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Aiming at the problem of coal fines plugging in the screen tube of coalbed methane wells, a two-dimensional and three-dimensional simulation models of the screen tube for coalbed methane wells were built with the help of COMSOL finite element simulation software, and the effect of ultrasonic action position and frequency on the sound pressure and the uniformity of the sound field in the screen tube area was studied by numerical analysis, and the possibility of using ultrasonic to unplug the screen tube was discussed. The results show that the sound pressure produced by ultrasonic can reach the minimum pressure value of cavitation effect, and it has the effect of unplugging the screen tube blocked by coal fines. When the ultrasonic wave acts on the center of the outer wall under the screen tube and the center of the inner wall under the screen tube, the change trend of the sound pressure amplitude is basically the same. The sound pressure amplitude is large, but the distribution uniformity of the sound field is poor. While the ultrasonic wave acts on the center of the screen tube, the sound pressure amplitude is small, and the distribution uniformity of the sound field is good. The absolute sound pressure and sound field uniformity show an overall upward trend with the increase of ultrasonic frequency. At the frequency of 60 kHz, the absolute sound pressure and sound field uniformity are larger and better. In the frequency range of 20 kHz to 40 kHz, the absolute sound pressure and sound field uniformity vary in a low range. In the frequency range of 40 kHz to 60 kHz, the absolute sound pressure and sound field uniformity fluctuate greatly with the change of frequency. Using ultrasonic technology to unplug the screen tube, if the ultrasonic wave acts on the center of the outer side wall under the screen tube and the center of the inner side wall under the screen tube, the ultrasonic frequency should be 50 kHz or 60 kHz; and if the ultrasonic wave acts on the center of the screen tube, the ultrasonic frequency should be 30 kHz or 60 kHz. In both cases, the absolute sound pressure in the screen region is larger and the sound field uniformity is better, the cavitation degree is higher, and the unplugging effect is better.

Germanium (Ge) is an excellent organophilic and dispersed semiconductor resource, which is irreplaceable in emerging industries such as new materials, new energy, aerospace, industrial smelting, national defense, military industry, and modern information technology, it has become an important direction of mineral resources exploration. Therefore, it is urgent to carry out research on the collaborative exploration model of coal and Ge deposits from a technical and economic perspective to lay a theoretical foundation for the collaborative exploration of coal and Ge. In this study, the Wulantuga coal–Ge deposit is taken as an example, according to the distribution characteristics of coal–Ge deposit and the response effect to the exploration technical means, the economical and effective exploration technical means, reasonable exploration project layout and resource estimation parameters of coal–Ge deposit are put forward, and the cooperative exploration mode of coal–Ge deposit is determined, it provides an important scientific basis for improving the strategic coordination ability of Ge mineral resources.

The deposition of coal fines in fractures can reduce the fracture conductivity and restrict the efficient and stable development of coalbed methane wells. A visual physical simulation experiment scheme for coal fines migration and blockage removal in fractures was designed. The variation of coal fines particle deposition area and sedimentary morpho-logical characteristics at different positions of fractures were analyzed and the dynamic law of coal fines migration and deposition was revealed based on the visual physical simulation experiment of coal fines migration in fractures. Using the visual physical simulation experiment of coal fines blockage removal in fractures, the influence of plugging time and flow rate on the area of deposited coal fines blockage removal in fractures was investigated and the dynamic law of coal fines starting and blockage removal was found. The experimental results show that the coal fines particles have different aggregation states in different directions and positions of the fractures. The deposition area of coal fines particles gradually decreases from the entrance to the two ends of the vertical main migration direction and the main migration direction, and the deposition area of coal fines particles gradually increases along the main migration direction in the branch channel. The morphology of coal fines deposition at the fracture throat, branch channel and main channel is eagle’s mouth shaped, layered and streamlined, respectively. The reason is that the resistance of different positions of the fracture to the coal fines-containing fluid is different, resulting in different deposition morphology of coal fines at different positions. At the same flow rate, with the increase of blockage removal time, the blockage removal effect of coal fines is better, but the area of blockage removal in the early stage is large, and the area of blockage removal in the later stage is small. The blockage removal effect of coal fines at the fracture throat is obviously better than that in the branch channel. The reason is that the loose and easy blockage removal coal fines particles will be deblocked first, and as time goes on, the remaining unblocked coal fines particles need a larger starting flow rate. The larger the flow rate is, the larger the area of coal fines blockage removal at the fracture throat and branch channel is. The reason is that increasing the flow rate can enhance the fluidity of coal fines particles.

