Understanding the mechanism of molecular self-assembly to form well-organized nanostructures is essential in the field of supramolecular chemistry. Particularly, amphiphilic copolymers incorporated with polyhedral oligomeric silsesquioxanes (POSSs) have been one of the most promising materials in material science, engineering, and biomedical fields. In this review, new ideas and research works which have been carried out over the last several years in this relatively new area with a main focus on their mechanism in self-assembly and applications are discussed. In addition, insights into the unique role of POSSs in synthesis, microphase separation, and confined size were encompassed. Finally, perspectives and challenges related to the further advancement of POSS-based amphiphilics are discussed, followed by the proposed design considerations to address the challenges that we may face in the future.
A facile and sustainable electrochemical umpolung of bromide ion protocol was developed under mild reaction conditions. Transition metal catalysts and exogenous chemical oxidants were obviated for the bromination of C–H bond. Notably, graphite rod, which is commercially available at supermarkets and is inexpensive, was employed as the electrode material. This operationally easy and environmentally friendly approach accomplished the synthesis of 3-bromoindole in excellent yield and regioselectivity.
Solvents
for spherical agglomerates preparation are usually selected
according to the Lifshitz–van der Waals acid–base theory
with negative adhesion free energies. However, some solvents with
positive adhesion free energies in which spherical agglomerates can
be obtained are easily ignored. This work proposes that solvents should
be screened comprehensively by theoretical calculation combined with
experiments using m-aminobenzoic acid (m-ABA) as a model compound. According to the Lifshitz–van der
Waals acid–base theory, water, isopropyl alcohol, and ethylene
glycol with negative adhesion free energies were screened out as the
possible solvents for the preparation of m-ABA spherical
agglomerates. Crystallization experiments showed that in addition
to the three solvents, methanol and ethanol with positive adhesion
free energies were also appropriate for spherical crystallization
of m-ABA. A common feature of the five solvents which
can form spherical agglomerates is that they have both hydrogen-bond-donating
and hydrogen-bond-accepting capabilities. The single-factor analysis
method was used to systematically investigate the effects of stirring
speed, terminal temperature, and supersaturation on spherical agglomerates
of m-ABA. The formation mechanism of m-ABA spherical agglomerates was elucidated with the help of the in
situ Pixact Crystallization Monitoring system. Comparative experiments
proved that the obtained spherical agglomerates exhibit better chemical
stabilities and crystal form stability than needle-like crystals.
The solubility of m-aminobenzoic acid (m-ABA) Form I in 12 pure solvents (methanol, ethanol, 1-propanol, 2propanol, 1-butanol, isobutyl alcohol, water, acetonitrile, acetone, methyl acetate, isopropyl acetate, 1,4-dioxane) was measured at temperatures from T = 283.15 to 323.15 K by a gravimetric method under atmospheric pressure. The mole fraction solubility values of m-ABA in these 12 solvents increase with increasing temperature in the following order: 1,4-dioxane > acetone > methanol > ethanol > methyl acetate > 2-propanol > 1-propanol > 1-butanol > isobutyl alcohol > isopropyl acetate > acetonitrile > water. The solubility of m-ABA is influenced by multiple factors, such as the hydrogen bond between the solute and solvent, solvent polarity, and the solvent−solvent interaction. The relationship between solubility and temperature was mathematically correlated by the modified Apelblat equation, van't Hoff equation, λh equation, and the Wilson model. The calculated ARD% values indicate that the correlation results are in good agreement with the experimental data. The most suitable model is the modified Apelblat equation.
HighlightsA float meter based system (FMBS) was designed for self-regulated discharging and feeding in an anaerobic semi-CSTR.The accuracy and feasibility of the FMBS were determined for anaerobic digestion of chicken litter.The FMBS had the advantages of much lower cost and better full working volume control than a digital accurate pump system (DAPS).Abstract. Given the rapidly rising costs in building lab-scale reactors, efforts are needed to examine innovative designs of reactor systems to reduce the expenses of scientific research. In this study, a float meter based system (FMBS) was designed for self-regulated discharging and feeding to operate a semi-CSTR for anaerobic digestion of chicken litter (CL) with wheat straw (WS). The FMBS functioned properly in following a feeding, reaction (stirring), settling, and discharging cycle based on the hydraulic retention time (HRT). However, clogging in the feeding or discharging lines of the reactor might occur for co-digestion of CL and WS with high TS content (C/N = 20, TS = 6%). Compared with a digital accurate pump system (DAPS), the FMBS showed the advantages of low cost ($182 << $6000) and better control of the full working volume. The longest HRT that could be achieved in this study with an exchange liquid volume of 2 L in each operating cycle was 100.7 h. In all, the FMBS design could serve as a low-cost option for designing lab-scale, semi-CSTR for anaerobic digestion as well as other reactor configurations. Keywords: Anaerobic semi-CSTR, Feeding and discharging, Float meter, Self-regulated.
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