On the Formation of the Supramolecular Structure of Poly(L-lactide) in the Process of Electrospinning Nanofibers

Herein, tetrabromoterepthalic acid (TBTA) is used as the potential co-crystal former with various organic base molecules containing free nitrogen atoms. The crystal structure of TBTA (compound 1) has been determined from powder X-ray diffraction (PXRD) data. In a systematic way, we have synthesized hydrated-TBTA (compound 2), two salts of TBTA [TBTA2––4,4′-bipy2+ (compound 3), 4,4′-bipy = 4,4′-bipyridine, and TBTA2––(3-AP+)2 (compound 4), 3-AP = 3-aminopyridine] and two co-crystals of TBTA [TBTA–DPTZ (compound 5), DPTZ = 3,6-di(pyridyl-2-yl)-1,2,4,5-tetrazine, and TBTA–(3-IP)2 (compound 6), 3-IP = 3-iodopyridine]. All of the compounds were characterized by structural, spectral, and thermal studies. Supramolecular structural analysis reveals that 1 forms a 2D supramolecular sheet structure by means of O–H···Br hydrogen bonding interactions and hydrated-2 forms a 3D supramolecular structure through water mediated hydrogen bonding interactions and π··· interactions. The O–H···N/O¯···H–N+ hydrogen bonding interactions between acid and base molecules give rise to 1D supramolecular chain structure in 3 and supramolecular trimers in 4, 5, and 6. Because of presence of charge assisted O¯···H–N+ hydrogen bonds between acid–base molecules, 3 and 4 form hydrogen bonds with solvent water molecules, and also both 3 and 4 form 3D supramolecular structures using both hydrogen bonding and π··· interactions. In co-crystal 5, solvent water molecules participate in crystallization in contrast to 6, and it has been observed that 5 forms 3D supramolecular structure, while 6 forms 2D supramolecular structure using both hydrogen bonding and π··· interactions. An investigation of intermolecular closed contacts has been carried out by Hirshfeld surface analysis, and associated 2D fingerprint plots reveal the similarities and differences of TBTA molecules in these six crystal structures. Photoluminescence spectra of all the compounds have been studied, and they reveal that with change of polarity around TBTA luminescent intensity of the compounds has been modified. I–V measurement indicates that 3 shows semiconducting behavior, and the ITO/3/Al sandwich structure acts as a Schottky barrier diode. The device exhibits an excellent rectification ratio (19 at ±1 V) with an ideality factor of 2.96. The semiconducting behavior of 3 is attributed to the formation charge assisted hydrogen bonding interactions between acid and base molecules.

The problems of the formation of the supramolecular and molecular structure of polymers are considered. Based on kinetic investigations of trioxane polymerization, the thermodynamic approach to the problem of regulating the supramolecular and molecular structure of polymers during synthesis is formulated. A method for producing polymers with the given supramolecular structure is suggested. It is noted that the application of this method allows one to regulate the structure during the synthesis of three-dimensional cross-linked polymer systems as single-component, filled, reinforced, and other composite materials.

Following a discussion of the historical perspective of the problem of order in amorphous polymers and a definition of terms, this paper reviews various topics in the literature. This problem and the related one of order in liquid alkanes (as a model for polyethylene) and amorphous polymers were omitted from or inadequately treated at this symposium. These topics relate both to short-range order (>50 Å) and long-range order (>100 Å) including supramolecular amorphous structure. Among the former are depolarized Rayleigh scattering and heats of mixing of normal alkanes; positron annihilation in polyisobutylene, x-ray scattering, dielectric loss data, and the constancy of the Tg/Tm ratio. Among the latter are the Mooney-Rivlin C2 constant and the general implications of short-range order for a supramolecular structure in long-chain polymer. Since local order exists in simple liquids, it must be present in amorphous polymers. A term, correlation of molecular orientations, CMO, introduced by Bothorel for low molecular weight liquids, is employed to express a feeling for this short-range order. The connectedness of an ensemble of polymer chains implies at once some supramolecular structure (even though being X-ray amorphous and, therefore, not having supramolecular order), since any given polymer chain can experience several CMO's not only with itself but with one or more neighboring chains. This supramolecular structure is dynamic above but frozen below Tg. This postulated supramolecular structure may result in the nodules seen by electron microscopy. The key unresolved problem of this symposium concerns the reality of, and the kinetics for, the assumed reversible transformation at Tm: random interpenetrating coils in melt chain-folded crystals in solid This dilemma is posed by neutron scattering on polyethylene showing (in some cases) random coils in the melt and by various types of physical evidence (not cited at the Symposium) for chain-folded crystals in the solid. A semicollapsed coil model with local order, proposed independently by Lindenmeyer and by Arzhakov et al., is consistent with a) ¯r0 2 1/2 values observed in the amorphous state, b) the existence of local order, and c) the reversible melting-recrystallization kinetics. Factors which favor a high CMO (local order) are 1) close-packing possibilities (no or small side chains), 2) polarity, 3) a stiff backbone, 4) regularity of backbone structure, and 5) a small temperature interval between the measuring temperature and Tg, i.e., small free volume. Elastomers as a class, especially when observed at T ≥ Tg + 100 °C, are least likely to exhibit local ordering but still are not completely free from it. It is observed that the ratio C2/C1 of the Mooney-Rivlin constants decreases with average area per chain molecule, suggestive of local order induced by orientation. Finally, suggestions are made for topics at a future symposium on amorphous order.

