Methyl Side Research Articles

Continuum elasticity and molecular dynamics of a pore in archaeal bolalipid membranes.

Archaea are famous for their ability to survive in extremely harsh environments, probably due to the unprecedented stability of their lipid membranes. Key features of archaeal lipids (bolalipids) that confer their stability are methyl side groups and cyclopentanes in the alkyl chains, as well as the specific shape of the molecule, which has two headgroups connected by two tails. However, the contribution of each structural parameter to membrane stability and the underlying physical mechanism remain unknown. Here, we used molecular dynamics simulations to develop a method for measuring the energy of pore formation in bolalipid membranes as an assessment of their stability. In addition, we improved our previously developed continuum model by introducing a new term responsible for the rigidity of the alkyl chain. We calculated the pore edge energy and evaluated the membrane stability in terms of membrane elasticity. We demonstrated that increased stability of bolalipid membranes resulted both from hindered lateral mobility of these amphiphilic molecules and increased pore energy due to specific structure of bolalipids. Methyl side groups of bolalipids reduce the mobility of the molecules and increase the pore line tension in the same way as in the case of conventional phytanyl lipids. Chain rigidity hinders the formation of the bend molecules at the pore edge, thus additionally increasing the pore formation energy.

Methyl side-groups control the Ia3̄d phase in core-non-symmetric aryloyl-hydrazine-based molecules.

Control of the formation of liquid crystalline Ia3̄d gyroid phases and their nanostructures is critical to advance materials chemistry based on the structural feature of three-dimensional helical networks. Here, we present that introducing methyl side-group(s) and slight non-symmetry into aryloyl-hydrazine-based molecules is unexpectedly crucial for their formation and can be a new design strategy through tuning intermolecular interactions: the two chemical modifications in the core portion of the chain-core-chain type molecules effectively lower and extend the Ia3̄d phase temperature ranges with the increased twist angle between neighboring molecules along the network. The detailed analyses of the aggregation structure revealed the change in the core assembly mode from the double-layered core mode of the mother molecule (without methyl groups) to the single-layered core mode. Such changes are explained in terms of modified intermolecular interactions in those phases employing quantum chemical calculations.

Self-Assembly of the Block Copolymer Containing Discotic Mesogens Driven by Liquid Crystalline Ordering Effect.

Block copolymers (BCPs) have attracted considerable attention due to their ability to form a variety of complex assemblies with diverse morphologies and functions in solution. By incorporating liquid crystalline (LC) moieties, the LC side chains significantly affect the morphologies and sizes of BCP assemblies. In this study, we synthesized the copolymer with an LC block containing triphenylene (HAT) discotic mesogen and short methylene side chains. By enhancing the π-π interaction between triphenylene discotic mesogens, and doping the discotic mesogens, the LC orderedness was significantly enhanced and able to dictate the self-assembly behaviors of the BCP in solution. Additionally, the lengths of resultant fibrillar micelles were easily tuned by adjusting the dopant content. More interestingly, two growth modes, nucleation growth and coupling, were observed during the formation of fibrils. Consequently, with long-term aging and sufficient concentration, a large portion of these fibrils underwent end-to-end coupling to form long fibrils, allowing the formation of organogel via inter-fibrillar entanglement.

SYNTHESIS OF THERMOPLASTIC POLYURETHANE USING AROMATIC DIOLS AS A CHAIN EXTENDER AND DEVELOPMENT OF ADHESIVE COMPOSITIONS BASED ON IT

