The Experts below are selected from a list of 504 Experts worldwide ranked by ideXlab platform
Fumitaka Horii - One of the best experts on this subject based on the ideXlab platform.
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reorganization of dynamic self assemblies of Cellulose Diacetate in solution dynamical critical like fluctuations in the lower critical solution temperature system
Biomacromolecules, 2002Co-Authors: Yoshisuke Tsunashima, Hiroyuki Kawanishi, Fumitaka HoriiAbstract:Dynamics of Cellulose Diacetate (CDA, the total degree of substitution (TDS) = 2.44) in dimethylacetamide (DMAc) in dilute solution was investigated at 2, 10, 20, 30, 40, 49.7, and 61.5 degrees C through dynamic light scattering in the quiescent state. The following three facts were made clear. First, CDA existed in three types of structures in the polar solvent, DMAc; one is a single CDA chain, and the others are dynamic structures, or self-assemblies, which were formed temporarily and locally by the solvent-mediated hydrogen bonding between the intermolecular C-6 position hydroxyls of the anhydroglucose units in the CDA backbone. Second, CDA showed a nature of low-temperature solubility in DMAc, that is, CDA is expected to dissolve molecularly below -12 degrees C but to take a phase separation above 65 degrees C, where two structures such as collapses of a single CDA chain and an aggregate appear. Third, a reorganization in the dynamic structures was detected at the temperature T = 33.8 degrees C. At this temperature, two dynamic structures showed the discontinuity in their correlation lengths, whereas the single CDA realized an uncorrelated chain state in the dynamical sense. In view of the low-temperature solubility of CDA in DMAc, this abnormal behavior around T was explained by dynamical critical-like fluctuations if T were treated as a kind of lower critical solution temperature (LCST) in the CDA/DMAc system. Here, the self-assemblies arise as the dynamical fluctuations under the spinodal decomposition situation and the competition between the hydrogen bonding (HB) and the hydrophobic interaction (HPhI) makes the conformation of CDA chains change drastically. In this scheme, the solvent-mediated HB and HPhI play important roles in the structure reorganization of Cellulose derivatives in strong electronegative solvents, though HB and HPhI cooperate with the inherent chain helicality.
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dynamic light scattering study of structural changes of Cellulose Diacetate in solution under couette flow
Macromolecules, 2000Co-Authors: Hiroyuki Kawanishi, Yoshisuke Tsunashima, Fumitaka HoriiAbstract:Dynamic light scattering (DLS) measurements were conducted under a simple shear flow, i.e., the Couette flow field, to Cellulose Diacetate (CDA; a typical polysaccharide) in semidilute N,N-dimethylacetamide (DMAc) solution. The shear rate y was varied from 0 to 5.25 s -1 . At quiescence, CDA showed three dynamic modes, which correspond to two kinds of associations and a single chain. In the weakly sheared system (0.402 s -1 ≤ γ ≤ 5.25 s -1 ), the three dynamic modes collapsed, and alternatively two completely different modes were observed. The fast mode experienced a transition around y = 0.81 s -1 , the decay rate distribution changing from a broader bimodal to a narrower unimodal shape with increasing shear. The slow mode had a unimodal decay rate distribution, but the length scale of fluctuations was larger by 3 orders of magnitude compared to those observed at y = 0 s -1 ; that is, the length distribution was extremely uniform irrespective of y, and the length ξ s was proportional to γ -1 . This ξ s γ -1 relation was interpreted by Taylor's treatment of the behavior of viscous drops. Thus, the repetition of the burst and the coalescence growth of the associations was suggested for the slow mode. The ξ s γ -1 relation implied that CDA was molecularly disperse in DMAc under the viscometric field in a capillary viscometer at γ = 920 s -1 .
