The aggregation behaviors of organic radicals in polar fluorinated arenes

Polarfluorinated arenes can promote organic free radical reactions,which have attracted scientists’interest in recent years.However,it is still unknown how these solvents interact weakly with organic radical molecules to influence their reactiv-ity.In this study,we investigated how organic free radicals aggregate infive polarfluorocarbon solvents,and demonstrated that different substituents can influence their aggregation behaviors.In these solvents,small organic radicals with simple substituents maintain a homogeneous solution;however,radicals with substituents that form intermolecular hydrogen bonds or with long-chain aliphatic hydrocarbons tend to aggregate in them,whereas substituents of long-chain aliphatic hydrocar-bons tend to promote aggregation better.The critical aggregation concentrations of these aggregates are measured by concentration-dependent UV–visible spec-troscopy.Their topological morphologies are all spherical based on TEM.The compactness and rotational motivation speed of radical molecules within these aggregates are determined by EPR spectroscopy.The particle sizes of these aggre-gates are determined by analyzing their cyclic voltammograms.Most excitingly,electrochemical experiments reveal that the aggregation behaviors of free radical molecules with intermolecular hydrogen bonds can significantly increase their cat-alytic rate for electro-oxidizing benzyl alcohol in such a solvent.The results of this study indicate that in polarfluorinated arenes organic radical molecules’aggregation behaviors are related to their structures.This may provide guidelines for regulating organic radical reactivity in these solvents in the future.

Superior aggregation, morphology and photovoltaic performance enabled by fine tuning of fused electron-deficient units in polymer donors

Copolymerization of an electron-rich donor(D)unit with an electron-deficient acceptor(A)unit to construct efficient D-π-A-πtype donors is an effective strategy for organic solar cell applications.The electron-deficient unit fusion,endows extendedπ-conjugation plane and insures excellent photoelectronic property,has great advantages to build A moiety and gradually receives considerable attention.In this work,we adopt benzo[2,1-b:3,4-b’]dithiophene and benzopyrazine(BP),benzothiadiazole(BT)and benzoselenadiazole(BS)to cleverly construct a series of fused A units with different electrondeficient ability,and further synthesize three polymer donors PBDP-BP,PBDP-BT,and PBDP-BS,respectively.The relationships between structure and performance were systematically investigated.PBDPBT shows a moderate aggregation behavior in both solution and film,and the highest hole mobility among the three polymers.After blending with Y6,the PBDP-BT:Y6-based film has the strongest absorption,favorable compatibility,superior crystallinity,and uniform phase separation morphology compared with PBDP-BP or PBDP-BS based blend films.Thus,the device based on PBDP-BT:Y6 has the highest and balanced charge mobility,suppressive recombination,reduced energy loss and achieves an outstanding PCE of 15.14%,which is superior to PBDP-BP:Y6(8.55%)and PBDP-BS:Y6(6.85%).These results provide learnable guidelines for future fused electron-deficient unit-based donor design for photovoltaic application.

Aggregation behavior of juvenile Neptunea cumingii and eff ects on seed production

Neptunea cumingii is an important nutrition-rich economic species in China.Juveniles of N.cumingii suff er from high mortality at low temperatures,which has proved a limiting factor in raising seedlings in artifi cial habitats.Previous research has shown that N.cumingii displays aggregation behavior in response to adverse environmental changes.Therefore,we determined the eff ects of temperature,food,size of juvenile snails,substratum type,and density of juvenile snails on the aggregation behavior of N.cumingii.Results show that,at a low(4°C)or a high(22°C)temperature,juvenile snails adjusted to the inhospitable environment by exhibiting increased aggregation behavior.However,their aggregation behaviors diff ered at these two temperatures.There was no signifi cant diff erence in the aggregation rate,but the typical aggregation size was larger at 4°C than at 22°C.At 10°C or 16°C,aggregation behavior of juvenile snails reduced.Aggregation increased in the satiation treatment at 10°C and 16°C.Small-sized juveniles tended to have higher aggregation rates(92.22%)and a larger typical aggregation size.More juveniles were distributed in the bottom of shaded substrata.A larger typical aggregation size or higher density signifi cantly reduced the mortality of juvenile snails at a low temperature(4°C).These results broaden our understanding of gastropod aggregation behavior and can be used to develop and improve commercial breeding strategies and resource recovery for N.cumingii.

