Adsorption and interlayer diffusion controlled growth and unique surface patterned growth of polyelectrolyte multilayers

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 layerby-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 © 2016. This manuscript version is made available under the Elsevier user license http://www.elsevier.com/open-access/userlicense/1.0/ 2 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.

Polyelectrolyte Multilayers: An Overview on Fabrication, Properties, and Biomedical and Environmental Applications

“…A low molecular mass will increase the risk of PE desorption at the contact with the oppositely charged PE, while a higher molecular mass will enhance the deposition of multilayers and will increase its stability. Additionally, it is generally accepted that PEMs consisting of high molecular mass PEs are more stable than PEMs based on low molecular mass PEs [ 65 , 66 , 67 ]. Studying the LbL deposition of PLL and HA, Shen et al [ 68 ] also observed that the molecular weight of HA influences the deposition of PEMs.…”

Layer-by-Layer Assembly and Electrochemical Study of Alizarin Red S-Based Thin Films

“…The thicknesses of the (BPEI/ARS) n , (BPEI/(PSS+ARS)) n and ((BPEI+ARS)/PSS) n films were measured using a profilometer for when n was 20, 40, 60, 80, 100 and 120 (Figure 4). All three types of assemblies showed linear growth behavior, indicating suppressed interlayer diffusion throughout the multilayer films [64]. When the bilayer number was 20, the thicknesses of (BPEI/ARS) 20 , (BPEI/(PSS+ARS)) 20 and ((BPEI+ARS)/PSS) 20 were 237, 226 and 955 nm, respectively; when the bilayer number increased to 120, the thicknesses of (BPEI/ARS) 120 , (BPEI/(PSS+ARS)) 120 and ((BPEI+ARS)/PSS) 120 reached 4620, 5840 and 9860 nm, respectively.…”

Porous Polyelectrolytes: The Interplay of Charge and Pores for New Functionalities

“…This model of pore formation was further exploited to engineer porous LbL films.L ee and co-workers prepared PA A/PAH polyelectrolyte multilayer films with tunable surface properties and hierarchical pores by using highmolecular-weight PA Hand PA A. [25] Zacharia and co-workers created pores by exposing poly(ethylene imine)/PAA films to an electric field. [21] Zhang and co-workers fabricated al ightsensitive porous film, and created pores 10-100 nm in size by degradation of poly-l-lysine (PLL) and DNAterminated with 5-(4-aminophenyl)-10,15,20-triphenylporphyrin (APP) groups by irradiation with light.…”

“…d) Top‐view SEM images of a (PAA/PAH) 20 film after immersion in an aqueous solution at pH 2.7 for 30 min without subsequent immersion in deionized water . e) SEM images of PAH 8.5 /PAA 3.5 films with 12.5 bilayers . f) Schematic illustration of the preparation and AFM images (before and after cross‐linking) of PAH/PAA porous polyelectrolyte LbL membranes .…”