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Influence of Long-Range Interactions on Diffusion Behavior in Semidilute Solution: Dynamics of Cellulose Diacetate in Quiescent State
Macromolecules, 1999Co-Authors: Yoshisuke Tsunashima, Hiroyuki Kawanishi, Ryosuke Nomura, Fumitaka HoriiAbstract:The dynamics of Cellulose Diacetate (CDA) in semidilute solution (1.4c* < c < 5c*) was investigated in a good and high-polarity solvent, dimethylacetamide (DMAc), by dynamic light scattering in the quiescent state at 30 °C. Two fast diffusion motions and a very slow diffusion motion were detected, all the behavior of which is not expected from the framework of dynamics for usual flexible polymers in good solvents. The fast (fast mode) and medium-fast (medium mode) motions gave the diffusion coefficients DF and DM as DF ∝ c0.40 and DM ∝ c0.55. Both were the cooperative diffusion motions, or the relaxations of concentration fluctuations in two types of coarse-dense structures, which were realized as a nest of structures in a dynamic sense in semidilute solution. However, the relaxation rates were suppressed by the long-ranged hydrogen-bond interaction between hydroxyl (OH) groups on CDA molecules, and the interactions brought the systems into the medium, not good, solvent state. The slow diffusion (slow mod...
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a nest of structures in dynamics of Cellulose Diacetate in n n dimethylacetamide in quiescent solution state studied by dynamic light scattering
Journal of Chemical Physics, 1998Co-Authors: Hiroyuki Kawanishi, Yoshisuke Tsunashima, Fumitaka HoriiAbstract:In the quiescent state, dynamic light scattering measurements were performed for a polysaccharide, Cellulose Diacetate (CDA, the degree of substitution 2.40), in a liquid-crystalline promoting solvent N, N-dimethylacetamide (DMAc) in the range from dilute to crossover concentrations. Three modes of motions were detected simultaneously over all concentrations measured. They are in a nest of structures, which are caused by long-range interactions acting between OH groups of glucose units in a highly dielectric-constant solvent DMAc. Denoting these modes as Mode I, II, and III from fast to slow motions, the decay rates Γ of each mode showed the squared scattering-vector dependence at lower angles, i.e., the diffusion nature. In dilute solution, fast Mode I is the translational diffusion of a single CDA chain and others represent the dissipation of locally associated CDA clouds which grow by the interactions specified above. Mode II is related to a coarse cloud formed in a limited time but spread over a wide ...
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change in chain stiffness in viscometric and ultracentrifugal fields Cellulose Diacetate in n n dimethylacetamide dilute solution
Journal of Chemical Physics, 1998Co-Authors: Hiroyuki Kawanishi, Yoshisuke Tsunashima, Shinichi Okada, Fumitaka HoriiAbstract:The molecular characteristics and the chain stiffness were investigated for fractionated samples of Cellulose Diacetate (CDA, degree of substitution DS = 2.40) in N, N-dimethylacetamide (DMAc) through the partial specific volume, the viscometric, the sedimentation velocity, and the sedimentation equilibrium measurements at 30 °C. It was found that CDA dispersed molecularly in DMAc under the external field such as in the viscometric and the sedimentation experiments. The molecular weight dependence of the intrinsic viscosity [η] and the sedimentation coefficient at infinite dilution s0 of the single CDA molecule were expressed by the relation [η] = 1.10×10−2Mw0.85 (cm3 g−1) and s0=2.25×10−14Mw0.20 (s), which exhibit the stiff, or semiflexible chain nature. The semiflexible chain parameters were evaluated by the Yamakawa–Fujii (YF) theory of the unperturbed wormlike cylinder model, first via a combination of the viscosity and the partial specific volume data (method A) and second via a combination of the se...
Yoshiyuki Nishio - One of the best experts on this subject based on the ideXlab platform.
