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The
Layer-by-Layer Assembly
This technique of preparation of thin films is taken
advantage of in many projects which are being pursued in
our group. The idea of the technique is very simple. A
charged substrate, for instance negatively charged
glass, is immersed in the solution of positively charged
polyelectrolyte. After rinsing with water, the latter
forms a submonolayer on the surface of the substrate,
which switches the surface charge to positive. When one
immerse it in the dispersion of negatively charged
nanoparticles or other nanocolloid, a new layer is
formed, which also switches the surface charge. This
makes possible the adsorption of a new layer of
polyelectrolyte. Thus, the whole cycle can be repeated
as many times as one wants. Additionally, we chemical
nature of the polyelectrolyte and/or the nanocolloid can
be varied as films are being assembled. This opens the
way of preparation of most diverse and flexible family
of nanocomposites with a variety of functionalities. For
instance, the nanoparticles can be semiconducting,
metallic, or magnetic. We also demonstrated the assembly
of clay sheets and carbon nanotubes. To add biological
functionality to the multilayer, layers of proteins or
other biopolymers can be added. Thus, LBL assembly can
be considered as a very convenient tool for making both
coatings and free-standing materials for a variety of
most challenging applications.
Ultra Strong Materials
The mechanical failure of hybrid materials made from
polymers and single wall carbon nanotubes (SWNT) is
primarily attributed to poor matrix-SWNT connectivity
and severe phase segregation. Both problems can be
successfully mitigated when the SWNTcomposite is made
following the protocol of layer-by-layer assembly. This
deposition technique prevents phase segregation of the
polymer/SWNT binary system, and after subsequent
cross-linking, the nm-scale-uniform composite with SWNT
loading as high as 50 wt% can be obtained. The
free-standing SWNT/polyelectrolyte membranes delaminated
from the substrate were found to be exceptionally strong
with tensile strength approaches that of hard ceramics.
Considering the light-weight nature of SWNT composites
the prepared free-standing membranes can serve as unique
components for a variety of long-life-time devices.
Projects
▪
Layer-by-layer
Assembled Nanocomposites from Montmorillonite Clay
Nanosheets and Cellulose Nanocrystals for Optical,
Biomedical, Automotive, and Space Applications /
Paul Podsiadlo
▪ Carbon
Nanotube–Polymer Nanocomposites /
Bongsup
Shim
▪
Layer-by-layer Assembly of Carbon Nanocolloids for Fuel
Cell /
Peter Ho
▪
Layer-by-Layer Assembly of
LED Thin Films /
G. Daniel Lilly
▪
Mulilayer Carbon Nanotube-Polyelectrolyte Strain and
Corrosion Sensors /
Professor J. P. Lynch /
UM News
Selected Publications
▪ Podsiadlo P, Kaushik AK, Arruda EM,
et al. Ultrastrong and stiff
layered polymer nanocomposites SCIENCE 318 (5847): 80-83 OCT 5 2007
▪
Podsiadlo P, Liu ZQ, Paterson
D, et al. Fusion of seashell nacre and marine bioadhesive analogs: High-strength nanocompoisite
by layer-by-layer assembly of clay and
L-3,4-dihydroxyphenylaianine polymer ADVANCED
MATERIALS 19 (7): 949+ APR 6 2007
▪
Podsiadlo P, Tang ZY, Shim
BS, et al. Counterintuitive effect of molecular strength
and role of molecular rigidity on mechanical properties
of layer-by-layer assembled nanocomposites NANO LETTERS
7 (5): 1224-1231 MAY 2007
▪
Loh KJ, Kim J, Lynch JP, et
al. Multifunctional layer-by-layer carbon nanotube-polyelectrolyte
thin films for strain and corrosion sensing SMART
MATERIALS & STRUCTURES 16 (2): 429-438 APR 2007
▪ Tang ZY, Wang Y, Podsiadlo P, et
al.
Biomedical applications of layer-by-layer assembly:
From biomimetics to tissue engineering ADVANCED
MATERIALS 18 (24): 3203-3224 DEC 18 2006
▪
Wang Y, Tang ZY, Podsiadlo P, et
al.
Mirror-like photoconductive layer-by-layer thin
films of Te nanowires: The fusion of semiconductor,
metal, and insulator properties ADVANCED MATERIALS
18 (4): 518+ FEB 17 2006
▪
Podsiadlo P, Paternel S,
Rouillard JM, et al.
Layer-by-layer assembly of
nacre-like nanostructured composites with antimicrobial
properties LANGMUIR 21 (25): 11915-11921 DEC 6 2005
▪
Tang ZY, Kotov NA,
Magonov S, et al.
Nanostructured artificial nacre NATURE MATERIALS
2 (6): 413-U8 JUN 2003
▪
Mamedov AA, Kotov NA,
Prato M, et al.
Molecular design of strong single-wall
carbon nanotube/polyelectrolyte multilayer composites NATURE
MATERIALS 1 (3): 190-194 NOV 2002
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