Higher Crosslinking Density Research Articles

Design and Modulation of Negative Thermal Expansion for Epoxy Polymers.

Modulating the coefficient of thermal expansion (CTE) and realizing low or negative thermal expansion (NTE) for epoxy polymers are challenging issues. In this study, we developed an effective strategy to prepare epoxy polymers with an NTE performance. A novel motif DBCOD-NH2 based on the dibenzocyclooctadiene (DBCOD) was designed, synthesized, and utilized as a curing agent for several commercial epoxy resins. DBCOD-NH2 suppressed the thermal expansion of the epoxy polymer due to the conformational transition of DBCOD from boat to chair, resulting in low or negative CTE. The AFG90-based polymer showed the most significant thermal contraction behavior (-43.6 ppm/K, 40-80 °C) in the glassy state due to the high DBCOD content, chain rigidity, and cross-link density, which resulted from the high epoxy values, rigidity, and functionality of AFG90 resins. The structure-property interactions were examined and applied to modulate the NTE of epoxy polymers. Our findings are useful for the regulation of thermal expansion and the preparation of materials with desired CTE values.

An oxidative depolymerized lignin treated by potassium ferrate and its use in preparation of epoxy resin

AbstractLignin, as an industrial by‐product, can be used as a phenolic substancen. In this study, enzymatic hydrolysis lignin (L) was treated with potassium ferrate and phenol respectively to obtain oxidized lignin (OL) and phenolated lignin (PL). Their phenolic hydroxyl content (PhOH) increased by 29.1% and 40.5%, respectively. Then four kinds of epoxy resins were prepared, namely lignin‐free epoxy resin (LFER), L epoxy resin (LER), PL epoxy resin (PLER), and OL epoxy resin (OLER). Gel permeation chromatography (GPC) and Fourier transform infrared analyses indicated that potassium ferrate oxidation could decline the molecular weight (Mw) and increase the PhOH of L. Mechanical properties test and dynamic mechanical analysis (DMA) results show that cured OLER (OLEN) has higher crosslinking density and better mechanical properties (shear strength increased by 14%, tensile strength increased by 15%) than cured LER (LEN). Thermogravimetric analysis results show that OLEN has better thermal stability than cured LFER (LFEN) and LEN. In addition, scanning electron microscopy images showed that the modified L had better compatibility. This study presents a novel approach for lignin oxidation.

Convenient synthesis of phthalonitrile‐containing mono‐benzoxazines with exceptional thermal stability and improved curing activity

AbstractSimple synthesis and high performance are eternal pursuit for polymers. To lower the curing temperature, lower the melt viscosity and improve the processability of high performance phthalonitrile resins, a solvent‐free method was applied to synthesize three from different phenols. Their chemical structure was confirmed by FTIR and NMR spectra, the curing behavior was investigated by DSC and rheology. It was found that the polymerization of phthalonitrile groups could be effectively promoted by benzoxazine moieties and the curing temperature of phthalonitrile groups dropped to around 240°C. Consequently, owing to the high curing reactivity, polymers obtained at relatively low curing temperature possessed high crosslinking density and extremely high thermal stability. P‐apn‐200, which was cured at 200°C, showed 5 wt% weightloss temperature (Td5) of 472°C and char yield (Yc) of 75.77% at 800°C. Moreover, the polymers obtained after curing at 280°C showed superior dimensional stability, CN‐apn‐280 showed extremely low linear expansion coefficient (CTE) of 10.7 ppm/°C. And mP‐apn‐280 showed HR capacity of 3.99 J/g‧K, peak HRR of 4.0 W/K and total HR of 0.8 kJ/g.

Combining machine learning and molecular dynamics to predict strength-toughness and energy dissipation mechanisms of hybrid double-crosslinked CNT networks

Cross-linking has a significant strengthening effect on the mechanical properties of carbon nanoparticles, but there are still great challenges in how to control their mechanical properties through precise cross-linking ratios. Therefore, we use coarse-grained molecular dynamics (CGMD) to simulate its mechanical properties as data samples and combine it with machine learning methods to predict the optimal strength and toughness of carbon nanotubes (CNTs) corresponding to optimal cross-linking conditions. We found that the cross-linking density range is 2.60 ∼ 2.75 × 10-4/nm3, and the strong and weak cross-linking ratio range is 91 % S+9% W∼95 % S+5% W, which is the optimal range to achieve the mechanical properties of CNTs. Excessively high cross-link density and strong bond ratios can reduce the total number of cross-link bond breaks, thus decreasing their toughness. Meanwhile, high cross-linking density has a greater impact on the shear and slip between CNTs, tending to make CNTs brittle. Our proposed new approach for extracting data from coarse-grained models can obtain substantial optimization results without requiring much simulation computation. Furthermore, these cross-linking strategies and machine learning algorithms proposed in this work can provide a theoretical basis for controlling the mechanical properties of CNT materials, and also open up a new way for functional network materials other than CNTs.

