Adsorption of cationic photoluminescent nanoparticles on softwood cellulose fibres: Effects of particles stabilization and fibres’ beating

The present investigation focuses on the adsorption of cationic photoluminescent polymer nanoparticles on negatively charged bleached softwood cellulose fibres. The synthesis of the copolyfluorene–fluorenone and its miniemulsification with tetradecyltrimethylammonium bromide (TTAB) as surfactant has been optimized to obtain highly charged cationic nanoparticles. Cellulose pulp beating was performed as mechanical treatment to increase fibres hydration and specific surface area. Although beating promoted nanoparticles adsorption, photoluminescence of handsheets prepared with beaten fibres was less intense comparing to those obtained with untreated fibres. The photoluminescence drop was attributed to the loss of a large fraction of cellulosic fine elements present in the beaten pulp during handsheets preparation. Cationic nanoparticles adsorption kinetics on cellulose fibres and the resulting photoluminescence efficiency was monitored in two cases: with or without the stabilization of nanoparticles in the pulp slurry by TTAB. Pulps preconditioning with TTAB avoided nanoparticles flocculation and led to a homogeneous coverage of the fibres surface giving more efficient photoluminescent papers. However, the formation of a continuous layer on the fibre surface induced a drop in the mechanical resistance of the paper which was ascribed to a decrease of interfibre hydrogen bonding.