A method for locating monomer molecules in hexagonal liquid crystals based on contrast-matched small-angle neutron scattering

Abstract

This invention discloses a method for locating monomer molecules in a hexagonal liquid crystal based on contrast-matched neutron small-angle scattering. The method includes: (1) constructing a surfactant / water / monomer ternary liquid crystal system; (2) theoretically calculating the scattering length density of each component in the liquid crystal system and the theoretical volume fraction of D2O required for overall contrast matching; (3) solving for the experimental contrast matching point of the liquid crystal system; (4) using computer software to construct theoretical structural models under various monomer positioning assumptions and simulating the theoretical contrast matching point corresponding to each theoretical structural model; (5) quantitatively comparing the experimental contrast matching point obtained in step (3) with the contrast matching point of each theoretical structural model in step (4), and determining the positioning of the monomer in the liquid crystal phase based on the comparison results. The method of this invention achieves quantitative and accurate characterization of the spatial distribution of different hydrophilic monomers in a hexagonal liquid crystal system.

Description

Technical Field

[0001] This invention relates to the field of soft matter nanomaterial characterization technology, and in particular to a method for locating monomer molecules in a hexagonal phase liquid crystal based on contrast-matched neutron small-angle scattering. Background Technology

[0002] Hexagonal lyotropic liquid crystals (HLLCs) are highly ordered mesoscopic phase structures formed by the self-assembly of amphiphilic molecules in aqueous solutions. With their regularly arranged nanocolumnar channels as the core feature, they have shown broad application prospects in nanofiltration membrane preparation, catalyst supports and adsorption materials.

[0003] Introducing active monomers into liquid crystal systems and then photo-initiating polymerization is a key approach to transforming flexible liquid crystal templates into solid nanoporous materials with mechanical strength. However, in this process, thermodynamic incompatibility exists between the nascent polymer chains and the flexible liquid crystal template, which can easily lead to deformation or even collapse of the mesoscopic phase structure during polymerization, severely limiting the fidelity of the final material's pore structure.

[0004] The spatial positioning of monomers in the liquid crystal phase is crucial for maintaining interfacial structural stability. The anchoring position of monomer active groups at the surfactant / water interface directly determines the stability of the interfacial curvature, thus affecting the ability to maintain the hexagonal prism morphology during polymerization.

[0005] Currently, researchers typically use 13 Nuclear magnetic resonance (NMR) is used to infer the distribution of crosslinking agents in liquid crystal systems. This involves analyzing the intensity and peak evolution of the chemical shifts of carbon atoms in amphiphilic molecules to qualitatively predict the macroscopic distribution trend of monomers. However, this method can only distinguish different positioning modes based on obvious differences in hydrophilicity and hydrophobicity (such as strongly hydrophobic monomers and strongly hydrophilic monomers), and it is powerless to address positioning differences caused by subtle structural variations.

[0006] Given that the soft liquid crystal mesosphere is extremely sensitive to the molecular configuration of foreign guest molecules, even a small structural change may induce a phase transition or structural instability. Therefore, a characterization method that can quantitatively resolve the precise position of monomers is needed.

[0007] Small-angle neutron scattering (SANS) is a non-destructive analytical technique that uses neutron beams to study the nanoscale structure of materials. It possesses unique advantages such as strong penetration, sensitivity to light elements, and the ability to utilize isotopic contrast variations, making it a powerful tool for characterizing the structure of soft matter at the nanoscale (approximately 1–500 nm). Especially effective for hydrogen (…). 1 H) and deuterium ( 2D) The significant differences in the neutron scattering cross sections of the atoms make it possible to achieve "selective visualization" of specific components of the system by adjusting the H2O / D2O ratio.

[0008] However, there are currently no reports on methods for applying contrast-matched small-angle scattering (CM-SANS) technology to the precise localization of different hydrophilic monomers in liquid crystal phases. Furthermore, there is a lack of complete technical solutions for quantitatively comparing experimental contrast-matched points (CMPs) with theoretical simulations based on structural models to distinguish the distribution of monomers in surfactant head regions, hydrophobic tail regions, or aqueous phase regions. Summary of the Invention

[0009] This invention provides a method for locating monomer molecules in hexagonal liquid crystals based on contrast-matched neutron small-angle scattering, which solves the technical problem that existing qualitative methods such as NMR cannot distinguish the monomer location differences caused by minute structural differences, and realizes quantitative and accurate characterization of the spatial distribution of different hydrophilic monomers in hexagonal liquid crystal systems.

