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Search Publications by

Christopher Stafford (Fed)

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Displaying 26 - 50 of 187

Buckling Instabilities in Polymer Brush Surfaces via Postpolymerization Modification

October 30, 2017
Wei Guo, Cassandra M. Reese, Li Xiong, Phillip K. Logan, Brittany J. Thompson, Christopher Stafford, Anton Ievlev, Bradley S. Lokitz, Olga S. Ovchinnikova, Derek L. Patton
We report a simple route to engineer ultrathin polymer brush surfaces with wrinkled and creased morphologies using postpolymerization modification (PPM), where the length scale of the buckled features can be tuned using PPM reaction time and sequence. We

Wrinkling-to-delamination transition in thin polymer films on compliant substrates

October 9, 2017
Adam J. Nolte, Jun Y. Chung, Chelsea S. Davis, Christopher Stafford
Compressing a thin, stiff film attached to a thick, compliant substrate can lead to a number of different modes of mechanical deformation depending upon the material properties of the system. In this article we explore direct transitions from surface

Film Confinement Induced "Jump-Percolation" Wetting Transition in Amphiphilic Block Copolymer Films

October 1, 2017
Namrata Salunke, Asritha Nallapaneni, Guangcui Yuan, Christopher Stafford, Hui Niu, Matthew D. Shawkey, R. A. Weiss, Alamgir Karim
A sharp surface wettability transition with varying film thickness dependent morphology was observed in cast films of an amphiphilic triblock copolymer comprised of poly(2-(N-ethylperfluotooctanesulfonamido) ethyl methylacrylate), poly(FOSM), and poly(N,N'

Entropy-Driven Segregation of Polymer-Grafted Nanoparticles under Confinement

February 22, 2017
Ren Zhang, Bongjoon Lee, Christopher Stafford, J. F. Douglas, Andrey V. Dobrynin, Michael R. Bockstaller, Alamgir Karim
Polymer-grafted nanoparticles (PGNPs) have attracted much attention due to the enhanced dispersion in polymeric materials via an interacting brush layer that enables unique functionality and stability. The miscibility and organization of nanoparticles

Scalable Manufacturing of Layer-by-Layer Membranes for Water Purification

December 1, 2016
Christopher M. Stafford
Water is critical to the health and security of our nation. And as our population expands and water scarcity becomes a reality, we as a people need to think creatively on how we safeguard access to clean water. The manufacturing of today’s state-of-the-art

Ultraviolet/Ozone as a tool to control grafting density in surface-initiated controlled-radical polymerizations via ablation of bromine

July 21, 2016
Richard J. Sheridan, Sara V. Orski, Shinichiro Muramoto, Christopher M. Stafford, Kathryn L. Beers
We used an ultraviolet-ozone (UVO) cleaner to create substrates for atom-transfer radical polymerization (ATRP) with varying surface initiator coverage. We collected complementary time-of-flight secondary ion mass spectrometry (ToF-SIMS) and X-ray

Pattern-Directed Phase Separation of Polymer-Grafted Nanoparticles in a Homopolymer Matrix

May 12, 2016
Ren Zhang, Bongjoon Lee, Michael R. Bockstaller, Sanat K. Kumar, Christopher Stafford, Jack F. Douglas, Dharmaraj Raghavan, Alamgir Karim
The controlled organization of nanoparticle (NP) constituents into superstructures of well- defined shape, composition and connectivity represents a continuing challenge in the development of novel hybrid materials for many technological applications. We

Enhancing Single-Wall Carbon Nanotube Properties Through Controlled Endohedral Filling

May 10, 2016
Jochen I. Campo, Yanmei Piao, Stephanie Lam, Christopher Stafford, Jason K. Streit, Jeffrey R. Simpson, Angela R. Hight Walker, Jeffrey Fagan
Chemical control of the endohedral volume of single-wall carbon nanotubes (SWCNTs) via liquid-phase filling is demonstrated to be a facile strategy to controllably modify properties of the nanotubes in manners significant for processing and proposed

Interlaboratory study towards a climate-specific test: spectroscopic characterizations of EVA in glass/EVA/glass systems

