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Polymer Crystals (polymer + crystal)

Distribution by Scientific Domains
Polymers and Materials Science80%

Selected Abstracts

Coordinatively Immobilized Monolayers on Porous Coordination Polymer Crystals,

ANGEWANDTE CHEMIE, Issue 31 2010
Mio Kondo Dr.
Flächenspezifisch: Koordinativ immobilisierte Monoschichten (CIMs) fluoreszierender Farbstoffe wurden auf spezifischen Einkristalloberflächen poröser Koordinationspolymere (PCPs) erzeugt (siehe Bild). Der Ansatz ermöglicht die Herstellung von funktionellen PCP-Kristalloberflächen mit präziser Steuerung von Fluoreszenz-Gating und Sensoreigenschaften. [source]

Selective preparation of poly(p -oxybenzoyl) by using fractional polycondensation

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 8 2006
Kunio Kimura
Abstract Selective preparation of poly(p -oxybenzoyl) (POB) in the copolymerization system of p -acetoxybenzoic acid (p -ABA) and m -acetoxybenzoic acid (m -ABA) was examined by using reaction-induced crystallization of oligomers. Polymer crystals mainly composed of p -oxybenzoyl moiety were precipitated when the content of m -ABA in the feed was 30 mol %. The formation of the polymer crystals was attributed to both the reactivity of monomer and the phase-separation behavior of oligomer. Reactivity of p -ABA was twice higher than that of m -ABA, and thereby, the homo-oligomers of p -oxybenzoyl moiety were more rapidly formed in solution than do co-oligomers at the early stage in polymerization. They were selectively precipitated by crystallization to form crystals because of low miscibility. Co-oligomers containing m -oxybenzoyl moiety were also formed in solution, but they were unable to be phase-separated because of higher miscibility. Further polycondensation occurred between oligomers in the precipitated crystals, leading to the formation of POB. This polymerization proceeded with selecting certain monomers by crystallization and afforded a new methodology for fractional polycondensation. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2732,2743, 2006 [source]

Impact of Nanoscale Confinement on Crystal Orientation of Poly(ethylene oxide)

MACROMOLECULAR RAPID COMMUNICATIONS, Issue 4 2010
Haopeng Wang
Abstract Using a layer-multiplying coextrusion process to fabricate films with thousands of alternating polymer nanolayers, we report here a new crystalline morphology in confined polymer nanolayers and an abrupt transition in the crystallization habit. At higher temperatures, poly(ethylene oxide) crystallizes as large, in-plane lamellae. A 5,°C change in the crystallization temperature produces an on-edge lamellar orientation. The results point to a transition from heterogeneous nucleation to substrate-assisted nucleation. This may be a general phenomenon that accounts for previously unexplained differences in the preferred chain alignment of confined polymer crystals. [source]

Crystalline/Crystalline Phase Transitions in Polymer Systems Consisting of Finite-Size Crystals in Each Crystalline Phase: Generalized Gibbs-Thomson Equation

MACROMOLECULAR THEORY AND SIMULATIONS, Issue 7 2010
Matsuo Hirami
Abstract For polymer systems of two crystalline phases of one polymer component, each phase being consisted of polymer crystals of a finite size, we derive the crystalline-crystalline phase transition relationship, i.e., generalized Gibbs-Thomson equation. Its application combined with the crystalline-liquid transition relationship (usual Gibbs-Thomson equation) to the phase behavior of PT phase diagram of polyethylene (PE) is investigated, where the orthorhombic-hexagonal phase transition of PE crystal under high pressure being involved. Comparison with experimental data leads to the estimates of the structural characteristics such as the ratios of (the end surface free energy of polymer crystal/crystal length) for the respective crystalline phases. [source]