Hiroaki Yoshimizu

The presence of nanopores in mesophase of syndiotactic polystyrene estimated from gas sorption behaviour

Abstract Thermal and spectroscopic properties of the annealed cast syndiotactic polystyrene (SPS) films were investigated and it was shown that the sample annealed at lower temperature than 170°C exhibited the presence of a conformational order but lack of crystalline regularity. This result indicated the formation of mesophase by annealing cast SPS films. CO 2 sorption properties of such a film were also examined and dual-mode sorption model was applied to clarify the SPS structure. The hole saturation constant for the Langmuir sorption ( C H ′) evaluated from the dual-mode sorption model reflected the fine structure of the annealed SPS (mesophase) and depended on the annealing time when annealed at a certain temperature. From these results we supposed that the samples annealed at lower temperature contained many nanopores between SPS chains of mesophase, i.e. desorption sites of solvent.

Study on δ-form complex in a syndiotactic polystyrene/organic molecules system, 1: Preferential complexing behavior of xylene isomers

To investigated the preferential complexing behavior of isomeric xylenes, syndiotactic polystyrene (sPS) membranes are prepared using varying compositions of p- and m-xylene. Complex formation between sPS and xylenes was studied by means of thermogravimetric and FT-IR analyses to determine the exact amounts of solvent molecules present per styrene repeating unit. A preferential complexing ability of p-xylene was revealed due to its favorable interaction with sPS.

Structure and gas permeability of siloxane-imide block copolymer membranes: 1. Effect of siloxane content

Abstract Siloxane-imide block copolymer membranes with various siloxane contents were prepared and their dynamic viscoelasticity, sorption of carbon dioxide, and permeability of carbon dioxide, oxygen and nitrogen were studied. The siloxane-imide block copolymer consists of a microphase separated structure of imide-rich and siloxane phases, and the mechanical properties of the siloxane-imide block copolymer are well retained up to a siloxane content of about 20 wt%. The amount of carbon dioxide sorbed into the siloxane-imide block copolymer decreases with the introduction of siloxane, reflecting the less-sorptive capability of the siloxane group. The sorption behaviour of the block copolymers is interpreted in terms of a dual-mode sorption theory, which is applied to glassy imide-rich phases. On the other hand, the permeability coefficients of carbon dioxide, oxygen and nitrogen are remarkably increased with siloxane content when the latter is more than 10 wt%, and the permselectivity of oxygen to nitrogen is decreased with siloxane content. These behaviours are interpreted by considering the arrangement of the two phases in the membrane.

The structural organization in syndiotactic polystyrene film induced by toluene vapour sorption

Abstract Toluene vapour sorption behaviours in syndiotactic polystyrene (SPS) film were measured at 25°C by the quartz crystal microbalance method. The sorption isotherm of this system was concave toward the pressure axis below the activity of toluene vapour ( p / p 0 =0.3), indicating a strong interaction between toluene vapour and sorption sites in the mesophase consisting of TTGG conformation. On the other hand, the sorption isotherm of toluene vapour in atactic polystyrene film showed a normal good solvent type and could be described by Flory–Huggins thermodynamics. In addition, the structural changes in SPS film by toluene vapour sorption were characterized by Infrared spectroscopy. The absorbance at 933 cm −1 , which is assigned to TTGG conformation, was found to be constant below p / p 0 =0.3; however, it increased above p / p 0 =0.3 and was saturated above p / p 0 =0.6. These results showed that toluene vapours penetrated into the pre-existing sorption sites composed of TTGG conformation to form the clathrate structure (δ form) below p / p 0 =0.3. Furthermore, in the range of p / p 0 =0.3–0.6, the sorption of toluene vapour could induce a large increase in the ordered structure (δ form), i.e., TTGG confirmation. The changes in the non-clathrate structure with toluene (α form) composed of TT conformation, could be characterized by the absorbance at 1222 cm −1 . It was confirmed that the α form could be also increased by toluene vapour sorption above p / p 0 =0.4. The sorption enthalpy of toluene vapour (Δ H s ), estimated from sorption isotherms showed a negative value below p / p 0 =0.6, but showed a positive value above p / p 0 =0.6, even though the polymer–good solvent pair. This result also supports the structural organization in SPS film by toluene vapour sorption.

Characterization and CO2 sorption behaviour of polystyrene/polycarbonate blend system

Abstract The CO 2 sorption isotherms of samples of polystyrene/polycarbonate blends with different compositions which were prepared by casting from 1,4-dioxane solutions were obtained as a function of composition of the polymer blend at 25°C using a Cahn-sorption apparatus. The characterization of the polymer blend system was obtained from the point of thermal behaviour such as differential scanning calorimetry, X-ray diffraction, and 13 C CP/MAS n.m.r. From the characterization of the polymer blend, it was confirmed that there was a small amount of crystallinity of polycarbonate. Basically the polymer blend system studied here is heterogeneous (i.e. phase-separated) but it was found that a small amount of polystyrene is partly miscible with polycarbonate and this probably disrupts the crystallization of polycarbonate especially at the higher polystyrene content. CO 2 sorption isotherms of the blend system including two homopolymers appeared to obey the dual mode sorption isotherm, which is a characteristic of the glassy state. The change of the CO 2 sorption amount for the polymer blend was mainly explained by the amount of the crystallite of polycarbonate, indicating that the effect of the partly miscible region on the CO 2 sorption behaviour is very small.