Bio-Based Polyurethane Composites from Macauba Kernel Oil: Part 1, Matrix Synthesis from Glycerol-Based Polyol

Polyurethanes are the result of a reaction between an isocyanate and a polyol. The large variety of possible reagents creates many possible polyurethanes to be made, such as soft foams, rigid foams, coatings, and adhesives. This polymer is one of the most produced and consumed polymers in the world with an ever-increasing demand. Despite its usual petrochemical nature, research on bio-based polyurethanes flourishes due to the ease in creating bio-based polyols. This work covers the synthesis of a novel macauba kernel oil polyol by the epoxidation of the oil, followed by a ring-opening reaction of the epoxide with glycerol, used for the preparation of polyurethane foams using different NCO/OH ratios. The FTIR and H1 results confirm the formation of the epoxide and polyol, and the polymers in all NCO/OH ratios were confirmed by FTIR, showing great similarities between the samples, especially PU 1.0 and PU 1.2. Despite the TGs showing close behaviors for the three samples, their DTGs showed great difference between the samples, with PU 1.0 presenting a regular PU DTG profile with three degradation peaks while the other two sample presented five degradation peaks, indicating a higher crosslinking density in them.

Digital Light Processing (DLP) 3D Printing of Caprolactone Copolymers with Tailored Properties through Crystallinity.

Digital light processing (DLP) 3D printing has shown great advantages such as high resolution in the fabrication of 3D objects toward a range of applications. Despite the rapid development of photocurable materials for DLP printing, tailoring properties to meet the specific demands for various applications remains challenging. Herein, we introduce copolymers of caprolactone and allyl caprolactone offering built-in functionality for thiol-ene photochemistry, thereby omitting the need for postfunctionalization. A crystalline block copolymer and an amorphous statistical copolymer were synthesized with the same comonomer composition and molecular weight. Thio-ene photocuring with a tetrafunctional thiol cross-linker was studied at different thiol to double-bond ratios for the copolymers and their blends. All formulations undergo rapid photocuring within several seconds of irradiation with slightly higher gel fractions observed for the statistical copolymer over the block copolymer under the same conditions, suggesting a somewhat higher cross-link density. Thermal properties of the networks were dependent on the presence of the semicrystalline block copolymer, where higher melting enthalpies were reached at higher block copolymer content. Similarly, crystallinity was found to be the main contributor to the mechanical properties. For a comparable composition, the modulus of a block copolymer network was found to be 31 times higher than that of the statistical copolymer network (27.7 vs 0.89 MPa). Intermediate moduli could be obtained by blending the two copolymers. DLP-printed scaffolds from these copolymers retained their thermal properties, therefore offering an efficient approach to tailoring mechanical properties, through crystallinity. Moreover, the printed scaffold displayed shape memory properties as the first example of poly(carprolactone) (PCL) copolymers in DLP printing. These materials are readily synthesized, offer fast and high-resolution 3D printing, and are degradable and cell compatible. They offer a straightforward approach to tailoring properties of PCL-based biomaterials and devices.

Mild condition lignin modification enabled high-performance anticorrosive polyurethane coating

The diverse active hydroxyl groups of lignin pose challenges in the preparation of lignin-based polyurethane coatings with exceptional long-term anticorrosive properties. Here, the dense and defect-free lignin-based polyurethane coating with a thickness of 25 ± 5 μm was successfully synthesized using a mild hydroxypropyl lignin modification approach, exhibiting outstanding barrier properties (|Z| > 109 Ω cm2) and long-term anti-corrosion performance exceeding 120 d. Under ambient conditions (i.e., 25 °C and atmospheric pressure), propylene oxide was directly blended with the alkali solution of lignin to effectively convert phenolic hydroxyl groups into more reactive aliphatic hydroxyl groups, while also minimizing the significant increase in molecular weight caused by lignin condensation. As a result, the high crosslinking density of lignin polyurethane coatings effectively prevented the penetration of corrosive media and enhanced the long-term corrosion resistance of the coatings. Overall, the results demonstrate that a mild hydroxypropyl modification process is an effective and facile strategy to prepare highly reactive lignin-based polyols, which is crucial for the development of high-performance bio-based polyurethane anticorrosive coatings.