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Molecular orientation and optical anisotropy in drawn films of Cellulose Diacetate-graft-PLLA: comparative investigation with poly(vinyl acetate-co-vinyl alcohol)-graft-PLLA
Cellulose, 2011Co-Authors: Takeshi Unohara, Yoshikuni Teramoto, Yoshiyuki NishioAbstract:Cellulose Diacetate- graft -poly(L-lactide) (CDA- g -PLLA) and poly(vinyl acetate- co -vinyl alcohol)- graft -PLLA (P(VAc- co -VOH)- g -PLLA) were synthesized over a range of compositions, by ring-opening copolymerization of L-lactide at the original hydroxyl positions of the respective trunk polymers, CDA (acetyl DS = 2.15) and P(VAc- co -VOH)- g -PLLA (VAc = 64.2 mol%). All the products of both graft copolymer series were non-crystallizable and their solution-cast films showed no domain segregation of the two components that constituted the trunk and side-chains. A comparative study on the molecular orientation and optical anisotropy induced by uniaxial stretching of film samples was undertaken for the two copolymer series with various side-chain lengths. Overall behaviour of the orientation was estimated from the statistical second () and fourth () moments obtained by a fluorescence polarization method using a rod-like probe of ~2.5 nm. Upon stretching, any film of both series imparted a positive orientation function, i.e., f = (3 − 1)/2 > 0, which increased with the extent of deformation. The degree of molecular orientation was higher in the CDA-graft series with a semi-rigid trunk, and, in both series, it declined monotonically with increasing content of the PLLA side-chain. With regard to the optical anisotropy, CDA- g -PLLA films always exhibited a positive birefringence (Δ n > 0) upon stretching, while drawn films of P(VAc- co -VOH)- g -PLLA displayed a negative one. This contrast in polarity reflects a difference in the intrinsic birefringence between the two trunk polymers. Of interest was the finding of a discontinuous change in Δn value with copolymer composition (PLLA content) for the respective graft series, when compared at a given stage of elongation of the films. Discussion took into consideration the locally different orientation manners of the attached PLLA chain segments.
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biodegradable Cellulose Diacetate graft poly l lactide s enzymatic hydrolysis behavior and surface morphological characterization
Biomacromolecules, 2004Co-Authors: Yoshikuni Teramoto, Yoshiyuki NishioAbstract:Enzymatic hydrolysis of selected copolymers of Cellulose Diacetate-graft-poly(l-lactide)s (CDA-g-PLLAs) were conducted with proteinase K for film specimens, which were solely quenched from the molten state or, further, annealed at temperatures below or above their glass transition temperatures. The hydrolysis rates depended seriously on the thermal history, as well as on the graft modification. Especially, the heat treatment, followed by physical aging or crystallization of the originally amorphous materials, was a key factor to control subtly their enzymatic degradation behavior. Atomic force microscopy revealed that the enzymatic hydrolysis transformed the surface of the respective films into a more undulated one with a number of fine protuberances, for example, of several hundred nanometers in height and a few micrometers in width. Attenuated total reflection FTIR spectroscopy ensured selective release of lactyl units from the surface region. In visual appearance, some degraded films exhibited even an ...
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biodegradable Cellulose Diacetate graft poly l lactide s thermal treatment effect on the development of supramolecular structures
Biomacromolecules, 2004Co-Authors: Yoshikuni Teramoto, Yoshiyuki NishioAbstract:Thermal transition property of Cellulose Diacetate-graft-poly(l-lactide) (CDA-g-PLLA) varies depending seriously on the molar substitution (MS) of lactyl unit, as represented by a drastic Tg depression with increasing MS (0 < MS ≤ 8) and a subsequent crystallization of the PLLA side chains (MS ≥ 14). To make clear the thermally induced development of supramolecular structures for this series of graft copolymers, physical aging and crystallization experiments were conducted under isothermal conditions at temperatures, respectively, comparable to and higher than their Tg's. For aged copolymers with lower MSs of 4.7 and 22, an enthalpy relaxation was followed by differential scanning calorimetry. The analysis of time evolution of the relaxed enthalpy in terms of a Kohlrausch−Williams−Watts relation revealed that the overall relaxation time and the distribution of relaxation times were, respectively, rather longer and much narrower compared with the corresponding data for plain PLLA. For crystallized copolyme...