Self-assembly of supramolecular structure based on copper-lipopeptides isolated from e-waste bioleaching liquor.

The relationship between substance characteristic temperatures: autoignition, melting, flash, boiling is demonstrated and analyzed. Based on the oscillatory and step changes presence, a conclusion was made about the supramolecular structures presence and periodicity in the n-alkanes homologous series. A method for modeling equivalent lengths of peroxide supramolecular structures for predicting the explosion and fire hazard parameters of n-alkanes is proposed. An approximation dependence was developed for predicting autoignition temperatures tai of n-alkanes. It is shown that stoichiometric concentrations of the various supramolecular peroxide structures formation accord to different flammability and explosion limits. A correlation between tai and Anti-Knock Index (AKI) was established. An approximation dependence was developed for predicting n-alkanes AKI. The detonation propensity index КD was introduced based on cluster supramolecular structures modeling and melting temperatures. It is shown that КD indicator correlates with the n-alkanes AKI and with the explosives detonation velocity. The possibility of taking into account during calculations the supramolecular structures presence at the combustion stage confirms their existence.

Production, characterization and foamability of α-lactalbumin/glycomacropeptide supramolecular structures

Review: 108 refs.

Mechanofluorochromic or piezochromic fluorescence chemistry involves the switching and tuning of the luminescent properties of solid-state materials induced by exogenous forces, such as grinding, shearing, compression, tension, and so forth. Up until now, most reported mechanochromic systems, including liquid crystals, organic molecules, organometallic compounds, polymers, and dye-doped polymers, have displayed reversible two-color changes, which arise from either supramolecular or chemical structure transformations. However, fluorescent materials that undergo mechanically induced multicolor changes remain rare; this Minireview is focused on such materials. Topics are categorized according to the different applied forces that are required to induce the multicolor change, including mechanical control of either the supramolecular structures or the chemical structures, and mechanical control of both the supramolecular structures and chemical structures.

It is important to understand how the supramolecular structure of molecular junctions affects their performance. Such studies are challenging because it is difficult to separate electronic effects from supramolecular structural effects because both depend on each other. Here we show that by changing the connector group that connects the active component (a ferrocene unit) of a molecular diode to the backbone (an alkyl chain), both the electronic and supramolecular structures of the junctions are modified. The connector group determines the tilt angle of the Fc unit which in turn affects the packing structure of the molecular diodes. In this case, the supramolecular structure dominates over the electronic structure of the molecular diodes, and junctions with loosely packed SAMs result in poorly performing molecular diodes, while stiff, densely packed SAMs result in well-performing molecular diodes.

Study of the lignin model compound supramolecular structure by combination of near-field scanning optical microscopy and atomic force microscopy

