Monomer Concentration Research Articles

Liquid crystal polymers with dual properties of fluorescence and selective reflection-design, synthesis and characterisation

ABSTRACT In this paper, two series of side chain fluorescent cholesteric liquid crystal polymers (FL-ChLCPs) were prepared by one-step method with polymethyl-hydrosiloxane (PMHS) as the main chain. Two series of polymers differ in the structure of vinyl flexible chains of fluorescent monomer, the comparative study was conducted on their performance of liquid crystal and fluorescence. The compounds and polymers were characterised using conventional methods. The results indicated all polymers possessed dual optical properties of fluorescence and selective reflection, they also had excellent thermal stability. The FL-ChLCPs emitted different intensity fluorescence under UV light, the fluorescence intensity has a certain relationship with temperature and aggregation-caused quenching effect only occurs when the content of fluorescent monomer in the polymer exceeds 20%.

Universal scaling of the osmotic pressure for dense, quasi-two-dimensionally confined polymer melts reveals transitions between fractal dimensions.

A scaling law for the osmotic pressure of quasi-two-dimensional polymer melts as a function of concentration is obtained, which shows fractal characteristics. Structural properties such as the chains' contour length and their inner-monomer pair distribution function display fractal scaling properties as well. These predictions are confirmed with mesoscale numerical simulations. The chains are swollen and highly entangled, yet Flory's exponent is always ν = 1/2. The melt can be considered a fluid of "blobs" whose size becomes renormalized in terms of the contour's length while the fractal dimension df increases monotonically between 5/4 and 2, as the monomer concentration is increased. The semidilute scaling of the pressure is recovered when df = 1. Our results agree with recent experiments and with numerical reports on quasi-2d melts. This work provides a new paradigm to study and interpret thermodynamic and structural data in low-dimensional polymer melts, namely as fractal macromolecular objects.

Effect of enrichment conditions of secondary feeding on the synthesis of polyhydroxyalkanoates (PHAs) by activated sludge

ABSTRACT Polyhydroxyalkanoates (PHAs) are biodegradable plastics with great performance and development prospects. However, their traditional anaerobic/aerobic enrichment process requires a high concentration of dissolved oxygen (DO), resulting in high energy consumption. In this study, an anaerobic/oxygen-limited with secondary feeding enrichment mode was used to enhance the synthesis of PHAs while reducing energy consumption. The enrichment process of PHAs-synthesizing bacteria lasted up to 100 days, and the experiment was conducted to investigate the change of the PHAs synthesizing ability of the system in this mode by detecting the PHAs content and community distribution of the activated sludge under different stages. Under these conditions, the system enriched two major genera of PHAs-synthesizing bacteria, Thauera (30.21%) and Thiothrix (21.30%). The content of PHAs in the sludge increased from 4.51% to 30.87% and was able to achieve a concomitant increase in poly(3-hydroxyvalerate) (PHV) monomer content. After nitrogen limitation (C/N = 150) treatment, the content of PHAs reached 63.05%. The results showed that the enrichment mode of anaerobic/oxygen-limited with secondary feeding could enrich more PHAs-synthesizing bacteria and significantly increase the synthesis amount of PHAs, which revealed the great potential of this mode in solid waste value-added and reduce the production cost of PHAs and could provide a theoretical basis for the production of PHAs from activated sludge.

Naked-Eye Visual Thermometer Based on Glycerol─Nonclose-Packed Photonic Crystals for Real-Time Temperature Sensing and Monitoring.

