Preparation and characteristics of anionic polyacrylamides containing direct dye with a high affinity for cellulose

Shingo Yokota, Takefumi Ohta, Takuya Kitaoka, Toshihiro Ona, Hiroyuki Wariishi

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3 Citations (Scopus)


Direct dye with a high affinity for cellulose substrate was utilized as a cellulose anchor to promote retention of paper strengthening additives under various conditions associated with the wet end of a paper machine. Direct Red 28 (DR) was covalently linked to anionic polyacrylamide (A-PAM) via a condensation reaction using water-soluble carbodiimide. The DR-conjugated A-PAM (DR-A-PAM) demonstrated good retention efficiency, resulting in strength enhancement of handsheets. Anionic trash showed no interference with the performance of DR-A-PAM in the wet end, while the additive performance was sensitive to calcium ions. Surface plasmon resonance analysis gave useful information on the cellulose-anchoring ability of DR-A-PAM. Dye molecules were irreversibly adsorbed onto the cellulose substrate under aqueous conditions, while A-PAM possessed no significant affinity for cellulose. These results suggest that anionic DR moieties in DR-A-PAM molecules served as a cellulose-anchor, possibly due to multiple CH-π interaction between hydrophobic face of cellulose substrate and π-conjugated system of dye molecules. Such a unique interaction of direct dye and cellulose provides a new insight into the wet end system, and does not depend on conventional electrostatic attraction.

Original languageEnglish
Pages (from-to)497-508
Number of pages12
Issue number2
Publication statusPublished - May 2009

All Science Journal Classification (ASJC) codes

  • Environmental Engineering
  • Bioengineering
  • Waste Management and Disposal


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