Cold Crystallization and the Molecular Structure of Imidazolium-Based Ionic Liquid Crystals with a p-Nitroazobenzene Moiety

Large-scale cultivation of Synechocystis sp. PCC6803 for the production of Poly(3-hydroxybutyrate) and its potential applications in the manufacturing of bulk and medical prototypes

Polyhydroxyalkanoates (PHAs) are biopolymers produced by microorganisms under nutrient limiting conditions and in the presence of excess carbon source. PHAs have gained popularity as a sustainable alternative to traditional plastics. However, large scale production of PHAs is economically challenging due to the relatively high costs of organic carbon. Alternative options include using organisms capable of phototrophic or mixotrophic growth. This study aimed at the production of poly(3-hydroxybutyrate) P(3HB), a type of PHA, at pilot scale using the freshwater cyanobacterium Synechocystis sp. PCC6803. First, to identify optimal conditions for P(3HB) production from Synechocystis sp. PCC6803, different supplemental carbon source concentrations and salinity levels were tested at laboratory scale. The addition of 4 g/L acetate with no added NaCl led to P(3HB) accumulation of 10.7 % dry cell weight on the 28th day of cultivation. Although acetate additions were replicated in an outdoor 400 L serpentine photobioreactor, P(3HB) content was lower, implying uncontrolled conditions impact on biopolymer production efficiency. An optimized P(3HB) extraction methodology was developed to remove pigments, and the biopolymer was characterized and subjected to 3D printing (fused deposition modelling) to confirm its processability. This study thus successfully led to the large-scale production of P(3HB) using sustainable and environmentally friendly cyanobacterial fermentation.

Crystallization kinetics of (S)-4'-(1-methylheptyloxycarbonyl)biphenyl-4-yl 4-[4-(2,2,3,3,4,4,4-heptafluorobutoxy)but-1-oxy]-2-fluorobenzoate

Chiral liquid crystalline compounds belonging to the homologous series of (S)-4'-(1-methylheptyloxycarbonyl)biphenyl-4-yl 4-[m-(2,2,3,3,4,4,4-heptafluorobutoxy)alk-1-oxy]-2-fluorobenzoates show various behaviors on cooling depending on the length of the CmH2m chain. The homologue with m = 2 crystallizes, while for m = 5, 6, 7, and presumably also for m = 3, the glass of the anticlinic smectic CA* phase is formed. The previous results for m = 4 suggest that this homologue may also be a glassformer. This paper presents the study of the crystallization kinetics for the compound with m = 4 in isothermal conditions (by polarizing optical microscopy) and for the 5-40 K min-1 cooling rates (by differential scanning calorimetry). Microscopic observations enable estimation of the energy barrier for nucleation, which equals 409 kJ mol-1. The threshold cooling rate necessary for complete vitrification of the smectic CA* phase, obtained by extrapolating the enthalpy change during crystallization to zero, is equal to 81 K min-1 or 64 K min-1 for the linear and parabolic fits, respectively. The structural studies by X-ray diffraction show that crystal phases have lamellar structures both in the pristine sample and after crystallization from the melt but with different layer spacing. A weak relaxation process is detected in the sample after melt crystallization, revealing the presence of the conformational disorder. The dynamic glass transition temperature of the SmCA* phase, estimated from the relaxation time of the PH process (as the α-relaxation time could not be registered in a wide enough temperature range), is 244 K.

A comparative study of ammonia solubility in imidazolium-based ionic liquids with different structural compositions

Four imidazolium-based ionic liquids (ILs) with two cations 1-pentyl-3-butylimidazolium [PBIM]+ and 1-benzyl-3-butylimidazolium tetrafluoroborate [BzBIM]+, and two anions tetrafluoroborate (BF4-) and trifluoromethanesulfonate (OTf-) were synthesized for NH3 solubility enhancement. The structural, thermal, and electrochemical stabilities, ionic conductivity, and viscosity of the four ILs, namely, [PBIM]BF4, [BzBIM]BF4, [PBIM]OTf, and [BzBIM]OTf, were investigated. Due to the intermolecular interaction of the benzyl group attached to the imidazolium ring, [BzBIM]+-based ILs exhibited higher thermal stability but lower ionic conductivity compared to [PBIM]+-based ILs. Further, the NH3 solubility in all ILs was measured using a custom-made setup at temperatures ranging from 293.15 to 323.15 K and pressures ranging from 1 to 5 bar. The effects of the cation and anion structures of ILs, as well as pressure and temperature, on the NH3 solubility in the ILs were also investigated. [PBIM]BF4 showed the best solubility because of its high free volume and low viscosity. Density functional calculations validated the superior NH3 solubility in [PBIM]BF4, attributable to the minimal reorganization of the [cation]anion complex geometry during the solvation process, yielding a low solvation free energy. The findings of this study suggest that ILs exhibit a high NH3 solubility capacity and cation and anion structures considerably affect the NH3 solubility in ILs.