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biodegradable Cellulose Diacetate graft poly l lactide s enzymatic hydrolysis behavior and surface morphological characterization
Biomacromolecules, 2004Co-Authors: Yoshikuni Teramoto, Yoshiyuki NishioAbstract:Enzymatic hydrolysis of selected copolymers of Cellulose Diacetate-graft-poly(L-lactide)s (CDA-g-PLLAs) were conducted with proteinase K for film specimens, which were solely quenched from the molten state or, further, annealed at temperatures below or above their glass transition temperatures. The hydrolysis rates depended seriously on the thermal history, as well as on the graft modification. Especially, the heat treatment, followed by physical aging or crystallization of the originally amorphous materials, was a key factor to control subtly their enzymatic degradation behavior. Atomic force microscopy revealed that the enzymatic hydrolysis transformed the surface of the respective films into a more undulated one with a number of fine protuberances, for example, of several hundred nanometers in height and a few micrometers in width. Attenuated total reflection FTIR spectroscopy ensured selective release of lactyl units from the surface region. In visual appearance, some degraded films exhibited even an iridescent color due to an effect of interference of visible light reflected on the surface. These observations suggest a conception of "spatiotemporally controlled degradation", leading to a new method not only for regulation of the overall rate of degradation but also for fine surface abrasion of polymer materials.
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Cellulose Diacetate graft poly lactic acid s synthesis of wide ranging compositions and their thermal and mechanical properties
Polymer, 2003Co-Authors: Yoshikuni Teramoto, Yoshiyuki NishioAbstract:Abstract Cellulose Diacetate-graft-poly(lactic acid)s (CDA-g-PLAs) were synthesized successfully over a wide range of composition in combination of different ways of graft polymerization: a copolycondensation of lactic acid; a ring-opening copolymerization of l -lactide in dimethyl sulfoxide; and a copolymerization similar to the second, but in bulk, each initiated at residual hydroxyl positions on CDA. Differential scanning calorimetry revealed that all the copolymer products gave a single glass transition temperature Tg, which decreased sharply from 202 °C of the original CDA to ∼60 °C, close to Tg of PLA homopolymer, with an increase in molar lactyl substitution (MS) to 8 corresponding to w PLA ≈67 wt % in PLA content. When the MS reached 14 (w PLA ≈79 wt %) or above, PLA side-chains of the graft copolymers became crystallizable at temperatures above their respective Tgs (48–58 °C) unlike the CDA-g-PLAs of MS≤8. In tensile measurements conducted at 80–100 °C for film sheets of melt-quenched CDA-g-PLAs, it was observed that their drawability increased drastically with increasing PLA content and, at a certain wPLA of MS≥14, the elongation at rupture reached a maximum of ca. 2000%. The synergistic behaviour is discussed in correlation to the composition-dependent thermal characteristics of CDA-g-PLAs.
Yoshikuni Teramoto - One of the best experts on this subject based on the ideXlab platform.