Real-time sensing and monitoring of temperature are of great significance for assessing human health. The sensitivity and stability are inevitable issues for thermometers. In this study, a thermometer with the cylindrical thermochromic hydrogel was prepared for real-time visual monitoring of temperature, which had excellent temperature sensitivity, angle-independence axially, and environmental stability. The customization of their initial optical properties depended on the PMMA concentrations and the content of the hydrogel monomer. The glycerol introduced with solvent displacement formed hydrogen bonds with the hydrogel network, which stabilized their mechanical properties, and the reflection peak blue-shifted from 653 to 499 nm when tensile strain was 57.85%. At the same time, the environmental stability originated from the moisturizing properties of the glycerol, which enabled the hydrogel to reliably transmit the information on temperature into the air without losing moisture. The reflection peak of the cylindrical thermochromic hydrogel shifted from 657 to 455 nm when the temperature increased from 22 to 45 °C, which realized temperature visual monitoring in the full-color range. The temperature sensitivity of the glycerol─nonclose-packed photonic crystals remained stable for 1 month, which provided an optimal option for continuous visual temperature monitoring.

Soybean and maize differentially metabolize deuterated ferulic and sinapic acids before polymerizing them into the root cell wall

Hydroxycinnamates induce lignification in young plants, leading to the overproduction of lignin as a defense mechanism. Phenylpropanoids-containing oligosaccharides are thought to be a signal of pathogen attack on the cell wall polysaccharides. However, it is unclear if hydroxycinnamates induce lignification by acting solely as stress elicitors or feeding the phenylpropanoid pathway as lignin precursors. To examine this hypothesis, we added 1 mM deuterated ferulic acid (FA) or sinapic acid (SA) to the nutrient solution in which we cultivated soybean or maize plantlets. After 24 h, we assessed the biometric parameters and the contents of ester-linked FA and SA, total lignin, monolignol ratio, and heavy monolignols. FA treatment increased the content of ester-linked FA, syringyl, and guaiacyl monomers measured by nitrobenzene oxidation, lignin content, and reduced root growth in both soybean and maize plants. p-Coumaric acid content ester-linked to the cell wall increased in soybean but decreased in maize after treatment with FA. Treatment with SA also induced lignification in soybean but not in maize. SA increased S-lignin and sinapoyl esters content in the cell wall polymers in both soybean and maize. Residues of deuterated hydroxycinnamates were detected in the lignin of both plants in both treatments. The assay demonstrated that exogenously applied SA and FA were metabolized through the phenylpropanoid pathway. Furthermore, they were, at least partially, exported to the apoplast, where they were ester-linked to cell wall polymers. This suggests hydroxycinnamic acids are metabolized differently by plants with different types of cell walls.

Root-derived carbon stocks in formerly deep-ploughed soils – A biomarker-based approach

Roots can add significant amounts of carbon (C) to the subsoil, which improves soil physical properties and can mitigate climate change. About 5% of croplands in Germany have been deep-ploughed (30–120 cm) at least once. This can provide better root access to the subsoil and may increase yields, but little is known on the fate of root-derived C in the subsoil (at depth greater than 30 cm) after deep-ploughing. We hypothesized that five decades after deep-ploughing, root-derived C stocks were higher than conventionally ploughed treatments due to better root development. We analysed suberin and cutin monomers as tracers for root- and shoot-derived C at three former deep-ploughed sites in Northern Germany with different soil textures and deep-ploughing depths. Concentrations of suberin monomers in the soil positively correlated with root biomass; this was most pronounced at one sandy site, but had higher variability at the other two sites due to crops with different root systems in the crop rotation, lower root development, and more favourable conditions for C decomposition. Suberin contributed more to the bulk soil organic carbon (SOC) stocks than cutin throughout the soil profile at all sites. The contribution of suberin monomers to the bulk SOC stock at silty site Banteln and the sandy site Essemühle was 38% higher in the deep-ploughed plots than at the reference plot, respectively, these differences were most visible in the subsoil of Essemühle. We conclude that as C stocks and root development increase, suberin SOC stocks also increase, especially in sandy subsoils with low pH.

The Influence of Contemporary Denture Base Fabrication Methods on Residual Monomer Content, Flexural Strength and Microhardness.

