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Search Publications by: Christopher Stafford (Fed)

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Displaying 126 - 150 of 394

Swelling of ultrathin crosslinked polyamide water desalination membranes

December 27, 2012
Author(s)
Edwin P. Chan, Allison P. Young, Jung-Hyun Lee, Jun-Young Chung, Christopher M. Stafford
We study the water swelling behavior of semi-aromatic crosslinked polyamide ultrathin films in order to characterize the materials properties of the polymer network. Specifically, we utilize X-ray reflectivity and quartz crystal microbalance to measure

Anisotropic, Hierarchical Surface Patterns via Surface Wrinkling of Nanoimprinted Polymer Films

October 22, 2012
Author(s)
Junghyun Lee, Hyun W. Ro, Rui Huang, Thomas Germer, Paul Lemaillet, Christopher Soles, Christopher Stafford
we demonstrated the wrinkling behavior of nanopatterned PS films, whose wrinkle wavelength and resultant morphology depend strongly on geometric parameters of surface patterns as well as the direction of the applied strain relative to the nanopattern

Viscoelastic and poroelastic relaxations of polymer-loaded hydrogels

July 5, 2012
Author(s)
Blessing Deeyaa, Christopher Stafford, Edwin Chan, Peter M. Johnson
In this work, we study the viscoelastic and poroelastic contributions on the relaxation behavior of a polymer-loaded hydrogel using a recently develop Poroelastic Relaxation Indentation (PRI) measurement technique. By applying a generalized relaxation

Synthesis and characterization of model crosslinked polyamide films for water purification

June 24, 2012
Author(s)
Peter M. Johnson, Edwin Chan, Jun Y. Chung, Junghyun Lee, Christopher Stafford
Reverse osmosis (RO) and nanofiltration (NF) membranes are comprised of a dense active layer supported by a porous support. Commercial active layer are highly crosslinked polyamides that are formed through interfacial polymerization directly on the support

Rippling Instability of Supported Polymer Nanolines

February 21, 2012
Author(s)
Vijaya R. Tirumala, Christopher M. Stafford, Leonidas E. Ocola, Jack F. Douglas, L. Mahadevan
The swelling response of polymer line gratings supported on a rigid substrate has direct implications on their mechanical stability during pattern transfer in nanofabrication. The polymer lines, when swollen in a good solvent, undergo a rippling

Spherical indentation testing of poroelastic relaxations in thin hydrogel layers

December 16, 2011
Author(s)
Edwin Chan, Yuhang Hu, Peter M. Johnson, Zhigang Suo, Christopher Stafford
In this work, we present the Poroelastic Relaxation Indentation (PRI) testing approach for quantifying the mechanical and transport properties of thin layers of poly(ethylene glycol) hydrogel materials with thicknesses on the order of 200 m. Specifically

Mechanical Properties of Polymer Nano-Films

November 28, 2011
Author(s)
Junghyun Lee, Jun Y. Chung, Christopher Stafford
Three fundamental mechanical properties of supported glassy polystyrene films with thickness ranging from 250 nm to 9 nm were quantitatively determined by a recently developed wrinkling-cracking method. Films below about 40 nm showed a decrease in both