Smooth Model Surfaces from Lignin Derivatives. II. Adsorption of Polyelectrolytes and PECs Monitored by QCM-D

Abstract

For the first time to the knowledge of the authors, well-defined and stable lignin model surfaces have been utilized as substrates in polyelectrolyte adsorption studies. The adsorption of polyallylamine (PAH), poly(acrylic acid) (PAA), and polyelectrolyte complexes (PECs) was monitored using quartz crystal microgravimetry with dissipation (QCM-D). The PECs were prepared by mixing PAH and PAA at different ratios and sequences, creating both cationic and anionic PECs with different charge levels. The adsorption experiments were performed in 1 and 10 mM sodium chloride solutions at pH 5 and 7.5. The highest adsorption of PAH and cationic PECs was found at pH 7.5, where the slightly negatively charged nature of the lignin substrate is more pronounced, governing electrostatic attraction of oppositely charged polymeric substances. An increase in the adsorption was further found when the electrolyte concentration was increased. In comparison, both PAA and the anionic PEC showed remarkably high adsorption to the lignin model film. The adsorption of PAA was further studied on silica and was found to be relatively low even at high electrolyte concentrations. This indicated that the high PAA adsorption on the lignin films was not induced by a decreased solubility of the anionic polyelectrolyte. The high levels of adsorption on lignin model surfaces found both for PAA and the anionic PAA-PAH polyelectrolyte complex points to the presence of strong nonionic interactions in these systems.

Lignin-based polyoxyethylene ether enhanced enzymatic hydrolysis of lignocelluloses by dispersing cellulase aggregates

“…The mechanism of enhancing the enzymatic hydrolysis of microcrystalline cellulose with high lignin content by EHL-PEG 3.2.1. Effect of EHL-PEG on the nonproductive adsorption of cellulase on the lignin film QCM-D has been reported to monitor the adsorption behavior of polyelectrolyte (Norgren et al, 2007), soy protein (Salas et al, 2013) and cellulase (Rahikainen et al, 2013;Sammond et al, 2014) on the lignin film in real time dynamics. Here, QCM-D was used to investigate the effect of EHL-PEG and PEG4600 on the nonproductive adsorption of cellulase on the lignin film.…”

New insights into the structure of polyelectrolyte complexes

“…In a study by Thünemann et al [23], "tart" type structured PEC nanoparticles comprised of retinoic acid (polyanion) and different polyamino acids (polycations) were visualized by freezefracture TEM of the dispersions. PECs formed from mixtures of oppositely charged PELs and later deposited/adsorbed and dried on different substrates have however been investigated quite extensively [1,11,15,22,23,27]. Generally, the validity of transpositions of structural information determined for dried PECs into PEC dispersions needs to be carefully examined due to the possibilities of artifact generation, e.g.…”

Study of thin films of kraft lignin and two DHPs by means of single-molecule force spectroscopy (SMFS)

“…The KL was isolated from the black liquor of pulping of Picea abies (SW) as was the case in the studies of Norgren et al (2006) , Notley and Norgren (2007), Norgren et al (2007) , Notley andNorgren (2008 , 2010) . Typically, SW lignin consists of guaiacyl propan units ( > 95 % ), which is the results of the dehydrogenative polymerization of coniferyl alcohol.…”

“…The thin fi lms technique -obtained from well-defi ned lignin polymer samples -is also suited for studying noncovalent interactions (Constantino et al 1996(Constantino et al , 1998(Constantino et al , 2000Micic et al 2000Micic et al , 2001aMicic et al ,b, 2004Pasquini et al 2002Pasquini et al , 2005Norgren et al 2006Norgren et al , 2007Notley andNorgren 2006, 2008 ;Tammelin et al 2006 ). Several authors studied the physicochemical properties of KL at an interface based on smooth, well-characterized fi lms (Norgren et al , 2007Notley andNorgren 2006, 2008) .…”

“…Several authors studied the physicochemical properties of KL at an interface based on smooth, well-characterized fi lms (Norgren et al , 2007Notley andNorgren 2006, 2008) . In particular, the interaction of aqueous solvent with lignin was in focus as a function of solution conditions including pH and ionic strength by monitoring the amount of water within a lignin fi lm (Norgren et al 2007 ). There was no signifi cant water uptake into the thin fi lm at pH < 9.…”