(1) Background: Digital technologies are available for denture base fabrication, but there is a lack of scientific data on the mechanical and chemical properties of the materials produced in this way. Therefore, the aim of this study was to investigate the residual monomer content, flexural strength and microhardness of denture base materials as well as correlations between investigated parameters. (2) Methods: Seven denture base materials were used: one conventional heat cured polymethyl methacrylate, one polyamide, three subtractive manufactured materials and two additive manufactured materials. High-performance liquid chromatography was used to determine residual monomer content and the test was carried out in accordance with the specification ISO No. 20795-1:2013. Flexural strength was also determined according to the specification ISO No. 20795-1:2013. The Vickers method was used to investigate microhardness. A one-way ANOVA with a Bonferroni post-hoc test was used for the statistical analysis. The Pearson correlation test was used for the correlation analysis. (3) Results: There was a statistically significant difference between the values of residual monomer content of the different denture base materials (p < 0.05). Anaxdent pink blank showed the highest value of 3.2% mass fraction, while Polident pink CAD-CAM showed the lowest value of 0.05% mass fraction. The difference between the flexural strength values of the different denture base materials was statistically significant (p < 0.05), with values ranging from 62.57 megapascals (MPa) to 103.33 MPa. The difference between the microhardness values for the different denture base materials was statistically significant (p < 0.05), and the values obtained ranged from 10.61 to 22.86 Vickers hardness number (VHN). A correlation was found between some results for the material properties investigated (p < 0.05). (4) Conclusions: The selection of contemporary digital denture base manufacturing techniques may affect residual monomer content, flexural strength and microhardness but is not the only criterion for achieving favourable properties.

Copolymerization of pyrrole and carbazole onto polyester textile.

The purpose of this study was the polymerization of carbazole (Cz), pyrrole (Py) and copolymerization of them onto polyester (PES) textile with chemical oxidative method by using FeCl3. First, in order to determine the optimum conditions, the effect of polymerization steps, the immersion order of the PES to the oxidant and monomer solutions, time, monomer, oxidant, and surfactant concentrations and types on the conductivities of PES/PCz composite were investigated and at this conditions, conductive composite, PES/P[Py-co-Cz] was obtained. The highest conductivities were obtained as 12.4 mS/cm and 9.0 mS/cm for PES/PCz and PES/P[Py-co-Cz], respectively. Further characterization of PES/P[Py-co-Cz] was performed by conductivity, FTIR, scanning electron microscopy (SEM), and dynamic mechanical analysis (DMA) measurements, and results were compared with PES/PCz and also PES/PPy. The presence of Py and Cz in the same polymer chain created synergy and improved the conductivity and mechanical properties of the composite.

Near‐Unity Quantum Yield ZnSeTe Quantum Dots Enabled by Controlling Shell Growth for Efficient Deep‐Blue Light‐Emitting Diodes

AbstractCore–shell structural ZnSeTe/ZnSe/ZnS quantum dots (QDs) have attracted great attention for advanced illumination and displays because of their environmentally friendly composition, but still suffering from poor photoluminescence (PL) and electroluminescence (EL) performance due to severe non‐radiative charge recombination. Herein, a stepwise injection shell growth process to manipulate the monomer concentration and ensure adequate growth interval is devised, which enables the controllable uniform epitaxial growth of ZnSe and ZnS shells on the ZnSeTe core, thus relieving the lattice distortion and defects to greatly suppress the non‐radiative charge recombination. The ZnSeTe/ZnSe/ZnS QDs presented deep‐blue emission at 448 nm with narrow full width at half maximum (FWHM, 23 nm), and near‐unity PL quantum yield (PLQY, ≈100%) The light‐emitting diodes (LEDs) based on the QDs exhibited a high external quantum efficiency (EQE) of 10.9%, a maximum brightness of 10240 cd cm−2, and a high current efficiency of 7.9 cd A−1, demonstrating a good performance for deep blue QDs LEDs (QLEDs) This shell growth strategy will be an effective approach to achieving efficient QDs and QLEDs.

