Quantitative Analysis of "Polymer-Balls" in Aqueous Solutions by Small-Angle Neutron Scattering

Mitsuhiro Shibayama,Satoshi Okabe,Michihiro Nagao,Shinji Sugihara,Sadahito Aoshima,Tamotsu Harada,Hideki Matsuoka 한국고분자학회 2002 Macromolecular Research Vol.10 No.6

Phase Transition and Phase Separation of Polymer Gels

Mitsuhiro Shibayama 한국고분자학회 1997 한국고분자학회 학술대회 연구논문 초록집 Vol.1997 No.4

Quantitative Analysis of ″Polymer-Balls″ in Aqueous Solutions by Small-Angle Neutron Scattering

Shibayama, Mitsuhiro,Okabe, Satoshi,Nagao, Michihiro,Sugihara, Shinji,Aoshima, Sadahito,Harada, Tamotsu,Matsuoka, Hideki The Polymer Society of Korea 2002 Macromolecular Research Vol.10 No.6

The quantitative analysis of polymer micelles consisting of amphiphilic block copolymers was carried out by small-angle neutron scattering (SANS). The block copolymers, made of poly(2-ethoxyethyl vinyl ether-b-2-hydroxyethyl vinyl ether)(poly(EOVE-b-HOVE)), exhibited a sharp morphological transition from a homogeneous solution to a micelle structure with increasing temperature. This transition is accompanied by a formation of spherical domains of poly(EOVE) with a radius around 200 $\AA$. The variations of the size and its distribution of the domains were investigated as a function of polymer concentration and temperature. The validity of SANS analysis, including the wavelength- and incident-beam-smearing effects of the SANS instrument, was examined with a pre-calibrated polystyrene latex.

Research Pares : Morphological observation on development of juvenile seedlings of Monochoria vaginalis establishing on a flooded paddy soil surface

( Mitsuhiro Matsuo ),( Hidejiro Shibayama ) 한국잡초학회 2002 Weed Biology and Management Vol.2 No.3

Phase Behavior of Hexa-<i>peri</i>-hexabenzocoronene Derivative in Organic Solvent

Kim, Hyo-Sik,Lee, Ji-Hwan,Kim, Tae-Hwan,Okabe, Satoshi,Shibayama, Mitsuhiro,Choi, Sung-Min American Chemical Society 2011 The Journal of physical chemistry B Vol.115 No.22

<P>The phase behavior of HBC-C12 in <I>p</I>-xylene at various concentrations has been investigated by differential scanning calorimetry, polarized optical microscopy, small angle neutron scattering and wide-angle X-ray scattering techniques, and a phase diagram depending on concentration and temperature has been determined with detailed structural information. At room temperature, HBC-C12 in <I>p</I>-xylene forms needle-like crystalline aggregates with a rectangular columnar packing which is essentially the same as the crystalline phase of HBC-C12 in bulk. Upon heating, it undergoes two transitions, a transition from the rectangular columnar packing to another rectangular columnar packing with a small step change in the lattice parameter <I>c</I>, and then a transition to isotropic phase. In the isotropic phase, HBC-C12 molecules form stacked cylindrical particles which consist of ∼11–13 molecules depending on temperature. Upon cooling, HBC-C12 in <I>p</I>-xylene makes an abrupt transition from the isotropic to the rectangular columnar packing, which is in contrast with the gradual columnar to isotropic transition upon heating. These results provide important information for optimizing the conditions of discotic liquid crystal solution for the fabrication of DLC thin films using solution-processing techniques.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpcbfk/2011/jpcbfk.2011.115.issue-22/jp200882n/production/images/medium/jp-2011-00882n_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp200882n'>ACS Electronic Supporting Info</A></P>

Structural Analysis of High Performance Ion-Gel Comprising Tetra-PEG Network

Asai, Hanako,Fujii, Kenta,Ueki, Takeshi,Sakai, Takamasa,Chung, Ung-il,Watanabe, Masayoshi,Han, Young-Soo,Kim, Tae-Hwan,Shibayama, Mitsuhiro American Chemical Society 2012 Macromolecules Vol.45 No.9