Multiphase hydrogen bonding strategies room temperature self-healing, recyclable polyurethane elastomers for applications in flame retardant materials

Novel elastomers offer new opportunities to develop multifunctional materials in terms of combining mechanical strength, room-temperature self-healing properties and recyclability. However, self-healing polymers have high mechanical strength at high internal cross-linking density, but restrict the movement of molecular chain segments leading to reduced self-healing efficiency. The presence of microphase-separated structures makes the polymers poorly efficient for repair at room temperature. In this paper, a multiphase hydrogen bonding (H-bonding) strategy is used to introduce an aliphatic ring into the system to form a repeating unit with the hard segments, as well as a bis-benzene ring structure with a methylene linkage to disrupt the crystallization of the hard domains. Specifically, PUPI-M2I3 has a mechanical tensile strength of 17.93 MPa, an excellent tensile ratio of 1109.88 %, the sample can recover 95.93 % at room temperature after 24 h of fracture and stretching, with excellent room temperature self-healing performance and recyclability. Meanwhile, the self-healing flame-retardant material based on PUPI-M2I3 is developed by comprehensive consideration, which opens a new way for the research and development of flame-retardant materials.

Impact of Annealing Chemistry on the Properties and Performance of Microporous Annealed Particle Hydrogels.

Microporous annealed particle (MAP) hydrogels are a promising class of in situ-forming scaffolds for tissue repair and regeneration. While an expansive toolkit of annealing chemistries has been described, the effects of different annealing chemistries on MAP hydrogel properties and performance have not been studied. In this study, we address this gap through a controlled head-to-head comparison of poly(ethylene glycol) (PEG)-based MAP hydrogels that were annealed using tetrazine-norbornene and thiol-norbornene click chemistry. Characterization of material properties revealed that tetrazine click annealing significantly increases MAP hydrogel shear storage modulus and results in slower in vitro degradation kinetics when microgels with a higher cross-link density are used. However, these effects are muted when the MAP hydrogels are fabricated from microgels with a lower cross-link density. In contrast, in vivo testing in murine critical-sized calvarial defects revealed that these differences in physicochemical properties do not translate to differences in bone volume or calvarial defect healing when growth-factor-loaded MAP hydrogel scaffolds are implanted into mouse calvarial defects. Nonetheless, the impact of tetrazine click annealing could be important in other applications and should be investigated further.

Programmable bionanocomposite coated fertilizers for prolonged controlled release of nitrogen

Controlled-release fertilizers (CRFs) present a promising solution for alleviating food and nutrient scarcity. However, their development has been mainly hindered by both rapid and unsynchronized nutrient release and unsustainable coating materials. In this study, we address this issue by developing a new coating layer for CRFs using a programmable biopolyurethane nanocomposite. This nanocomposite is prepared from diphenylmethane diisocyanate (MDI)-functionalized bentonite nanoclay (BNT-MDI) and a biopolyol from biomass waste. The results show that the BNT-MDI-doped CRFs (BCRFs) exhibit an impressive nitrogen (N)-release longevity of approximately 120 days at a 4 wt% coating ratio, surpassing previous CRF formulations. In a 30-day snap bean cultivation study, BCRF significantly improved root length (1000 %), leaf length (257 %), leaf width (400 %), and plant height (1400 %) compared to the control. The superior performance of BCRF is attributed to the PU-nanoclay biocomposite film, with full nano-exfoliation, controllable porosity, and high crosslinking density. Furthermore, we introduce a new dynamic release mechanism and establish a quantitative relationship between the nanostructure, property, and release performance of BCRF by combining the multiplicative and diffusion models for porous materials. This study provides a theoretical framework and a straightforward methodology for designing programmable nanocomposite structures for future biobased CRFs.