3D printable aliphatic polycarbonate networks from cationic ring-opening photopolymerization of spiro-orthocarbonates

We demonstrate light-based 3D printing of pure poly(ether carbonate) networks free of shrinkage stress. Expanding the recently pioneered concept of pure cationic double ring-opening photopolymerization of spiro-orthoesters at elevated temperatures, we herein investigate spiro-orthocarbonates. Thereof resulting poly(ether carbonate) networks could find manyfold applications in biological and medical settings as well as in applications searching for more sustainable material solutions. We have determined the dependence of single and double ring-opening and the presence of backbiting side reactions for three synthesized spiro-orthocarbonate monomers in combination with an oxetane crosslinker on the ring size and photopolymerization temperature to optimize the photogenerated network and thus material properties. The absence of residual stresses in the polymer network was confirmed by tracking the decrease of sample birefringence with increasing spiro-carbonate monomer content of the sample. Based on this fundamental study, the best-performing monomer was printed in combination with an oxetane crosslinker.

Copolymerization of ethylene with polar styrene monomers catalyzed by phosphino‐dihydronaphtholate neutral nickel catalysts

AbstractThe physical properties of traditional polyolefin materials can be significantly improved by introducing polar groups, especially polar aromatic groups. However, it remains a major challenge to realize the highly effective copolymerization of ethylene with styrene derivatives. In this study, the direct copolymerization of ethylene with various polar styrene monomers bearing functional groups (o‐OMe, m‐OMe, p‐OMe, o‐Cl, m‐Cl, p‐ClSt, o‐F, o‐Br, p‐Me, p‐Ph, p‐Vinyl, p‐COOH, and C6F5) was achieved using phosphino‐dihydronaphtholate neutral nickel catalysts Ni1‐Ni3. Additionally, the catalytic behavior and the applicability of the polar monomer were evaluated in detail by copolymerization results. Catalysts Ni1‐Ni3 demonstrated inactivity towards the polymerization of polar styrene monomers but exhibited moderate catalytic activities in the copolymerization of ethylene with polar styrene monomers, yielding moderate‐molecular‐weight (Mw &gt; 10 kDa) copolymers with the polar monomer contents ranging from 1.32 to 4.16 mol%. The steric and electronic effects of the substituent depending on the types and position in the phenyl ring considerably influenced the copolymerization behavior. Furthermore, comprehensive NMR analyses of the produced copolymers revealed that the polar monomers formed in‐chain insertions, saturated chain ends, and unsaturated chain ends after incorporation.

Novel chiral composite membranes coated by microporous hyper-crosslinked polymer for efficiently enantioselective separation

With the rapid development of the pharmaceutical industry, efficient enantiomeric resolution is of great significance for the preparation of single enantiomer drugs. Herein, several kinds of chiral hyper-crosslinked polymer composite membranes (CHCPs/PSS) were fabricated by surface-initiated Friedel-crafts alkylation reaction on the porous SiO2 substrate for enantioseparation. The membrane fabrication conditions were optimized by changing various monomer concentrations, polymerization times and substrate pore sizes using phenylalanine as separated substance and the percent enantiomeric excess (ee%) reached 91.2 % with a permeability up to 6.31 × 10−2 m2/h which was 1012 folders higher than the traditional chiral polymer membranes. Besides, the enantioseparation of disparate enantiomers including clinical drug were also evaluated using CHCPs/PSS membranes to expand its application scope. The ee% and permeability reached 9.48 % and 5.13 × 10−1 m2/h for tryptophan and 24.4 % and 1.56 m2/h for ibuprofen, respectively. Static adsorption and quantum chemical computation were utilized to analyze the separation mechanism and the results indicated that the adsorption energy difference which resulted from the multiple interactions contributed to the effective separation of enantiomers. Consequently, this work will provide a new method for the application of chiral hyper-crosslinked polymer membranes in enantiomeric separation.