The establishment of cooperative exploration model between coal and strategic metal resources in coal-bearing strata is the precondition for the transformation from strategic metal elements in coal-bearing strata to metal resources. The research on the basic theory and key technology of cooperative exploration of coal and strategic metal resources in coal-bearing strata is the core task of establishing cooperative exploration model. Based on the analysis of the basic characteristics of strategic metal elements in coal-bearing strata, the necessity of implementing the cooperative exploration of coal and strategic metal resources in coal-bearing strata is demonstrated. Through review on the evolution history of the concept of cooperative exploration, the relationship between comprehensive coal exploration and cooperative exploration is revealed, and considered that the cooperative exploration is the inheritance and development of comprehensive exploration, emphasizes the coordination and orderly and scientific organization in the process of comprehensive exploration of two or more mineral resources, and its core is the cooperative organization of exploration projects and cooperative implementation of key technologies. Based on the discussion on the principle of cooperative exploration of coal and strategic metal resources in coal-bearing strata, the theory and technical method system framework of cooperative exploration of coal and strategic metal resources in coal-bearing strata is put forward, which is the basis of establishing the model of cooperative exploration of coal and strategic metal resources in coal-bearing strata. The cooperative exploration of coal and strategic metal resources in coal-bearing strata should be based on the study of the enrichment and mineralization mechanism, combination types and occurrence rules of the strategic metal elements in coal-bearing strata, based on the multi-disciplinary theories of coal geology, ore deposit, geochemistry, geophysics and exploration engineering, and supported by the cooperative exploration technology system composed of key technologies such as precision drilling, fine geophysical exploration and fine geochemical exploration. Also, it should be based on the solid mineral exploration norms and other standards, follow the general principles of solid mineral resources exploration, comprehensive exploration and single mineral resource exploration, as well as the principles of research first, technical effectiveness, fine exploration, dynamic adjustment, zoning policy implementation, coordination and synchronization, and cooperate in the organization of exploration projects and implementation of key technologies, in order to achieve the balance of the best technical benefits and the best economic benefits of the cooperative exploration of coal and strategic metal resources in coal-bearing strata. On the basis of the completion of coal geological exploration tasks, it is expected to find out the geological characteristics and development geological conditions of the associated strategic metal resources, to obtain the corresponding resources or distribution characteristics of strategic metal elements, and to provide geological basis for the comprehensive development and utilization of mineral resources in coal-bearing strata. The core issues of cooperative exploration of coal and strategic metal resources in coal-bearing strata are as follows: determination of cooperative exploration objects, selection and cooperative implementation of exploration technologies, cooperative deployment of exploration projects, and scientific estimation of resources.

The problem of coal fines restricts the efficient development of coalbed methane in China. The coal sample of No. 3 coal seam in the Shanxi Formation in the Hancheng mining area was selected for carrying out a physical simulation experiment on the effect of different hydrochemical properties on the migration of coal fines in the propped fractures. The change in the permeability of fracture diversion system and the output mass concentration of coal fines were investigated, the influence of different hydrochemical properties on coal fines migration in the propped fractures was explored. Experimental results show that in the displacement condition of Na2SO4 solution, the output mass concentration of coal fines decreases with the increase of salinity. Under the condition of high salinity, the coal fines have strong agglomeration and sedimentation, which can block the crack channels. In the displacement condition of NaHCO3 solution, the output mass concentration of coal fines increases with the increase of salinity. With the increase of salinity, OH− is generated by hydrolysis, which increases the negative charge on the surface of coal fines particles, enhances the repulsive force between coal fines, alleviates the coal fines aggregation effect, and produces part of coal fines particles. Under the condition of 6 000 mg/L solution of Na2SO4 and NaHCO3 solution, the fluid has more distribution space and the highest permeability. In the displacement condition of the MgCl2 solution, the output mass concentration of coal fines increases with the increase of salinity. High salinity is conducive to the aggregation of coal fines. The internal relative balance of the experimental sample is broken, and the output of coal fines increases. The clogging degree of coal fines inside the experimental sample is roughly the same, and the permeability value does not change much. Under the condition of the same salinity (10 000 mg/L), the mass concentration of coal fines output in the experiments of different hydrochemical types is: NaHCO3 > Na2SO4 > MgCl2, and the average permeability of the experimental sample is: MgCl2 > NaHCO3 > Na2SO4. The degree of coal fines aggregation affects the output of coal fines to a certain extent. The agglomeration effect of Na2SO4 and NaHCO3 is lower than that of MgCl2, and part of the coal fines will migrate. The degree of clogging at the end of the experimental sample is higher than that of the MgCl2 solution. The hydrolysis of NaHCO3 generates OH−, and the coal fines are in an alkaline environment, which improves the clogging of the experimental sample and increases the permeability. According to the three trends of the rising state, falling state and slight fluctuation state of permeability fluctuation in the simulation experiment, combined with the measured permeability value, the period time of the permeability change trend was counted, and the relationship between the mass concentration of coal fines output and the permeability of coal samples was analyzed. The R2 of the regression model is 0.834, indicating that the fluctuation of the coal fines migration affects the experimental permeability.