<P>The structure of Tetra-PEG ion gel, which is tetra-arm poly(ethylene glycol) (Tetra-PEG) network in ionic liquid (IL) and has recently established in our group and possesses high ion conductivity and high mechanical properties, was investigated as functions of polymer concentration (ϕ) and molecular weight (<I>M</I><SUB>w</SUB>) by using small-angle neutron scattering (SANS) measurements. The results were compared with those of Tetra-PEG hydrogel. The macromer solutions of tetra-amine terminated PEG (TAPEG) macromers, which is one of the two constituents forming Tetra-PEG network, were found to interpenetrate each other in IL and exhibited a scaling relationship, ξ ∼ ϕ<SUP>–3/4</SUP>, where ξ is the correlation length. The SANS functions, <I>I</I>(<I>q</I>), for the ion gels made by cross-end-coupling of TAPEG and TNPEG (tetra-arm PEG with active ester groups) were represented by the so-called Ornstein–Zernike equation, suggesting absence of frozen inhomogeneites. The same scaling relationship to the macromer solutions, ξ ∼ ϕ<SUP>–3/4</SUP>, was also obtained for the ion gels. Furthermore, the SANS curves were superimposed to a single master curve with <I>I</I>(<I>q</I>)/ξ<SUP>5/3</SUP>ϕ vs <I>ξq</I> irrespective of <I>M</I><SUB>w</SUB> and ϕ. In contrast, the Tetra-PEG ion gels made by reswelling of a dried hydrogel showed a large upturn, indicating that the ion gels made by the “re-swollen” method caused the network inhomogeneities.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/mamobx/2012/mamobx.2012.45.issue-9/ma300244u/production/images/medium/ma-2012-00244u_0001.gif'></P>

Small-Angle Neutron Scattering Study on Defect-Controlled Polymer Networks

Nishi, Kengo,Asai, Hanako,Fujii, Kenta,Han, Young-Soo,Kim, Tae-Hwan,Sakai, Takamasa,Shibayama, Mitsuhiro American Chemical Society 2014 Macromolecules Vol.47 No.5

<P>Tetra-PEG gels are classified to near-“ideal” networks with significantly low inhomogeneities, which were confirmed by small-angle neutron scattering (SANS). In this study, we systematically introduced two types of defects into Tetra-PEG gels and investigated effects of defects on structure. First, we prepared defect-rich networks by simply reducing prepolymer concentration, and observed the evolution of network structure by time-resolved SANS during gelation process. In this case, both the scattering intensity and the correlation length increased with reaction time in the ϕ < ϕ* region, while they scarcely changed in the ϕ > ϕ* region. Here, ϕ and ϕ* are the polymer volume fractions at observation and that at chain-overlap concentration, respectively. Second, we prepared “<I>p</I>-tuned” Tetra-PEG gels by tuning the reaction probability, <I>p</I>, and soaked them in water to expose the inhomogeneities. It was revealed that SANS profiles of as-prepared gels did not change noticeably, while those of swollen gels systematically changed with decreasing <I>p</I>. On the basis of these results, we discuss the relationship between the defects of polymer network and inhomogeneities by using simple schematic pictures of polymer network.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/mamobx/2014/mamobx.2014.47.issue-5/ma402590n/production/images/medium/ma-2013-02590n_0009.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ma402590n'>ACS Electronic Supporting Info</A></P>

Structural Analysis of Lipophilic Polyelectrolyte Solutions and Gels in Low-Polar Solvents

Nishi, Kengo,Tochioka, Saki,Hiroi, Takashi,Yamada, Taihei,Kokado, Kenta,Kim, Tae-Hwan,Gilbert, Elliot Paul,Sada, Kazuki,Shibayama, Mitsuhiro American Chemical Society 2015 Macromolecules Vol.48 No.11

<P>Lipophilic polyelectrolyte gels capable of large swelling in low-polar solvents (3 ≤ ε ≤ 10) were developed by Ono et al. (Nature Mater.<x> </x>2007), where ε is the dielectric constant. These gels were prepared by introducing tetraphenylborate as a lipophilic anion (tetrakis(3,5-bis(trifluoromethyl)phenyl)borate; TFPB<SUP>–</SUP>) and tetraalkylammonium with long alkyl chains as a lipophilic cation (tetra(<I>n</I>-butyl)ammonium; TBA<SUP>+</SUP>) into a poly(octadecyl acrylate) (pODA) backbone chain. Here, we investigated the structure of the lipophilic polyelectrolyte gels and corresponding polymer solutions in CH<SUB>2</SUB>Cl<SUB>2</SUB> with small-angle neutron scattering (SANS) and dynamic light scattering (DLS). From SANS, it was revealed that individual pODA chain is regarded as a rod with the cross-section radius of 15 Å and the length of ca. 160 Å and is little changed by introduction of charges or cross-linking. In addition to this, it was revealed from SANS measurements that the second virial coefficient of pODA in CH<SUB>2</SUB>Cl<SUB>2</SUB> was positive. In combination with DLS measurements, we observed several characteristic features similar to polyelectrolyte aqueous systems such as (i) the clear appearance of slow diffusional motion in polymer solutions, (ii) an increase of diffusion coefficient in gels, and (iii) an increase of osmotic modulus in solutions and gels when ionic groups are incorporated in pODA. These experimental findings clearly show that [TBA<SUP>+</SUP>][TFPB<SUP>–</SUP>] dissociates enough and pODA, accompanying these ionic groups, acts as a polyelectrolyte even in a low-polar solvent such as CH<SUB>2</SUB>Cl<SUB>2</SUB> (ε = 8.9). It is concluded that the good compatibility of pODA with CH<SUB>2</SUB>Cl<SUB>2</SUB> and the introduction of dissociable ionic groups into pODA result in high-swelling capability of the lipophilic polyelectrolyte gels.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/mamobx/2015/mamobx.2015.48.issue-11/acs.macromol.5b00753/production/images/medium/ma-2015-00753f_0012.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ma5b00753'>ACS Electronic Supporting Info</A></P>