Microbially synthesized poly(hydroxybutyrate-co-hydroxyhexanoate) with low to moderate hydroxyhexanoate content: Properties and applications

Plastic pollution is the biggest environmental concern of our time. Breakdown products like micro- and nano-plastics inevitably enter the food chain and pose unprecedented health risks. In this scenario, bio-based and biodegradable plastic alternatives have been given a momentum aiming to bridge a transition towards a more sustainable future. Polyhydroxyalkanoates (PHAs) are one of the few thermoplastic polymers synthesized 100 % via biotechnological routes which fully biodegrade in common natural environments. Poly(hydroxybutyrate-co-hydroxyhexanoate) [P(HB-co-HHx)] is a PHA copolymer with great potential for the commodity polymers industry, as its mechanical properties can be tailored through fine-tuning of its molar HHx content. We have recently developed a strategy that enables for reliable tailoring of the monomer content of P(HB-co-HHx).Nevertheless, there is often a lack of comprehensive investigation of the material properties of PHAs to evaluate whether they actually mimic the functionalities of conventional plastics. We present a detailed study of P(HB-co-HHx) copolymers with low to moderate hydroxyhexanoate content to understand how the HHx monomer content influences the thermal and mechanical properties and to link those to their abiotic degradation. By increasing the HHx fractions in the range of 2 – 14 mol%, we impart an extension of the processing window and application range as the melting temperature (Tm) and glass temperature (Tg) of the copolymers decrease from Tm 165 °C to 126 °C, Tg 4 °C to −5.9 °C, accompanied by reduced crystallinity from 54 % to 20 %. Elongation at break was increased from 5.7 % up to 703 % at 14 mol% HHx content, confirming that the range examined was sufficiently large to obtain ductile and brittle copolymers, while tensile strength was maintained throughout the studied range. Finally, accelerated abiotic degradation was shown to be slowed down with an increasing HHx fraction decreasing from 70 % to 55 % in 12 h.

Entropy-Driven Phase Transition in Nanonucleation via Reciprocal Relations.

Depletion forces, commonly modeled with rigid body assumptions, inadequately describe nanoparticle behavior. This study introduces the roles of Soret and Dufour effects in nanoparticle systems, focusing on mass and energy gradient interchange. The Dufour effect drives energy flow through mass gradients, which implies the possibility of driving the energy flow near the nanoparticles to induce phase transitions via manipulating the monomer concentrations. Our experimental platform confirmed these theories, synthesizing HCP quantum dots from Au, Ag, Pd, and mixed halide perovskites under varied precursor concentrations. By analyzing energy flow and nucleation dynamics through the Dufour effect, we mapped phase transition thresholds, linking them to material entropy. This study provides insight into nanoparticle assembly and phase behavior, highlighting the significance of entropy in nucleation dynamics.

A PEGylated PVDF Antifouling Membrane Prepared by Grafting of Methoxypolyethylene Glycol Acrylate in Gama-Irradiated Homogeneous Solution.

In this study, methoxypolyethylene glycol acrylate (mPEGA) served as a PEGylated monomer and was grafted onto polyvinylidene fluoride (PVDF) through homogeneous solution gamma irradiation. The grafting process was confirmed using several techniques, including infrared spectroscopy (FTIR), thermodynamic stability assessments, and rotational viscosity measurements. The degree of grafting (DG) was determined via the gravimetric method. By varying the monomer concentration, a range of DGs was achieved in the PVDF-g-mPEGA copolymers. Investigations into water contact angles and scanning electron microscopy (SEM) images indicated a direct correlation between increased hydrophilicity, membrane porosity, and higher DG levels in the PVDF-g-mPEGA membrane. Filtration tests demonstrated that enhanced DGs resulted in more permeable PVDF-g-mPEGA membranes, eliminating the need for pore-forming agents. Antifouling tests revealed that membranes with a lower DG maintained a high flux recovery rate, indicating that the innate properties of PVDF could be largely preserved.

