The COVID-19 pandemic has caused the loss of many lives and transformed the global educational system. This has resulted in a rapid transition from face-to-face classroom meetings to online education delivery. Online education provides another opportunity to engage students during crises, such as pandemics. However, during the transition to online education, both students and educators faced tremendous challenges, especially at rural locations. To shed light on these experiences, we conducted a survey to learn more about student learning and engagement in two similarly sized institutions in Dhule, India, and St. Cloud, USA. The data collected provides an insight into student engagement and their learning during the crisis. About 49% of participants from Dhule reported that internet issues were a major challenge they faced, while 19% of participants reported a financial burden as a major challenge met during the pandemic. In comparison, 63% of participants from St. Cloud reported that internet issues were a major challenge they faced, while 11% of participants reported financial burden as a major challenge they faced. However, only 22% and 9% of the students from Dhule and St. Cloud, respectively, rated the level of chemistry learned during the crisis as exceptional. Through analysis of these results, strategies to overcome some of the challenges and improve student learning outcomes are presented.

A series fo cross-linked fluorescent polystyrene (PS) microbeads with narrow size distribution and intense solid state emission was developed. Fluorophores based on perylene bisimide (PBI) and oligo(p-phenylenevinylene) (OPV) designed as acrylic cross-linkers were introduced into the polymerization recipe in a two-stage dispersion polymerization, carried out in ethanol in the presence of poly(vinylpyrrolidone) (PVP) as stabilizer. The structural design permitted introduction of up to 10(-5) moles of the fluorophores into the polymerization medium without fouling of the dispersion. The particle size measured using dynamic light scattering (DLS) indicated that they were nearly monodisperse with size in the range 2-3 μm depending on the amount of fluorophore incorporated. Fluorescence microscope images of ethanol dispersion of the sample exhibited intense orange red emission for PS-PBI-X series and green emission for PS-OPV-X series. A PS incorporated with both OPVX and PBIX exhibited dual emission upon exciting at the OPV wavelength of 350 nm and PBI wavelength of 490 nm, respectively. The low incorporation of fluorophore resulted in almost complete absence of aggregation induced reduction in fluorescence as well as red-shifted aggregate emission. The solid state emission quantum yield measured using integrating-sphere setup indicated a very high quantum yield of ϕpowder = 0.71 for PS-OPV-X and ϕpowder = 0.25 for PS-PBI-X series. The cross-linked PS microbeads incorporating both OPV and PBI chromophores had a ϕpowder = 0.33 for PBI emission and ϕpowder = 0.20 for OPV emission. This strategy of introducing fluorophore as cross-linkers into the PS backbone is very versatile and amenable to simultaneous addition of different suitably designed fluorophores emitting at different wavelengths.

Various types of specific interactions are believed to supplement the major entropic driving forces responsible for spontaneous liquid−liquid phase separations in mixtures of oppositely charged polyelectrolytes. Among these interactions, hydrophobicity has recently been probed experimentally via the synthesis and complex formation of polyelectrolytes bearing hydrophobic pendant groups or backbones. In this work, poly(4-vinylpyridines), P4VP, were N-alkylated with chains from one to six carbons in length. The fully alkylated polycations were complexed with poly(sodium methacrylate) to yield polyelectrolyte complexes or coacervates (PECs). Counterintuitively, PECs made with N-methyl to N-butyl P4VP were less stable to the addition of salt the longer the alkane chain, being easier to dope and having a lower critical salt concentration for dissolution. In contrast, the linear viscoelastic response of these PECs varied little. A transition in doping and properties was observed with N-pentyl and N-hexyl chains, the latter having a much higher modulus and much less sensitivity to salt concentration. Smallangle X-ray scattering suggested a new morphology for the N-pentyl and N-hexyl P4VP PECs, with interacting/phase separating alkane chains providing a transition into hydrophobicity-dominated PECs.

Color-tunable solid-state emitting polystyrene (PS) microbeads were developed by dispersion polymerization, which showed excellent fluorescent security ink characteristics along with sensitive detection of vapors of nitro aromatics like 4-nitro toluene (4-NT). The fluorophores pyrene and perylenebisimide were incorporated into the PS backbone as acrylate monomer and acrylate cross-linker, respectively. Solid state quantum yields of 94 and 20% were observed for the pyrene and perylenebisimide, respectively, in the PS/Py and PS/PBI polymers. The morphology and solid state fluorescence was measured by SEM, fluorescence microscopy, and absorbance and fluorescence spectroscopy techniques. The ethanol dispersion of the polymer could be used directly as a fluorescent security "invisible" ink, which became visible only under ultraviolet light. The color of the ink could be tuned depending on the amounts of the pyrene and perylenebisimide incorporated with blue and orange-green for pyrene alone or perylenebisimide alone beads respectively and various shades in between including pure white for beads incorporating both the fluorophores. More than 80% quenching of pyrene emission was observed upon exposure of the polymer in the form of powder or as spin-coated films to the vapors of 4-NT while the emission of perylenebisimide was unaffected. The limit of detection was estimated at 10(-5) moles (2.7 ppm) of 4-NT vapors. The ease of synthesis of the material along with its invisible ink characteristics and nitro aromatic vapor detection opens up new opportunities for exploring the application of these PS-based materials as optical sensors and fluorescent ink for security purposes.