Thermoplastic polyurethane based on oligobutyleneglycoladipinate, 4,4'-diphenylmethanediisocyanate and a chain extender has been synthesized, as which it is proposed to use aromatic diol - 2,2-bis-[4-(2-hydroxyethoxy)phenyl]propane. The synthesis was carried out in a one-step method with a ratio of reagents providing a lack of isocyanate groups. The final product was a linear copolymer with terminal hydroxyl groups. To compare properties using a similar technology, a thermoplastic was obtained in which the role of the chain extension was performed by aliphatic diol - 1,4-butanediol. The sample obtained with the participation of aromatic diol is amorphous, low-modulus and there is no residual deformation after rupture. The use of aliphatic diol leads to the formation of a crystallized high-modulus polymer with high residual deformation and hardness. The observed differences are associated with the introduction of side methyl groups and simple ether bonds into the structure of a rigid polymer block formed by an aromatic diol. The latter violate the ordering of the packaging of macromolecules and increase their ability to elastic recovery. In addition, the content of aromatic fragments in the hard block increases due to the use of aromatic diol. They contribute to the amorphization of the polymer, increase its strength, and also increase the temperature of the beginning of destruction and the coke residue. At the same time, the thermoplastics under discussion are inferior to the analog synthesized using aliphatic diol in terms of temperatures corresponding to the half-life of the decomposition stage and the completion of the decomposition stage. This is due to the presence of in the hard block of the first, relatively non-thermally stable simple ether bonds. On the basis of the proposed thermoplastic, a two-component adhesive has been developed, which, in terms of bonding strength, surpasses household adhesives, which include polyurethane thermoplastic obtained using aliphatic diol. For citation: Bakirova I.N., Mineeva T.A. Synthesis of thermoplastic polyurethane using aromatic diols as a chain extender and development of adhesive compositions based on it. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2024. V. 67. N 11. P. 106-113. DOI: 10.6060/ivkkt.20246711.7040.

Synthesis and properties of modified polyimides containing multiple side methyl and biphenyl structures

With the rapid development of 5 G technology and microelectronics, there is an urgent demand to design and develop modified polyimide films with low dielectric constant as flexible matrix materials. In this work, a diamine containing multiple side methyl and biphenyl groups was synthesized by aromatic nucleophilicsubstitution reaction and oxidation-reduction reaction, respectively. Furthermore, this monomer was used to polymerize with four different commercially available dianhydrides (ODPA, BTDA, BPDA, and PMDA) to produce a class of polyimides (PI 3a∼3d). The structures of the diamine and its PIs are characterized, and the relationship between the structure and properties of the obtained PI films is investigated. These modified PIs are easy to cast into films and have low dielectric constants and water absorption. Their dielectric constants and dielectric losses are in the range of 2.66–2.91 and 0.00579–0.00677 at 1 MHz, respectively. Meanwhile, these PIs also maintains good thermal stability, with glass transition temperatures (T g) higher than 284 °C and 10% weight loss temperatures in the range of 496–505 °C at N2.

Controlling curcumin/acrylic polymer interactions for tailored delivery systems

Controlling curcumin/acrylic polymer interactions for tailored delivery systems

Tribological Behavior of Sulfonated Polyether Ether Ketone with Three Different Chemical Structures under Water Lubrication.

With the development of the shipbuilding industry, it is necessary to improve tribological properties of polyether ether ketone (PEEK) as a water-lubricated bearing material. In this study, the sulfonated PEEK (SPEEK) with three distinct chemical structures was synthesized through direct sulfonated polymerization, and high fault tolerance and a controllable sulfonation degree ensured the batch stability. The tribological and mechanical properties of SPEEK with varying side groups (methyl and tert-butyl) and rigid segments (biphenyl) were compared after sintering in a vacuum furnace. Compared to the as-made PEEK, as the highly electronegative sulfonic acid group enhanced the hydration lubrication, the friction coefficient and wear rate of SPEEK were significantly reduced by 30% and 50% at least without affecting the mechanical properties. And lower steric hindrance and entanglement between molecular chains were proposed to be partially responsible for the lowest friction behavior of SPEEK with methyl side groups, making it a promising and competitive option for water-lubricated bearings.

Linearly-Changed Thermal Behavior and Depressed Brill Transition in Long-Chain Polyamides Substituted by Methyl Side Groups.