In the process of coalbed methane exploitation, the problem of coal fines blocking the screen tube seriously affects the continuous and stable drainage and production of coalbed methane wells. Aiming at the problem of clogging the screen tube with coal fines, the method of using ultrasonic technology to unblock the screen tube is proposed. The experiments of unblocking the screen tube blocked by coal fines with different particle sizes and compositions are carried out, and the unblocking effect and influencing factors of ultrasonic technology on the screen tube are discussed. The results show that with the increase of coal fines particle size（＜63 μm, 63-125 μm and >125-300 μm）, the specific surface area of coal fines decreases, the adhesion of coal fines decreases, and the effect of ultrasonic technology on screen tube blockage removal increases. Kaolinite can improve the hydrophilicity of coal fines. With the increase of the proportion of kaolinite in coal fines, the hydrophobic attraction between coal fines particles decreases, the adhesion of coal fines decreases, and the effect of ultrasonic technology on screen tube unblocking is enhanced. The action time of ultrasonic technology for blocking removal is within 0-30 min. With the increase of ultrasonic action time, the efficiency of ultrasonic blocking removal decreases. Among them, the action time is most obvious in the time period of 0-10 min. It is recommended that the action time of ultrasonic blocking removal is longer than 10 min.

Contact metamorphism occurs when magma intrudes into the coal seam, resulting in changes to the microfraction, grade, chemical composition, physico-chemical structure and process properties of the coal. Different types of contact metamorphic products are formed under different tectonic-thermal conditions. In order to reveal the variability of different types of contact metamorphic coals and their controlling factors from the macromolecular structure scale, a comparative study of natural coke series samples from the Tashan mine in Datong, Shanxi Province and coal-based graphite series samples from the Lutang mine in Hunan Province was carried out using industrial analysis, elemental analysis, reflectance determination, X-ray diffraction (XRD) and Raman spectroscopy (Raman) test methods, and combined with geological background analysis. The results show that the small shallow-formed rocks have a short thermal action time, poor thermal confinement conditions, belong to high temperature and low pressure condition, narrow contact metamorphic zone, and develop natural coke - thermal transformation coal sequence; the series is in the carbonation stage, and the coal macromolecular structure is dominated by chemical changes, with aromatization and ring condensation dominating. It shows carbon enrichment, dehydrogenation, deoxygenation, reduction of defects in the active sites such as side chains and functional groups, growth of aromatic structural units leading to an increase in defects within the aromatic level, and the aromatic lamellae are not ordered. The acidic and moderately acidic deep-formed rock bodies such as strains and bases intruded in a regional extrusive tectonic setting are well heated, thermally confined and under high temperature and pressure conditions, and the contact metamorphic width can exceed 1km, developing graphite-semi-graphite-anthracite metamorphic sequences; the chemical composition of the coal-based graphite series is highly mature and less variable, and the macromolecular structure is dominated by physical changes, mainly occurring as collagenesis and rank physicochemical interactions. The non-oriented aromatic lamellae are spliced and stacked and rotated and oriented by forces, with a continuous reduction of defects and a transition to a three-dimensional ordered crystal structure.

