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Search Publications by: Christopher Stafford (Fed)

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Displaying 76 - 100 of 200

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

Influence of chain stiffness on thermal and mechanical properties of polymer thin films

October 25, 2011
Author(s)
Jessica M. Torres, Chengqing C. Wang, E. B. Coughlin, John P. Bishop, Richard A. Register, Robert A. Riggleman, Christopher Stafford, Bryan D. Vogt
The effect of main chain stiffness and side chain flexibility on the elastic modulus and glass transition temperature (Tg) of thin polymer films is investigated using non-traditional polymers formed from 5-(2-phenylethylnorbornene). Depending on the

Block copolymer photonic gel for mechanochromic sensing

September 19, 2011
Author(s)
Edwin Chan, Joseph J. Walish, Edwin L. Thomas, Christopher Stafford
In this work, we describe a strategy based on mechanochromic sensing, the coupling between mechanical and optical properties, of a block copolymer photonic gel. Although this phenomena has been observed in many materials, we demonstrate this concept for

Characterizing the Mechanical Properties and Degradation of Thin Polymer Membranes

August 28, 2011
Author(s)
Christopher M. Stafford, Jun Y. Chung, Junghyun Lee
The elasticity, strength, and toughness of thin polymer membranes are of considerable interest since direct knowledge of these key mechanical properties can provide insight into performance, durability, and underlying degradation mechanisms that occur over

Controlled Vapor Deposition Approach to Generating Surface Energy/Chemistry Gradients

June 9, 2011
Author(s)
Julie N. Albert, Joey D. Kim, Christopher Stafford, Thomas H. Epps
Substrate surface energy/chemistry gradients provide a means for high-throughput exploration of the surface interactions that are important for many chemical and biological processes. We describe the implementation of a controlled vapor deposition approach

Quantitative Subsurface Contact Resonance Force Microscopy of Model Polymer Nanocomposites

March 16, 2011
Author(s)
Jason P. Killgore, Jennifer Y. Kelly, Christopher M. Stafford, Michael J. Fasolka, Donna C. Hurley
We present experimental results on the use of quantitative contact resonance force microscopy (CR-FM) for mapping the planar location and depth of 50 nm silica nanoparticles buried beneath polystyrene films 30 nm to 165 nm thick. The presence of shallowly

Flexure-induced structural and electronic changes in polymer supported membranes of length purified single-wall carbon nanotubes

February 22, 2011
Author(s)
John M. Harris, Ganjigunte R. Iyer, Daneesh O. Simien, Jeffrey Fagan, JiYeon Huh, Jun Y. Chung, Steven Hudson, Jan Obrzut, Jack F. Douglas, Christopher Stafford, Erik K. Hobbie
Thin membranes of length purified single-wall carbon nanotubes (SWCNTs) are uniaxially compressed by depositing them on prestretched polymer substrates. Upon release of the strain, the topography, microstructure and conductivity of the films are

Effect of interfaces and adhesion on the creep compliance of thin polymer coatings

February 13, 2011
Author(s)
Peter M. Johnson, John A. Howarter, Christopher Stafford
Thin film indentation experiments on viscoelastic materials allowed for the deconvolution of the bulk compliance from interfacial responses at the buried interface. This technique could discriminate both large changes in the interfacial strength due to

Manipulation of adhesion via sub-surface patterning

February 13, 2011
Author(s)
John A. Howarter, Peter M. Johnson, Jun Y. Chung, Christopher Stafford
The delamination characteristics of patterned and hierarchical interfaces are of great interest due to the advanced adhesion capabilities found with many biological surfaces. Using nature-inspired design principles, micro- and nanostrucutred surfaces have

OCT For Depth Detection of Buried Particles in Polymeric Materials

February 13, 2011
Author(s)
Robert C. Chang, Anant Agrawal, Peter M. Johnson, Christopher Stafford
In this work, we demonstrate a method to produce novel optical phantoms usable for the characterization of OCT axial resolution and contrast. By varying the diameter of the microspheres and the thickness of the polymer layers, different spatial frequencies

System-independent assessment of OCT axial resolution with a “bar chart” phantom

February 10, 2011
Author(s)
Robert C. Chang, Jeeseong Hwang, Christopher M. Stafford, Anant Agrawal, T. Joshua Pfefer, Megan Connors
We present a novel optical phantom approach for the characterization of OCT axial resolution and contrast via multilayered “bar charts.” We explored two methods to fabricate these phantoms: the first is based on a combinatorial methods approach from

Comment on Viscoelastic properties of con ned polymer lms measured via thermal wrinkling by Edwin P. Chan, Kirt A. Page, Se Hyuk Im, Derek L. Patton, Rui Huang and Christopher M. Stafford, Soft Matter (Communications), 5, 4638 4641 (2009).

January 11, 2011
Author(s)
Paul A. O'Connell, Greg B. McKenna, Edwin Chan, Christopher Stafford
Recently Chan et al. published a paper describing a method to use the wrinkling of a thin elastic film on which is adhered a thin polymer film to extract the viscoelastic properties of the polymer. Results were presented for the rubbery plateau modulus and