Side substitution is an effective way of functionalizing and modifying the properties of polyamides. Meanwhile, side substitution would significantly influence the crystallization kinetics and polymorphic phase transition of polyamides, which, however, has not been well elucidated. Herein, we synthesized the side-substituted long-chain polyamides with various content of methyl pendent groups and investigated their crystallization and phase transition behaviors. We find that the thermal parameters of side-substituted polyamides vary linearly with the side group content, analogous to the isomorphic crystallization of random copolymers. All the solution-crystallized polyamides experience the α-γ Brill transition during heating, with the Brill transition temperature linearly decreasing as the side group content increases. Intriguingly, the γ-α transition of polyamides during cooling is suppressed with the presence of side methyl groups due to the difficulty in H-bond reorganization and gauche-trans conformational changes. This work has demonstrated the critical role of side substitution in the polymorphic crystallization and phase transition of long-chain polyamides.

Enhanced energy storage characteristics of the epoxy film with rigid phenyl-flexible etherified methylene chains

Enhanced energy storage characteristics of the epoxy film with rigid phenyl-flexible etherified methylene chains

Synthesis of a novel polysiloxane as an inhibitor in water-based drilling fluids and an assessment of the inhibition mechanism

Synthesis of a novel polysiloxane as an inhibitor in water-based drilling fluids and an assessment of the inhibition mechanism

N-heterocyclic carbenes – The design concept for densely packed and thermally ultra-stable aromatic self-assembled monolayers

N-heterocyclic carbenes – The design concept for densely packed and thermally ultra-stable aromatic self-assembled monolayers

Synthesis and properties of biodegradable poly(ethylene succinate) containing two adjacent side methyl groups

Synthesis and properties of biodegradable poly(ethylene succinate) containing two adjacent side methyl groups

Silicone Polymer Thin Films Fabricated by Ion‐Assisted Deposition Methods

The ion‐assisted vapor deposition (IAD) method is utilized to prepare silicone polymer thin films with low surface energy. Methacryl‐modified silicone oligomer is deposited under irradiation of argon ions with various ion energies and currents. Fourier transform infrared analysis and solvent durability test reveal that the polymerization reaction is enhanced with increasing ion energy. Smooth and insoluble films are obtained under ion irradiation at the energy of 1 kV. The films have surface free energy of about 26 mJ m−2, and the peeling strength of an adhesive tape on their surface can be controlled by the ion current of IAD. X‐ray photoelectron spectroscopy analysis shows that the ion irradiation induces dissociation of methyl side groups and cross‐linking by Si–O network formation, leading to an increase in the peeling strength and improvement in film robustness. The silicone films deposited by IAD have potential applicability to the anti‐adhesive surfaces.

Enhancement of tracking resistance of silicone rubber through charge dissipation and radical capture by fluorosilane-grafted iron oxide

Fluorosilane-grafted iron oxide (F-Fe2O3) was prepared via surface grafting reaction between iron oxide and perfluorooctyltriethoxysilane. The effect of F-Fe2O3 on the tracking resistance (TR) of addition-cured liquid silicone rubber (ALSR) was investigated by the inclined-plane test (IPT), surface potential decay test (SPDT), thermogravimetry (TGA), corona aging test and scanning electron microscopy (SEM). F-Fe2O3 delayed the occurrence of the intensive arc discharge and reduced the number of arc discharges. The corona resistance and TR of ALSR were effectively improved. ALSR/F-Fe2O3 with 0.15 phr F-Fe2O3 content passed the IPT at 4.5 kV, showing an erosion mass of 3.17%. The hydrophobicity and thermal stability of ALSR were also enhanced. The SPDT showed that F-Fe2O3 effectively dissipated charge. The results of thermal stability and corona resistance tests revealed that F-Fe2O3 could capture free radicals generated by the oxidation of methyl side groups of ALSR chains and thus inhibit the thermal degradation of ALSR during the arc discharge. Moreover, the charge dissipation by F-Fe2O3 could diminish the accumulation of charges in ALSR and reduce the damage of charges to the chains during arc discharge. Therefore, the TR of ALSR was enhanced.