Dicopper(II) complexes, namely [Cu2L(O2C–CHCH–C6H4-p-OH)]·2H2O (1·2H2O), [Cu2L(O2C–CH2–C6H4-p-OH)]·2H2O (2·2H2O) and [Cu2L(O2C–CH2CH2–C6H4-p-OH)]·0.5H2O (3·0.5H2O), having different carboxylate ligands with a p-hydroxyphenyl moiety and the pentadentate Schiff base N,N′-1,3-diylbis(salicylaldimino)propan-2-ol (H3L) in its trianionic form, were prepared and structurally characterized by X-ray crystallography. The complexes have a dicopper(II) unit with an alkoxo bridge from the Schiff base and the carboxylate, showing a three-atom bridging mode. The metal centres in a square planar CuNO3 coordination geometry are antiferromagnetically coupled in the asymmetrically double-bridged dicopper(II) core. A significant effect of the –CHCH–, –CH2– and –CH2CH2– spacers of the carboxylate ligands on the formation of different supramolecular structures is observed. Complex [Cu2L(O2C–CHCH–C6H4-p-OH)], 1, forms a helical supramolecular structure due to hydrogen-bonding interactions involving the p-hydroxy group of the phenol from the carboxylate and one phenoxo oxygen atom from the Schiff base. The lattice waters form a helical one-dimensional chain, in which alternate water molecules are anchored to the supramolecular host and the chain propagates along the crystallographic 21 screw axis. Complex 2 forms water aggregates of quasi-linear and pseudo-hexameric cyclic chair conformations involving lattice water molecules, and the previously mentioned para OH group phenoxo oxygen atom. Complex 3·0.5H2O shows the formation of a supramolecular one-dimensional chain structure due to hydrogen-bonding interactions between the p-OH group and the phenoxo oxygen atom. Two such supramolecular structures are linked by hydrogen-bonding interactions involving the lattice water. Differential scanning calorimetry (DSC) of 1·2H2O gives two endotherms at 61.5 and 88.5 °C for the loss of the “free” and the “anchored” water molecules, respectively. The overall change of enthalpy per water molecule is ∼36 kJ mol−1. Complex 2·2H2O shows an endotherm at 131 °C with a shoulder at ∼126 °C. The enthalpy change per water molecule is ∼26 kJ mol−1. The reversibility in loss or addition of lattice water molecules and the corresponding effect on the overall structure is probed by X-ray powder diffraction studies.

A new supramolecular metal-organic complex, {[Fe(CN)6]3-(H2bipy)2+(Hbipy)+·3H2O} (where bipy ipywhere biolecular metal-organic complex, {[Fe(CN)ccepted: 30 October 2022rized by single crystal X-ray crystallographic study (SC-XRD), powder X-ray diffraction (PXRD) and other spectroscopic analysis. Structural analysis reveals that the complex crystallizes in monoclinic space group P21/c and is a 3 D supramolecular complex. Cyanide-water hydrogen bonding interactions between {Fe(CN)6}3- and guest water molecules form a wave-like 2 D supramolecular layer structure parallel to the crystallographic ac-plane with the formation of rectangular cavities of dimension 10.6 × 9.8 Å. These 2 D layers are further connected by O3W-H2W3···O1W hydrogen bonding interactions to form a 3 D supramolecular structure with the creation of 1 D supramolecular channels along the crystallographic a-axis. The bi-cationic (H2bipy)2+ form two different N+-H···water hydrogen bonding interactions (N8+-H8···O2W and N7+-H7···O3W) with two different water molecules and reside within the rectangular cavities. Monocationic (Hbipy)+ moieties form a 1 D supramolecular chain structure through repetitive N···H-N+ hydrogen bonding interactions and are present within the 1 D supramolecular channels. In addition, these two different types of bipy moieties are interconnected to each other through π···π interactions. Hirshfeld surface analysis and the corresponding 2 D fingerprint plots clearly identify the presence of different types of supramolecular interactions between the two differently charged bipyridyl moieties and the host framework, and N-H/H-N contacts, corresponding to the hydrogen bonding interactions, have a significant contribution to the total surface. Both the absorption and emission spectra of the complex have also been studied.

Supramolecular structures formed from intermolecular association of repeated units of redox- and photo-active molecular monomers, in solution or in bulk, are of greater significance due to their importance in biology performing various functions making life on earth possible. One such supramolecular organization is ‘photosynthetic antenna-reaction centre’ complex found in green plants and bacteria which is involved in converting sunlight into chemical energy. The core antenna complex in bacteria form concentric rings, LH1 and LH2. LH1 consists of 16 ab protomers with a 68 Å hole in the middle while the LH2 consists of 9 ab protomers. These work in synergy in terms of light capture, transport and generating charge separated states.Several covalent and supramolecular structures containing fullerenes have been described in literature, however, only a few examples where the components are either redox or photochemically amphoteric. This property becomes especially important in light energy harvesting where the presence of an electron donor-acceptor pair is a basic necessity with at least one of them being photo-active to promote photoinduced charge separation leading to the formation of radical ion-pairs. Here, we describe the synthesis, by tether-directed functionalization, of a [60]fullerene e -bisadduct carrying two Zn-porphyrins (see figure inset), its supramolecular organization, and photophysical events. Remarkably, the supramolecular assembly of the present bisporphyrin-C60 forms donuts-shape aggregates (see figure for AFM image), primarily via pi-pi type charge transfer interactions, as demonstrated by means of optical absorption and emission, variable temperature 1H NMR and AFM and supported by theoretical calculations. More importantly, upon photoexcitation, the supramolecular assembly generates long-lived charge separated states of ~1 ms lifetime due to electron/hole delocalization within the supramolecular structure. The unprecedented results of the present study demonstrate the success of supramolecular organization of donor-acceptor pairs in biomimetic light energy harvesting. Figure 1

