Extensional rheology and stability behavior of alumina suspensions in the presence of AMPS-modified polycarboxylate ether-based copolymers

A series of polycarboxylate ether-based copolymers that include acrylic acid, 2-acrylamido-2-methylpropane sulfonic acid, and polyethylene glycol-1000 was synthesized, and the performance of these copolymers as rheology modifiers in aqueous alumina suspensions was characterized. We discussed the effect of monomer feed ratio and molecular weight on dispersing ability of these copolymers and on extensional behavior of alumina suspensions. Results of zeta potential analysis determined that using the copolymers even at 0.5 wt.% results in all-negative zeta potentials for the entire pH range (2-12). These copolymers immensely affect the extensional rheological behavior of alumina suspensions-while 20 vol.% pure alumina suspension showed severe strain hardening behavior, suspensions with 1 wt.% copolymers and 35 vol.% alumina particles displayed no strain hardening. In this series, the copolymer with lowest molecular weight decreased the extensional viscosity of suspensions at the rupture of thread with three orders of magnitude as well

Integration of paper-based microfluidic devices with commercial electrochemical readers

The combination of simple Electrochemical Micro-Paper-based Analytical Devices (E$\mu$PADs) with commercially available glucometers allows rapid, quantitative electrochemical analysis of a number of compounds relevant to human health (e.g., glucose, cholesterol, lactate, and alcohol) in blood or urine.Chemistry and Chemical Biolog

Leisure Time Use, Meaning of Life, and Psychological Distress: Comparing Canadian and Korean Older Adults

Older adults’ day-to-day leisure time activities both reflect and stimulate physical, cognitive, and social capacities that contribute to their quality of life. To better understand how leisure activity choices and possible impacts vary across two cultures, this questionnaire-based study compared leisure time use, perceived meaning of life, and psychological distress for 617 older adults in Canada (n=298) and the Republic of Korea (Korea) (n=319). Compared to Koreans, Canadian respondents spent more time overall in leisure activities and devoted a higher percentage of their total leisure time to active, rather than passive, activities. They spent significantly more of their time on cognitively active activities, while Koreans preferred socially and physically active ones and scored significantly higher on both meaning of life and psychological distress. Both groups spent more of their time watching television than on any other single reported activity. Age group, retirement status, health, education, and income varied across the two countries and were significantly associated with aspects of leisure time use for each group. The results identify areas for improvement if Canadian and Korean older adults’ leisure time use is to effectively support their aging well

A PCE-based rheology modifier allows machining of solid cast green bodies of alumina

The performance of a poly(carboxylate ether) (PCE)-based superplasticizer to enable the machining of green bodies that are solid cast from suspensions of alumina was investigated. An alumina loading of 35 vol% in the presence of 1.25 wt% superplasticizer was established to be suitable for lathing and removal of significant amount of material through drilling. A reduction of 77% in the diameter of green bodies that corresponds to a 59% reduction in volume was achieved. The lathed green bodies exhibited smooth terraces without visible cracks. All of the green bodies were sintered without a polymer burnout step

Separation of Nanoparticles in Aqueous Multiphase Systems through Centrifugation

This paper demonstrates the use of aqueous multiphase systems (MuPSs) as media for rate-zonal centrifugation to separate nanoparticles of different shapes and sizes. The properties of MuPSs do not change with time or during centrifugation; this stability facilitates sample collection after separation. A three-phase system demonstrates the separation of the reaction products (nanorods, nanospheres, and large particles) of a synthesis of gold nanorods, and enriches the nanorods from 48 to 99% in less than ten minutes using a benchtop centrifuge.Chemistry and Chemical BiologyEngineering and Applied Science

Aqueous Multiphase Systems of Polymers and Surfactants Provide Self-Assembling Step-Gradients in Density

This Communication demonstrates the generation of over 300 phase-separated systems—ranging from two to six phases—from mixtures of aqueous solutions of polymers and surfactants. These aqueous multiphase systems (MuPSs) form self-assembling, thermodynamically stable step-gradients in density using a common solvent, water. The steps in density between phases of a MuPS can be very small (Δρ ≈ 0.001 g/cm3), do not change over time, and can be tuned by the addition of co-solutes. We use two sets of similar objects, glass beads and pellets of different formulations of Nylon, to demonstrate the ability of MuPSs to separate mixtures of objects by differences in density. The stable interfaces between phases facilitate the convenient collection of species after separation. These results suggest that the stable, sharp step-gradients in density provided by MuPSs can enable new classes of fractionations and separations based on density.Chemistry and Chemical BiologyEngineering and Applied Science

Synthesis and characterization of mixed ligand chiral nanoclusters

Chiral mixed ligand silver nanoclusters were synthesized in the presence of a chiral and an achiral ligand. The ratio of the ligands was changed to track the formation of these clusters. While the chiral ligand lead to nanoparticles, Presence of the achiral ligand induced the formation of nanoclusters with chiral properties