Effect of group electronegativity on spectroscopic, biological, chromogenic sensing and optical properties of 2-formyl-benzene sulfonic acid sodium salt-based Schiff bases

Effect of group electronegativity on spectroscopic, biological, chromogenic sensing and optical properties of 2-formyl-benzene sulfonic acid sodium salt-based Schiff bases

Thermal decomposition investigation on heat-resistant poly(dimethylsilylene ethynylenemethylphenylene-methylenemethylphenyleneethynylene) resins

Thermal decomposition investigation on heat-resistant poly(dimethylsilylene ethynylenemethylphenylene-methylenemethylphenyleneethynylene) resins

Experimental study on the effect of cold soaking with liquid nitrogen on the coal chemical and microstructural characteristics.

In this paper, the chemical microstructure of coal samples is quantitatively analyzed experimentally before and after liquid nitrogen cold soaking, by using elemental analyzer, X-ray diffractometer, and Fourier infrared spectrometer, including the reverse side of chemical composition of elements, organic matter, and functional groups. It was found that with the increase of coal metamorphism, the contents of carbon, nitrogen, and sulfur elements gradually increase, while those of hydrogen and oxygen elements gradually decrease. In addition, as the degree of metamorphism increases, the graphitization phenomenon of coal becomes weaker, the interlayer spacing of aromatic rings (d002) increases, the structure of coal crystal nucleus is loose, its order is weakened, the crystal volume becomes smaller, and the void structure unit increases. The FTIR spectra of each coal sample could be divided into four absorption bands, i.e., the aromatic structure, oxygen-containing functional group, aliphatic group, and hydroxyl absorption band. After cold soaking of liquid nitrogen, the peak intensity areas of aromatic and aliphatic structures decrease, while those of oxygenated functional groups and hydroxyl groups increase, and the values of A(C = O)/A(C-O) increase and those of A(CH3)/A(CH2) decrease, mainly due to the gradual decrease of methylene side chains and increase of methylene straight chains. The present results are helpful to further reveal the mechanism of adsorption-resolution deformation of coal body due to cold immersion of liquid nitrogen.

Flexibility, size and hydrophobicity of alkyl side groups in methoxy-poly (ethylene glycol)-polypeptide for the nano-assembly and thermo-sensitivity

Tailoring of amino acid residues is a feasible strategy to design the structure of peptide for special application. We selected poly(ethylene glycol) and α-amino acids with hydrophobic alkyl side group (L-alanine，L-valine and L-leucine) to synthesize di-block co-polypeptide. The copolymers with methyl side group self-assembled into random coil in majority and aggregated further into stable spherical nanoarchitectures with a little filament owing to the small size, less flexibility and less hydrophobicity of methyl group. By lengthening peptide block, the copolymer self-organized into overwhelming β-sheet and ordered nanorods or nanofibers due to the strengthening hydrophobicity as the copolymers with isopropyl side group did. The copolymers with isobutyl side groups showed cloudy solutions and irregular morphology because the flexibility and large size of isobutyl groups hampered the regular stacking of β-plated sheets and agglomerated into micro-sized precipitates despite of the most hydrophobicity. As temperature rising, both the transition of α-helix to β-sheet and PEG dehydration contributed to the sol-gel transition for the copolymers with methyl side group, while PEG dehydration was the primary reason of sol-gel transition for the copolymers with isopropyl side group. In this article, we first disclosed the self-organization process of mPEG-b-polypeptide, which would lay the foundation for the designing of polypeptide-related materials with well-defined properties. How the alkyl side group affects the preliminary secondary structure and the further coordinated self-organized process of the polypeptide materials that we discussed in this paper. Based on the experimental results about secondary structures and morphologies of the comparable copolymers with different side groups, we proposed a three levels of organization process for the copolymers. By this mode of self-organization process, compared to the hydrophobicity, the flexibility or rigid nature of the side group, namely the variation of the side group configuration was more important to determine the stacking regularity of the β-sheet layers and therefore the stability of self-assembled basic nano-structural units and their final size of aggregating entities. • Less flexible and small methyl group caused random coil. • Flexible and large isobutyl groups hampered the regular stacking of β-sheets. • Appropriate flexibility, size and hydrophobicity of alkyl side groups provoked ordered β-sheet stacking. • Transition of random coil to β-sheet and PEG dehydration induced sol-gel transition. • Ordered stacking of β-sheets stabilized polypeptide against thermal stimulus.

