Methyl Side Research Articles

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

In this work, we investigate the interaction between curcumin and biocompatible polymethacrylates (methyl, ethyl, and n-butyl side groups). Blend samples were produced using the salt leaching technique to increase the contact area in the ionic medium with pH 2.0, 5.0, 7.4, and 8.0. Using curcumin photoluminescence (PL) spectra to determine release profiles, we found a 6-fold higher quantity and a 3-fold higher release ratio for poly(n-butyl methacrylate) (PnBMA). Changes in the ionic form of curcumin were observed with PL blue shift and decrease in the characteristic time, from ca. 435 min at pH 2.0 and 5.0 to 192 min at pH 7.4 for PnBMA. The relative importance of curcumin interactions with the side and main polymer chains could be determined by interpreting the release profiles. With curcumin interaction controlled by pH and the length of the polymer side chain, one may envisage tailored drug delivery systems focusing on prolonged release.

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

The introduction of highly polarized flexible segments into polymer molecular chains is an effective means to improve the dielectric constant and mechanical flexibility of polymers, which is important for improving the energy storage characteristics and applicability for the roll-to-roll process of metallic film capacitors. However, the introduction of flexible segments may adversely affect the heat resistance of polymer materials, which limits their application at high working temperatures. In this work, we have prepared a novel epoxy film with excellent comprehensive properties by introducing rigid phenyl and flexible etherified methylene side chains. For instance, the optimal epoxy film showed an energy storage density of 7.06 J cm–3 and 85% charge-discharge efficiency at room temperature and 420 kV mm–1. At 200 kV mm–1 and 110 °C, a working condition for the application of the electric vehicle, the prepared film still showed an energy storage density of 1.5 J cm–3 and charge-discharge efficiency of 86%, which is 3 times that of BOPP film. This work provides an idea for material designs of high-performance polymer film capacitors.

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

In oil and gas well engineering, shale wellbore stability poses significant challenges. Developing shale inhibitors with high inhibition and resistance to elevated temperatures is crucial to address wellbore stability in deep wells. In this study, an amphoteric polysiloxane known as SC-POTD was synthesized as a heat-resistant shale inhibitor for water-based drilling fluid. The inhibition properties were evaluated using linear swelling, rolling recovery, and rheological tests, and the results were compared with the properties of potassium chloride and commercial polyamines. Various analysis methods were conducted to understand the interaction mechanism between the clay particles and polymer molecules, including X-ray diffraction test, Zeta potential determination, particle size analysis, contact angle measurement, and scanning electron microscope observation. SC-POTD with an amphoteric structure can effectively adsorb on the clay surface through electrostatic force, compressing the electric double layer of clay and forming a hydrophobic layer. Furthermore, SC-POTD can embed in the crystal interlayer, exchange cations and discharge interlayer water, effectively inhibiting hydration. With the flexibility of the Si-O backbone and the small steric hindrance of methyl side groups, SC-POTD may have a better affinity with bentonite containing siloxane tetrahedrons, and cooperate with the quaternary ammonium group to enhance clay interlayer interaction. In addition, the temperature resistance of SC-POTD can be improved by the siloxane backbone with larger bond energy. The results indicated that modified polysiloxane may find a promising application as heat-resistant drilling fluid additives.

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

Self-assembled monolayers (SAMs) of N-heterocyclic carbenes (NHCs) on metal substrates are currently one of the most promising systems in context of molecular-scale engineering of surfaces and interfaces, crucial for numerous applications. Interest in NHC SAMs is mainly driven by their assumingly higher thermal stability compared to thiolate SAMs most broadly used at the moment. Most of the NHC SAMs utilize imidazolium as an anchoring group for linking molecules to the metal substrate via carbene C atom. It is well established in the literature that standing up and stable NHC SAMs are built only when using bulky side groups attached to nitrogen heteroatoms in imidazolium moiety, which, however, leads to monolayers exhibiting much lower packing density compared to thiolate SAMs. Here, by combined X-ray photoelectron spectroscopy, near-edge X-ray absorption fine structure spectroscopy, and temperature-programmed secondary ion mass spectrometry analysis, we demonstrate that using NHCs with small methyl side groups in combination with simple, solution-based preparation leads to the formation of aromatic monolayers exhibiting at least doubled surface density, upright molecular orientation, and ultra-high thermal stability compared to the NHC SAMs reported before. These parameters are crucial for most applications, including, in particular, molecular and organic electronics, where aromatic SAMs serve either as a passive element for electrode engineering or as an active part of organic field effect transistors and novel molecular electronics devices.