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Molecular orientation and optical anisotropy in drawn films of Cellulose Diacetate-graft-PLLA: comparative investigation with poly(vinyl acetate-co-vinyl alcohol)-graft-PLLA
Cellulose, 2011Co-Authors: Takeshi Unohara, Yoshikuni Teramoto, Yoshiyuki NishioAbstract:Cellulose Diacetate- graft -poly(L-lactide) (CDA- g -PLLA) and poly(vinyl acetate- co -vinyl alcohol)- graft -PLLA (P(VAc- co -VOH)- g -PLLA) were synthesized over a range of compositions, by ring-opening copolymerization of L-lactide at the original hydroxyl positions of the respective trunk polymers, CDA (acetyl DS = 2.15) and P(VAc- co -VOH)- g -PLLA (VAc = 64.2 mol%). All the products of both graft copolymer series were non-crystallizable and their solution-cast films showed no domain segregation of the two components that constituted the trunk and side-chains. A comparative study on the molecular orientation and optical anisotropy induced by uniaxial stretching of film samples was undertaken for the two copolymer series with various side-chain lengths. Overall behaviour of the orientation was estimated from the statistical second () and fourth () moments obtained by a fluorescence polarization method using a rod-like probe of ~2.5 nm. Upon stretching, any film of both series imparted a positive orientation function, i.e., f = (3 − 1)/2 > 0, which increased with the extent of deformation. The degree of molecular orientation was higher in the CDA-graft series with a semi-rigid trunk, and, in both series, it declined monotonically with increasing content of the PLLA side-chain. With regard to the optical anisotropy, CDA- g -PLLA films always exhibited a positive birefringence (Δ n > 0) upon stretching, while drawn films of P(VAc- co -VOH)- g -PLLA displayed a negative one. This contrast in polarity reflects a difference in the intrinsic birefringence between the two trunk polymers. Of interest was the finding of a discontinuous change in Δn value with copolymer composition (PLLA content) for the respective graft series, when compared at a given stage of elongation of the films. Discussion took into consideration the locally different orientation manners of the attached PLLA chain segments.
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nanoindentation of biodegradable Cellulose Diacetate graft poly l lactide copolymers effect of molecular composition and thermal aging on mechanical properties
Journal of Polymer Science Part B, 2007Co-Authors: Seunghwan Lee, Yoshikuni Teramoto, Siqun Wang, G M Pharr, Timothy G RialsAbstract:Nanoindentation of Cellulose Diacetate-graft-poly(lactide)s (CDA-g-PLLAs) synthesized by ring opening graft copolymerization of L-lactide in bulk onto the residual hydroxyl positions on CDA were conducted to investigate the effect of the molecular composition and thermal aging on mechanical properties and creep behavior. Continuous stiffness measurement (CSM) technique was used to obtained hardness and elastic modulus. These material properties were expressed as a mean value from 100 to 300 nm depths and an unloading value at final indentation depth. The hardness and elastic modulus in all CDA-g-PLLAs were higher than those in pure CDA, indicating that the introduction of PLLA increases the hardness and elastic modulus. With an increase of crystallinity by thermal aging, the hardness and elastic modulus were increased in both CDA-g-PLLA and PLLA. The creep test performed by CSM showed that the creep strain of CDA was decreased by the grafting of PLLA. Thermal aging decreased the creep strain of CDA-g-PLLA and PLLA. With an increase of holding time, hardness was decreased, whereas elastic modulus was kept almost constant. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1114–1121, 2007
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biodegradable Cellulose Diacetate graft poly l lactide s enzymatic hydrolysis behavior and surface morphological characterization
Biomacromolecules, 2004Co-Authors: Yoshikuni Teramoto, Yoshiyuki NishioAbstract:Enzymatic hydrolysis of selected copolymers of Cellulose Diacetate-graft-poly(l-lactide)s (CDA-g-PLLAs) were conducted with proteinase K for film specimens, which were solely quenched from the molten state or, further, annealed at temperatures below or above their glass transition temperatures. The hydrolysis rates depended seriously on the thermal history, as well as on the graft modification. Especially, the heat treatment, followed by physical aging or crystallization of the originally amorphous materials, was a key factor to control subtly their enzymatic degradation behavior. Atomic force microscopy revealed that the enzymatic hydrolysis transformed the surface of the respective films into a more undulated one with a number of fine protuberances, for example, of several hundred nanometers in height and a few micrometers in width. Attenuated total reflection FTIR spectroscopy ensured selective release of lactyl units from the surface region. In visual appearance, some degraded films exhibited even an ...