Study on polyurethane elastomer modification for improving low-temperature resistance of high-capacity polyurethane elastomeric bearing for bridges

• Side methyl groups in PTGL hindered the crystallization of soft segments in PUE. • Shear modulus of PUE decreased with incorporating PTGL at subzero temperatures. • HPEB prepared with new PUE still exhibited high enough vertical bearing capacity. • Adding PTGL could significantly improve the low-temperature resistance of HPEB. Seismic isolation laminated elastomeric bearings are applied worldwide in bridges to reduce vibration and prevent collapse. Currently, the high-capacity polyurethane elastomeric bearings (HPEB) are favored in long-span bridges due to their super-high bearing capacity, low cost, and simple manufacturing process. However, there are many countries and regions in the world with extremely cold climates and are covered by ice and snow. At subzero temperatures, the stiffness of polyurethane elastomers (PUEs), which are an important component of HPEB, increases significantly, rendering HPEB ineffective in protecting bridges in cold regions from earthquake hazards. In this work, an attempt was made to modify the PUE as well as to improve the low-temperature resistance of HPEB by introducing 3-methyl-tetrahydrofuran/tetrahydrofuran co-polyether glycol (PTGL). Specifically, a series of microscopic characterization experiments (FT-IR, AFM, DSC, and DMA) were performed to study microphase separation and crystallization phenomena of the newly developed PUE. Moreover, the mechanical verification experiments were performed for the PUE and HPEB with different amounts of PTGL, including tensile, compression, and shear tests. All tests are performed at 23, 0, −10, and −20 °C temperatures respectively. The mechanical experiments demonstrate that the introduction of PTGL significantly reduces the shear modulus ( G ) and horizontal stiffness ( K h ) of HPEB at low temperatures, that is, improves the low-temperature resistance of HPEB. Therefore, this research is of great significance for the application of isolation bearings in cold regions.

Effect of Hydrophobic Side Group on Structural Heterogeneities and Mechanical Performance of Gelatin-Based Hydrogen-Bonded Hydrogel

Hydrogen bonds stabilized by hydrophobic side groups have been widely applied to realize high toughness of hydrogels. Herein, we studied the effect of the content of the hydrophobic methyl side group on the structure and mechanical properties of tough hydrogen-bonded gelatin/poly (methacrylic acid–co-acrylic acid) (G/Mx-Ay) hydrogels by alternating the content of methacrylic acid (MAA) in the methacrylic acid–acrylic acid copolymer (MAA-co-AA). The content of MAA did not affect the hydrogen-bond formation between the MAA-co-AA and gelatin but affected the phase-separated structure. With an increase in the MAA content, the local structure of the hydrogels with similar water content transformed from a “network” structure to a “bicontinuous” phase-separated structure and to a phase-separated structure with wide size distribution. The hydrogels with the same structure exhibited similar viscoelastic behaviors, and the G/Mx-Ay hydrogels with “bicontinuous” phase separation exhibited the best mechanical properties with an optimal Young’s modulus of ∼7.5 MPa and fracture tensile stress of ∼10 MPa.