SANS and DLS Study of Tacticity Effects on Hydrophobicity and Phase Separation of Poly(<i>N</i>-isopropylacrylamide)

Nishi, Kengo,Hiroi, Takashi,Hashimoto, Kei,Fujii, Kenta,Han, Young-Soo,Kim, Tae-Hwan,Katsumoto, Yukiteru,Shibayama, Mitsuhiro American Chemical Society 2013 Macromolecules Vol.46 No.15

<P>The tacticity effect on phase separation process of poly(<I>N</I>-isopropylacrylamide) (PNiPAM) aqueous solutions was investigated by dynamic light scattering (DLS) and small angle neutron scattering (SANS) measurements. SANS measurement revealed that hydrophobicity of PNiPAM consisting of meso- and racemo-isomers increased with increasing the meso-content. This result is in accordance with the result of the previous experimental and simulation study on NiPAM dimers (DNiPAM) and trimers (TNiPAM) [Katsumoto<x>, </x>Y<x>.</x>; <etal></etal> J. Phys. Chem. B<x> </x>2010<x>, </x>114<x>, </x>13312−<lpage>13318</lpage>, and Autieri<x>, </x>E.; <etal></etal> J. Phys. Chem. B<x> </x>2011<x>, </x>115<x>, </x>5827<x>–</x><lpage>5839</lpage>]; i.e., meso-diad is more hydrophobic than racemo-diad. In addition, a series of scattering experiments revealed that the ratio of meso-diad does not affect the static structure or the shrinking behavior of a single chain, but strongly affects the aggregation behavior. The PNiPAMs with low meso-content suddenly associate around the phase separation temperature, while that of the high meso-content gradually aggregate with increasing temperature. We propose that phase transition behavior of PNiPAM aqueous solutions can be controlled by changing the stereoregularity of the polymer chain.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/mamobx/2013/mamobx.2013.46.issue-15/ma401349v/production/images/medium/ma-2013-01349v_0012.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ma401349v'>ACS Electronic Supporting Info</A></P>

Fabrication and Structural Characterization of Module-Assembled Amphiphilic Conetwork Gels

Hiroi, Takashi,Kondo, Shinji,Sakai, Takamasa,Gilbert, Elliot Paul,Han, Young-Soo,Kim, Tae-Hwan,Shibayama, Mitsuhiro American Chemical Society 2016 Macromolecules Vol.49 No.13

<P>Structural analysis of inhomogeneity-free poly(ethylene glycol)-poly(dimethylsiloxane) (PEG PDMS) amphiphilic conetwork gels has been performed by the complementary use of small-angle X-ray and neutron scattering. Because of the hydrophobicity of PDMS units, the PEG-PDMS gels exhibit a microphase-separated structure in water. Depending on the volume fraction of; PDMS, the microphase-separated structure varies from core-shell to lamellar. The obtained X-ray and neutron scattering profiles are reproduced well using a core-shell model together with a Percus-Yevick structure factor when the volume fraction of PDMS is small. The domain size is much larger than the size of individual PEG and PDMS unit, and this is explained using the theory of block copolymers. Reflecting the homogeneous dispersion conditions in the as-prepared state, scattering peaks are observed even at a very low PDMS volume fraction (0.2%). When the volume fraction of PDMS is large, the microphase-separated structure is lamellar and is demonstrated to be kinetically controlled by nonequilibrium and topological effects.</P>