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• All dispersants considered acted in synergy with resins in peptizing asphaltenes. • Ionic liquid yielded the best dispersing power and the highest self-association. • Significant electron-withdrawing sites were main contributors to dispersing power. • Steric hinderance associated with molecular structure affected dispersing behavior. In confronting the global climate change, reusing waste asphalt materials stands out as a key strategy for the transportation sector to preserve natural resources and reduce the carbon footprint. Recycling additives or rejuvenators are usually required in this practice, especially for boosting the recycling rate. Given the imperative need for a general compositional design principle of rejuvenators, we previously proposed an innovative formulation concept by combining softeners with asphaltene dispersants, and reported that the use of dispersants largely reduced the total quantity of rejuvenators needed and thus would minimize the environmental impacts. The present study is aimed for probing the molecular mechanisms underlying this observation, with additional interest focused on the synergistic effect of the dispersants with resins and also on the impacts due to their self-association. Selection of representative materials consisted of three types of dispersants including an ionic liquid, a phenolic amphiphile, and an ester plasticizer, in combination with an aromatic oil as the softener. Long-time molecular dynamics (MD) simulation was employed to inspect the aggregation of asphaltenes. Quantum chemical (QC) computation was performed to provide insights into the source of different dispersing behaviors. The results indicated that the three dispersants all acted in concert with resins in dispersing asphaltenes. The dispersion characteristics of asphaltenes could be viewed as a net result of the two competing mechanisms of the dispersing capability and self-association of the dispersant used. The ionic liquid exhibited much higher propensity to self-association at increasing concentrations than the phenolic dispersant, and yet the optimum performance was achieved for both when they were added at low dosages. The ester plasticizer showed minimal self-association and yielded improved dispersion with increasing concentrations. In all cases, the dispersing functionality mainly originated from the presence or formation of significant electron-withdrawing sites, collectively due to the highly electronegative cation and anion, hydrogen bonding, and polar groups. Comparison of the dispersing power was also conducted from different perspectives. The findings are expected to provide molecular insights for formulating versatile and more environmentally benign asphalt rejuvenators. [ABSTRACT FROM AUTHOR]

• Rejuvenators were formulated by combining asphaltene dispersants with softeners. • All rejuvenation schemes effectively restored the rheology and moisture resistance. • Rejuvenated asphalts exhibited similar or better long-term performance than virgin. • Ionic liquid yielded the best dispersing efficiency and aromatic softener the least. • Polar groups and forming hydrogen bonding were speculated as primary contributors. The search and development of various asphalt rejuvenators have been following a trial-and-error methodology in essence; the imperative need of improved efficiency and versatility yearns for a general principle/framework of formulating rejuvenators. In this study, we propose one such formulation concept that rejuvenators can be designed by combining asphaltene dispersants (interacting with and dispersing asphaltenes) with softeners (diluting asphaltenes). This concept was preliminarily validated in an experimental program involving three rejuvenation schemes, namely using an aromatic softener alone (as the reference) and using it together with an ionic liquid or a phenolic compound (both acting as dispersants). Immediate and long-term rejuvenating effectiveness was evaluated based on viscoelastic properties, fatigue resistance, and moisture susceptibility. The results indicated that at respective optimum dosages, the three schemes all yielded satisfactory immediate performance of rejuvenation. After long-term aging, the rejuvenated asphalts demonstrated more desired viscoelastic characteristics in resisting high-temperature deformation and low-temperature cracking, and were more fatigue resistant, as compared to the virgin binder. Rejuvenation in all cases also recovered the moisture resistance nearly to the virgin level. Infrared spectrum analysis indicated that the performance restoration was accomplished by the agents blending physically with the aged binder, which decreased the concentrations of oxidation functional groups (carbonyl and sulfoxide). The incorporation of dispersants improved the aging resistance (in terms of high temperature viscoelasticity), and substantially reduced the need of aromatic softener while providing similar or better performance compared to using the softener alone, which would lead to pronounced environmental and economic benefits. The much higher dosage efficiency was ascribed to the capability of the dispersants in peptizing and dissociating the asphaltenes, as investigated by molecular dynamics simulations. The different dispersing behaviors of the additives were examined with reference to their chemical compositions and molecular structures. [ABSTRACT FROM AUTHOR]

• Oxidative aging promoted and further stabilized asphaltene aggregation. • The driving force for aggregation was dispersion between the fused aromatic cores. • All additives reduced asphaltene aggregation and improved orientational randomness. • TBC exhibited the highest potential due to spatial distribution of four polar sites. Economic and environmental sustainability has been a significant stimulus to the use of recycled asphalt materials in the pavement industry. In this practice, rejuvenators are usually required to treat the oxidized asphalts with the aim to restore the physical properties and engineering performance. A critical function required for rejuvenators is that they can deagglomerate the asphaltene aggregates by effectively interacting with them. This study employed the techniques of molecular dynamics simulations and quantum chemical calculations, and investigated the impacts of oxidation on asphaltenes and the deagglomerating potential of three selected additives with different molecular structures and polarities, i.e., tributyl citrate (TBC), limonene, and myristamide. Analyses based on the aggregation number, orientational order parameter, and decomposition of the interaction energy indicated that oxidation strengthened the binding between the asphaltenes and thus promoted their aggregation behaviors. Among the three additives, TBC exhibited the highest rejuvenating effectiveness as it restrained the formation of large asphaltene aggregates and improved the orientational randomness of the aromatic cores. This capability was attributed to the highest number of polar sites in TBC and its three-dimensional spatial structure, which enhanced the compatibility and interactions with the aged asphaltenes. Based on the independent gradient model (IGM) method, the asphaltene aggregation is driven by the π-π interactions dominated by dispersion forces between the fused aromatic cores. The additives weakened the asphaltene interactions to different degrees, but the reversing effects were limited compared to the unaged state. [ABSTRACT FROM AUTHOR]

