Morphology Diagram of Single-Layer Crystal Patterns in Supercooled Poly(ethylene oxide) Ultrathin Films: Understanding Macromolecular Effect of Crystal Pattern Formation and Selection

A series of single-layer crystal patterns were observed in ultrathin films of 10 poly(ethylene oxide) fractions of molecular weights ranging from 2.02k to 932.0k g/mol. Morphology transitions between these different crystal patterns were quantitatively identified, and a morphology diagram with respect to supercooling and molecular weight dependencies was constructed. This will foster understanding of the macromolecular effects on the crystal pattern formation and selection critically associated with the parameters of molecular diffusion length and growth anisotropy.

Synthesis of fullerene-containing poly(ethylene oxide)-block-polystyrene as model shape amphiphiles with variable composition, diverse architecture, and high fullerene functionality

Click chemistry provides a precise and effective approach towards construction of fullerene-containing block polymers with diverse architecture, and high fullerene functionality.

Breaking symmetry toward nonspherical Janus particles based on polyhedral oligomeric silsesquioxanes: molecular design, "click" synthesis, and hierarchical structure

The design, synthesis, and self-assembly of a series of precisely defined, nonspherical, polyhedral oligomeric silsesquioxane (POSS)-based molecular Janus particles are reported. The synthesis aims to fulfill the "click" philosophy by using thiol-ene chemistry to efficiently install versatile functionalities on one of the POSS cages. In such a way, both the geometrical and chemical symmetries were broken to create the Janus feature. These particles self-organize into hierarchically ordered supramolecular structures in the bulk. For example, the Janus particle with isobutyl groups on one POSS and carboxylic groups on the other self-assembles into a bilayered structure with head-to-head, tail-to-tail arrangements of each particle, which further organize into a three-dimensional orthorhombic lattice. While the ordered structure in the layers was lost upon heating via a first-order transition, the bilayered structure persisted throughout. This study provides a model system of well-defined molecular Janus particles for the general understanding of their self-assembly and hierarchical structure formation in the condensed state.

Theory of X-ray reflection broadening for textures with double-axis averaging: from semicrystalline polymers exhibiting twisted lamellar growth to discotic liquid crystals

It is shown that textures with double-axis averaging similar to thea-texture, or Keller–Machin Type I texture, are not specific to semicrystalline polymers exhibiting twisted lamellar growth. In this work, such texture is observed in extruded fibers of a typical discotic molecule,trans-diC60-Zn porphyrin. Experimentally, these textures can be detected from the characteristic `comma'-like azimuthal profiles of the non-equatorial diffraction peaks in two-dimensional X-ray patterns. Analytical expressions for the azimuthal intensity distribution are developed, which are in good agreement with the experiment. In the proposed generalized coordinates, the diffraction peak shape becomes universal. This provides a simple means of checking the closeness of the sample morphology to thea-texture from just one two-dimensional pattern, without constructing the whole X-ray pole figure.

Epitaxial Phase Transformation between Cylindrical and Double Gyroid Mesophases

Complex phase transformation between the hexagonal cylinder (Hex) and double gyroid (G) phases in a polystyrene-block-poly(ethylene oxide) (PS-b-PEO) diblock copolymer was investigated using two-dimensional (2D) synchrotron small-angle X-ray scattering (SAXS), and transmission electron microscope (TEM). The PS-b-PEO sample contained a small population of another bicontinuous cubic phase having an Im3m symmetry. These two bicontinuous cubic phases (G and Im3m) had the same unit cell dimensions. Under a large-amplitude reciprocating shear, the bicontinuous cubic phases transformed into a “single-crystal”-like Hex phase. When annealed at 150 °C for 40 min, the Hex phase partially transformed into well-oriented twinned structures of the G and Im3m phases without significant loss of orientation in 2D SAXS measurements. Epitaxial phase transformation relationships between the Hex/G and Hex/ Im3m phases were identified. The mechanism of the Hex → G transformation was examined by TEM.

Poly(beta-alanoid-block-beta-alanine)s: synthesis via cobalt-catalyzed carbonylative polymerization and self-assembly

The titled diblock copolymers are synthesized via cobalt-catalyzed living carbonylative polymerization of N-alkylaziridines under moderate pressures followed by a deprotection step. The poly(beta-alanine) block is solubilized by the poly(beta-alanoid) block in chloroform and remains fully hydrogen-bonded in the form of a sheet-like assembly.