February 23, 2016
Jae Hyun Kim, Christopher M. Stafford, Yadong Lyu, Li C. Yu, Chiao-Chi Lin, Tinh Nguyen, Xiaohong Gu
EVA as an encapsulant material is exposed to various UV irradiation, thermal cycles, and humidity conditions. Degradation of EVA can reduce not only power generation due to yellowing, but also a structural integrity of a PV module. In order to investigate

Super Stiff and Highly Transparent Multilayer Thin Films Prepared through Hydrogen-Bonding Layer- by-Layer Assembly of Graphene and Polymer

February 8, 2016
Fangming Xiang, Dorsa Parviz, Tara M. Givens, Ping Tzeng, Eric Davis, Christopher Stafford, Micah J. Green, Jaime C. Grunlan
Since its discovery in 2004, graphene has been intensely studied due to its high elastic modulus, thermal conductivity, electrical conductivity, and gas impermeability. Although it is possible to use small quantities of graphene sheets for fundamental

Spray-deposition and photopolymerization of organic-inorganic thiol-ene resins for fabrication of superamphiphobic surfaces

June 9, 2014
Li Xiong, Laken Kendrick, Hannele Heusser, Bradley J. Sparks, Christopher Stafford, James T. Goetz, Sergei Nazarenko, Derek L. Patton
Superamphiphobic surfaces, exhibiting high contact angles and low contact angle hysteresis to both water and low surface tension liquids, have attracted a great deal of attention in recent years due to the importance in many practical applications. In this

Confinement-Driven Increase in Ionomer Thin-Film Modulus

April 28, 2014
Kirt A. Page, Ahmet Kusoglu, Christopher M. Stafford, Sangcheol Kim, Regis J. Kline, Adam Weber
Ion-conductive polymers, or ionomers, are critical materials for a wide range of electrochemical technologies. For optimizing the complex, heterogeneous structures in which they occur, there is a need to elucidate the governing structure/function

Tailoring the Permselectivity of Water Desalination Membranes via Nanoparticle Assembly

January 6, 2014
Edwin Chan, William Mulhearn, Jung-Hyun Lee, Daeyeon Lee, Christopher Stafford
: Thin film composite membranes can selectively separate mono- and di-valent ions from water via solution-diffusion of each species through a dense but ultrathin, highly crosslinked polymer ‘skin' layer - water is transported across the membrane faster

Elasticity and rigidity percolation in networks of type-purified single-wall carbon nanotubes on flexible substrates

October 29, 2013
John M. Harris, JiYeon Huh, Matthew R. Semler, Christopher Stafford, Steven Hudson, Jeffrey Fagan, Erik K. Hobbie
Wrinkles and folds in compressed thin films of type-purified single-wall carbon nanotubes (SWCNTs) on polydimethylsiloxane (PDMS) substrates are used to study the mechanical response of pristine nanotube networks. While the low-strain plateau moduli are

Swelling of Ultrathin Molecular Layer-by-Layer Polyamide Water Desalination Membranes

September 30, 2013
Edwin P. Chan, Allison P. Young, Jung-Hyun Lee, Christopher M. Stafford
The water vapor swelling behavior of ultrathin crosslinked aromatic polyamide films, synthesized via molecular layer-by-layer deposition, is characterized via specular X-ray reflectivity. The results show that these films expand only along the thickness

Feeling Small: Exploring the tactile perception limits

September 12, 2013
Lisa Skedung, Martin Arvidsson, Jun Y. Chung, Christopher Stafford, Birgitta Berglund, Mark W. Rutland
The human finger is exquisitely sensitive in distinguishing different materials, but the question remains as to what length scales are capable of being discriminated in active touch? We combine psychophysical approaches with materials science to

Molecular Layer-by-Layer Assembled Reverse Osmosis Membranes for Water Desalination

July 12, 2013
Joung-Eun Gu, Seunghye Lee, Wansuk Choi, Jong Suk Lee, Bo-Young Kim, Edwin Chan, Christopher Stafford, Jun-Young Chung, Joona Bang, Jung-Hyun Lee
Here, we report on the successful design, construction, and performance of membranes constructed using the mLbL process and show that these membranes exceed the performance of membranes synthesized through conventional interfacial polymerization. In our