Hydrogen bond effect plays a pivotal role in protein-ligand interaction and represents one of the fundamental bases in pharmaceutical design. To evaluate the influence of hydrogen bond interaction on the anti-breast cancer activity, fifteen dihydroartemisinin-isatin hybrids 7a-o with hydrogen bond donors at C-3 position of isatin moiety were designed, synthesized and evaluated for their antiproliferative activity against MCF-7, MDA-MB-231, MCF-7/ADR and MDA-MB-231/ADR breast cancer cell lines. The preliminary results illustrated that introduction of hydrogen bond donors especially thiosemicarbazide into C-3 position of isatin moiety was beneficial for the activity, and substituents at C-5 position of isatin fragment as well as the length of the carbon spacers between dihydroartemisinin and isatin moieties also have significant influence on the activity. The enriched structure-activity relationships may provide useful information for further rational design of the candidates with higher activity. [Display omitted] • Introduction of thiosemicarbazide into C-3 position of isatin moiety was beneficial for the activity • Substituents at C-5 position of isatin fragment have significant influence on the activity • The SAR may provide useful information for further rational design of the candidates with higher activity. [ABSTRACT FROM AUTHOR]

Although gelatinization property has been intensively investigated with its relation to starch structures, how a combination of starch molecular structures and moisture content affect the gelatinization remains unclear. The gelatinization of six rice starches with a wide range of amylose content was investigated under different moisture content in this study. Results showed that starch gelatinization temperatures increased and biphasic endothermic peaks appeared over the decreased moisture content. For the first time, amylose content was shown to have a parabolic relationship with gelatinization temperatures. Distinct linear relations among starch fine molecular structures with gelatinization parameters were observed under different moisture contents, which suggested that amylose short chains were involved in the first endothermic peak, while interactions among amylose intermediate chains and relatively shorter amylopectin trans-lamellar chains dominantly contributed to the second endothermic peak when gelatinized under limited moisture content. These results help in better understanding of starch structure-gelatinization relation. Critical starch structures and the possible mechanism in determining the biphasic endothermic peaks during the starch gelatinization under limited moisture content. [Display omitted] [ABSTRACT FROM AUTHOR]

Two new and six known ent -pimaranes were isolated from Flickingeria fimbriata. One of them possesses a rare carbon skeleton. It is the first time such a compound with this specific carbon skeleton has been isolated from a natural source. The structure and absolute configuration were determined by NMR, MS, and X-ray diffraction analysis. The biosynthetic pathway of the rare skeleton was proposed and suggested a new pathway for these nor- ent -pimarane analogues. All isolated compounds were screened for inhibitory activity against acetylcholinesterase (AChE). The compound 4 exhibits potent inhibitory effect on AChE with the 50% inhibitory concentration (IC 50) being 5.8 μM, which is close to that of the positive control (Huperzine A). This is the first report about inhibitory activity on AChE of ent -pimaranes. [Display omitted] • One rare skeleton compound was identified, and its chemical structure was confirmed by single crystal X-ray diffraction. • The skeleton of compound 1 suggests biosynthesis of nor- ent -pimaranes possibly relate to Bayer-Villiger reaction. • ent -Pimaranes are firstly reported for potent inhibitory effects against acetylcholinesterase. [ABSTRACT FROM AUTHOR]

The prepared β -CD/TMC-MWCNTs polyester membranes exhibited effective selectively separation performance for dye/salt mixture solution filtration. [Display omitted] • The high-flux β -CD/TMC polyester membrane supported by MWCNTs network was prepared. • The membrane showed selective separation for dye/salt mixture based on β -CD cavity. • The main mechanism was size exclusion, electrostatic interaction, Donnan effect. • Reusability, chlorine resistance, and antifouling ability of the membrane was good. The treatment of dye pollutant and salts by nanofiltration membrane technology usually has the difficulty of low permeability and higher pressure in the case of maintaining a high rejection. In this study, high flux polyester membranes of β -cyclodextrin/trimesoyl chloride - multiwalled carbon nanotubes (β -CD/TMC-MWCNTs) were fabricated on a modified multiwalled carbon nanotubes (MWCNTs) substrate via interfacial polymerization (IP) process. The modified MWCNTs substrate was not only beneficial to modulating the permeation and distribution of aqueous phase monomer (β -cyclodextrin, β -CD), but also in favor of the formation of an ultrathin loose selective polyester active layer due to the porous network structure. The optimization experiments about the reaction time and monomer concentrations were conducted. The experimental results showed that the pure water flux of the as-prepared β -CD/TMC-MWCNTs membrane was 179.93 L m-2h-1 bar-1 (at the pressure of 0.1 MPa) when the reaction time of IP process was 5 min. The single dye removal efficiency of β -CD/TMC-MWCNTs membrane was 97.41% for Brilliant Green (BG) and 96.39% for Congo red (CR), respectively. The removal efficiency of dye/salt mixture by the membrane was above 84% for BG and over 98% for CR, respectively. The results indicated that the membrane had the efficient selective separation performance for the dye/salt mixture benefiting from the special molecular sieving architectures with the precisely intrinsic inner cavity of β -CD/TMC-MWCNTs membrane. Furthermore, the reusability, chlorine resistance, and antifouling ability of the β -CD/TMC-MWCNTs membrane was relatively excellent, and the membrane could effectively remove BG (>93%) and CR (>98%) simultaneously for mixed BG/CR dyes in real water body. These results suggested that the as-prepared β -CD/TMC-MWCNTs membrane had the potential of practical application in dye wastewater treatment. [ABSTRACT FROM AUTHOR]