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

To adjust the structure and properties of biodegradable poly(ethylene succinate) (PES), a series of novel poly(ethylene succinate-co-2,3-butylene succinate) (2,3-PEBS) copolyesters with low contents of 2,3-butylene succinate unit (2,3-BS) were successfully synthesized in this research via a two-stage melt polycondensation. 2,3-PEBS showed the same main chain structure as PES, except that a few of two adjacent side methyl groups were randomly linked with the main chain; therefore, 2,3-PEBS may be regarded as novel PES containing two adjacent side methyl groups. The thermal parameters, crystallization behavior, and mechanical property of 2,3-PEBS copolyesters and PES were systematically studied and compared with each other. The compositions of ethylene succinate (ES) to 2,3-BS deviated significantly from the feed ratio of ethylene glycol to 2,3-butanediol (2,3-BDO) due to the low reactivity of 2,3-BDO. The results revealed that the introduction of a small amount of two adjacent side methyl groups brought an obvious variation in the thermal and mechanical properties of PES. However, 2,3-PEBS displayed the same crystallization mechanism and crystal structure as PES. Through the introduction of a few of two adjacent side methyl groups, novel PES with significantly improved mechanical properties was synthesized, which should be interesting and important for a better understanding of the structure and properties to prepare novel biodegradable polymers from a sustainable viewpoint.

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

In this study, 2-formylbenzenesulfonic acid sodium salt-based Schiff bases were synthesized from the reactions of 2-formylbenzenesulfonic acid sodium salt with 2-amino-4-chlorophenol and 2-amino-4-methylphenol. The structure of the compounds was determined by FTIR, UV–Vis and NMR spectroscopy methods using both experimental and DFT methods. The anion sensor properties of the compounds were investigated both UV–Vis spectroscopically and calorimetrically. In addition, the antimicrobial activities, interactions with DNA, DNA cleavage and antioxidant activities of Schiff bases were investigated. Additionally, the effects of group electronegativity on the spectroscopic, biological, chromogenic sensing and optical properties of chlorine and methyl side groups and sodium 2-sulfobenzalidene-aminophenol-based Schiff bases were investigated.

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

Thermal decomposition of heat resistant poly(dimethylsilylene ethynylenemethylphenylenemethylenemethylphenyleneethynylene) (PSMA) resins has been investigated by TGA, Py-GC–MS, and TGA-MS analysis techniques. The decomposition kinetics was studied with Kissinger-Akahira-Sunose method (KAS method). The results show that the decomposition of the cured PSMA resins is obviously influenced by the presence and locations of the side methyl groups on the benzene rings and their decomposed fragments are different. The side methyl groups on benzene rings easily break down, which make the resins decompose at lower decomposition temperatures. The cleavage of the side methyl groups further induces the decomposition of the main chains of the resins and results in low residue yields. The decomposition mechanisms of the cured PSMA resins are suggested.

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 random coil 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.

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.

(+)-Limonene-Lactam: Synthesis of a Sustainable Monomer for Ring-Opening Polymerization to Novel, Biobased Polyamides.

In this work, the synthesis of limonene lactam starting from limonene epoxide and its subsequent ring-opening polymerization (ROP) to novel polyamides is presented. Sustainable, biobased materials are gaining interest as replacements of conventional, petroleum-based materials, and even more important, as high-performance materials for new applications. Terpenes-structurally advanced biobased compounds-are therefore of great interest. In this research, limonene lactam, a novel biobased monomer for preparing sustainable polyamides via ROP, can be synthesized. Limonene lactam possesses an isopropylene and a methyl side group, thus stereocenters posing special challenges and requirements for synthesis, analysis and polymerization. However, these difficult-to-synthesize structural elements can generate novel polymers with unique properties, e.g., functionalizability. In this work, a sustainable monomer synthesis is established, and simplified to industrial needs. For the sterically demanding in-bulk ROP to limonene polyamides, various initiators and conditions are tested. Polyamides with more than 100 monomer units are successfully synthesized and confirmed via nuclear magnetic resonance (NMR) spectroscopy and gel permeations chromatography (GPC). Differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA) are used to analyze its thermal properties. In summary, a sustainable monomer synthesis is established, and promising polyamides with intact double bond and interesting thermal properties are achieved.

