Non-isothermal cold crystallization of liquid crystalline porphyrins.

A series of liquid crystalline porphyrins was synthesized, purified, and characterized. Differential scanning calorimetry (DSC) and hot-stage polarized optical microscopy (HS-POM) revealed that the porphyrins in the series with shorter alkyl arm lengths exhibit kinetic cold crystallization, wherein the molecules spontaneously organize into large, disc-like structures that remain stable upon cooling. Using DSC, the kinetic and thermodynamic parameters related to these materials were determined. Analysis of non-isothermal crystallization revealed the presence of multiple nucleation and growth processes related to cold crystallization.

Green Chemistry Teacher Professional Development in New York State High Schools: A Model for Advancing Green Chemistry.

Teaching green chemistry within the K-12 classroom has a positive impact on attitudes and perceptions of chemistry in society for future scientists and professionals, resulting in safer, less hazardous chemistry experiments and demonstrations. The state of New York has taken advantage of the benefits that green chemistry provide in the classroom and is a leader in professional development for high school teachers throughout the state. Between 2011 and 2016, Beyond Benign and Siena College implemented 14 workshops across the state as part of New York's Department of Environmental Conservation goal of reducing hazardous chemicals in schools. At these workshops, 224 teachers were introduced to green chemistry principles and practices and provided resources for replacing traditional laboratory experiments with alternatives that used safer materials. Two professional development models were implemented, a one-day introductory workshop and a three-day train-the-trainer style in-depth workshop, using collaborative, hands-on, intensive, and peer-learning techniques. In response to a 2021 follow-up survey, participants shared that they continue to use skills from the professional development they received and reported sharing about green chemistry with peers, parents, and administrators. The long-term engagement of the participants indicates that successful models were implemented to provide a path to develop teacher leaders. Professional development models are presented herein for sharing best practices and approaches for training high school teachers on green chemistry, providing numerous benefits to both teachers and students in high school classrooms.

Trithiocarbonate-mediated free-radical photopolymerization: improved uniformity in hologram recording.

A holographic material based on a photopolymerizable nematic acrylate was improved by the addition of the trithiocarbonate, EtO2CCH2SC(S)SCH2CO2Et, increasing uniformity and reproducibility in the formation of electrically switchable holographic gratings. Diffraction efficiencies as high as 34%, the thin-grating theoretical maximum, were achieved at large (10-14 microm) grating spacings. Improved diffraction efficiency was seen over a range of grating spacings (0.35-10 microm). The exposure window for grating formation was increased by an order of magnitude, resulting in much improved reproducibility.