Molecular aggregation by hydrogen bonding in cold-crystallization behavior of mixed nucleobases analyzed by temperature-controlled infrared spectroscopy

The cold-crystallization behaviors of dodecyl-substituted nucleobases (adenine, uracil, and thymine) were analyzed. The dodecyl derivative from uracil alone did not exhibit cold crystallization; however, a mixture of adenine and uracil derivatives at a molar ratio of 1 : 1 exhibited cold crystallization. These results are similar to the thermal behavior of dodecyl derivatives of adenine and thymine alone and in mixtures reported in a previous study. Temperature-controlled infrared spectroscopy was used to observe the molecular assembly states of the liquid, supercooled state, and cold-crystallized compounds. Hydrogen-bonded molecular pairs in the high-temperature liquid state, multiple hydrogen-bonded networks in the supercooled state, and reverse Hoogsteen-type complementary hydrogen bonds in cold-crystallized compounds were observed using infrared spectroscopy. The heterogeneity of the system, due to multiple types of hydrogen bonding, retarded the crystallization rate, resulting in supercooling and cold crystallization. Infrared spectroscopy, which can be used to measure the aggregation state of molecules, including the liquid and supercooled states, is an effective analytical method for clarifying the process of cold crystallization.

Remarkable Enhancement of Hole Mobility of Novel DA-D'-AD Small Molecules by Thermal Annealing: Effect of the D'-Bridge Block

Conjugated small molecules are advanced semiconductor materials with attractive physicochemical and optoelectronic properties enabling the development of next-generation electronic devices. The charge carrier mobility of small molecules strongly influences the efficiency of organic and hybrid electronics based on them. Herein, we report the synthesis of four novel small molecules and their investigation with regard to the impact of molecular structure and thermal treatment of films on charge carriers' mobility. The benzodithiophene-containing compounds (BDT) were shown to be more promising in terms of tuning the morphology upon thermal treatment. Impressive enhancement of hole mobilities by more than 50 times was found for annealed films based on a compound M4 comprising triisopropylsilyl-functionalized BDT core. The results provide a favorable experience and strategy for the rational design of state-of-the-art organic semiconductor materials (OSMs) and for improving their charge-transport characteristics.

Heating-Induced Switching to Hierarchical Liquid Crystallinity Combining Colloidal and Molecular Order in Zwitterionic Molecules

Hierarchical self-assemblies of soft matter involving triggerable or switchable structures at different length scales have been pursued toward multifunctional behaviors and complexity inspired by biological matter. They require several and balanced competing attractive and repulsive interactions, which provide a grand challenge in particular in the "bulk" state, i.e., in the absence of plasticizing solvents. Here, we disclose that zwitterionic bis-n-tetradecylphosphobetaine, as a model compound, shows a complex thermally switchable hierarchical self-assembly in the solvent-free state. It shows polymorphism and heating-induced reversible switching from low-temperature molecular-level assemblies to high-temperature hierarchical self-assemblies, unexpectedly combining colloidal and molecular self-assemblies, as inferred by synchrotron small-angle X-ray scattering (SAXS). The high-temperature phase sustains birefringent flow, indicating a new type of hierarchical thermotropic liquid crystallinity. The high-temperature colloidal-level SAXS reflections suggest indexation as a 2D oblique pattern and their well-defined layer separation in the perpendicular direction. We suggest that the colloidal self-assembled motifs are 2D nanoplatelets formed by the lateral packing of the molecules, where the molecular packing frustration between the tightly packed zwitterionic moieties and the coiled alkyl chains demanding more space limits the lateral platelet growth controlled by the alkyl stretching entropy. An indirect proof is provided by the addition of plasticizing ionic liquids, which relieve the ionic dense packings of zwitterions, thus allowing purely smectic liquid crystallinity without the colloidal level order. Thus, molecules with a simple chemical structure can lead to structural hierarchy and tunable complexity in the solvent-free state by balancing the competing long-range electrostatics and short-range nanosegregations.

Non-isothermal cold crystallization of liquid crystalline porphyrins

A series of liquid crystalline porphyrins was synthesized, purified, and characterized. Differential scanning calorimetry (DSC) and hot-stage polarized optical microscopy (HS-POM) revealed that the porphyrins in the series with shorter alkyl arm lengths exhibit kinetic cold crystallization, wherein the molecules spontaneously organize into large, disc-like structures that remain stable upon cooling. Using DSC, the kinetic and thermodynamic parameters related to these materials were determined. Analysis of non-isothermal crystallization revealed the presence of multiple nucleation and growth processes related to cold crystallization.

The crystal structure of imidazolium nitrate, C3H5O3N3

C3H5O3N3, tetragonal, P43212 (no. 96), a = 7.2479(2) Å, c = 21.6138(8) Å, V = 1135.42(8) Å3, Z = 8, Rgt (F) = 0.0344, wRref (F 2) = 0.0903, T = 100 K.

Cold crystallization and photo-induced thermal behavior of alkyl-derivatized diarylethene molecules

The thermal behavior of alkylated diarylethene molecules (2,3-bis(2,4,5-trimethyl-3-thienyl)-N-alkylmaleimides; DAE-Cn) was investigated. DAE-C1 and DAE-C2 exhibited cold crystallization, which is a heat-storage phenomenon. In addition, DAE-Cn showed photoisomerization; the open-ring isomer O-DAE-Cn was formed by visible light irradiation and transformed to the closed-ring isomer C-DAE-Cn by UV light irradiation. X-ray diffraction and optical microscopy analyses revealed that O-DAE-Cn exhibited cold crystallization and C-DAE-Cn showed poor crystallinity. UV irradiation (365 nm) inhibited cold crystallization, and visible light irradiation (525 nm) triggered cold crystallization, suggesting that heat storage by the cold crystallization of DAE-Cn can be photo-controlled.

The alkylated diarylethene molecules exhibited cold crystallization, and their thermal behavior can be photo-controlled.