Terphenyl-based colorless and heat-resistant polyimides with a controlled molecular structure using methyl side groups

A methyl regulation strategy is proposed and verified to balance the optical and thermal properties of aromatic polyimides.

Investigation of the Side Chain Effect on Gas and Water Vapor Transport Properties of Anthracene-Maleimide Based Polymers of Intrinsic Microporosity.

In the present work, a set of anthracene maleimide monomers with different aliphatic side groups obtained by Diels Alder reactions were used as precursors for a series of polymers of intrinsic microporosity (PIM) based homo- and copolymers that were successfully synthesized and characterized. Polymers with different sizes and shapes of aliphatic side groups were characterized by size-exclusion chromatography (SEC), (nuclear magnetic resonance) 1H-NMR, thermogravimetric (TG) analysis coupled with Fourier-Transform-Infrared (FTIR) spectroscopy (TG-FTIR) and density measurements. The TG-FTIR measurement of the monomer-containing methyl side group revealed that the maleimide group decomposes prior to the anthracene backbone. Thermal treatment of homopolymer methyl-100 thick film was conducted to establish retro-Diels Alder rearrangement of the homopolymer. Gas and water vapor transport properties of homopolymers and copolymers were investigated by time-lag measurements. Homopolymers with bulky side groups (i-propyl-100 and t-butyl-100) experienced a strong impact of these side groups in fractional free volume (FFV) and penetrant permeability, compared to the homopolymers with linear alkyl side chains. The effect of anthracene maleimide derivatives with a variety of aliphatic side groups on water vapor transport is discussed. The maleimide moiety increased the water affinity of the homopolymers. Phenyl-100 exhibited a high water solubility, which is related to a higher amount of aromatic rings in the polymer. Copolymers (methyl-50 and t-butyl-50) showed higher CO2 and CH4 permeability compared to PIM-1. In summary, the introduction of bulky substituents increased free volume and permeability whilst the maleimide moiety enhanced the water vapor affinity of the polymers.

Effect of the symmetry of polyether glycols on structure-morphology-property behavior of polyurethane elastomers

The macroscopic properties of polymers could be significantly affected by subtle structural changes in the building blocks, either in a beneficial or detrimental manner. Therefore, it is of essential importance to investigate the structure−property relationships of polymeric materials and provide guiding principles for realizing the optimal thermal, mechanical, and optoelectrical characteristics. Polyurethane (PU) is a kind of widely applied functional polymers with alternating soft and hard segments. The structure-morphology-property behavior of PU is dictated by both segments. Herein, PU elastomers (PUEs) are synthesized with identical hard segment and four kinds of soft segments (polyether diols) with similar chain length but different chain symmetry. The chosen polyether diols either have symmetrical and linear structure like poly(trimethylene ether) glycol (PO3G) and poly(tetramethylene ether) glycol (PTMG), or have asymmetrical chain structure with side methyl groups like poly(propylene glycol) (PPG), and 3-methyltetrahydrofuran/tetrahydrofuran copolyether glycol (3MCPG). The effects of structural symmetry of polyether diols on the structure, morphology, and mechanical properties of the as-prepared PUEs are investigated. The results reveal that the PO3G based PUE exhibits the highest value of hydrogen bonding (74.7%) and the highest degree of microphase separation among four PUE samples, along with the highest Young's modulus (42.7 MPa), tear strength (112.8 kN/m), and the best elastic resiliency capability, thanks to the high structural regularity of the PO3G chains. On the contrary, PPG based PUE typically have the deteriorated thermal and mechanical performance due to the interfered microscopic packing. This work highlights how the small structural changes of building blocks in PU would manipulate its macroscopic feature and provide an additional structural handle for designing advanced PU materials.