In order to carry out an in-depth study of the differences in the molecular structure evolution of the vitrinite and the inertinite during coalification, the chemical structure of 13 groups of vitrinite and inertinite with different coal ranks were comprehensively characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and 13C nuclear magnetic resonance (13C NMR). The correlation of structure parameters and vitrinite random reflectance (Ro, ran) were analyzed. The results show that three evolution stages of vitrinite were observed with Ro, ran at 0.35%–0.90%, 1.20%–2.67%, and 3.03%–4.20%, and two evolution stages of inertinite were marked with Ro, ran at 0.35%–2.07% and 2.07%–4.20%. The fa, DOC, I, fa', faH, faN, faB, Xb, La, Lc, and Nave of inertinite are always larger than vitrinite, whereas the A(CH2)/(CH3), fal, fal*, falH, d002 of inertinite are always smaller than vitrinite. When Ro, ran = 0.35%–0.90%, the oxygen-containing functional groups and aliphatic structure of vitrinite fall off rapidly, the condensation degrees of the aromatic ring, La, Lc, and Nave increase, whereas the lengths of side chains and d002 decrease. When Ro, ran = 1.20%–2.67%, the vitrinite structure variation follows the same trend as the first stage, but the evolution rate is significantly lower. When Ro, ran = 0.35%–2.07%, the oxygen-containing functional groups, methyl groups, and methylene groups of inertinite fall off at a slower rate than those of vitrinite. The aromaticity, condensation degree, aromatic carbon content, and order degree of microcrystalline structure also increase at a rate less than that of vitrinite. The vitrinite and inertinite structure variation becomes flat, and the structures of both macerals are similar in the high metamorphic stage. The content of oxygen-containing functional groups and aliphatic chain length decrease to the lowest, whereas the aromaticity increases to the maximum. This study contributes to a comprehensive understanding of the chemical structure differences between vitrinite and inertinite, which can provide a theoretical reference for the clean utilization of coal and coalbed methane (CBM) exploration and development.

The understanding of the nanopore structure in tectonically deformed coal (TDC) could be expanded from the perspective of a single maceral. A total of 10 TDCs with an increasing deformation degree (in the order of unaltered, cataclastic, porphyroclast, scaly, and powdery coal), were collected in a single coal seam and stripped into 10 vitrinite and 10 inertinite samples. Carbon dioxide (CO2) adsorption and nitrogen (N2) adsorption/desorption experiments were conducted to reveal the nanopore structure, whereas 13C solid-state nuclear magnetic resonance and X-ray diffraction experiments were conducted to detect the macromolecular structure. The results reveal that the macromolecular structures of both vitrinite and inertinite can be altered by tectonic stress. As the deformation degree increases, the aliphatic carbons decrease, the aromatic carbons increase, and the aromatic interlayer spacing decreases, whereas the crystallite stacking height and the average number of crystallites in a stack increase. For mesopores, the pore volume of vitrinite slowly decreases and then increases at the stage of scaly coal, whereas that of inertinite fluctuates with no obvious regularities. For micropores, the pore volume of vitrinite deceases as the deformation degree increases, whereas that of inertinite decreases since the deformation stage of porphyroclast coal, and little changed from the deformation stage of unaltered to cataclastic coal. As the coal deformation degree increases, the aromatic interlayer spacing decreases, resulting in a decrease in the micropore volume; however, the average crystallite stacking height and the average number of crystallites in a stack increase, leading to an increase in the micropore volume. Therefore, the micropore decreases and then increases as the coal deformation degree increases. However, the macromolecular changes weakly affect the mesopore evolution in the coal deformation process.

Hegang coalfield is one of the areas with abundant coal resources in Heilongjiang Province. Characteristics of minerals and geochemistry of No. 26 coal (lower Cretaceous coals) from Junde mine, Hegang coalfield, Heilongjiang province, China, were reported. The results showed that No. 26 coal of Junde mine is slightly enriched in Cs, Pb, and Zr compared with world coals. The minerals in No. 26 coal of Junde mine primarily include clay minerals and quartz, followed by calcite, siderite, pyrite, monazite, and zircon. The diagrams of Al2O3–TiO2, Zr/Sc–Th/Sc, Al2O3/TiO2–Sr/Y, and Al2O3/TiO2–La/Yb indicate that the enriched elements in No. 26 coal were mainly sourced from the Late Paleozoic meta-igneous rocks in Jiamusi block. The volcanic ash contribution to No. 26 coal seems very low. Sulfate sulfur indicating oxidation/evaporation gradually decreases during No. 26 coal formation.

