Adsorption and interlayer diffusion controlled growth and unique surface patterned growth of polyelectrolyte multilayers. (27th January 2017)

• Record Type: Journal Article
• Authors: Yu, Jing; Meharg, Brooke M.; Lee, Ilsoon
• Is Part Of: Polymer. Volume 109(2017)
• Page Start: 297
• Page End: 306
• Publication Date: 2017-01-27
• Subjects: Polyelectrolyte multilayers -- Film growth -- Adsorption -- Interlayer diffusion -- Surface morphology; Polymers -- Periodicals; Polymerization -- Periodicals; Polymères -- Périodiques; Polymérisation -- Périodiques; 547.7
• DOI: 10.1016/j.polymer.2016.12.055
• Languages: English
• ISSNs: 0032-3861

Abstract

Abstract: In this work, extremely high molecular weight ( M w ) poly(allylamine hydrochloride) (PAH, 900K g/mol) and poly(acrylic acid) (PAA, 225 K g/mol) were selected to amplify the difference in the growth of multilayers in comparison with low M w PAA (15K g/mol) and PAH (15K g/mol). By varying the pH conditions, the PAH/PAA multilayers were fabricated via the layer-by-layer (LbL) assembly in both linear and exponential growth regimes. In the linear growth regime with interlayer diffusion suppressed, high M w polyelectrolytes with low charge density could slow down the adsorption step, leading to the decrease of thickness compared to low M w polyelectrolytes when the deposition time was limited. However, the effect of M w could be reversed by increasing the deposition time, for the adsorption of low M w polyelectrolyte reached equilibrium, while the adsorption of high M w polyelectrolyte continued. The larger coil size of high M w polyelectrolyte could enable the surpassing of multilayer thickness compared with low M w polyelectrolyte. In the exponential growth regime, besides the slow adsorption, the application of high M w polyelectrolytes further suppressed the interlayer diffusion, leading to the decrease of multilayer thickness regardless of deposition time. We further studied the effects of deposition time, M w of polyelectrolytes, and the number of bilayers on the surface morphology in the exponential growth regime. Surface roughness significantly increased with the application of high M w PAA and the increase in deposition time. For the first time, the unique LbL film growth patterns of islet, ring and cantaloupe skin-like structures that consecutively formed on the surface of polyelectrolyte multilayers were reported by tuning the above parameters. Graphical abstract: Highlights: PAH and PAA with extremely different M w s were applied to fabricate PEMs. Growth behavior of PEMs was studied in both linear and exponential growth regime. M w effect on film growth is dependent on the deposition time and charge density. Unique surface topographies were obtained ranging from nano- to micro-scale.