Aggregation Behavior and Structure of Associated Polyacrylamide Hydrophobically Modified with 2-Phenoxylethylacrylate

The aggregation behavior and structure of hydrophobically modified block copolymers of acrylamide and 2-phenoxylethylacrylate were investigated by viscometry, 1H NMR relaxation, 2D NOESY, fluorescence and dynamic light scattering. It Was found that the aggregation behavior was strongly dependent on the concentration of polymer solution and the hydrophobe contents. With varying concentration from 2.0, 6.0, 8.0 to 12.0 g/L, there were different aggregate morphologies distributed in aqueous solutions, such as monopolymer chain, micelle-like aggregate, multi-micelle aggregate and cross-linked network. According to the model of aggregation, it can give a reasonable explanation on the large magnitude enhancement of viscosity with the increasing of polymer concentration. Additional data of 2D NOESY and fluorescence show that the copolymer with higher hydrophobe content（molar fraction≥ 1%） is likely to form intra-molecular association.

Factors influencing the aggregation behavior of residual associative polymer in produced oily fluids

The influence of emulsified oil, suspended solids, Fe3＋, Fe2＋, cationic water clarifier and sulfate-reducing （SR） bacteria on the aggregation behavior of residual hydrophobic modified polyacrylamide in treated oily wastewater from polymer flooding was studied by fluorescence spectroscopy and dynamic light scattering. The result of I1/I3 showed that the polarity of hydrophobic microdomains increased, whereas the size of the hydrophobic microdomains may be decreased, where the value of I1/I3 represents the ratio of the intensity of peak 11 （374.0 nm） to that of peak/3 （385.0 nm） of the vibration fine structure of pyrene monomer emission in residual polymer solution. The results of the ratio of I1 at 48 h to I1 at 0 h （I1,48h/I1,0h） indicated that oil and cationic water clarifier could inhibit the aggregation to some extent, while Fe2＋ and suspended solids were helpful for aggregation, and Fe3＋ and SR bacteria had no significant influence on the aggregation of polymer.

The Effects of Fe2+ on the Aggregation Behavior of Residual Hydrophobic Modified Polyacryamide

The influences of Fe2+ on the aggregation behavior of residual hydrophobic modified polyacryamide (HMPAM) in treated oily wastewater were studied by fluorescence spectrum and DLS. The result of I1/I3 showed that the polarity of hydrophobic domain increased and the size of hydrophobic domain may be decreased with the increasing of Fe2+ in produced water. Fe2+ was helpful for the increase of hydrophobic domain, therefore due to the aggregation degree for HMPAM.

Characterization and stability of sedimentary colloids in different ecology regions in Taihu Lake

Colloidal particles,heterogeneous mixture with various organic components and continuous molecular weight(MW)distribution,is omnipresent in lake sediments and substantially influence the retention,transportation,and fate of contaminants in lake ecosystem.We sampled and extracted sedimentary colloids from different ecology regions in Taihu Lake,Jiangsu,East China,in June 2020,and they were further separated into four different particle size ranges by tangent ultrafiltration,and the properties of colloids were studied in various methods,including zeta potential analysis,transmission electron micrograph images(TEM),Fourier transformation infrared(FTIR),and 3D fluorescence.Results show that the surface of the colloids is covered with organic macromolecular substances,such as humuslike substances and protein-like substances.There were significant differences in molecular weight and fraction content of colloids in the sediments from macrophyte-dominant(MD)area and algae-dominant(AD)area in the lake.Colloids from MD area are mainly composed of humic acid,protein,and fulvic acid;the content of fulvic acid is lower than that of humic acid and protein.The humic acid exists mainly in small molecular weight(10-100 kDa),protein exists in mainly large molecular weight colloids(0.45-1μm).Colloids from AD area are mainly composed of humic acid,and mainly distributed in the molecular weight(10 kDa-0.45μm).The presence of humic acid inhibits effectively the agglomeration of the colloids.Especially,the stability of colloids is closely related to the molecular weight,with low molecular weight from MD area show higher stability.The existence of humic acid in colloids increases the electrostatic repulsion between colloidal particles,which can effectively inhibit the agglomeration of colloids,thus enhancing the stability of colloids.Furthermore,both monovalent and divalent electrolytes enhance colloidal aggregation,and the low-molecular-weight(LMW)colloid fraction exhibits higher stability efficiency than the high-molecular-weight(HMW)colloidal.

