wellaligned microstructure in these materials. Liquid crystalline block copolymers incorporate the mesoscale selfassembly of mesogenic units within the broader context of microphase separation and block microdomain formation. The interplay of the two self-assembly processes and the consequences thereof on the structure-property relationships in these materials has been well studied by other workers in this field, 6-10 including work on mechanical shear alignment. 11,12

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Janus nanoparticles have been synthesized consisting of approximately 5 nm magnetite nanoparticles coated on one side with a pH-dependent and temperature-independent polymer (poly(acrylic acid), PAA), and functionalized on the other side by a second (tail) polymer that is either a pH-independent polymer (polystyrene sodium sulfonate, PSSNa) or a temperature-dependent polymer (poly(N-isopropyl acrylamide), PNIPAM). These Janus nanoparticles are dispersed stably as individual particles at high pH values and low temperatures, but can self-assemble at low pH values (PSSNa) or at high temperatures (>31 degrees C) (PNIPAM) to form stable dispersions of clusters of approximately 80-100 nm in hydrodynamic diameter. The Janus nanoparticle compositions were verified using FTIR and XPS, and their structures observed directly by TEM. Their clustering behavior is analyzed by dynamic light scattering and zeta potential measurements.

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SynopsisTo deformation and fracture behavior of several polypropylene (PP) and rubber-modified PP materials have been investigated. Plastic deformation mechanisms of these systems depend upon the test rate and temperature with high rates and low temperatures being in favor of crazing. The ductility and toughness of these materials are explained in light of the competition between crack formation and the degree of plastic deformation through crazing and shear yielding. The second phase morphology with smaller average rubber particle diameter D appears to be more efficient than that with larger Din toughening PP. Theoretical calculations indicate that the stresses imposed upon the rubber particles due to volume shrinkage of PP during crystallization are sufficient to compensate for the stresses due to differential thermal contraction in cooling from solidification temperature to end-use temperature. The difference between these two is small, and therefore they provide very little contribution to interfacial adhesion between rubber particle and PP matrix, the adhesion being insufficient for the rubber particles to be effective in controlling craze propagation. The rubber particles, in addition to promoting crazing and shear yielding, can also improve the fracture resistance of PP by varying the crystalline structure of PP (e.g., reducing the spherulite dimensions).

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A quantitative study of space charge solute segregation at grain boundaries in TiO, is conducted, using a new STEM method for the measurement of aliovalent solute accumulation. It is shown that the electrostatic potential at grain boundaries can be varied in sign and magnitude with doping, oxygen pressure, and temperature, and that the isoelectric point lies in slightly donor-doped compositions for samples annealed in air. The experimental results closely fit the space charge model in Part I. Space charge solute segregation is found even in defect regimes of high electron concentration. Approximately one in ten grain boundaries are "special" in exhibiting no detectable segregation; in one such instance a twin boundary is identified. Among boundaries with significant amounts of segregation, clear differences in potential also exist. From the potential determined in acceptor-and donor-doped compositions, the Frenkel energy (assumed to be lower than the Schottky energy in TiO,) can be separated into its individual terms. An average value for the titanium vacancy formation energy of gVn = 2.4 eV and an upper limit to the titanium interstitial formation energy of g , = 2.6 eV are obtained.while the solubility of Nb,O, is reported to be 0.7-3 m~l%'-~ in the temperature range used in this study.Another major distinction between this and previous studies is the use of a highly quantitative method for measuring aliovalent solute segregation. We have developed a scanning transmission electron microscope (STEM) method for accurately measuring the total accumulation of solute at an interface. From the net amount of acceptor or donor segregation as a function of composition and temperature, the relationship between the electrostatic potential and the lattice defect structure has been systematically studied. These results are reported here, and are quantitatively compared with the pxedictions of the model in Part I. Experimental Procedure ( I ) Sample PreparationPowders were coprecipitated from aqueous solutions of TiCI, (Johnson Matthey 99.999%) to which NbCl, (Puratronic 99.999%), AIC13.6H,0 (Puratronic 99.9995%), or Ga(NO,), (Puratronic 99.999%) was added in the desired concentrations. Polyethylene or Teflon labware and 18-MCl deionized water was used throughout powder processing to minimize impurities. A number of additional precautions, discussed in greater detail in Ref. 6, were necessary because of the high volatility of TiCI,, its highly exothermic reaction with water, and the hygroscopic and/or reactive nature of the dopant salts. The basic process' consists of first preparing an aqueous solution of TiCI, by mixing the chloride with water and ice. The dopant salts were dissolved into this solution and homogenized by stirring. To this colorless, precipitate-free solution, a 1 : 1 solution of NH,OH:H,O was slowly added while stimng to precipitate the metal hydroxides, reaching a solution pH of about 10. The precipitate was allowed to digest while stirring for at least 1 h, and then thoroughly washed by repeated dilution...