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Abstract: This paper compares the influence of the molecular weight of polylelectrolytes forming polyelectrolyte multilayers (PEM) on wood fibers on adhesion and paper strength. Sheets were made from fibers treated with poly(allylamine hydrochloride) (PAH)/poly(acrylic acid) (PAA) of molecular mass 70,000 and 240,000, respectively, and of poly(dimethyldiallylammonium chloride) (PDADMAC)/poly(styrene sulfonate) (PSS) of molecular mass 30,000 and 80,000, respectively. The results were compared to what has recently been reported for PEM formation on fibers using a low-molecular-mass combination of PAH and PAA and a high-molecular-mass combination of PDADMAC/PSS. There was a less significant improvement in the case of the low-molecular-mass PDADMAC/PSS and the high-molecular-mass PAH/PAA. The adsorbed amounts of PAH and PDADMAC were also determined, showing a lower adsorbed amount of the low-molecular-mass PAH than of the high-molecular-mass PDADMAC. The amount of low-molecular-mass PDADMAC was similar to that found for high-molecular-mass PDADMAC/PSS. Individual fibers were partly treated and studied, showing a less significant decrease in wettability with low-molecular-mass PDADMAC/PSS than with the high-molecular-mass combination. The effect of the molecular weight on the adhesion was discussed in terms of the structure and wettability of the PEMs. [Copyright &y& Elsevier]

Abstract: Polydimethyldiallylammonium chloride (PDADMAC) and polystyrene sulfonate (PSS) have been used to build-up polyelectrolyte multilayers (PEMs) on chemical soft wood fibres and on SiO2 at various electrolyte concentrations. Adsorption onto SiO2 was studied using a stagnation point adsorption reflectometer (SPAR), and the adsorbed amount of PDADMAC and PSS on the fibres was determined using nitrogen analysis and Schöniger burning, respectively. The adsorption onto the two substrates was then compared. Paper testing showed that the tensile index (TI) increased by about 90% when 11 layers had been adsorbed, and that there was a correlation between the adsorbed amount and the increase in TI. It was also shown that the particular polymer present in the outermost layer significantly influenced the TI, and that PDADMAC produced a higher TI. A correlation between the adsorbed amount and the TI was also found. Individual fibres were partly treated with a PEM and analysed using a dynamic contact angle analyser (DCA) and environmental scanning electron microscopy (ESEM). [Copyright &y& Elsevier]

Abstract: Polyallylamine hydrochloride (PAH) and polyacrylic acid (PAA) have been used to build up polyelectrolyte multilayers (PEM) on wood fibres and on silicon oxide surfaces, under various pH conditions. Consecutive adsorption onto silicon oxide surfaces of PAH and PAA were studied using stagnation point adsorption reflectometry, and the results showed a steady build-up of multilayers. Furthermore, by altering pH, the build-up of the multilayer could be made either linear or exponential in terms of adsorbed amount. Nitrogen analysis of sheets prepared from modified fibres showed that the adsorbed amount of PAH increased throughout PEM build-up, the amount of increase depending on pH during adsorption. Strength measurements of the sheets, i.e., stress at break and strain at break, showed significant improvements ranging from 60 to 200%, depending on both pH during adsorption and type of polyelectrolyte in the outer layer. A good correlation between the adsorbed amount of PAH and the improved strength properties of the paper was also found. [Copyright &y& Elsevier]