A neural m^(6)A pathway regulates behavioral aggregation in migratory locusts

RNA N6-methyladenosine(m^(6)A),as the most abundant modification of messenger RNA,can modulate insect behaviors,but its specific roles in aggregation behaviors remain unexplored.Here,we conducted a comprehensive molecular and physiological characterization of the individual components of the methyltransferase and demethylase in the migratory locust Locusta migratoria.Our results demonstrated that METTL3,METTL14 and ALKBH5 were dominantly expressed in the brain and exhibited remarkable responses to crowding or isolation.The individual knockdown of methyltransferases(i.e.,METTL3 and METTL14)promoted locust movement and conspecific attraction,whereas ALKBH5 knockdown induced a behavioral shift toward the solitary phase.Furthermore,global transcriptome profiles revealed that m^(6)A modification could regulate the orchestration of gene expression to fine tune the behavioral aggregation of locusts.In summary,our in vivo characterization of the m^(6)A functions in migratory locusts clearly demonstrated the crucial roles of the m^(6)A pathway in effectively modulating aggregation behaviors.

HYDROPHOBICALLY ASSOCIATING POLYACRYLAMIDES MODIFIED BY A NOVEL SELF-ASSOCIATIVE CATIONIC MONOMER

A series of hydrophobically associating polyacrylamides modified by small amounts （〈 3 mol%） of a self- associative cationic monomer 4-（2-（acryloyloxy） ethoxy） benzyl tri-ethyl ammonium bromide （AEBA） as hydrophobe were synthesized by radical copolymerization in aqueous solutions without external surfactants. The resulting eopolymers containing a multiblock structure exhibited a high tendency for hydrophobic association and a high thickening capacity. Solution properties and aggregation structures were investigated by viscometry and fluorescence technique. The high viscosity enhancement was found as the polymer concentration beyond a critical value c＊ and strongly depended on the copolymer microstructures. The number and length of hydrophobic microblocks within the copolymer backbones could be controlled by changing the AEBA concentration in copolymerization system. Addition of salt induced more hydrophobic association and viscosity enhancement. The synthesis method used was simple and environmentally friendly without any external surfactant contamination in comparison with the conventional micellar copolymerization.

Risk of group aggregative behavior during COVID-19 outbreak: A case report

BACKGROUND At the end of 2019,a new epidemic of viral pneumonia emerged in China and was determined to be caused by a novel coronavirus,which was named coronavirus disease 2019(COVID-19)by the World Health Organization.The epidemic quickly spread,causing a worldwide pandemic.Scientists and clinicians across the globe have shifted their research efforts towards understanding the virus itself and its epidemiology.CASE SUMMARY In mid-January 2020,a Chinese family made a visit to a local city,and within the next 2 wk one after another fell ill with COVID-19.At the beginning of their first illness onset,the family had eaten in a restaurant,which led to the subsequent illness onset in another two families.All cases were diagnosed as COVID-19 by real-time fluorescent reverse transcription-polymerase chain reaction.Epidemiological investigation showed that the transmission chain was complete.CONCLUSION This chain of social exposure highlights the danger of group aggregative behavior for spread of COVID-19.

Trichoderma metabolites trigger aggregation behavior in Formosan subterranean termites (Coptotermes formosanus)

