POLYMERS Vol.64　No.2 February 2015

POLYMERS　Vol.64　No.2

COVER STORY
A Strong Property Produced from Weakness

COVER STORY: Highlight Reviews

The Role of Hydrogen Bonds in Bio-Nanomaterials

Akira ISOGAI

<Abstract> Crystalline bio-nanomaterials with widths <100 nm can be prepared from native celluloses or chitins by maintaining hydrogen bonds inside crystaline microfibrils and simultaneously position-selective cleavage of inter-fibrillar hydrogen bonds. In the preparation of composites with cellulose or chitin nanofibers, they have to be present in the matrix polymers as individual nanofiber elements without agglomeration owing to formation of inter-fibrillar hydrogen bonds. Thus, the control of hydrogen bonds at various levels or orders for the crystalline celluloses and chitins has a significant influence on efficient preparation of nanofibers, their morphologies/yields/surface structures, and their applications. TEMPO-mediated oxidation allows wood cellulose fibers to be converted to completely individualized cellulose nanofibrils with homogeneous ～3 nm widths and high aspect ratios >150. Because these cellulose nanofibrils have anionic carboxylate groups densely and regularly on each nanofibril surface, formation of hydrogen bond between nanofibrils or between nanofibrils and matrix polymer molecules is controllable by controlling counter ions of carboxyl groups of the nanofibrils.
Keywords: Cellulose / Chitin / Nanofiber / TEMPO / Microfibril / Composite Materials

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Polymer Crystals with Hydrogen Bond

Chizuru HONGO, Takashi NISHINO

<Abstract> Hydrogen bonds between the polymer chains play an important role of polymer crystal structure and properties. The elastic modulus of the crystalline regions in the direction parallel to the chain axis (E_l) and perpendicular to the chain axis (E_t) of cellulose, collagen and silk as natural polymers and nylons as synthetic polymers are discussed from the effects of hydrogen bonds. The E_l can be related to the skeletal conformation, where intramolecular hydrogen bonds were described to influence the rigidity of cellulose. The intra/inter-molecular hydrogen bonds controll the skeletal conformations of collagen (triple helix) and silk fibroin (antiparallel β-sheet) in the crystal, which also affect their mechanical properties. The E_l values of nylons show high temperature dependence through high chain motion even in the crystal lattice. The intermolecular hydrogen bonds of nylons bring high anisotropy of the E_t values, where low E_t value (ca. 4 GPa) corresponds to van der Waals interaction, while high E_t value (>10 GPa) to the hydrogen bonds.
Keywords: Polymer Crystal / Hydrogen Bond / Crystal Modulus / Cellulose / Collagen / Silk / Nylon / X-ray Diffraction

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Computational Modeling of Polymer with Hydrogen Bonds

Takeshi AOYAGI

<Abstract> Hydrogen bonds are critical inter-molecular interactions, and it is very important to estimate the contribution of hydrogen bonds to predict structures and properties of polymer assembly by computational modeling. In this article, we introduce how various techniques of computational modeling, e.g. quantum mechanics, force field calculation and coarse-grained modeling, handle hydrogen bonds for polymer modeling. Furthermore, we introduce examples of a molecular dynamics study of polymers with hydrogen bonds such as cellulose and polyamide.
Keywords: Quantum Mechanics / Molecular Dynamics / Coarse-Grained Modeling / Hydrogen Bond

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COVER STORY: Topics and Products

Effect of Hydrogen Bonding on the Thermo-Mechanical Properties

Osamu URAKAWA

<Abstract> Hydrogen bonding polymer blends: poly(vinylphenol) (PVPh) and poly(2-vinylpyridine) (P2VP), were studied in detail from the preparation methods to their thermo-mechanical properties. Complexation (hydrogen bonding) of PVPh and P2VP took place in a dioxane solution and resulted in the precipitation of the hydrogen bonded polymer components with the compositions of PVPh:P2VP close to the 1:1 stoichiometry. By using a DMSO solution, we found it possible to prepare the blends with any compositions. The composition dependence of the glass transition temperature and that of the zero share viscosity exhibited positive deviation from the linear additivity rules. These behaviors also indicate the existence of strong hydrogen bonding interactions between component polymers.
Keywords: Hydrogen Bond / Polymer Complex / Glass Transition / Rheology

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The Role of “Weak Hydrogen Bond” in the Crystal Structure of Biodegradable Polyetsers

Harumi SATO

<Abstract> It was found that weak hydrogen bonds are present in the crystal structure of the biodegradable polyesters such as poly(3-hydroxybutyrate) (PHB), poly(3-hydroxyvarelate) (PHV), polyglycolic acid (PGA), by using Infrared (IR) spectroscopy, X-ray diffraction, and quantum chemical calculations. It is very likely that the CH･･･O hydrogen bonding stabilizes the crystal structures of PHB, PHV, PGA, and related copolymers. Even if the CH･･･O hydrogen bonding is relatively weak, it is extremely important for the stabilization of lamellae. We confirmed the crucial role of C-H･･･O interactions toward the unique “folded” structure of the PHB molecule chain, the crystalline structure stabilization, high melting temperature, and the high copolymer crystallization.
Keywords: Weak Hydrogen Bond / Biodegradable Polyester / Crystal Structure / Infrared Spectroscopy / X-ray Diffraction / Quantum Chemical Calculation

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Single-Molecular Devices made of DNA Origami

Akinori KUZUYA

<Abstract> DNA origami is the process in which long single-stranded DNA molecules are folded into arbitrary planar nanostructures with the aid of many short staple strands. Since its striking introduction, DNA origami has dramatically widened the scope of applications of DNA nanotechnology based on the programmed assembly of branched DNA junctions. DNA origami can be used to construct not only arbitrary two-dimensional nanostructures but also nano-sized breadboards for the arraying of nanomaterials or even complicated three-dimensional nano-objects. This review briefly summarizes the basic designs principle of DNA origami as well as its application to functional single-molecular devices.
Keywords: DNA / DNA Nanotechnology / DNA Origami / AFM / Molecular Devices / Molecular Robotics

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Polymer Science and I: A Personal Account

Aiming To Be A Researcher Who Uses Not Only Synchrotron Radiation

Hiroki OGAWA

<Abstract> In the construction period of BL03XU at SPring-8, I really had a great experience. In future, I need to develop my research using not only synchrotron radiation but also neutron scattering methods.

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Front-Line Polymer Science

Photo-Induced Living/Controlled Radical Polymerization Reaction

Shigeru YAMAGO, Yasuyuki NAKAMURA

<Abstract> Recent developments in photo-induced living/controlled radical polymerization (LRP) reaction are summarized. Photochemistry offers unique solutions to several problems in the conventional LRP, such as increase of the fidelity of α-polymer end structure in TERP and RAFT and significant decrease of the amount of metal catalysts used in ATRP. It also provides new opportunity to attain new control, such as time and spatial control in addition to the control of molecular weight of the resulting polymers. In sharp contrast to conventional photochemical reactions which requires high-intensity light source and uses high-energy UV-light, the reactions described here usually take place under mild irradiation conditions by using long-UV or visible lights by using low-intensity light sources. These unique features offer new possibilities in both basic and applied researches in LRP.
Keywords: Living/Controlled Radical Polymerization / Photochemistry / TERP / ATRP / RAFT / Polymerization Control

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