An accurate understanding of molecular structure evolution during pyrolysis is essential for the clean utilization of coal. In this study, middle-rank coal was taken as the research subject, and vitrinite and inertinite samples were stripped from coal using a hand picking and sink–float separation process. In situ Fourier transform infrared (FTIR) spectroscopy and in situ X-ray diffraction (XRD) were performed to compare the macromolecular structure changes between vitrinite and inertinite during pyrolysis. The results show that the aromaticity (I), the polycondensation degree of aromatic rings (DOC), the average lateral sizes (La) of basic structure unit (BSU), and the stacking heights (Lc) of BSU in both vitrinite and inertinite during pyrolysis increase continuously with increasing temperature. The values of these parameters for inertinite are higher than those of vitrinite, suggesting that the aromatization degree of inertinite has always been higher than that of vitrinite. In situ FTIR spectroscopy shows that the macromolecular structure evolution of vitrinite and inertinite could be divided into three stages based on temperature: 30–200 °C, 200–300 °C, and 300–500 °C. The content of C–O–C, aromatic C=O, O–H groups, and aromatic ring C=C gradually decreases, while that of the CH2 in aliphatic hydrocarbons increases between 30 °C and 200 °C. The 200–300 °C stage is mainly filled by the synergistic effects of aliphatic and aromatic groups. The content of aliphatic groups, C–O–C groups, aromatic C=O, and aromatic ring C=C of both vitrinite and inertinite decreases greatly. The 300–500 °C stage is dominated by the aromatization and condensation of macromolecules. The substituents of the aromatic system gradually detach, leading to an increase in I and DOC. From 30 °C to 1000 °C, in situ XRD results reveal a difference in macromolecular structural evolution between vitrinite and inertinite. The arrangement of aromatic layers in vitrinite tends to be ordered during pyrolysis, whereas there are no significant changes in the inertinite. However, the aromatic layers of inertinite are always more compact than that of vitrinite. In addition, the aliphatic side chains of inertinite are more stable than that of vitrinite during the pyrolysis process.

The physical properties of thick coal seams show strong vertical heterogeneity; thus, an accurate characterization of their pore structure is essential for coalbed methane (CBM) exploration and production. A total of 18 coal samples, collected from a thick coal seam in the Yili Basin of NW China, were tested by a series of laboratory experiments to investigate the peat mire evolution and pore structure characteristics. The results show that the No. 4 coal seam has undergone multiple stages of evolution in the peatification stage, and was divided into four water-transgression/water-regression cycles according to the regular cyclic changes of the vitrinite/inertinite ratio, structure preservation index, gelification index, vegetation index, trace element ratios, and stable carbon isotopes of organic matter. The changes of pore structure characteristics with the changes of coal deposition cycles are also analyzed. It is concluded that pore structure characteristics of the four cycles are quite different. In each water-transgression cycle, the vitrinite gradually increased and the inertinite gradually decreased, resulting in a decrease of the porosity, pore volume, specific surface area, and fractal dimension. While in each water-regression cycle, the vitrinite gradually decreased and the inertinite gradually increased, leading to an increase of the porosity, pore volume, specific surface area, and fractal dimension. A strong relationship exists between the porosity, pore volume, specific surface area, fractal dimension, and submacerals, with fusinite and semifusinite which contained more pores having a positive correlation, desmocollinite and corpovitrinite which contained few pores having a negative correlation.

Coal fines produced during drainage of coalbed methane reservoirs can affect the permeability of the coal reservoir and damage production facilities such as downhole pumps, shafts, and valves. Thus, to clarify the mechanism of coal fines output is very important to high production of coalbed methane. The characteristics of coal fines can be used to identify the sources of the coal fines and to develop reasonable means of controlling coal fines output. In this study, different coal fines characteristics were investigated to reveal the output mechanism of coal fines. The coal fines samples were collected from 16 coalbed methane wells, which located in Eastern Ordos Basin of China. And the wells are in different drainage stages. The coal fines samples were analyzed by using transmission light microscopy, reflection polarized optical microscopy, laser particle size analysis, X-ray diffraction, and scanning electron microscopy with energy dispersive X. The results show that the concentration of coal fines is in the range of 3–8% (volume percent). The sizes of the coal fine particles tended to be below 200 µm. The main components of pulverized coal are vitrinite and inorganic minerals and the average content of inorganic minerals account for 50.56% and the standard deviation is 0.0685. The morphology analysis results show that the shape of coal fines is different in different parts of the coalbed methane wells. The coal fines concentration increases with the increase in the thickness of the deformed coal, and decreases with the increase in the burial depth. The concentration of coal fines becomes higher with the increase of casing pressure and coal fines concentration increases with the increase of the variation of bottom hole pressure.