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biodegradable Cellulose Diacetate graft poly l lactide s thermal treatment effect on the development of supramolecular structures
Biomacromolecules, 2004Co-Authors: Yoshikuni Teramoto, Yoshiyuki NishioAbstract:Thermal transition property of Cellulose Diacetate-graft-poly(l-lactide) (CDA-g-PLLA) varies depending seriously on the molar substitution (MS) of lactyl unit, as represented by a drastic Tg depression with increasing MS (0 < MS ≤ 8) and a subsequent crystallization of the PLLA side chains (MS ≥ 14). To make clear the thermally induced development of supramolecular structures for this series of graft copolymers, physical aging and crystallization experiments were conducted under isothermal conditions at temperatures, respectively, comparable to and higher than their Tg's. For aged copolymers with lower MSs of 4.7 and 22, an enthalpy relaxation was followed by differential scanning calorimetry. The analysis of time evolution of the relaxed enthalpy in terms of a Kohlrausch−Williams−Watts relation revealed that the overall relaxation time and the distribution of relaxation times were, respectively, rather longer and much narrower compared with the corresponding data for plain PLLA. For crystallized copolyme...
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biodegradable Cellulose Diacetate graft poly l lactide s enzymatic hydrolysis behavior and surface morphological characterization
Biomacromolecules, 2004Co-Authors: Yoshikuni Teramoto, Yoshiyuki NishioAbstract:Enzymatic hydrolysis of selected copolymers of Cellulose Diacetate-graft-poly(L-lactide)s (CDA-g-PLLAs) were conducted with proteinase K for film specimens, which were solely quenched from the molten state or, further, annealed at temperatures below or above their glass transition temperatures. The hydrolysis rates depended seriously on the thermal history, as well as on the graft modification. Especially, the heat treatment, followed by physical aging or crystallization of the originally amorphous materials, was a key factor to control subtly their enzymatic degradation behavior. Atomic force microscopy revealed that the enzymatic hydrolysis transformed the surface of the respective films into a more undulated one with a number of fine protuberances, for example, of several hundred nanometers in height and a few micrometers in width. Attenuated total reflection FTIR spectroscopy ensured selective release of lactyl units from the surface region. In visual appearance, some degraded films exhibited even an iridescent color due to an effect of interference of visible light reflected on the surface. These observations suggest a conception of "spatiotemporally controlled degradation", leading to a new method not only for regulation of the overall rate of degradation but also for fine surface abrasion of polymer materials.
Hiroyuki Kawanishi - One of the best experts on this subject based on the ideXlab platform.
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reorganization of dynamic self assemblies of Cellulose Diacetate in solution dynamical critical like fluctuations in the lower critical solution temperature system
Biomacromolecules, 2002Co-Authors: Yoshisuke Tsunashima, Hiroyuki Kawanishi, Fumitaka HoriiAbstract:Dynamics of Cellulose Diacetate (CDA, the total degree of substitution (TDS) = 2.44) in dimethylacetamide (DMAc) in dilute solution was investigated at 2, 10, 20, 30, 40, 49.7, and 61.5 degrees C through dynamic light scattering in the quiescent state. The following three facts were made clear. First, CDA existed in three types of structures in the polar solvent, DMAc; one is a single CDA chain, and the others are dynamic structures, or self-assemblies, which were formed temporarily and locally by the solvent-mediated hydrogen bonding between the intermolecular C-6 position hydroxyls of the anhydroglucose units in the CDA backbone. Second, CDA showed a nature of low-temperature solubility in DMAc, that is, CDA is expected to dissolve molecularly below -12 degrees C but to take a phase separation above 65 degrees C, where two structures such as collapses of a single CDA chain and an aggregate appear. Third, a reorganization in the dynamic structures was detected at the temperature T = 33.8 degrees C. At this temperature, two dynamic structures showed the discontinuity in their correlation lengths, whereas the single CDA realized an uncorrelated chain state in the dynamical sense. In view of the low-temperature solubility of CDA in DMAc, this abnormal behavior around T was explained by dynamical critical-like fluctuations if T were treated as a kind of lower critical solution temperature (LCST) in the CDA/DMAc system. Here, the self-assemblies arise as the dynamical fluctuations under the spinodal decomposition situation and the competition between the hydrogen bonding (HB) and the hydrophobic interaction (HPhI) makes the conformation of CDA chains change drastically. In this scheme, the solvent-mediated HB and HPhI play important roles in the structure reorganization of Cellulose derivatives in strong electronegative solvents, though HB and HPhI cooperate with the inherent chain helicality.