Investigation of thermomechanical behaviors of acrylate-based shape memory polymers by molecular dynamics simulation

Shape memory polymers (SMPs) have received a lot of attention lately due to their potential use as actuators in various applications, including robotics and biomedical device. SMPs are a better choice than other smart materials due to their remarkable ability to recover from significant deformations and their ability to be stimulated remotely. Here, we investigate the mechanical and recovery behaviors of SMPs composed of acrylate-based monomers and crosslinkers with varying crosslink densities, using full-atomistic molecular dynamics (MD) simulations. Physical parameters, such as density and glass transition temperature, are determined for systems with different crosslinking densities. Tensile loading is applied to characterize the mechanical characteristics and shape memory behaviors. Furthermore, the shape-memory behavior of the system with highest crosslinking density is investigated to understand the effects of recovery temperature and deformation temperature on shape recovery. Our findings shed light on the critical structural elements that determine shape recovery ability, giving insights for advanced SMP material design and development. This study adds to our fundamental understanding of SMP behavior and has ramifications for a wide range of technological applications.

Molecular Dynamics Simulations of Gas Transport Properties in Cross-Linked Polyamide Membranes: Tracing the Morphology and Addition of Silicate Nanotubes.

This study employs molecular dynamics (MD) simulations to fundamentally provide insight into the role of cross-link density in the CO2 separation properties of interfacially polymerized polyamide (PA) membranes. For this purpose, two atomistic models of pure polyamide membranes with different cross-link densities are constructed by MD simulations to conceptually determine how the fractional free volume of polyamide affects the gas separation performance of the membrane. The PA membrane with a lower cross-link density (LCPA) shows a higher gas diffusion coefficient, a lower gas solubility coefficient, and a higher gas permeability than the PA membrane with a higher cross-link density (HCPA). Moreover, the pristine and modified silicate nanotubes (SNTs) as the fast gas transport channels are incorporated into the polyamide membranes to assess the effect of the SNT/PA interface chemistry on the CO2 separation properties of the membranes. SNTs are systematically modified by three modifying agents with different CO2-philic groups and different interfacial interaction energies with the polyamide matrix. The results of MD simulations demonstrate that the incorporation of silicate nanotubes into the PA matrix increases the gas diffusivity and permeability and decreases the CO2/gas selectivity. Moreover, the membranes containing modified SNTs possessing high CO2-philicity and high SNTs/PA interfacial interactions show a high CO2 separation performance.

Temperature- and Rate-Dependent Fracture in Disulfide Vitrimers.

The fracture behaviors of disulfide vitrimers are highly rate-dependent. Our investigation revealed that the temperature-dependent fracture behaviors of disulfide vitrimers cannot be entirely explained by a simple time-temperature superposition model. This Letter explores the impact of the dynamic nature of molecular defects on the temperature- and rate-dependent fracture behaviors of disulfide vitrimers. Considering that the high cross-linking density remains constant during the associated bond exchange reaction, we identify loop defects in the network as the primary dynamic defects. By employing small amplitude oscillatory shear, we measured the loop defect fraction in EPS25 disulfide vitrimers at varied temperatures, revealing an increased presence of loop defects at elevated temperatures. Furthermore, our findings indicate that the temperature-dependent fracture behaviors are attributed to the temperature-dependent number of loop defects in disulfide vitrimers.

Trifluorovinyl-ether (TFVE) substituted side-chain polynorbornene for preparing crosslinked polymer with high performance

Characteristics and properties of polynorbornene can be regulated through side-chain engineering. In this contribution, a linear polynorbornene (PNI-TFVE) containing trifluorovinyl-ether (TFVE) side groups was synthesized via ring-opening metathesis polymerization. This linear polynorbornene was soluble in common organic solvents and showed good film-forming ability. Upon thermal post-polymerization, this linear PNI-TFVE can be easily transformed into crosslinked polynorbornene (PNI-PFCB) with perfluorocyclobutyl linkers. The resulted PNI-PFCB exhibited outstanding thermal stability with ultra-high glass transition temperature above 350 °C and a 5 % weight loss temperature of 479 °C. Due to the high crosslinking density and high fluorine content of PFCB, crosslinked PNI-PFCB also exhibited low thermal expansion of 73 ppm °C−1, as well as favourable storage modulus and hydrophobicity.

