Katsuhiro Inomata

Shape memory properties of polyurethane/poly(oxyethylene) blends

Shape memory behavior of polymer blends consisting of thermoplastic polyurethane (PU) and crystalline poly(oxyethylene) (POE) have been investigated. PU is in a rubbery state at room temperature and has an ability to recover from a deformed temporary shape to a permanent shape by entropic elasticity, and POE has a role to fix the temporary shape by crystallization and solidification of the system. As a result, excellent shape memory properties can be obtained by blending elastic PU and crystalline POE. With increasing POE content in the blend, the shape fixity ratio below crystallization temperature was increased to almost 100%, but shape recovery above melting temperature occurred more slowly. These experimental results were reasonably described by viscoelasticity and the phase separated morphology of the PU/POE blend. The effect of changing molecular weight of POE on the shape memory behavior was not remarkable. The shape recovery behavior was found to be expressed by using a simple mechanical viscoelastic model.

Aggregation behavior of poly(N, N-diethylacrylamide) in aqueous solution

Aggregation behavior of poly(N,N-diethylacrylamide) (PDEA) in dilute aqueous solution has been studied by using the static and dynamic light scattering. It has been demonstrated that PDEA is not molecularly dissolved in water but forms molecular aggregates below the cloud point in one phase region. The association number of aggregates is of the order of 100, and the aggregate is suggested to be like a swollen micro-gel. The aggregation does not come from difficulty of dissolving a frozen structure in solid state, but the aggregates are also formed in solution starting from aggregation-free state by changing the solvent quality. The detailed aggregate size and structure depend on the dissolution process of the solid sample in making the solution. Once the aggregate is formed, it is stable, and does not change its association number and dimension for a long time. But, the association number may change with temperature and depends on thermal history.

Association and physical gelation of ABA triblock copolymer in selective solvent

Association behavior and physical gelation mechanism of ABA triblock copolymer dissolved in B-selective solvent have been studied systematically from dilute to moderately concentrated solutions. Static and dynamic light scattering and nuclear magnetic resonance measurements for dilute solutions of poly(methyl methacrylate)-block-poly(tert-butyl acrylate)-block-poly(methyl methacrylate) (PMMA – Pt BuA – PMMA) in 1-butanol (Pt BuA selective solvent) indicated that PMMA– Pt BuA – PMMA chains are molecularly dissolved above 50 8C. With decreasing temperature, the triblock copolymers form associated micelles consisting PMMA associated core and Pt BuA shell. Linear dynamic viscoelastic measurements for solutions with moderate concentration (3.9– 12.0 wt%) revealed that the system was viscous sol state at 60 8C. Drastic increase of shear storage modulus ðG 0 Þ occurred with decreasing temperature, and at 25 8C, G 0 showed rubbery plateau with weak frequency dependency, means the formation of elastic physical gel. The consistency between the temperature for micelle formation and that at the increase in G 0 indicates that the physical gelation is owing to the network formation as the result of the association of PMMA chains and the bridging Pt BuA chains connecting the PMMA cores. Master curves for the dynamic moduli were derived by time – temperature superposition along the frequency axis. Just above sol –gel transition concentration ðCgelÞ; the master curves suggest the existence of fairy amount of aggregate that is not incorporated in the macroscopic network. With the increase in polymer concentration, the master curves become to reveal Maxwell-type viscoelasticity with narrow relaxation time distribution, suggesting the formation of transient network with easily generation and destruction of crosslinks. Concentration dependency of the plateau modulus is stronger than the theoretically expected, means the macroscopic transient network grows with polymer concentration by increasing the fraction of elastically effective bridging Pt BuA chain above Cgel: q 2003 Elsevier Ltd. All rights reserved.

Strain-Responsive Structural Colored Elastomers by Fixing Colloidal Crystal Assembly

Colloidal crystal assembly film was prepared by using monodispersed colloidal particles of cross-linked random copolymer of methyl methacrylate and ethyl acrylate prepared by soap-free emulsion polymerization. The colloidal crystal film exhibited structural color when swollen with ethyl acrylate monomer. The structural color was maintained even after polymerization of the swelling monomer and cross-linker, suggesting the colloidal crystalline order was successfully fixed and embedded in the matrix of poly(ethyl acrylate) elastomer. Stretching deformation of the structural colored elastomer induced a sensitive change to shorter wavelength color. Peak wavelength of the UV-vis absorption spectrum of the stretched elastomer revealed an excellent proportional relationship with film thickness. In the swollen colloidal crystal film, ethyl acrylate was absorbed in the colloidal particle; therefore, poly(ethyl acrylate) chain should be penetrating into the colloidal particle after the polymerization of the matrix elastomer. This interpenetrated polymer network structure was considered to be effective for the rubber-like elasticity and sensitive strain-responsive color-changing phenomena of the structural colored elastomer.

Phase behaviour of rod with flexible side chains/coil/solvent systems: poly(α,l-glutamate) with tri(ethylene glycol) side chains, poly(ethylene glycol), and dimethylformamide

Abstract Phase behaviour is investigated for ternary solutions composed of rodlike α-helical poly(α, l -glutamate) having triethylene glycol monomethyl ether at the end of the side chains (P3EGLG), randomly-coiled poly(ethylene glycol), and N , N -dimethylformamide (DMF) as solvent. The solution containing lower molecular weight poly(ethylene glycol) (PEG10) separates into an isotropic phase, which is rich in PEG10, and an anisotropic (cholesteric) phase, which is rich in P3EGLG, when the total polymer volume fraction is higher than ca 0.13. The homogeneous anisotropic region, in which a detectable amount of PEG10 exists, is recognized along the P3EGLG-DMF axis in the triangle phase diagram. When the molecular weight of poly(ethylene glycol) is larger, additional phase-separation regions are observed: That is, isotropic-isotropic biphasic region and anisotropic-isotropic-isotropic triphasic region. Theoretical treatments based on the lattice model for nematic solutions are conducted for these rod/coil/solvent ternary systems. Calculated phase diagrams with considering flexible side chains of rodlike solute and isotropic interaction parameters are found to qualitatively reproduce the variation of the experimental phase behaviour with the change of the molecular weight of the coiled component.