Our previous studies have shown that some Trichoderma fungi trigger aggregation behavior in Formosan subterranean termites,Coptotermes formosanus Shiraki.However,the mechanisms underlying the induction of termite aggregation by Trichoderma fungi remain unclear.Here,we found that the aqueous or acetone extract of Trichoderma asperellum Samuels,Lieckfeldt&Nirenberg and Trichoderma virens Pers.ex Fries isolated from the gut or cuticle of C.formosanus elicited significant termite aggregation in 2-choice tests.We then screened 9 Trichoderma metabolites(3-acetoxy-2-butanone,phenol,3-ethoxypropionic acid,ethyl 2,4-dioxovalerate,diglycolic acid,d-valine,styrene,3-aminopyridine,and hexyl acetoacetate)that triggered termite aggregation.Among them,phenol(1000μg/mL),3-ethoxypropionic acid(10μg/mL),ethyl 2,4-dioxovalerate(1000μg/mL),and diglycolic acid(1000μg/mL)showed the strongest activities,triggering termite aggregation throughout the 24-h period.As T.asperellum and T.virens produce different metabolites that trigger aggregation behavior in termites,the mechanisms underlying the interaction between subterranean termites and Trichoderma fungi likely vary.Future studies are needed to test whether these chemicals can attract termites and increase bait consumption.

Effect of cationic monomer structure on the aggregation behavior of amphoteric acrylic polymer around isoelectric point

Amphoteric polymer can be used as retanning agent in leather manufacture.It is particularly useful in chrome-free tanning systems since it can regulate the charge properties of chrome-free leather and enhance the fixation of anionic post-tanning chemicals in leather.However,the aggregation and precipitation of amphoteric polymer retanning agents around the isoelectric point(pl)hinder their wide application.Herein,we synthesized five amphoteric acrylic polymers(AAPs)by free radical copolymerization with acrylic acid and five different cationic acrylic monomers.The effect of cationic monomer structure on the aggregation behavior of AAPs was investigated.The aggregation of AAPs in aqueous solution showed pH and concentration dependence.Light scattering analysis showed that Poly(AAA-co-MAPTAC)and Poly(AA-co-DMAPMA)were in the shape of coiled linear flexible chains with small particle size(R_(g)7.6 nm and 14.8 nm,respectively)near the pl.However,Poly(AA-co-DAC),Poly(AA-co-DMC)and Poly(AA-co-DMAEMA)were in the shape of hollow spheres and exhibited serious aggregation.Quantum chemical calculations suggested that the amide groups in the cationic monomers MAPTAC and DMAPMA enhanced the nucleophilicity of AAPs.Thus the corresponding AAPs could carry a large number of cationic charges to slow their aggregation when the pH just climbed over the pl.The results are expected to provide theoretical reference for the synthesis and wide-spread application of AAPs.

Ultrafast photoexcitation dynamics behavior of hydrogen-bonded polyfluorenol

Exciton behavior is crucial to the exploitation of light-emitting conjugated polymer(LCPs)for optoelectronic devices.Singlet excitons are easily trapped by the intrinsically defect structures.Herein,we set a polyfluorenol(PPFOH)as an example to systematically investigate its photophysical behavior to check the role of defect structures in LCPs.According to time-resolved photoluminescence analysis,the feature emission peaks from individual chain of PPFOH in diluted DMF solution is effectively avoided the influence of fluorenone formation,but the residual green-band emission at 550nm is easily observed in the PL spectra of PPFOH dilute toluene solution obtained delay 1.5 ns,confirmed the formation of“guest”physical aggregation-induced defect structure.Remarkably,efficient and ultrafast energy transfer from individual chain to defect structure is observed in PPFOH films.Interestingly,the efficient energy transfer happened for the film obtained from DMF solution(200 ps)than those of toluene ones(600 ps).Meanwhile,compared to relatively stable green-band emission in PPFOH film from toluene solution,red-shifted emission peak(11 nm)of PPFOH film from DMF solutions exposed to saturated DNT vapor also confirmed their different aggregation-induced green-band emission.Therefore,this aggregation defect structures are influenced on the photophysical property of LCPs in solid states.

Fecal volatile components elicit aggregation in the oriental migratory locust, Locusta.migratoria manilensis （Orthoptera： Acrididae）