Waterborne bio-based UV-thermal dual-curable coatings with excellent mechanical properties and thermal resistance based on citric acid modified epoxidised soybean oil

Waterborne bio-based UV-curable coatings have attracted enormous attentions due to their environment friendliness and safety. However, residual neutralizing agents, long-chain aliphatic hydrocarbons derived from epoxidised soybean oil, and the oxygen inhibition inherent in the UV curing process often cause poor thermal resistance and mechanical properties of the epoxidised soybean oil-based waterborne bio-based UV-curable coatings. Herein, the epoxidised soybean oil was hydrophilized by citric acid and poly (ethylene glycol) diglycidyl ether without the use of neutralizing agents. The hydrophilized epoxidised soybean oil was subsequently compounded with bisphenol A epoxy resin to prepare high-performance waterborne bio-based epoxy methacrylates. Finally, a high-performance waterborne bio-based UV-thermal dual-curable coating was obtained by blending waterborne bio-based epoxy methacrylates with waterborne isocyanate curing agent. The results demonstrated that waterborne bio-based epoxy methacrylates possess high bio-based content, low viscosity, and remarkable storage stability. Furthermore, waterborne bio-based UV-thermal dual-curable coatings with high cross-linking density exhibited outstanding mechanical properties and thermal resistance. For example, the waterborne bio-based UV-thermal dual-curable coatings P0805I4 exhibits a breaking elongation of 30.75%, maximum tensile strength of 16.68 MPa, T10% at 285.33 °C, and adhesion class level of 0. Our research not only introduces high-performance waterborne bio-based UV-thermal dual-curable coatings, thereby extending the application domains of soybean oil-derived waterborne bio-based coatings, but also presents a valuable strategy for advancing high-performance, sustainable, waterborne, and environmentally friendly materials.

Recyclable azine polyurethane thermosets and carbon fiber reinforced composites with excellent thermostability and mechanical properties

Carbon fiber reinforced composites (CFRCs) have received increasingly concerns and widely used in high-end applications, owing to their outstanding mechanical properties. Most of the polymers used in CFRCs were thermosets. However, a large number of applications brought enormous wastes due to the stable structure of thermosets which is difficult to degrade or recycle. CFRCs based on dynamic covalent polymers (DCPs) were developed to resolve the recycling problem. Polyurethanes were used for fabricating CFRCs applied in energy absorbing materials, vehicle interiors, sporting goods, and constructing materials, owing to excellent toughness, bonding abilities and low VOCs. Although some recyclable PU CFRCs were developed to resolve the recycling of CFs, there remain the problems of excess catalysts, low chemical resistance or thermostability due to the dynamic feature of DCPs. Herein, a series of azine polyurethane thermosets (APUTs) were prepared from hexamethylene diisocyanate (HDI) trimer and dihydroxy azines with different lengths of carbon chains. The resulting APUTs displayed excellent thermal stabilities with all Td, 5 % exceeding 320 °C, owing to high exchange temperature of azine moieties and high crosslinking density. APUTs-6 showed the highest tensile strength of 36.72 ± 1.18 MPa. APUTs-6 could be easily degraded in 0.1 M acetone/water solution at 50 °C. APUTs-6 showed excellent reprocessing properties and tensile strength could maintain 83.1 % of its initial one. The APUTs-6/CFs composites exhibited excellent mechanical properties, chemical resistance and recyclability. CFs could be readily recycled by acid degradation and maintain excellent mechanical properties. The tensile strength of recycled composites could recover 94.36 % of the original one after two times of recycling. The recovery ratio of tensile strength of recycled CF filaments was 95.7 %. The application of phenyl azine provided a feasible solution for the industrialization of recyclable CFRCs.

Meldrum's acid-functionalized bismaleimide, polyaspartimide and their thermally crosslinked resins: Synthesis and properties

Bismaleimides (BMI) and their corresponding polymers could be obtained with diamine compounds as precursors. In this work, a new Meldrum's acid (MA)-functionalized BMI compound (MA-BMI) and a MA-functionalized polyaspartimide (MA-PAsI) were synthesized with a MA-diamine precursor. Based on the MA-mediated ketene chemistry, additional crosslinking reactions and high crosslinking densities were introduced to the crosslinked MA-BMI (CR_MA-BMI) and crosslinked MA-PAsI (CR_MA-PAsI) polymers. This modification brought high glass transition temperatures of 340 °C and 313 °C to crosslinked CR_MA-BMI) and CR_MA-PAsI, respectively. Moreover, the air-trapped microcavities formed with the evolved CO2 from MA thermolysis reaction attribute to reduce dielectric constants of the crosslinked polymers. The dielectric constants at 40 GHz of CR_MA-BMI and CR_MA-PAsI are 3.01 and 2.21, respectively. Novel maleimide-based resins for high speed and high frequency communication technologies have been demonstrated.

