Effect of process parameters on layer-by-layer self-assembly of polyelectrolytes on cotton substrate

To our knowledge, the present study is the first attempt to evaluate the effect of different process parameters on the amount of polyelectrolyte adsorbed on a cotton textile substrate via sequential adsorption of negatively charged poly (styrene sulphonate) (PSS) and positively charged poly (allylamine hydrochloride) (PAH) using layer-by-layer (LBL) self-assembly nanocoating process. A considerably different polymer adsorption behaviour was observed from thick adsorbed layers to thin adsorbed layer with different degree of layer penetration and ionic pair formation over the pH range (2.5 - 9.0) studied. The amount of polyelectrolyte adsorption on cotton fabric was evaluated by measuring the colour value (K/S) of methylene blue absorbed cotton surface. Contact angle measurement revealed that the extent of binding of the oppositely charged polyions on the fabric depends on the pH of the polyelectrolyte solution and 'zipped-up' structure with more ion pair formation was observed at the pH range 4.5 - 6.5. At higher temperature, the amount of polyelectrolyte adsorbed within the multilayers was higher. An increased deposition of PSS and PAH was observed with increase in electrolyte (NaCl) concentration. The amount of PSS and PAH adsorption increased up to 0.03 (M) of PSS and 0.01 (M) of PAH concentrations, respectively. A dipping time of 5 min was sufficient to have a maximum deposition of the polyelectrolyte multilayers