Postdoc papers (2002-2005)

Du, K. ; Knutson, C. R. ; Glogowski, E. ; McCarthy, K. D. ; Shenhar, R. ; Rotello, V. M. ; Tuominen, M. T. ; Emrick, T. ; Russell, T. P. ; Dinsmore, A. D. Self-Assembled Electrical Contact to Nanoparticles Using Metallic Droplets. Small 2009, 5 1974-1977.Abstract

Self‐assembly of nanoparticles on liquid‐metal droplets (see image) provides a simple, effective approach to electronic devices with nanoscale control of the metal/nanoparticle junctions. This approach enables the inexpensive fabrication of a large number of devices and deposition on large‐area substrates.

18. electrical contact to nanoparticles with metallic droplets

Shenhar, R. ; Jeoung, E. ; Srivastava, S. ; Norsten, T. B. ; Rotello, V. M. Crosslinked nanoparticle stripes and hexagonal networks obtained via selective patterning of block copolymer thin films. Advanced Materials 2005, 17, 2206-2210.Abstract

Robust arrays of ordered nanoparticles (see Figure and cover) have been created by combining two self‐assembly strategies: microphase separation of block copolymers and coordination chemistry. Thin films of a microphase‐separated block copolymer serve as templates for patterning of terpyridine‐functionalized gold nanoparticles. Subsequent treatment with iron salts crosslinks the patterned nanoparticles via the formation of iron–terpyridine complexes.

14. Advanced Materials 2005   Advanced Materials 2005

Shenhar, R. ; Xu, H. ; Frankamp, B. L. ; Mates, T. E. ; Sanyal, A. ; Uzun, O. ; Rotello, V. M. Molecular recognition in structured matrixes: Control of guest localization in block copolymer films. Journal of the American Chemical Society 2005, 127, 16318-16324.Abstract

We demonstrate the use of molecular recognition to control the spatial distribution of guest molecules within block copolymer films. Block copolymers bearing recognition units were combined with complementary and noncomplementary molecules, and the extent of segregation of these molecules into the different domain types within microphase-separated thin films was quantitatively analyzed using dynamic secondary ion mass spectrometry (SIMS). Complementarity between the guest molecules and the polymer functionalities proved to be a key factor and an efficient tool for directing the segregation preference of the molecules to the different domain types. The effect of segregation preference on the glass transition temperature was studied using differential scanning calorimetry (DSC), and the results corroborate the SIMS findings. In a complementary study, guests with tunable sizes (via dendron substituents) were used to control block copolymer morphology. Morphological characterization using transmission electron microscopy (TEM) and X-ray diffraction reveal that selectivity differences can be directly translated into the ability to obtain different morphologies from recognition unit-functionalized block copolymer scaffolds.

15. Roy JACS 2005

Shenhar, R. ; Norsten, T. B. ; Rotello, V. M. Polymer-mediated nanoparticle assembly: Structural control and applications. Advanced Materials 2005, 17, 657-669.Abstract

Nanoparticle-polymer composites are diverse and versatile functional materials, with applications ranging from electronic device fabrication to catalysis. This review focuses on the use of chemical design to control the structural attributes of polymer-mediated assembly of nanoparticles. We will illustrate the use of designed particles and polymers to create nanocomposites featuring interesting and pragmatic structures and properties. We will also describe applications of these engineered materials.

16. Polymer-mediated nanoparticle assembly

Shenhar, R. ; Sanyal, A. ; Uzun, O. ; Rotello, V. M. Anthracene-functionalized polystyrene random copolymers: Effects of side-chain modification on polymer structure and behavior. Macromolecules 2004, 37, 92-98.Abstract
Copolymers consisting of styrene and 4-chloromethylstyrene (CMS) were functionalized via reaction with 9-anthracenecarboxylic acid, providing the corresponding esters. Increasing degrees of functionalization were found to increase the glass transition temperature, influence chain packing density, and induce microphase separation in block copolymer structures. The approach demonstrated in this study facilitates the investigation of the relationship between structure of side-chain groups and polymer properties, providing a general approach for the study of the effect of chemical functionality on material properties of polymers.
Shenhar, R. ; Sanyal, A. ; Uzun, O. ; Nakade, H. ; Rotello, V. M. Integration of recognition elements with macromolecular scaffolds: Effects on polymer self-assembly in the solid state. Macromolecules 2004, 37, 4931-4939.Abstract
Polystyrene scaffolds were grafted with model functionalities featuring strongly interacting hydrogen bonding and aromatic stacking elements. Both glass transition temperatures and degree of microphase separation in functionalized block copolymers depend on the nature of the functionality and in particular on the strength of intermolecular interactions. The polymers under study were amorphous; it was found, however, that domain periodicities of functionalized diblock copolymers in the microphase-separated state are extremely sensitive to local interactions between functionalities and can express even subtle differences in interaction strength. The results emphasize the ability to fine-tune polymer microstructure and thermomechanical behavior using supramolecular chemistry.
Shenhar, R. ; Rotello, V. M. Nanoparticles: Scaffolds and building blocks. Accounts of Chemical Research 2003, 36, 549-561.Abstract

Nanoparticles provide key tools for bridging the gap between ``bottom-up'' synthetic methods and ``top-down'' fabrication. In this Account we describe some of the unique structural aspects of nanoparticles and the use of these attributes to the creation of devices with tunable specificity and environmental response. We also explore the use of nanoparticles as ``building blocks'' for the creation of nanocomposite materials that feature structural control from the molecular to the micron scale.

9. Nanoparticles: Scaffolds and building blocks   Accounts of Chemical Research 2003