A high-resolution solid-state 13C NMR study on conformation and molecular motion of low-sulfur keratin protein films obtained from wool

Abstract 13C high-resolution solid-state NMR spectra of S-carboxymethyl kerateine film obtained from wool (SCMKA) were measured under unstretched and stretched conditions. In the unstretched SCMKA film, the observed 13C chemical shift values and the lineshapes for all the carbons in the spectrum at 100°C are close to those at room temperature, although the molecular motions of the side-chain carbons are different from each other. On the other hand, the lineshapes for the main-chain carbons in the stretched films are significantly changed, although the 13C spin-lattice relaxation times and dipolar-dephasing times for all the carbons are almost unchanged by stretching until 300%. From the spectrum simulation of the Cα methine carbons using the conformation-dependent 13C chemical shifts of homopolypeptides as reference data, the appearance of the β-sheet form by stretching was recognized.

NMR Studies of Higher-order Structures of Solid Polymers

Publisher Summary This chapter discusses the most recent high-resolution nuclear magnetic resonance (NMR) studies of solid polymers, including synthetic and natural polymers, with emphasis on revealing the higher-order structures. It provides a new dimension to the polymer structures, and in addition is concerned with engineering plastics, high-performance polymers, liquid crystalline polymers, polymer alloys, and natural polymers. It is clear that the solid-state high resolution NMR is an indispensable technique for the routine analysis as well as for the study of the structures and dynamics of the polymers in bulk. Engineering plastics and high-performance polymers are the most popular polymers in polymer materials. Their physical properties and functions are closely related to the structure and dynamics in the solid-state. From such a situation, solid-state high-resolution NMR spectroscopy has provided the potential perspective of becoming a powerful means of determining the higher-order structure and dynamics of the polymers in the solid state, associated with the physical properties and functions. The physical blending of two or more polymers provides new polymer materials with suitable physical properties. Such polymer blends are often referred to as “polymer alloys.”. Solid-state NMR is a powerful tool for the determination of protein structure and the advantages of this method are described in this chapter.

Analysis of gas transport properties of PPO/PS blends by 129Xe NMR spectroscopy

Abstract Relationships among variations of microvoids and gas transport properties for miscible poly(2,6-dimethyl-1,4-phenylene oxide) (PPO)/polystyrene (PS) blends in the glassy state have been investigated by Xe sorption, Xe permeation, and 129 Xe NMR measurements. Xe sorption isotherms of the blends can be interpreted successfully on the basis of the dual-mode sorption model. Decrease in the permeability of Xe is attributed to the decrease in the diffusivity of that in the Langmuir site. 129 Xe NMR spectra of 129 Xe in the blends show non-linear low-field shift with increasing sorption amount of Xe because of a fast exchange of Xe atoms between Henry and Langmuir sites. From the analysis of 129 Xe NMR chemical shifts, it is found that the mean volume of individual microvoids varies with a negative deviation against volume fraction of PPO in the blend. For PPO/PS blends, it has been clarified that the contraction of individual microvoids occurs by blending and highly affects gas transport properties.

Control of gas permeability for cellulose acetate membrane by microwave irradiation

Abstract It can be expected that a microwave acts as an accelerator of the mobility of polar functional groups such as hydroxyl groups in polymeric membranes, and then gas permeability improves because of the increasing free volume and/or temperature of the membranes. The permeability coefficients of CO 2 for a cellulose acetate (CA) membrane were measured at 25°C using a hand-made apparatus which can irradiate a microwave (2,450 MHz) to the membrane. Both the permeability and diffusion coefficients of CO 2 for CA membranes are increased by irradiation of the microwave, and degree of enhancement increased with power of the microwave.

The guest-induced oscillation of a monolayer composed of polypeptide containing β-cyclodextrin at the terminal

We prepared a rod-like amphiphile with a molecular recognition end group, alpha-helical and hydrophobic poly(gamma-methyl L-glutamate) (PMG) containing hydrophilic beta-cyclodextrin (CyD) as an active end group (PMG-CyD), and formed its monolayer at the n-hexane/water interface. The interfacial pressure (pi)-area (A) isotherms of the monolayer showed that alpha-helix rod of PMG-CyD could be vertically oriented at the oil/water interface, facing the hydrophilic terminal CyD group to the water phase, by increasing the interfacial concentration of the polypeptide. Under the condition 2-p-toludinyl-naphthalene-6-sulfonate (TNS), an intimate guest molecule for the CyD in water was introduced into the water phase beneath the monolayer. Within a minute the monolayer began to oscillate which could be monitored by the rhythmic response of the interfacial pressure of the monolayer. The oscillation continued over ten minutes and then terminated. The mode of the oscillation was found to change with time, i.e., the initial stage showing a periodic sharp reduction in the interfacial pressure (period I), the second stage having sharp increase in the pi value (period II), and the last stage of irregular oscillations (period III). The Fourier analysis of each period also supported the three stages during the oscillatory process. It was also found that when the alpha-helix rod of PMG-CyD lay down in the monolayer, the guest TNS did not induce any changes in the interfacial tension. This nonlinear rhythmic interfacial phenomenon was explained in terms of the periodic movement of the PMG-CyD monolayer resulting from the binding and releasing of the guest TNS across the oil/water interface. (c) 1999 American Institute of Physics.