High-Throughput Synthesis and Characterization of Aryl Silicones by Using the Piers-Rubinsztajn Reaction.

Arylsilicones are widely exploited for their thermal and optical properties. The creation of phenylsilicone elastomers with specific physical properties is typically done by a "one-off" formulation and test process. Herein, it is demonstrated that high-throughput synthesis methods can be used to rapidly prepare a series of arylsilicone elastomers and then the relative impact of different aryl groups on their physical properties is assessed. Aromatic groups were incorporated into polydimethylsiloxane (PDMS) elastomers by exploiting the relative reactivity of different functional groups in the Piers-Rubinsztajn reaction. To analyze trends in the silicone mechanical properties as a function of increasing aryl concentration-structure/property relationships-libraries of elastomers were both quickly synthesized and characterized by using high-throughput suites starting from low viscosity silicone oils/monomers in 96-well plates. Liquid handling parameters were optimized to effectively work with the silicones. Incorporating aryl instead of alkyl crosslinkers into the PDMS backbone increased the silicone elastomer modulus by approximately 50 % (at a crosslink density of 6 %); elastomers prepared with an aromatic crosslinker with three contact points led to much higher moduli compared with those with one contact point at the same crosslink density. When located at precise rather than random points on the silicone chains, diphenylsilicones had lower moduli than analogous monophenylsilicones.

Face Covered and Six Feet Apart: Behavioral Awareness Predicts Greater Adherence to Public Health Guidelines during the COVID-19 Pandemic.

The COVID-19 pandemic has deleteriously impacted physical and mental health. Guidelines to limit the spread of COVID-19 include wearing a face covering in public, limiting close contacts, and physical distancing. In combatting this and future pandemics, it is essential to understand predictors of adherence, such as psychological flexibility. We hypothesized higher psychological flexibility would relate to greater adherence to public health guidelines. Participants (n = 265) were English-reading/speaking adults in the United States and were recruited through Amazon's Mechanical Turk. Included in the present analyses are data from June (n = 360) and July 2020 (n = 265). Measures included the Comprehensive Assessment of ACT Processes (CompACT), which measured psychological flexibility. Outcome measures included mask-wearing and number of close contacts, which were operationalized categorically (100% mask-wearing in public, ≤10 close contacts in past week). Two logistic regression models examined psychological flexibility and distress as predictors of adherence to mask-wearing and limiting close contacts, while controlling for demographic correlates. Results indicated that greater behavioral awareness predicted greater odds of mask-wearing and limiting close contacts. Psychological flexibility, and behavioral awareness specifically, should be investigated in future research as targets for intervention amidst global disasters.

Trace water affects tris(pentafluorophenyl)borane catalytic activity in the Piers-Rubinsztajn reaction.

Improved methods to control silicone synthesis are required due to the sensitivity of siloxane bonds to acid/base-mediated chain redistribution/depolymerization. The Piers-Rubinsztajn reaction employs tris(pentafluorophenyl)borane as an efficient catalyst (<0.1 mol%) for siloxane bond formation from hydro- and alkoxysilanes - typical reactions proceed in open flasks at room temperature within minutes. While advantageous under ideal conditions, the boron catalyst activity may be affected by age, storage conditions and various environmental factors, particularly humidity. Under conditions of high humidity it may be necessary to apply heat and/or use increased catalyst loading in the reactions; there is often an induction time. We examine induction times in the Piers-Rubinsztajn reaction as a function of water concentrations in the reagent or catalyst solution and show that water in the reagent solution or atmosphere is less problematic than water found in the catalyst stock solution. A relatively linear increase in induction time accompanied higher water concentrations in the catalyst solution - no such effect was observed when the water was in the reagent solution. Reaction rates in both scenarios were similar, i.e., not affected by the induction time. Improvements in the stability of catalyst solutions were observed when B(C6F5)3 was stored in low molecular weight silicone oils, and pre-complexed with HSi(OSiMe3)3. These outcomes are ascribed to the ability of HSi groups to outcompete water in binding with B(C6F5)3 to initiate reaction, unless the boron is pre-complexed with water.

Suggestibility is associated with alcohol self-administration, subjective alcohol effects, and self-reported drinking behavior.

BACKGROUND: Suggestibility, defined as an individual's inclination to accept and internalize messages, has not been studied in relation to alcohol use. Peer conformity, a component of suggestibility, may be related to alcohol use, as peer groups show similarities in patterns of alcohol use. Few studies have assessed how suggestibility and peer conformity relate to alcohol self-administration or to reinforcing effects of alcohol. AIMS: This study assessed whether suggestibility and peer conformity were associated with drinking behavior, alcohol self-administration, subjective response to alcohol, and drinking motives and expectancies. METHODS: Study 1 participants were alcohol drinkers (n=20), who completed a laboratory study of free-access intravenous alcohol self-administration. Study 2 participants were adolescents and young adults, age 14-25 (n=150), with lifetime alcohol use. Participants completed surveys of suggestibility and drinking patterns (Study 1 and 2), subjective alcohol effects (Study 1 only), and alcohol motives and expectancies (Study 2 only). RESULTS/OUTCOMES: In Study 1, participants with higher levels of suggestiblity self-administered more alcohol, and reported greater subjective alcohol effects. Peer conformity, though correlated with suggestibility, was not related to these measures. In Study 2, participants with higher suggestiblity reported more alcohol consumption, higher drinking motives and alcohol expectancies. Peer conformity was not related to alcohol consumption, but was related to coping and enhancement drinking motives, and all expectancies measures. CONCLUSIONS/INTERPRETATION: Results indicate that suggestibility, beyond peer conformity, may be a critical factor to study when examining alcohol consumption behavior, and may provide insight into the development of alcohol use disorder.

Sequential Functionalization of a Natural Crosslinker Leads to Designer Silicone Networks.

Precise silicone networks are difficult to prepare from multiple starting materials because of poor spatial control over crosslink location, competing side reactions, and incompatible catalysts among other reasons. We demonstrate that cure processes catalyzed by B(C6 F5 )3 (the Piers-Rubinsztajn reaction) and platinum-catalyzed hydrosilylation are perfectly compatible, and can be used in either order. It is possible to perform three different, selective, sequential reactions in the same pot using H-terminated silicones as chain extenders in all cases to give explicit networks. Eugenol, a readily available aromatic compound, acts as a trifunctional crosslinker (HO, MeO, HC=CH2 ), each functional group of which can be induced to undergo selective reaction. With platinum catalysis, the reaction of SiH groups with alkenes is fastest, while B(C6 F5 )3 catalyzes reaction at phenols much faster than methoxybenzene. Thus, a variety of H-terminated telechelic siloxanes can be used to form chain extended polymers or elastomers or foams in which the morphology of the material and its constituent parts can be manipulated at will.