DOI: 10.31081/1681-309X-2024-0-2-32-43 Specialty 161. U.D.C. 552.576.1: 66.040.2: 661.183.2 CONVERTING LONG-FLAME COAL INTO NANOPOROUS CARBON MATERIAL DURING CARBONISATION WITH POTASSIUM HYDROXIDE © V.O. Kucherenko, Doctor of Chemical Scienses, Y.V. Tamarkina, Ph.D. in Chemical Sciences, A.V. Redko (L.M. Litvinenko Institute of Physical-Organic and Coal Chemistry of the National Academy of Sciences of Ukraine, 02160, Kyiv, Kharkiv Highway St., 50, Ukraine) The article is devoted to the study of changes in the supramolecular and porous structure of longflame coal during its transformation into a nanoporous material in the process of carbonisation with potassium hydroxide at a low KOH/coal ratio RKOH = 1.0 g/g. Samples of carbonaceous materials (CM) were prepared in argon by heating (4 deg/min) to a given temperature t (in the range of 350-825 °C), isothermal holding for 1 h, cooling, alkali washing, and drying. The samples are denoted as СM(t). The yield and elemental composition of CM were determined. The supramolecular structure of the CM was studied by XRD (Bruker D8). The interlayer distance in crystallites d002, height Lc, average diameter La and crystallite volume Vc, intensity I002 of the reflex (002) were determined. Based on the low-temperature (77 K) nitrogen adsorptiondesorption isotherms by the 2D-NLDFT-NS method, the integral and differential dependences of the specific surface area of SDFT (m2/g) and the pore volume V (cm3/g) on the average pore diameter (D, nm) were calculated (SAIEUS software). From these, the volumes of ultramicropores (Vumi), supermicropores (Vsmi), and micropores (Vmi) were calculated. The total pore volume was calculated from the amount of nitrogen adsorbed at a relative pressure of p/p0~1.0. Similarly, the specific surfaces of ultramicropores (Sumi), supermicropores (Ssmi), and micropores (Smi) were determined. It has been established that under conditions of alkaline carbonisation with KOH, long-flame coal is converted into СM with a yield of 45.3-70.2 %, a specific surface area of up to 1530 m2/g and a total volume of adsorbing pores of up to 1.091 cm3/g. With increasing temperature, the carbon content of CM decreases from 77.2 % to 71.3 % (at 500 °C), and then increases to 85.9 % (at 825 °C). The oxygen content increases to a maximum at 500 °C due to reactions in which KOH is a donor of Oatoms, and then decreases due to thermal destruction of functional groups and condensation reactions that increase the size of polyarenes of the secondary framework of the СM and form single Car-Car bonds between them. The main changes in the supramolecular structure occur above 400 °C and lead to an increase in d002 from 0.407 nm to 0.446 nm, a decrease in Lc from 0.872 nm to 0.699 nm, and an increase in the size of polyarenes La from 1.46 nm to 3.30 nm. Judging by the ~3-fold decrease in the I002 intensity, the crystallite content decreases significantly with increasing temperature, and the degree of amorphousness of the spatial framework of the CM increases. It was found that the thermally initiated reactions of coal with KOH form mainly pores with D ≤ 5 nm. With increasing temperature, the total pore volume and micropore volume increase monotonically. The values of Vumi and Vsmi increase up to 600 °C, and at 600-825 °C, the volume of Vumi decreases, since ultramicropores (D ≤ 0.7 nm) are transformed into supermicropores (D = 0.7-2.0 nm) due to the burnout of pore walls. The proportion of ultramicropore volume is maximum (23.9 %) in the sample СM(600). The proportion of the specific surface area of ultramicropores is maximum (56.3 %) in СM(500). The proportion of the micropore surface is dominant (92.6-97.0 %) in the CM obtained at t≥450 °C. The distributions of pore volume and specific surface area are characterised by maxima corresponding to subnanopores with D ≤ 1 nm, supermicropores and mesopores with D = 3-5 nm. For the СM samples obtained at 450-750 °C, there are no supermicropore maxima, but their formation occurs. It was determined that the most microporous CM are formed at 785-825 °C and are characterised by a specific surface area of 1514-1522 m2/g, a pore volume of 1.047-1.091 cm3/g, and a micropore surface area of 1415-1443 m2/g, which is not less than 93 % of the total surface. Keywords: long-flame coal, alkaline treatment, carbonisation, carbonaceous material, supramolecular structure, porosity. Corresponding author Y.V. Tamarkina, e-mail: tamarkina@nas.gov.ua

The impact of polymers’ supramolecular structure on water vapour sorption and drug release from films on the basis of some polysaccharide