Enhanced interfacial, mechanical, and anti-hygrothermal properties of carbon fiber/cyanate ester composites with the catalytic sizing agents of titanium epoxy

The mechanical properties of composites are closely related to the interfacial behavior, especially under the hygrothermal circumstance. A catalytic sizing agent of titanium epoxy is designed to enhance interfacial, mechanical, and anti-hygrothermal properties of high modulus carbon fiber (HMCF)/cyanate ester composites simultaneously. The mechanisms of interface enhancement and low hygroscopicity of composites are investigated. The titanium epoxy is synthesized and its catalytic effect on the curing of cyanate ester is proved. The interfacial properties of HMCF composites with catalytic sizing agents are improved to 95.5 MPa, which is attributed to the interphase with high crosslinking density and sufficient triazine rings and oxazolidinone structure due to preferential curing induced by interfacial catalysis, stimulating the smooth transition of interphase modulus. Further, the formed interphase exhibits few interface defects and low content of hydroxyl groups, which changes the moisture diffusion path and reduces saturated water absorption of composites to only 0.36 %, resulting in the release of interfacial wet stress concentration and high retention of mechanical properties in hygrothermal environment. The resultant composites with high stiffness, excellent temperature resistance, superior dimensional stability and low moisture absorption are expected to be applied to high-orbit space, aerospace, precision instruments.

Effect of polymer concentration and cross-linking density on the microstructure and properties of polyimide aerogels

Polyimide aerogels display excellent mechanical strength, high thermal stability, low thermal conductivity, and outstanding dielectric properties. Typically, the synthesis of polyimide aerogels involves the polycondensation of dianhydride and diamine into poly(amic acid) (PAA) oligomers, which are then cross-linked and chemically imidized into polyimide. The stoichiometry of dianhydride and diamine determines the number of repeat units and length of the PAA oligomers, which in turn determines the cross-linking density. Despite the critical role of polymer concentration and number of repeating units in determining the microstructure and properties of polyimide aerogels, few detailed studies exist on these two parameters. Here, we synthesized and characterized 16 polyimide aerogel formulations from the common monomers biphenyl-3,3′,4,4′-tetracarboxylic dianhydride (BPDA) and 4,4′-oxydianiline (ODA), with different repeat units (n = 5, 15, 30, 45) and total polymer concentrations (4, 7, 10, 13 wt%). An increased polymer concentration accelerated gelation and enhanced the mechanical performance of aerogels, but surprisingly, it also led to higher volumetric shrinkage during aging, solvent exchange, and supercritical drying (SCD). Specific surface areas (SSAs) reached a maximum at intermediate polymer concentrations. A shorter oligomer chain length, i.e., a higher cross-linking density, led to moderately higher SSAs (between 320 and 400 m2/g) and reduced shrinkage, resulting in lower densities for a given polymer concentration. The density dependence of the thermal conductivity exhibits a pronounced U-shaped curve with a minimum in thermal conductivity of 21–23 mW/(m·K) between 0.080 and 0.120 g/cm3, with somewhat lower values for more highly cross-linked aerogels. This systematic study of polyimide aerogels forms the basis for designing polyimide aerogels with tailored properties for targeted applications.Graphical

Fabrication of chitosan-based fluorescent hydrogel membranes cross-linked with bisbenzaldehyde for efficient selective detection and adsorption of Fe2+

Chitosan, as a natural biomass material, is green, recyclable, sustainable and well biocompatible. The molecular chain is rich in active groups such as amino and hydroxyl groups, and its preparation of fluorescent probes has the advantages of biocompatibility and efficient detection performance. In this study, a bis(benzaldehyde) (BHD) fluorescent functional molecule was designed. Then a series of fluorescent chitosan-based hydrogel films (CSBHD) were prepared using chitosan as raw material and BHD as cross-linking agent. As a fluorescent probe for metal ions, CSBHD was able to efficiently detect Fe2+ with a linear correlation of fluorescence intensity in the range of 0–160 μM, and the limit of detection (LOD) was 0.55 μM. Moreover, it has excellent adsorption performance for Fe2+ ions, with a maximum adsorption capacity of 223.5 g/mg at 500 mg/L Fe2+ concentration. Finally, we characterised the structure and microscopic morphology of CSBHD films and found that CSBHD as a hydrogel film has a high cross-linking density, good water resistance, excellent thermal stability, strong resistance to swelling, and excellent stability in cycling tests. Hence, it has great potential for application in adsorption and detection of Fe2+ ions. It also provides a good strategy for the application of chitosan based fluorescent probe materials in environmental monitoring and heavy metal ion adsorption.