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dynamic light scattering study of structural changes of Cellulose Diacetate in solution under couette flow
Macromolecules, 2000Co-Authors: Hiroyuki Kawanishi, Yoshisuke Tsunashima, Fumitaka HoriiAbstract:Dynamic light scattering (DLS) measurements were conducted under a simple shear flow, i.e., the Couette flow field, to Cellulose Diacetate (CDA; a typical polysaccharide) in semidilute N,N-dimethylacetamide (DMAc) solution. The shear rate y was varied from 0 to 5.25 s -1 . At quiescence, CDA showed three dynamic modes, which correspond to two kinds of associations and a single chain. In the weakly sheared system (0.402 s -1 ≤ γ ≤ 5.25 s -1 ), the three dynamic modes collapsed, and alternatively two completely different modes were observed. The fast mode experienced a transition around y = 0.81 s -1 , the decay rate distribution changing from a broader bimodal to a narrower unimodal shape with increasing shear. The slow mode had a unimodal decay rate distribution, but the length scale of fluctuations was larger by 3 orders of magnitude compared to those observed at y = 0 s -1 ; that is, the length distribution was extremely uniform irrespective of y, and the length ξ s was proportional to γ -1 . This ξ s γ -1 relation was interpreted by Taylor's treatment of the behavior of viscous drops. Thus, the repetition of the burst and the coalescence growth of the associations was suggested for the slow mode. The ξ s γ -1 relation implied that CDA was molecularly disperse in DMAc under the viscometric field in a capillary viscometer at γ = 920 s -1 .
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Influence of Long-Range Interactions on Diffusion Behavior in Semidilute Solution: Dynamics of Cellulose Diacetate in Quiescent State
Macromolecules, 1999Co-Authors: Yoshisuke Tsunashima, Hiroyuki Kawanishi, Ryosuke Nomura, Fumitaka HoriiAbstract:The dynamics of Cellulose Diacetate (CDA) in semidilute solution (1.4c* < c < 5c*) was investigated in a good and high-polarity solvent, dimethylacetamide (DMAc), by dynamic light scattering in the quiescent state at 30 °C. Two fast diffusion motions and a very slow diffusion motion were detected, all the behavior of which is not expected from the framework of dynamics for usual flexible polymers in good solvents. The fast (fast mode) and medium-fast (medium mode) motions gave the diffusion coefficients DF and DM as DF ∝ c0.40 and DM ∝ c0.55. Both were the cooperative diffusion motions, or the relaxations of concentration fluctuations in two types of coarse-dense structures, which were realized as a nest of structures in a dynamic sense in semidilute solution. However, the relaxation rates were suppressed by the long-ranged hydrogen-bond interaction between hydroxyl (OH) groups on CDA molecules, and the interactions brought the systems into the medium, not good, solvent state. The slow diffusion (slow mod...
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a nest of structures in dynamics of Cellulose Diacetate in n n dimethylacetamide in quiescent solution state studied by dynamic light scattering
Journal of Chemical Physics, 1998Co-Authors: Hiroyuki Kawanishi, Yoshisuke Tsunashima, Fumitaka HoriiAbstract:In the quiescent state, dynamic light scattering measurements were performed for a polysaccharide, Cellulose Diacetate (CDA, the degree of substitution 2.40), in a liquid-crystalline promoting solvent N, N-dimethylacetamide (DMAc) in the range from dilute to crossover concentrations. Three modes of motions were detected simultaneously over all concentrations measured. They are in a nest of structures, which are caused by long-range interactions acting between OH groups of glucose units in a highly dielectric-constant solvent DMAc. Denoting these modes as Mode I, II, and III from fast to slow motions, the decay rates Γ of each mode showed the squared scattering-vector dependence at lower angles, i.e., the diffusion nature. In dilute solution, fast Mode I is the translational diffusion of a single CDA chain and others represent the dissipation of locally associated CDA clouds which grow by the interactions specified above. Mode II is related to a coarse cloud formed in a limited time but spread over a wide ...
