Influence of Polymer Molecular Weight on the Parabolic and Linear Growth Regime of PDADMAC/PSS Multilayers

Abstract

The buildup of polyelectrolyte multilayers is investigated in solution with multiple angle null-ellipsometry. Polyanion poly(styrenesulfonate) (PSS) and polycation poly(diallyldimethylammonium) (PDADMAC) are adsorbed sequentially from 0.1 M NaCl solution. First the films grow parabolically. After N trans deposited PDADMAC/PSS layer pairs a transition from a parabolic to a linear growth occurs. For molecular weights above a threshold (M w(PSS) > 25 kDa and M w(PDADMAC) > 80 kDa), N trans is 15, the thickness per layer pair in the linear growth regime is 12.3 nm. If either the PDADMAC or the PSS molecular weight is decreased below the threshold value, N trans either falls (for PDADMAC, lowest value observed is 8) or rises (for PSS, highest value observed is 33), respectively. Simultaneously, in the linear growth regime, the thickness per layer pair decreases (down to 4.3 nm) or rises (up to 25 nm). Furthermore, for low molecular weight PSS, three growth regimes are observed: exponential, parabolic, and linear. The opposite effect of PDADMAC and PSS molecular weight reduction is discussed in terms of persistence lengths and linear charge density. The data suggest that molecular weight provides a way to control growth and internal structure of polyelectrolyte multilayers.

Oligolayer-Coated Nanoparticles: Impact of Surface Topography at the Nanobio Interface

“…These characteristic nanostructures were already reported for higher layer numbers on silica substrates 45. The high molecular weight and the fact that PD is completely charged leads to a strong electrostatic repulsion of the polymer segments and to a coiled surface conformation(Figure 2 D, G) 46,47. As the bi-layered sample already showed this characteristic nanostructure, it can be assumed that even a single layer of PD is most likely sufficient to completely cover the surface features of the gold substrate.…”

Swelling of Polyelectrolyte Multilayers: The Relation Between, Surface and Bulk Characteristics

“…This growth behavior was often described in literature. 32,33 Because of the low ionic strength (0.1 M NaCl) during preparation, the nonlinear growing regime is small in terms of thickness. The thickness increment grows from 1.0 to 4.0 nm at the end of the nonlinear growing regime.…”

Influence of the degree of ionization on the growth mechanism of poly(diallyldimethylammonium)/poly(acrylic acid) multilayers

“…The PEM build‐up can be characterized by different growth mechanisms: The adsorbed mass m ( n ) and/or the total film thickness d ( n ) as a function of the number of adsorbed bilayers, n , respectively, can increase either linearly, exponentially, or parabolically . Multilayers from synthetic polyelectrolytes, which are characterized by high charge densities (e.g., PSS/PAH), mostly grow in a linear fashion, whereas multilayers consisting of natural polyelectrolytes having low charge densities but large hydration shells (e.g., poly‐ l ‐glutamic acid (PGA) and poly‐ l ‐lysine (PLL) or hyaluronic acid and PLL) tend to grow exponentially.…”

“…However, deviating from this general classification, supralinear growth was observed for multilayer systems made from synthetic polyelectrolytes under certain conditions: In the case of PDADMA/PSS multilayers Guzmán et al observed linear growth at low salt concentrations, and exponential growth at high salt concentrations . Nestler et al investigated PDADMA/PSS multilayers and found that above a certain salt concentration the initial growth law is parabolic up to a critical layer number, above which it changes to a linear law. The critical layer number depends on the molecular weight .…”

“…Nestler et al investigated PDADMA/PSS multilayers and found that above a certain salt concentration the initial growth law is parabolic up to a critical layer number, above which it changes to a linear law. The critical layer number depends on the molecular weight . Bieker et al investigated the growth behavior of the weak synthetic polyelectrolytes PAH and PAA in dependence on pH and found alternating linear and exponential growth regimes.…”