A stimuli-responsive hydrogel for reversible information storage, encryption and decryption

Smart hydrogel materials, known for their sensitivity to external stimuli, exhibit a reversible dynamic response and find applications in diverse fields, particularly in information storage. Despite significant efforts in this domain, developing a hydrogel with high-resolution, repeatable recording, and robust information encryption/decryption capabilities still remains a challenge. In this study, we synthesized a polymer hydrogel, namely polyvinyl alcohol-n-isopropylacrylamide-octadecyl polyoxyethylene ether acrylate hydrogel (PPNS), which features multiple hydrogen bonds through copolymerization, by using N-isopropylacrylamide, polyvinyl alcohol, and octadecyl polyoxyethylene ether acrylate (SGA15) as raw materials. The PPNS hydrogel demonstrated outstanding high-resolution, repeatable recording capabilities, enabling reversible recording, encryption, and decryption of information using anhydrous ethanol as the inducer. Varying the SGA15 monomer concentration revealed that the PPNS-2% hydrogel, prepared with 2% SGA15, outperformed the other hydrogels in terms of information recording and encryption/decryption when immersed in anhydrous ethanol and deionized water. Furthermore, the PPNS-2% hydrogel exhibited the ability to undergo multiple information cycles while maintaining excellent mechanical properties even after 25 cycles. Notably, ethanol served as a specialized ink for inscribing different patterns on the hydrogel surface for information recording. The recorded information could be erased through water wiping or ethanol volatilization, enabling reversible information recording, encryption, and decryption. Due to their responsive and dynamic nature of PPNS hydrogels are positions them as promising candidates for use as innovative information storage platforms.

Drug delivery in thermo-responsive silicone catheters by grafting of N-vinylcaprolactam using gamma radiation

Radiation-induced graft polymerization of poly(N-vinylcaprolactam) onto silicone catheters by direct irradiation method was studied. The effects of the irradiation dose, as well as the monomer concentration, on the grafting efficiency were studied. The conditions for achieving maximum grafting yield were observed at 30% of monomer concentration in toluene at 50 kGy. The graft polymerization was examined by different characterization methods, including measurements such as thermogravimetric analysis, infrared, water contact angle, and swelling. The temperature-responsive behavior of smart grafted copolymer was studied by swelling at different temperatures. Differently from pristine silicone catheter, the N-vinylcaprolactam-grafted catheters were able to load vancomycin and sustain the release for 30 h.Graphical abstract

A Theoretical Investigation of the Polyaddition of an AB2+A2+B4 Monomer Mixture.

Hyperbranched polymers (HBPs) are widely applied nowadays as functional materials for biomedicine needs, nonlinear optics, organic semiconductors, etc. One of the effective and promising ways to synthesize HBPs is a polyaddition of AB2+A2+B4 monomers that is generated in the A2+CB2, AA'+B3, A2+B'B2, and A2+C2+B3 systems or using other approaches. It is clear that all the foundational features of HBPs that are manufactured by a polyaddition reaction are defined by the component composition of the monomer mixture. For this reason, we have designed a structural kinetic model of AB2+A2+B4 monomer mixture polyaddition which makes it possible to predict the impact of the monomer mixture's composition on the molecular weight characteristics of hyperbranched polymers (number average (DPn) and weight average (DPw) degree of polymerization), as well as the degree of branching (DB) and gel point (pg). The suggested model also considers the possibility of a positive or negative substitution effect during polyaddition. The change in the macromolecule parameters of HBPs formed by polyaddition of AB2+A2+B4 monomers is described as an infinite system of kinetic equations. The solution for the equation system was found using the method of generating functions. The impact of both the component's composition and the substitution effect during the polyaddition of AB2+A2+B4 monomers on structural and molecular weight HBP characteristics was investigated. The suggested model is fairly versatile; it makes it possible to describe every possible case of polyaddition with various monomer combinations, such as A2+AB2, AB2+B4, AB2, or A2+B4. The influence of each monomer type on the main characteristics of hyperbranched polymers that are obtained by the polyaddition of AB2+A2+B4 monomers has been investigated. Based on the results obtained, an empirical formula was proposed to estimate the pg = pA during the polyaddition of an AB2+A2+B4 monomer mixture: pg = pA = (-0.53([B]0/[A]0)1/2 + 0.78)υAB2 + (1/3)1/2([B]0/[A]0)1/2, where (1/3)1/2([B]0/[A]0)1/2 is the Flory equation for the A2+B4 polyaddition, [A]0 and [B]0 are the A and B group concentration from A2 and B4, respectively, and υAB2 is the mole fraction of the AB2 monomer in the mixture. The equation obtained allows us to accurately predict the pg value, with an AB2 monomer content of up to 80%.