Micellization behavior of diblock copolymers in solution near the critical micelle temperature

Abstract Micellization behavior near the critical micelle temperature (c.m.t.) has been studied for polystyrene-block-poly(dimethylsiloxane) (PS-b-PDMS) in a mixed solvent of 1,2-dichlorobenzene/benzyl alcohol, which forms micelles with PDMS as cores. Static and dynamic light scattering experiments have demonstrated the following behaviors. The dilute solution (c≅0.1–4 wt %) shows three different characteristic behaviors depending on the copolymer concentration c. In the concentrated region, the temperature dependence of scattered-light intensity exhibits a large peak just below c.m.t., which is similar to the anomalous micellization. Detailed light scattering studies have revealed the following: in this concentration region, compact micelles are formed at low temperatures and as the temperature is increased, the micelles change into expanded swollen micelles discontinuously at a certain temperature. This change occurs rather reversibly, and may be explained by a strong condensation of the core due to the decrease in solvent quality with decreasing temperature. This can be a mechanism of the anomalous micellization.

Gas phase NMR of 1,2-dimethoxyethane

In this work we wish to report preliminary results of the gas phase NMR studies on 1,2-dimethoxyethane. The conformation of the compound has been previously studied in solution using the same NMR technique [9]. The results obtained compare favorably with those observed in nonpolar solvent

Conformation and conformational energies of dimethoxymethane and 1,1-dimethoxyethane

Abstract The 13 C− 1 H NMR vicinal coupling constant 3 J C H 3 OC H 2 was measured for dimethoxymethane CH 3 OCH 2 OCH 3 in the gas phase as well as in various solvents. The observed values tend to decrease slightly with temperature. The energy difference E σ between the gg and tg forms was estimated to be −2.5 ± 0.2 kcal mol −1 in the gas phase. The coupling constant parameters determined concomitantly are as follows: ( J T + J G− )/2 = 6.7 ± 0.1 and J G = 2.0 Hz. Values of E σ observed in nonpolar solvents were found to fall in the same range. A somewhat smaller value (ca. −2.2 kcal mol −1 ) was derived from the measurements in (CD 3 ) 2 SO. These values are reasonably consistent with the results of recent MO calculations by Wiberg and Murcko. A similar 13 C NMR analysis of 1,1-dimethoxyethane CH 3 OCH(CH 3 )OCH 3 indicates that the g− g and tg conformers exists in nearly equal amounts, i.e. E τ = E g− g − E tg ≅ 0 kcal mol −1 . In the latter compound, the anomeric conformation ( g − ) involves unfavorable steric interactions around the g− bond.

Morphology of associated polymer blends: one-end-aminated polystyrene/one-end-car☐ylated or sulfonated poly(ethylene glycol)

Abstract Small-angle X-ray scattering (SAXS) profiles have been measured for blends of one-end-aminated polystyrene (APS) and one-end-car☐ylated or -sulfonated poly(ethylene glycol) (CPEG or SPEG) with weight fraction of 50/50 per cent. In the profiles of blend solutions in toluene (TL), PS/CPEG/TL and APS/SPEG/TL with solvent weight fraction of 0.2 at 80°C, there exists a scattering maximum around a Bragg spacing of 203Afor the system containing SPEG, whereas there is no peak for the system containing CPEG. Similarly, the scattering peak is absent in the profile of the blend APS/CPEG without solvent, and is observed in that of APS/SPEG at 80°C. The APS/SPEG blend sample cooled to a temperature below the melting point of SPEG shows a more intense SAXS peak than that at higher temperature. The similarly cooled blend of APS/CPEG exhibits a weak scattering maximum, and its position is nearly identical to that of pure CPEG. From these observations and previous studies on the phase diagram of blend solutions in TL, it has been suggested that the APS/SPEG blend behaves like a diblock copolymer owing to the strong association between the terminal amino and sulfonic acid groups, and an ordered structure that is similar to those observed in diblock copolymers is formed even in bulk melt and concentrated solution. Because of the weak association between amino and car☐yl groups, the APS/CPEG system behaves like an ordinary polymer blend, and crystallization of the CPEG chain may occur in a similar manner to the homopolymer in the macroscopically separated domain.

Preparation of high oxygen permeable transparent hybrid copolymers with silicone macro-monomers

In this study, high oxygen permeable transparent hybrid copolymers were prepared with hydrophilic monomer such as 2-hydroxyethylmethacrylate (HEMA) or N,N-dimethylacrylamide (DMAA) and mono- or difunctional silicone macro-monomer introduced methacryl groups. In HEMA-based hybrid copolymers, difunctional silicone macro-monomer and ethylene glycol dimethacrylate (EGDMA) as cross-linker were required in order to prepare transparent hybrid materials, while high transparent DMAA-based hybrid copolymers could be prepared without EGDMA cross-linker. The polymerization kinetics investigation revealed that this difference between HEMA and DMAA in preparation condition to transparent hybrid material originated to monomer reactivity in copolymerization and DMAA showed high reactivity compared with HEMA. Moreover, DMAA-based hybrid copolymers indicated high water content and high oxygen permeability as against HEMA-based hybrid copolymers because of its low cross-linking density.