The Juhugeng mining area in the Qilian Mountains is the only district of China where terrestrial gas hydrate has been found. This paper aimed at studying the gas migration for gas hydrates based on fluid inclusion and apatite fission track experiments with samples being collected in both the hanging wall (Triassic strata, non-hydrocarbon source rocks) and footwall (Jurassic strata, hydrocarbon source rocks) of drilling cores. Fluid inclusions are found in both the hanging wall and footwall, and are characterized by two generations: the first generation includes gaseous and liquid hydrocarbon fluid inclusions with the homogenization temperature of concomitant saline water inclusions being 83–115°C, and the second generation includes gaseous fluid inclusions with the concomitant homogenization temperature of saline water inclusions being 115–149 °C, suggesting two periods of gas migration. Combining with the reconstruction of the burial and thermal histories, the gas migration history can be elaborated as follows: (1) In the Late Paleogene period (>30 Ma), the gas in the footwall migrated to the hanging wall because of the thrusting of Triassic strata, with the temperature being more than 110 ± 10°C (derived from apatite fission track results), corresponding well with the homogenization temperature of the saline water inclusions of the first generation being 115–149 °C; (2) In the Late Neogene to Quaternary (

Four-wave-mixing microscopy is widely researched in both biology and medicine. In this paper, we present a simplified near-degenerate four-wave-mixing microscopy (SNDFWM). An ultra-steep long-pass filter is utilized to produce an ultra-steep edge on the spectrum of a femtosecond pulse, and a super-sensitive four-wave-mixing (FWM) signal can be generated via an ultra-steep short-pass filter. Compared with the current state-of-the-art FWM microscopy, this SNDFWM microscopy has the advantages of simpler experimental apparatus, lower cost, and easier operation. We demonstrate that this SNDFWM microscopy has high sensitivity and high spatial resolution in both nanowires and biological tissues. We also show that the SNDFWM microscopy can achieve an ultra-sensitive detection based on the electron-resonance effect. This method might find an important application in tracking of nano drugs in vivo.

In order to study the evolution of the mechanical properties and macromolecular structures in different macerals of tectonically deformed coal (TDC), vitrinite and inertinite samples were handpicked from six block TDCs in the same coal seam with an increasing deformation degree (unaltered, cataclastic, porphyroclast, scaly and powdery coal). The micro mechanical properties were tested by the nanoindentation experiment and the macromolecular structures were measured using 13C nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopy (FTIR). The results show that the range of hardness and elastic modulus of inertinite is 0.373–1.517 GPa and 4.339–12.158 GPa, respectively, which is significantly higher than that of vitrinite with values of 0.278–0.456 GPa and 4.857–7.810 GPa, respectively. From unaltered coal to powdery coal, the hardness of vitrinite and inertinite gradually decreases, with the difference between these macerals becomes smaller and the elastic modulus of vitrinite shows an increasing trend, while that of inertinite was more variable. Both the NMR and FITR results reveal that the macromolecular structure of inertinite has similar structural transitions as vitrinite. As the degree of deformation increases, the aliphatic side chains become shorter and the aromaticity is increasing. Macromolecular alterations caused by tectonic stress is expected to produce defects in the TDCs, therefore there should be more interspacing among the macromolecular groups for the extrusion of macromolecules caused by the indenter of the nanoindentation experiment, thereby reducing the hardness. The elastic modulus of coal is believed to be related to intermolecular forces, which are positively correlated to the dipole moment. By calculating the dipole moments of the typical aromatic molecular structures with aliphatic side chains, the detachment of the aliphatic side chains and the growth of benzene rings can both increase the dipole moment, which can promote elastic modulus. In addition, the increasing number of benzene rings can create more π-π bonds between the molecules, which can lead to an increase in the intermolecular forces, further increasing the elastic modulus.