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.
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.
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.
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.
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.
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.
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.