Effect of Synthesis Temperature on Adsorbent Performance of Blending Anionic and Cationic Gels in Divalent Metal Ions Adsorption

In this study, the anionic and cationic gels were synthesized separately using copolymerization between N-isopropylacrylamide (NIPAM) and acrylic acid or chitosan through a polymerization reaction using N,N'-methylenebisacrylamide (MBAA) as a cross-linker with various monomer concentrations and synthesis temperature. The anionic and cationic gels were blended to minimize inter-intra particle association and to improve the adsorption ability. The FTIR analysis found that the synthesis of the NIPAM-co-acrylic acid and NIPAM-co-chitosan gels was successfully carried out, indicating no presence of a vinyl group in the functional group. The result showed that the ion adsorption amount of Pb2+ ions blending gels increased significantly, almost twice compared to the adsorption before blending. The adsorption amount of Pb2+ ions increased with increasing the gel synthesis temperature. The adsorption amount follows the order of Pb2+ &gt; Fe2+ &gt; Ni2+. The adsorption amount of Pb2+ tends to decrease with increasing sedimentation volume. The higher the synthesis temperature, the larger the porous diameter formed. These results demonstrate that blending gel of NIPAM-co-chitosan and NIPAM-co-acrylic acid is a feasible alternative for removing heavy metal ions owing to its good adsorption performance.

Preparation of Low-Molecular-Weight Polyacrylamide as the Delayed Crosslinking Plugging Agent for Drilling Fluid.

Deep wells and ultra-deep wells often encounter cracks, karst caves, and other developed strata, which can lead to leakage during drilling. Conventional bridge slurry plugging technology is prone to leaking due to the poor plugging effect of the plugging agent. The gel plugging agent possesses characteristics of flexible plugging and adaptive matching of formation leakage channels. It can fill cracks or caves and enhance the pressure-bearing capacity of the formation. A controllable crosslinking plugging agent based on low-molecular-weight polyacrylamide was studied. Polyacrylamide with different molecular weights is synthesized from acrylamide and an initiator. A crosslinking time-controllable polymer is synthesized from low-molecular-weight polyacrylamide by adding crosslinking agent and retarder. The low-molecular-weight polyacrylamide plugging agent has low viscosity before gelation and good fluidity in the wellbore. After being configured on the ground, it is transported by pipeline and sent underground to reach the thickening condition. The gel solution rapidly solidifies, and its strength improves after high-temperature crosslinking. The synthesis conditions of the polymer were as follows: a monomer concentration of 9%, initiator 3.5%, synthesis temperature of 65 °C, and hydrogen peroxide initiator. The optimal formula of the gel plugging agent is as follows: a polymer concentration of 6%, a crosslinking agent concentration of 1%, and a retarder concentration of 8%. The generated polymer molecular structure contains amide groups. This crosslinking time-controllable plugging agent based on low-molecular-weight polyacrylamide has stable rheology, and its temperature resistance can reach 150 °C. At 150 °C, the gelation time can be controlled by adjusting the concentration of retarder, and the longest can reach 4 h. The plugging efficiency of the gel plugging agent is more than 95%. With the increase in seam width, the pressure of the gel plugging agent gradually decreases.