The Experts below are selected from a list of 186 Experts worldwide ranked by ideXlab platform

Stefan Spirk - One of the best experts on this subject based on the ideXlab platform.

  • Cellulose carbamate derived Cellulose thin films: preparation, characterization and blending with Cellulose Xanthate
    Cellulose, 2019
    Co-Authors: Michael Weißl, Mathias Andreas Hobisch, Leena Sisko Johansson, Kay Hettrich, Eero Kontturi, Bert Volkert, Stefan Spirk
    Abstract:

    Cellulose carbamate (CC) was employed as a water-soluble precursor in the manufacturing of Cellulose based thin films using the spin coating technique. An intriguing observation was that during spin coating of CC from alkaline aqueous solutions, regeneration to Cellulose was accomplished without the addition of any further chemicals. After rinsing, homogeneous thin films with tunable layer thickness in a range between 20 and 80 nm were obtained. Further, CC was blended with Cellulose Xanthate in different ratios (3:1, 1:1, 1:3) and after regeneration the properties of the resulting all -Cellulose blend thin films were investigated. We could observe some slight indications of phase separation by means of atomic force microscopy. The layer thickness of the blend thin films was nearly independent of the ratio of the components, with values between 50 and 60 nm for the chosen conditions. The water uptake capability (80–90% relative to the film mass) determined by H_2O/D_2O exchange in a quartz crystal microbalance was independent of the blend ratio.

  • Homogeneous Cellulose thin films by regeneration of Cellulose Xanthate: properties and characterization
    Cellulose, 2018
    Co-Authors: Michael Weißl, Katrin Niegelhell, David Reishofer, Armin Zankel, Josef Innerlohinger, Stefan Spirk
    Abstract:

    The preparation and characterization of Cellulose thin films derived from Cellulose Xanthate is reported. The films are prepared by depositing alkaline aqueous solutions of Cellulose Xanthate onto silicon wafers, followed by a spin coating step. Depending on the Xanthate concentration used for spin coating, films with 50 and 700 nm thickness are obtained. The Cellulose Xanthate is converted to Cellulose by exposing the films to HCl vapors over a period of 20 min. The conversion is monitored by ATR-IR spectroscopy, which allows for tracking the rupture of C–S and C=S bonds during the regeneration process. The conversion is accompanied by a reduction of the film thickness of ca 40% due to the removal of the bulky Xanthate group. The films feature a homogenous, but porous morphology as shown by atomic force microscopy. Further, the films were investigated towards their interaction with Bovine Serum Albumin (BSA) and fibrinogen by means of multi-parameter surface plasmon resonance spectroscopy. Similar as other Cellulose thin films BSA adsorption is low while fibrinogen adsorbs to some extent at physiological pH (7.4).

Michael Weißl - One of the best experts on this subject based on the ideXlab platform.

  • Cellulose carbamate derived Cellulose thin films: preparation, characterization and blending with Cellulose Xanthate
    Cellulose, 2019
    Co-Authors: Michael Weißl, Mathias Andreas Hobisch, Leena Sisko Johansson, Kay Hettrich, Eero Kontturi, Bert Volkert, Stefan Spirk
    Abstract:

    Cellulose carbamate (CC) was employed as a water-soluble precursor in the manufacturing of Cellulose based thin films using the spin coating technique. An intriguing observation was that during spin coating of CC from alkaline aqueous solutions, regeneration to Cellulose was accomplished without the addition of any further chemicals. After rinsing, homogeneous thin films with tunable layer thickness in a range between 20 and 80 nm were obtained. Further, CC was blended with Cellulose Xanthate in different ratios (3:1, 1:1, 1:3) and after regeneration the properties of the resulting all -Cellulose blend thin films were investigated. We could observe some slight indications of phase separation by means of atomic force microscopy. The layer thickness of the blend thin films was nearly independent of the ratio of the components, with values between 50 and 60 nm for the chosen conditions. The water uptake capability (80–90% relative to the film mass) determined by H_2O/D_2O exchange in a quartz crystal microbalance was independent of the blend ratio.

  • Homogeneous Cellulose thin films by regeneration of Cellulose Xanthate: properties and characterization
    Cellulose, 2018
    Co-Authors: Michael Weißl, Katrin Niegelhell, David Reishofer, Armin Zankel, Josef Innerlohinger, Stefan Spirk
    Abstract:

    The preparation and characterization of Cellulose thin films derived from Cellulose Xanthate is reported. The films are prepared by depositing alkaline aqueous solutions of Cellulose Xanthate onto silicon wafers, followed by a spin coating step. Depending on the Xanthate concentration used for spin coating, films with 50 and 700 nm thickness are obtained. The Cellulose Xanthate is converted to Cellulose by exposing the films to HCl vapors over a period of 20 min. The conversion is monitored by ATR-IR spectroscopy, which allows for tracking the rupture of C–S and C=S bonds during the regeneration process. The conversion is accompanied by a reduction of the film thickness of ca 40% due to the removal of the bulky Xanthate group. The films feature a homogenous, but porous morphology as shown by atomic force microscopy. Further, the films were investigated towards their interaction with Bovine Serum Albumin (BSA) and fibrinogen by means of multi-parameter surface plasmon resonance spectroscopy. Similar as other Cellulose thin films BSA adsorption is low while fibrinogen adsorbs to some extent at physiological pH (7.4).

