Impact of thermal annealing on wettability and antifouling characteristics of alginate poly-L-lysine polyelectrolyte multilayer films

Polyelectrolyte multilayers (PEMs) of poly-L-lysine (PLL) and alginic acid sodium salt (Alg) are fabricated applying the layer by layer technique and annealed at a constant temperature; 37, 50 and 80 degrees C, for 72 h. Atomic force microscopy reveals changes in the topography of the PEM, which is changing from a fibrillar to a smooth surface. Advancing contact angle in water varies from 36 degrees before annealing to 93 degrees, 77 degrees and 95 degrees after annealing at 37, 50 and 80 degrees C, respectively. Surface energy changes after annealing were calculated from contact angle measurements performed with organic solvents. Quartz crystal microbalance with dissipation, contact angle and fluorescence spectroscopy measurements show a significant decrease in the adsorption of the bovine serum albumin protein to the PEMs after annealing. Changes in the physical properties of the PEMs are interpreted as a result of the reorganization of the polyelectrolytes in the PEMs from a layered structure into complexes where the interaction of polycations and polyanions is enhanced. This work proposes a simple method to endow bio-PEMs with antifouling characteristics and tune their wettability. (C) 2016 Elsevier B.V. All rights reserved.