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change in chain stiffness in viscometric and ultracentrifugal fields Cellulose Diacetate in n n dimethylacetamide dilute solution
Journal of Chemical Physics, 1998Co-Authors: Hiroyuki Kawanishi, Yoshisuke Tsunashima, Shinichi Okada, Fumitaka HoriiAbstract:The molecular characteristics and the chain stiffness were investigated for fractionated samples of Cellulose Diacetate (CDA, degree of substitution DS = 2.40) in N, N-dimethylacetamide (DMAc) through the partial specific volume, the viscometric, the sedimentation velocity, and the sedimentation equilibrium measurements at 30 °C. It was found that CDA dispersed molecularly in DMAc under the external field such as in the viscometric and the sedimentation experiments. The molecular weight dependence of the intrinsic viscosity [η] and the sedimentation coefficient at infinite dilution s0 of the single CDA molecule were expressed by the relation [η] = 1.10×10−2Mw0.85 (cm3 g−1) and s0=2.25×10−14Mw0.20 (s), which exhibit the stiff, or semiflexible chain nature. The semiflexible chain parameters were evaluated by the Yamakawa–Fujii (YF) theory of the unperturbed wormlike cylinder model, first via a combination of the viscosity and the partial specific volume data (method A) and second via a combination of the se...
Yoshiyuki Sugahara - One of the best experts on this subject based on the ideXlab platform.
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effect of the graft density of Cellulose Diacetate modified layered perovskite nanosheets on mechanical properties of the transparent organic inorganic hybrids bearing covalent bonds at the interface
Cellulose, 2017Co-Authors: Satoru Sato, Kenji Shintani, Naokazu Idota, Takashi Nishino, Yoshiyuki SugaharaAbstract:Transparent organic–inorganic hybrids with a whitish colour were prepared from Cellulose Diacetate (CDA) nanosheets derived from Dion–Jacobson-type ion-exchangeable layered perovskite HLaNb2O7·xH2O (HLaNb) to prepare CDA-based hybrids bearing covalent bonds between HLaNb nanosheets and CDA matrices for improved mechanical properties. An n-decoxy derivative of HLaNb (C10_HLaNb) was exfoliated in acetonitrile by ultrasonication. TEM and AFM images revealed that C10_HLaNb was exfoliated into individual nanosheets. In order to explore the local environment around HLaNb nanosheets, a very small amount of CDA was reacted with a C10_HLaNb nanosheet dispersion [molar ratio COH:(NbOH + NbOC10H21) = 4:1] at 80 °C, and solid-state 13C NMR with cross polarization and magic angle spinning techniques showed that an alcohol-exchange-type reaction was proceeded to graft the CDA chains to the HLaNb nanosheets via new Nb–O–C covalent linkages. The CDA-based hybrids were prepared by dispersing 5 mass% of HLaNb nanosheets in CDA and subsequent heating at 80 °C for 1–7 days to cause a grafting reaction, and the product prepared by a 1-day grafting reaction exhibited improved mechanical properties compared to neat CDA; the Young’s modulus, tensile strength and toughness increased by 18, 34 and 78%, respectively. The mechanical properties deteriorated with further extension of the reaction period, however. In addition, a hybrid film prepared by mixing CDA and a C10_HLaNb nanosheet dispersion exhibited only a slight improvement in mechanical properties. These results clearly indicate that formation of an appropriate number of Nb–O–C bonds at the nanosheet/CDA interfaces is effective for improving mechanical properties.