The aggregation components from fecal volatiles of the oriental mi- gratory locust, Locusta migratoria manilensis were identified with gas chromatographic/electroantennographic detector （GC-EAD）, GC-MS （mass spectrometry） analyses and behavioral bioassays. Both last instar nymphs and adults of the oriental migratory locust have similar aggregation pheromones in their volatiles. A total of 11 electrophysiologically active compounds, namely, hexanal, cyclohexanol, heptanal, phenol, 2,5-dimethyl- pyrazine, benzyl alcohol, benzaldehyde, guaiacol, nonanal, 2,6,6-trimethyl-2-cyclohexene- 1,4-dione and decyl aldehyde were identified in the fecal volatiles of 2-day-old immature adult male locusts. Only hexanal, nonanal, benzaldehyde, cyclohexanol and 2,5-dimethyl- pyrazine elicited significant aggregation responses in immature 2-day-old adult males. However, adult males had significantly lower behavioral responses to synthetics of five single compounds than the blend of cyclohexanol, 2,5-dimethyl-pyrazine, benzaldehyde, nonanal, hexanal in ratios of 100 ： 100 ： 2 ： 60 ： 30 in the range of 30 60 μg/mL. We propose that it is the blend of these five compounds that plays a key role in eliciting and sustaining aggregation in gregarious oriental migratory locusts. These results also showed that the aggregation pheromones of the oriental migratory locust are significantly different from those found in the desert locust.

Alkyl-chain branched effect on the aggregation and photophysical behavior of polydiarylfluorenes toward stable deep-blue electroluminescence and efficient amplified spontaneous emission

The control of the condensed superstructure of light-emitting conjugated polymers(LCPs)is a crucial factor to obtain high performance and stable organic optoelectronic devices.Side-chain engineering strategy is an effective platform to tune inter chain aggregation and photophysical behaviour of LCPs.Herein,we systematically investigated the alkyl-chain branched effecton the conformational transition and photophysical behaviour of polydiarylfluorenes toward efficient blue optoelectronic devices.The branched side chain will improve materials solubility to inhibit interchain aggregation in solution according to DLS and optical analysis,which is useful to obtain high quality film.Therefore,our branched PEODPF,POYDPF pristine film present high luminance efficiency of 36.1%and 39.6%,enhanced about 20%relative to that of PODPF.Compared to the liner-type sides'chain,these branched chains also suppress chain planarization and improve film morphological stability effectively.Interestingly,the branched polymer also had excellent stable amplified spontaneous emission(ASE)behaviour with low threshold(4.72μJ/cm2)and a center peak of 465 nm,even thermal annealing at 220℃in the air atmosphere.Therefore,side-chain branched strategy for LCPs is an effective means to control interchain aggregation,film morphology and photophysical property of LCPs.

Effect of cationic monomer structure on the aggregation behavior of amphoteric acrylic polymer around isoelectric point

Amphoteric polymer can be used as retanning agent in leather manufacture. It is particularly useful in chrome-free tanning systems since it can regulate the charge properties of chrome-free leather and enhance the fixation of anionic post-tanning chemicals in leather. However, the aggregation and precipitation of amphoteric polymer retanning agents around the isoelectric point (pI) hinder their wide application. Herein, we synthesized five amphoteric acrylic polymers (AAPs) by free radical copolymerization with acrylic acid and five different cationic acrylic monomers. The effect of cationic monomer structure on the aggregation behavior of AAPs was investigated. The aggregation of AAPs in aqueous solution showed pH and concentration dependence. Light scattering analysis showed that Poly (AA-co-MAPTAC) and Poly (AA-co-DMAPMA) were in the shape of coiled linear flexible chains with small particle size (Rg 7.6 nm and 14.8 nm, respectively) near the pI. However, Poly (AA-co-DAC), Poly (AA-co-DMC) and Poly (AA-co- DMAEMA) were in the shape of hollow spheres and exhibited serious aggregation. Quantum chemical calculations suggested that the amide groups in the cationic monomers MAPTAC and DMAPMA enhanced the nucleophilicity of AAPs. Thus the corresponding AAPs could carry a large number of cationic charges to slow their aggregation when the pH just climbed over the pI. The results are expected to provide theoretical reference for the synthesis and widespread application of AAPs.

MULTI-AGENT AGGREGATION BEHAVIOR ANALYSIS: THE DYNAMIC COMMUNICATION TOPOLOGY

The authors extend the Gazi＇s swarm model with local neighbor rules and the dynamic communication topology, and study its aggregation properties. Results of analysis show that all agents in the models aggregate and eventually form a cohesive cluster of finite size around the swarm center or the appointed point. Finally, simulations are provided to testify some of the results. Models in the paper are more applicable to the reality for the advantage that each agent only needs the partial information of the entire dynamic system when making motion decision.