TY  - JOUR
A1  - Dodoo, Samuel
A1  - Balzer, Bizan N.
A1  - Hugel, Thorsten
A1  - Laschewsky, André
A1  - von Klitzing, Regine
T1  - Effect of ionic strength and layer number on swelling of polyelectrolyte multilayers in water vapour
JF  - Soft materials
N2  - The swelling behavior of polyelectrolyte multilayers (PEMs) of poly(sodium-4 styrene sulfonate) (PSS) and poly(diallyl dimethyl ammonium chloride) (PDADMAC) prepared from aqueous solution of 0.1 M and 0.5 M NaCl are investigated by ellipsometry and Atomic Force Microscopy (AFM). From 1 double-layer up to 4 double-layers of 0.1 M NaCl, the amount of swelling water in the PEMs decreases with increasing number of adsorbed double layers due to an increase in polyelectrolyte density as a result of the attraction between the positively charged outermost PDADMAC layer and the Si substrate. From 6 double layers to 30 double layers, the attraction is reduced due to a much larger distance between substrate and outermost layer leading to a much lower polyelectrolyte density and higher swelling water. In PEMs prepared from aqueous solution of 0.5 M NaCl, the amount of water constantly increases which is related to a monotonically decreasing polyelectrolyte density with increasing number of polyelectrolyte layers. Studies of the surface topology also indicate a transition from a more substrate affected interphase behavior to a continuum properties of the polyelectrolyte multilayers. The threshold for the transition from interphase to continuum behavior depends on the preparation conditions of the PEM.
KW  - Continuum properties
KW  - Interphase behavior
KW  - Ionic strength
KW  - Multilayers
KW  - Polyelectrolytes
KW  - Substrate effect
KW  - Swelling behavior
KW  - Threshold
KW  - Water vapor
Y1  - 2013
U6  - https://doi.org/10.1080/1539445X.2011.607203
SN  - 1539-445X
VL  - 11
IS  - 2
SP  - 157
EP  - 164
PB  - Taylor & Francis Group
CY  - Philadelphia
ER  - 
TY  - JOUR
A1  - Micciulla, Samantha
A1  - Dodoo, Samuel
A1  - Chevigny, Chloe
A1  - Laschewsky, André
A1  - von Klitzing, Regine
T1  - Short versus long chain polyelectrolyte multilayers: a direct comparison of self-assembly and structural properties
JF  - Physical chemistry, chemical physics : a journal of European Chemical Societies
N2  - Successful layer-by-layer (LbL) growth of short chain (similar to 30 repeat units per chain) poly(sodium styrene sulfonate) (PSS)-poly(diallyl dimethylammonium chloride) (PDADMAC) multilayers is presented for the first time and compared with the growth of equivalent long chain polyelectrolyte multilayers (PEMs). A detailed study performed by quartz crystal microbalance with dissipation (QCM-D) is carried out and three main processes are identified: (i) initial mass uptake, (ii) adsorption desorption during layer equilibration and (iii) desorption during rinsing. In contrast to the high stability and strong layer increment of high molecular weight (HMW) PEMs, layer degradation characterizes low molecular weight (LMW) multilayers. In particular, two different instability phenomena are observed: a constant decrease of sensed mass during equilibration after PDADMAC adsorption, and a strong mass toss by salt-free rinsing after PSS adsorption. Yet, an increase of salt concentration leads to much stronger layer growth. First, when the rinsing medium is changed from pure water to 0.1 M NaCl, the mass loss during rinsing is reduced, irrespective of molecular weight. Second, an increase in salt concentration in the LMW PE solutions causes a larger increment during the initial adsorption step, with no effect on the rinsing. Finally, the mechanical properties of the two systems are extracted from the measured frequency and dissipation shifts, as they offer a deeper insight into the multilayer structures depending on chain length and outermost layer. The paper enriches the field of PE assembly by presenting the use of very short PE chains to form multilayers and elucidates the role of preparation conditions to overcome the limitation of layer stability.
Y1  - 2014
U6  - https://doi.org/10.1039/c4cp03439b
SN  - 1463-9076
SN  - 1463-9084
VL  - 16
IS  - 40
SP  - 21988
EP  - 21998
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  -