Takehiko Midorikawa - One of the best experts on this subject based on the ideXlab platform.

  • fiber preparation of n acylchitosan and its Cellulose blend by spinning their aqueous Xanthate solutions
    Carbohydrate Polymers, 1998
    Co-Authors: Shigehiro Hirano, Akihiro Usutani, Masatoshi Yoshikawa, Takehiko Midorikawa
    Abstract:

    Abstract This study aims to develop a method of preparing novel fibers of N-acylchitosan and N-acylchitosan–Cellulose by spinning an aqueous alkaline solution of their sodium Xanthates. A solution of sodium N-acylchitosan salt in aqueous 14% NaOH was treated with carbon disulfide to afford an aqueous solution of sodium N-acylchitosan Xanthate. The solution of sodium N-acylchitosan Xanthate, and its solution mixed with sodium Cellulose Xanthate, were spun at 45–50°C through a viscose-type spinneret into a coagulation bath containing aqueous 10% H2SO4, 32% Na2SO4 and 1.3% ZnSO4. A total of eight fibers of N-acetylchitosan, N-propionylchitosan, N-acetylchitosan–Cellulose (6 : 4, 4 : 5 and 3 :7 w/w) and N-propionylchitosan–Cellulose (4 : 6, 5 : 5 and 3 :7 w/w) were prepared. All these fibers were white and had good mechanical properties.

  • novel fibers of n acylchitosan and its Cellulose composite prepared by spinning their aqueous Xanthate solutions
    Carbohydrate Polymers, 1997
    Co-Authors: Shigehiro Hirano, Akihiro Usutani, Takehiko Midorikawa
    Abstract:

    Novel fibers of N-acylchitosan and N-acylchitosan-Cellulose composite were prepared. An aq. 14% NaOH solution of sodium N-acylchitosan Xanthate [O-(sodium thio) thiocarbonyl N-acylchitosan] and of its mixture with sodium Cellulose Xanthate [O-(sodium thio) thiocarbonyl Cellulose) was spun at 45–50 °C through a viscose-type spinneret into a coagulating bath containing aq. 10% H2SO4, 32% Na2SO4 and 1.3% ZnSO4. All the fibers obtained were white. N-Propionylchitosan-Cellulose composite filament had better mechanical properties than did N-acetylchitosan-Cellulose composite filament. These fibers were digested by chitinase and lysozyme, in which the hydrolysis rate was controlled by the N-acyl structure of chitosan.

Shigehiro Hirano - One of the best experts on this subject based on the ideXlab platform.

  • fiber preparation of n acylchitosan and its Cellulose blend by spinning their aqueous Xanthate solutions
    Carbohydrate Polymers, 1998
    Co-Authors: Shigehiro Hirano, Akihiro Usutani, Masatoshi Yoshikawa, Takehiko Midorikawa
    Abstract:

    Abstract This study aims to develop a method of preparing novel fibers of N-acylchitosan and N-acylchitosan–Cellulose by spinning an aqueous alkaline solution of their sodium Xanthates. A solution of sodium N-acylchitosan salt in aqueous 14% NaOH was treated with carbon disulfide to afford an aqueous solution of sodium N-acylchitosan Xanthate. The solution of sodium N-acylchitosan Xanthate, and its solution mixed with sodium Cellulose Xanthate, were spun at 45–50°C through a viscose-type spinneret into a coagulation bath containing aqueous 10% H2SO4, 32% Na2SO4 and 1.3% ZnSO4. A total of eight fibers of N-acetylchitosan, N-propionylchitosan, N-acetylchitosan–Cellulose (6 : 4, 4 : 5 and 3 :7 w/w) and N-propionylchitosan–Cellulose (4 : 6, 5 : 5 and 3 :7 w/w) were prepared. All these fibers were white and had good mechanical properties.

  • novel fibers of n acylchitosan and its Cellulose composite prepared by spinning their aqueous Xanthate solutions
    Carbohydrate Polymers, 1997
    Co-Authors: Shigehiro Hirano, Akihiro Usutani, Takehiko Midorikawa
    Abstract:

    Novel fibers of N-acylchitosan and N-acylchitosan-Cellulose composite were prepared. An aq. 14% NaOH solution of sodium N-acylchitosan Xanthate [O-(sodium thio) thiocarbonyl N-acylchitosan] and of its mixture with sodium Cellulose Xanthate [O-(sodium thio) thiocarbonyl Cellulose) was spun at 45–50 °C through a viscose-type spinneret into a coagulating bath containing aq. 10% H2SO4, 32% Na2SO4 and 1.3% ZnSO4. All the fibers obtained were white. N-Propionylchitosan-Cellulose composite filament had better mechanical properties than did N-acetylchitosan-Cellulose composite filament. These fibers were digested by chitinase and lysozyme, in which the hydrolysis rate was controlled by the N-acyl structure of chitosan.

Sun Chunbao - One of the best experts on this subject based on the ideXlab platform.