Christopher James Durning
806 S W Mudd, Mail Code: 4721
Phone: +1 212-854-8161
Fax: +1 212-854-3054
Email:
Our research focuses on ways of exploiting "soft" materials in a
variety of new applications. The important themes in this work are to
understand and control:
I Transport and diffusion in polymeric systems.
II Surface and interfacial behavior in polymeric systems.
III Association and self-assembly of soft materials.
1).
Nano-structured materials, i.e. thin layers and bulk materials with
organized structures on length scales in the range 1-100 nanometers.
Such materials offer unique advantages in many applications, for
example in high capacity magnetic storage media, in achieving
ultra-small photonic and electronic devices, in graded layers and films
for super-mirrors and notch filters, and in achieving "labs on a chip".
We work to develop new schemes for generating nano-structures via
supra-molecular chemistry and self-assembly. A particularly important
specific goal is to understand and control the development of lateral
(in-plane) order at surfaces, interfaces and in thin layers.
2).
"Smart" or responsive materials which respond in a favorable way to
external conditions. Examples include thin surface layers which promote
interfacial slip at precisely predictable conditions, or chemically
active surfaces engineered to exhibit thermally, electrically,
photo-lytically or chemically triggered surface property changes or
surface release mechanisms.
The systems we examine rely mainly
on designed synthetic polymers, which are high molecular weight organic
species with very specific molecular architectures. Examples include
block and graft copolymers and hyper-branched or "dendritic" polymers.
A few recent projects are described below.
a). ADSORPTION AND SELF-ASSEMBLY OF DENDRIMERS AT THE SOLID-LIQUID INTERFACE.
We
are studying the surface activity of recently developed dendrimeric
polymers and their supramolecular analogs. Dendrimers are monodisperse,
branched, water-soluble polymers with an abundance of surface active
end groups. They consist of a multifunctional core with "generations"
of multi-functional monomers attached in tiers around the core. A
homologous series can be made in ascending "generation" G (number of
tiers attached to the core). Dendrimers exhibit rigidity, and thus
resemble "soft-spheres" with sizes in the range 1-10 nm. Further, they
exhibit "container" properties enabling delivery to surfaces of
functional "cargo". These have great potential for preparation of
nano-structured thin film composites if one can control
particle-surface (P-S) and particle-particle (P-P) interactions well
enough to promote self-assembly at an interface. We are systematically
studying clustering in solution and adsorption onto solids in-situ by
micro-balances, AFM and by scattering methods.
b). MOLECULAR MOBILITY IN POLYMER THIN FILMS.
Experimental
studies in the past five years of the thermal and dynamic properties of
ultra thin polymer films (i.e. films with thickness approaching the
size of the polymer molecules) indicate that such films have
significantly different properties than the corresponding bulk. This
has an important impact on the preparation of ultra small photonic and
electronic devices via various lithographic methods. Experimental
results in the literature to date are not consistent, and in some
cases, contradictory. We are systematically studying mobility of probe
molecules in such films using photo-physical methods to understand the
physics in detail, and develop a consistent, clear experimental picture
of thin polymer film behavior.
c). STRUCTURE AND DYNAMICS OF POLYMER MELTS
AT "ENGINEERED" SOLID/LIQUID INTERFACES.
In
a number of new technologies the behavior of melts of high molecular
weight flexible polymers at the solid-liquid interface is critical. An
example is modern recording technologies, where a thin film of
polymeric lubricant plays a critical role in the mechanics of
read-write operations. The goal of our work is to understand how to
control the structure and dynamic behavior of the region of immediately
adjacent to a solid surface, critical to lubrication and adhesion
phenomena. Our study of this issue involves (i) studying the static
structure of melts in contact with "engineered" solid surfaces bearing
adsorbed polymers or polymeric brushes, and (ii) studying the same
situation but with an imposed steady shear field. Among the techniques
used, x-ray and neutron reflection is employed to study the molecular
level events at the solid-melt interface.
Selected
Publications:
CONTRIBUTED PAPER, "Sorption and Diffusion of n-Alkyl Acetates in Poly(methyl acrylate)/Silica Nano-composites,´ AIChE Annual Meeting, 11/8/09-11/13/09, Nashville TN, Symposium: Diffusion in Polymers I paper 651a; co-authors D. Janes, S. Harton, L. Rong.
**K.M.A. Rahman, C.J. Durning, N.J. Turro and D.A. Tomalia, "Adsorption of Poly(amido amine) Dendrimers on Gold," Langmuir, accepted.
A. Ponomarev, T. Sewell, C.J. Durning, "Adsorption of Isolated, Flexible Polymers on a Strongly Attractive Surface," Macromolecules, 33, 2662-2669 (2000).
M.M. Hassan, C.J. Durning, "Effects of Polymer Molecular Weight and Temperature on Case II Transport," J. Polym. Sci. Part B: Polym. Phys., 37, 3159-3171 (1999).*K. Tseng, N.J.Turro, C.J. Durning, "Molecular Mobility in Polymer Thin Films," Phys. Rev. E, 61, 1800-1811 (2000).
C.J.
Durning, U. Sawhney, B. O'Shaughnessy, G.S. Smith, J. Majewski, D.
Nguyen, "Irreversible Adsorption of Polymethylmethacrylate Melts on
Quartz," Macromolecules, 32, 6772-6781 (1999).
S.J. Huang and C.J. Durning, "Nonlinear Viscoelastic Diffusion in Concentrated Polystyrene-Ethylbenzene Solutions," J. Polym. Sci.: Part B: Polym. Phys., 35, 2103-2119 (1997).