The Stability of Cyclodextrin Complexes in Solution.

Reduced transition metal colloids: a novel family of reusable catalysts

The chemical effects of ultrasound derive primarily from acoustic cavitation. Bubble collapse in liquids results in an enormous concentration of energy from the conversion of the kinetic energy of the liquid motion into heating of the contents of the bubble. The high local temperatures and pressures, combined with extraordinarily rapid cooling, provide a unique means for driving chemical reactions under extreme conditions. A diverse set of applications of ultrasound to enhance chemical reactivity has been explored with important uses in synthetic materials chemistry. For example, the sonochemical decomposition of volatile organometallic precursors in low-volatility solvents produces nanostructured materials in various forms with high catalytic activities. Nanostructured metals, alloys, oxides, carbides and sulfides, nanometer colloids, and nanostructured supported catalysts can all be prepared by this general route. Another important application of sonochemistry in materials chemistry has been the preparation of biomaterials, most notably protein microspheres. Such microspheres have a wide range of biomedical applications, including their use in echo contrast agents for sonography, magnetic resonance imaging, contrast enhancement, and oxygen or drug delivery. Other applications include the modification of polymers and polymer surfaces.

Applications of ultrasound to materials chemistry

Mass production and commercial availability are prerequisites for the viability and wide application of graphene. The exfoliation of graphite to give graphene is one of the most promising ways to achieve large-scale production at an extremely low cost. This review focuses on discussing different exfoliation techniques based on a common mechanical mechanism; because a deep understanding of the exfoliation mechanism can provide fruitful information on how to efficiently achieve high-quality graphene by optimizing exfoliation techniques. We highlight the recent progress on mechanical exfoliation for graphene production during the last decade. The emphasis is set on the widely used sonication method with the latest insight into sonication-induced defects, the newly explored ball milling method, the fluid dynamics method that has emerged in the last three years, and the innovative supercritical fluid method. We also give an outlook on how to achieve high-quality graphene efficiently using mechanical exfoliation techniques. We hope this review will point towards a rational direction for the scalable production of graphene.

A review on mechanical exfoliation for the scalable production of graphene

Engineering applications of synthetic polymers are widespread due to their availability, processability, low density, and diversity of mechanical properties (Figure 1a). Despite their ubiquitous nature, modern polymers are evolving into multifunctional systems with highly sophisticated behavior. These emergent functions are commonly described as “smart” characteristics whereby “intelligence” is rooted in a specific response elicited from a particular stimulus. Materials that exhibit stimuli-responsive functions thus achieve a desired output (O, the response) upon being subjected to a specific input (I, the stimulus). Given that mechanical loading is inevitable, coupled with the wide range of mechanical properties for synthetic polymers, it is not surprising that mechanoresponsive polymers are an especially attractive class of smart materials. To design materials with stimuli-responsive functions, it is helpful to consider the I-O relationship as an energy transduction process. Achieving the desired I-O linkage thus becomes a problem in finding how to transform energy from the stimulus into energy that executes the desired response. The underlying mechanism that forms this I-O coupling need not be a direct, one-step transduction event; rather, the overall process may proceed through a sequence of energy transduction steps. In this regard, the network of energy transduction pathways is a useful roadmap for designing stimuli-responsive materials (Figure 1b). It is the purpose of this review to broadly survey the mechanical to chemical * To whom correspondence should be addressed. Phone: 217-244-4024. Fax: 217-244-8024. E-mail: jsmoore@illinois.edu. † Department of Chemistry and Beckman Institute. ‡ Department of Materials Science and Engineering and Beckman Institute. § Department of Aerospace Engineering and Beckman Institute. Chem. Rev. XXXX, xxx, 000–000 A

Mechanically-induced chemical changes in polymeric materials

Ultrasonic degradation of water-soluble polymers

The adiabatic compressibility of aqueous solutions of octyl-, decyl-, dodecyl- and tetradecyltrimethylammonium bromides has been determined from measurements of ultrasound velocity and density at 25°C. A theoretical treatment giving the adiabatic compressibility as a function of concentration has been developed, and the apparent adiabatic compressibility of a surfactant in the monomeric and micellar forms is derived from the experimental results. The apparent adiabatic compressibility of surfactant in either form is constant, independent of concentration, so that it is identified with the apparent adiabatic compressibility in each form. The adiabatic compressibility in the monomeric form decreases from −0.25 × 10 −5 bar −1 for the octyl to −2.52 × 10 −5 bar −1 for the tetradecyl derivative, while that in the micellar form increases from 3.41 × 10 −5 bar −1 for the octyl to 4.17 × 10 −5 bar −1 for the tetradecyl derivative. The former includes the hydration of ionic head group of the surfactant, while the latter is related to the structure of micelle. If the same treatment is applied to the literature data, the apparent adiabatic compressibility of sodium alkyl sulfate in the monomeric form changes conversely with the alkyl chain length, while that in the micellar form is qualitatively similar.

Adiabatic compressibility of alkyltrimethylammonium bromides in aqueous solutions

The adiabatic compressibility of aqueous solutions of octyl-, decyl-, dodecyl- and tetradecyl-trimethylammonium bromides has been determined from measurements of density and ultrasound velocity at different temperatures ranging from 20 to 45 °C at 5 °C intervals. Based on the theoretical treatment in which the adiabatic compressibility is given as a function of concentration, the apparent adiabatic compressibilities of the surfactant in the monomeric (1) and micellar (m) forms are obtained from the experimental results at each temperature. The values for 1 increase with increased temperature, and its temperature coefficient is constant for methyl, octyl and decyl derivatives, but changes sharply between 30 and 40 °C for the dodecyl and tetradecyl derivatives. The value of m increases linearly with increased temperature, and its temperature coefficient increases with increasing alkyl chain length. The linear changes of 1 and m with temperature are related to the change of hydrophilic hydration, while the sharp change of 1 for dodecyl and tetradecyl derivatives is attributed to the change of hydrophobic hydration.

Temperature dependence of adiabatic compressibility of aqueous solutions of alkyltrimethylammonium bromides

Heat-capacity measurements of aqueous solutions of mono-, di-, and tri-saccharides using an isoperibol twin calorimeter

The salt-induced sphere-rod transition of micelles of dodecyltrimethylammonium bromide in aqueous NaBr solutions as studied by the ultrasound velocity measurements

Hiroyasu Nomura

Papers

Ultrasonic degradation of water-soluble polymers

Adiabatic compressibility of alkyltrimethylammonium bromides in aqueous solutions

Temperature dependence of adiabatic compressibility of aqueous solutions of alkyltrimethylammonium bromides

Heat-capacity measurements of aqueous solutions of mono-, di-, and tri-saccharides using an isoperibol twin calorimeter

The salt-induced sphere-rod transition of micelles of dodecyltrimethylammonium bromide in aqueous NaBr solutions as studied by the ultrasound velocity measurements