An optofluidic system was constructed from a diode laser as the energy source, an aqueous suspension of plasmonic nanostructures as the photothermal transducer, and a glass capillary for measuring the volumetric expansion of the suspension. The suspension could be driven to move up the capillary by more than 30 mm and be used to control the operation of an electrical switch.

Assembly of oppositely charged triblock copolyelectrolytes into phase-separated gels at low polymer concentrations (<1% by mass) has been observed in scattering experiments and molecular dynamics simulations. Here we show that in contrast to uncharged, amphiphilic block copolymers that form discrete micelles at low concentrations and enter a phase of strongly interacting micelles in a gradual manner with increasing concentration, the formation of a dilute phase of individual micelles is prevented in polyelectrolyte complexation-driven assembly of triblock copolyelectrolytes. Gel phases form and phase separate almost instantaneously on solvation of the copolymers. Furthermore, molecular models of self-assembly demonstrate the presence of oligo-chain aggregates in early stages of copolyelectrolyte assembly, at experimentally unobservable polymer concentrations. Our discoveries contribute to the fundamental understanding of the structure and pathways of complexation-driven assemblies, and raise intriguing prospects for gel formation at extraordinarily low concentrations, with applications in tissue engineering, agriculture, water purification and theranostics.

We present scattering and rheology studies on model polyelectrolyte complex (PEC) hydrogels that form upon self-assembly of symmetric oppositely charged triblock polyelectrolytes in aqueous media. The hydrogel assembly is driven by associative phase separation of charged end-blocks to form PECs while the neutral mid-blocks restrict bulk phase separation of the PECs, leading to three-dimensional networks with PEC domains surrounded by neutral polymer coronae at sufficiently high polymer concentrations. Comprehensive characterization of the hydrogel structure (PEC domain size, morphology, spacing, and ordering) was enabled by a series of triblock polyelectrolytes with independently varying block lengths, facilitating the construction of morphology maps that offered direct comparisons with earlier theoretical predictions and highlighted the contributions of the charged and neutral blocks in directing PEC morphologies and hydrogel microstructures. Comparisons between the microstructure and shear rheology response emphasize the interplay between PEC domain morphologies and hydrogel flow behaviors. Furthermore, by drawing parallels with rheological models for associating polymer networks, we present preliminary insights into the role of chain-exchange dynamics between the PEC domains and cooperative electrostatic interactions in influencing the hydrogel flow properties.

Antibiotic resistance among highly pathogenic strains of bacteria and fungi is a growing concern in the face of the ability to sustain life during critical illness with advancing medical interventions. The longer patients remain critically ill, the more likely they are to become colonized by multidrug-resistant (MDR) pathogens. The human gastrointestinal tract is the primary site of colonization of many MDR pathogens and is a major source of life-threatening infections due to these microorganisms. Eradication measures to sterilize the gut are difficult if not impossible and carry the risk of further antibiotic resistance. Here, we present a strategy to contain rather than eliminate MDR pathogens by using an agent that interferes with the ability of colonizing pathogens to express virulence in response to hostderived and local environmental factors. The antivirulence agent is a phosphorylated triblock high-molecular-weight polymer (here termed Pi-PEG 15-20) that exploits the known properties of phosphate (P i ) and polyethylene glycol 15-20 (PEG 15-20) to suppress microbial virulence and protect the integrity of the intestinal epithelium. The compound is nonmicrobiocidal and appears to be highly effective when tested both in vitro and in vivo. Structure functional analyses suggest that the hydrophobic bis-aromatic moiety at the polymer center is of particular importance to the biological function of Pi-PEG 15-20, beyond its phosphate content. Animal studies demonstrate that Pi-PEG prevents mortality in mice inoculated with multiple highly virulent pathogenic organisms from hospitalized patients in association with preservation of the core microbiome.