Search Results

You are looking at 1 - 7 of 7 items for

  • Author or Editor: T. Iyoda x
  • Refine by Access: All Content x
Clear All Modify Search

Summary Thermally induced structural transformation of fibrous hydrogen-bonded molecular assemblage formed from an amphoteric pyridinecarboxylic acid of 6-[2-propyl- 4-(4-pyridylazo)phenoxy]hexanoic acid (C5PR) was studied using differential scanning calorimetry (DSC), differential thermal analysis (DTA), and thermogravimetry (TG). The organized fibrous morphology formed in an aqueous solution was stable at temperatures below 150°C. The ordered crystalline solid phase (K1) of the original fibrous material altered to a disordered crystalline solid phase (K2) at 150°C and subsequently to an isotropic phase (I) at 172°C. In the isotropic state, the C5PR molecule was slowly decomposed by decarboxylation. Once the molecular assemblage was subjected to the mesophase by heating, another ordered crystalline solid phase (K3) appeared reversibly at 17°C. The heat budget analyses by DSC indicated that a conformational entropy change such as the side-chain propyl group and the main-chain pentamethylene unit in the hydrogen-bonded molecular assemblage took place between the two ordered crystalline solid phases K1 and K3.

Restricted access

Summary The mixing state of amphiphilic di-block copolymers consisted of poly(ethylene oxide) and poly(methacrylate) having azobenzene moieties in the side chains p(EO)114pMA(Az)24 and poly(ethylene oxide) p(EO)114 was investigated from the viewpoints of isothermal crystallization and nano-scale ordered structure. The chemical potential, which required establishing the constant crystal growth rate, decreased with the p(EO) content up to 60%. The hexagonal packed cylinder structure was observed for the blends with the p(EO) content up to 60% and the lattice spacing of (100) and (110) planes increased with the p(EO) content up to 60%. The blends of amphiphilic p(EO)114pMA(Az)24 and p(EO)114 were miscible without in the p(EO) content below 60%.

Restricted access

Abstract  

The thermally induced structural transformation of a hydrogen-bonded crystal formed from an amphoteric molecule of 6-[2-methoxy-4-(pyridylazo)phenoxy]hexanoic acid MeO was studied using differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction measurement (XRD). Crystal form of the hydrogen-bonded crystal was measured by single crystal four circle diffractometer (Mo-Kα radiation). As a result, the crystal of MeO was stabilized by many C–H⋅⋅⋅O hydrogen bonds, and the C–H⋅⋅⋅O hydrogen bonds were broken by thermal energy reversibly. After transformation the supramolecular architecture was composed of supramolecular polymer including free-rotation pentamethylene main chains.

Restricted access

Abstract  

The effects of high pressure carbon dioxide (CO2) on the isotropic transition of three different amphiphilic di-block copolymers, PEOm-b-PMA(Az)n, namely PEO114-b-PMA(Az)40, PEO272-b-PMA(Az)46 and PEO454-b-PMA(Az)47, and on PMA(Az)30 homopolymer have been investigated by scanning transitiometry. Under CO2 pressure, the isotropic transition temperature decreased with the increase of pressure up to around 30 MPa due to CO2 sorption and increased above 40 MPa. Transition entropy of the isotropic transition indicated that the depression of the isotropic transition temperature was caused by the adsorption of CO2 into the azobenzene moieties and that the increase above 40 MPa was caused by the desorption of CO2 into the azobenzene moieties. Comparison between PEOm-b-PMA(Az)n copolymers and PMA(Az) homopolymer clarified PEO domain acted CO2 pathway to approach the equilibrium state rapidly.

Restricted access

Abstract  

The effects of nitrogen (N2) pressure on amphiphilic di-block copolymer, PEO114-b-PMA(Az)40, were investigated by scanning transitiometry. The isotropic transition temperature increased with the increase of pressure above 20 MPa. The hydrostatic pressure effects evaluated with the Clapeyron equation were smaller than the value obtained by mercury as a pressurizing medium because the amount of absorbed gas decreases the volume change at the isotropic transition.

Restricted access

Abstract  

Phase transition process of PEOm-b-PMA(Az)n was investigated by the simultaneous DSC-XRD measurement using the synchrotron radiation facility. Four endothermic DSC peaks were observed during heating process. These DSC peaks were assigned to the melting of PEO, the transition from SmX, which is a mixture of super-cooled SmC and crystal, to SmC, from SmC to SmA, and from SmA to isotropic liquid state as determined by XRD profiles. In SmC phase, the liner expansion coefficient calculated from the spacing variation of the smectic layer distance was larger than that of the other phases. This result reflected the fact azobenzene moieties in the long-side chains of PMA(Az)n forming the smectic layers and then they were tilted and stood up during the heating process.

Restricted access
Journal of Thermal Analysis and Calorimetry
Authors: S. Boyer, J-P. Grolier, L. Pison, C. Iwamoto, H. Yoshida, and T. Iyoda

Abstract  

The present work deals with the interactions between carbon dioxide, used as pressure medium, either in the gas state (GCO2) or in the supercritical state (SCCO2) and amphiphilic di-block copolymers PEOm-b-PMA(Az)n. The effect of pressure on the isotropic transition of the PEOm-b-PMA(Az)n copolymer was investigated using scanning transitiometry (ST). The experimental results were compared with those measured when using ‘relatively inert’ mercury (Hg) as pressure medium. Morphological observation of a PEOm-b-PMA(Az)n thin film submitted to SCCO2 was performed by atomic force microscopy (AFM) to investigate the nano-structure organization. These results indicate the possibility of modifying the nano-structure in a specific way depending on the CO2 physical state.

Restricted access