<p>Cellulose pulp (CP) is composed mainly of cellulose which is one of the most useful and sustainable natural polymers. Cellulose-based materials, such as completely dispersed nanofibers and water-soluble cellulose, are transparent in water. Additionally, chemical modification of CP has been employed as a pretreatment for the preparation of nanofibers and to impart absorption properties derived from anionic functional groups. However, little is known about chemically modified CPs comprising micron-scale fibers that are transparent in water.In this study, we synthesized transparent sulfated cellulose pulp (TSCP) that exhibits good dispersion stability, high transparency in water, and highly swollen fiber structures. The sulfation method involved heating sulfamic acid and urea supported on CP. TSCP synthesized using a sulfamic acid amount relative to CP (<i>Q</i>) of 18.5, a molar ratio of urea to sulfamic acid (<i>R</i>) of 0.80, and a reaction temperature of 140&#xa0;°C exhibited the highest total light transmittance (94.7%) in water, a degree of polymerization (535), and amount of sulfate groups (1.73&#xa0;mmol/g). Polarization microscopy confirmed that most TSCP fibers swelled in water along the fiber width direction. The structure of hydrous-state TSCP was further confirmed using low-vacuum scanning electron microscopy. The maximum fiber width of the swollen TSCP reached 122&#xa0;μm, which was approximately six times than that of CP. The crystallinity was equivalent to that of the original CP with a Cellulose I-type crystalline structure. This transparent, hydrous-state TSCP, comprising predominantly swollen CP fibers, demonstrates potential for applications as a transparent material.</p>

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Development of sulfation for cellulose pulp to change its fiber morphology and appearance to transparent in water

  • Ayato Nishimura,
  • Tetsuya Uchida

摘要

Cellulose pulp (CP) is composed mainly of cellulose which is one of the most useful and sustainable natural polymers. Cellulose-based materials, such as completely dispersed nanofibers and water-soluble cellulose, are transparent in water. Additionally, chemical modification of CP has been employed as a pretreatment for the preparation of nanofibers and to impart absorption properties derived from anionic functional groups. However, little is known about chemically modified CPs comprising micron-scale fibers that are transparent in water.In this study, we synthesized transparent sulfated cellulose pulp (TSCP) that exhibits good dispersion stability, high transparency in water, and highly swollen fiber structures. The sulfation method involved heating sulfamic acid and urea supported on CP. TSCP synthesized using a sulfamic acid amount relative to CP (Q) of 18.5, a molar ratio of urea to sulfamic acid (R) of 0.80, and a reaction temperature of 140 °C exhibited the highest total light transmittance (94.7%) in water, a degree of polymerization (535), and amount of sulfate groups (1.73 mmol/g). Polarization microscopy confirmed that most TSCP fibers swelled in water along the fiber width direction. The structure of hydrous-state TSCP was further confirmed using low-vacuum scanning electron microscopy. The maximum fiber width of the swollen TSCP reached 122 μm, which was approximately six times than that of CP. The crystallinity was equivalent to that of the original CP with a Cellulose I-type crystalline structure. This transparent, hydrous-state TSCP, comprising predominantly swollen CP fibers, demonstrates potential for applications as a transparent material.