[0010] The technical solution of the present invention is as follows: A method for locating monomer molecules in a hexagonal phase liquid crystal based on contrast-matched small-angle neutron scattering includes the following steps: (1) Construct a surfactant / water / monomer ternary liquid crystal system, wherein the liquid crystal system has a regular mesoscopic ordered structure; (2) Calculate the scattering length density of each component in the liquid crystal system theoretically, and calculate the theoretical volume fraction of D2O required for overall contrast matching of the liquid crystal system based on the scattering length density and volume fraction of each component. (3) With the liquid crystal system composition unchanged, a series of samples with different neutron scattering contrasts were prepared by gradually replacing H2O in the aqueous phase with D2O. Neutron small-angle scattering tests were performed on the series of samples to solve the experimental contrast matching point of the liquid crystal system. (4) Based on the geometric characteristics of the liquid crystal phase, computer software is used to construct theoretical structural models under various single-unit positioning assumptions, simulate and calculate the theoretical contrast matching points corresponding to each theoretical structural model, and establish a theoretical contrast matching point reference database. (5) Quantitatively compare the experimental contrast matching points obtained in step (3) with the contrast matching points of each theoretical structural model in step (4), and determine the theoretical structural model that the liquid crystal system conforms to based on the comparison results, thereby determining the positioning of the monomer in the liquid crystal system.

[0011] Preferably, in step (2), the formula for calculating the scattering length density (SLD) is: ; in, Let Avogadro's constant be 1. For sample density, molar mass For the first The coherent scattering length of a type of atom.

[0012] Preferably, in step (2), the SLD calculator tool of SasView software is used to calculate the scattering length density (SLD).

[0013] Preferably, in step (3), solving for the experimental contrast matching point of the liquid crystal system includes: The integral area of ​​the scattering peaks in the scattering spectrum of each sample was extracted, and the relationship between the square root of the scattering peak intensity and the volume fraction of D2O in the sample was plotted and linearly fitted. The volume fraction of D2O corresponding to the intersection of the fitted line and the x-axis is the experimental contrast matching point of the sample.

[0014] More preferably, the scattering peaks include primary scattering peaks and / or secondary scattering peaks; the integral areas of the primary scattering peaks and / or secondary scattering peaks are extracted respectively, and the relationship between the square root of the peak intensity and the volume fraction of D2O is plotted to obtain the experimental contrast matching points of the primary peaks and / or the secondary peaks respectively.

[0015] Preferably, for hydrophobic monomer liquid crystal systems, it is also necessary to extract the integral area of ​​the secondary scattering peak and calculate its experimental contrast matching point, which is then used in conjunction with the experimental contrast matching point of the primary peak for monomer localization determination.

[0016] In step (4), the theoretical structural models under various monomer localization assumptions are constructed using Mantid software.

[0017] Further preferred, step (4) includes: based on the geometric characteristics of the liquid crystal phase, using computer software to construct theoretical structural models under various monomer positioning assumptions; changing the H2O / D2O ratio in the theoretical structural model system to construct several simulated samples, extracting the square root of the integral area of ​​the scattering peak of each simulated sample's SANS spectrum, plotting the D2O volume fraction of the simulated sample and linearly fitting it, the intersection of the fitted line and the x-axis is the theoretical contrast matching point of the corresponding theoretical structural model, and establishing a theoretical contrast matching point reference database.

[0018] Preferably, in step (4), the theoretical structural model includes: Two-region model: includes two uniform regions: the surfactant whole and the continuous aqueous phase. The monomer is set to be entirely located in the surfactant region or entirely located in the continuous aqueous phase region. The three-region model includes three regions: the hydrophobic tail chain region, the hydrophilic head group region, and the continuous aqueous phase region of the surfactant. The monomer is set to be located in the hydrophobic tail chain region, the hydrophilic head group region, or the continuous aqueous phase region. The four-region model includes the hydrophobic tail chain region of the surfactant, the hydrophilic head group region, the continuous aqueous phase region, and the hydrophobic monomer enrichment region located in the core of the column. The hydrophobic monomers are concentrated in the micelle hydrophobic core.

[0019] Preferably, step (5) includes: selecting the theoretical structure model corresponding to the theoretical contrast matching point that is closest to the experimental contrast matching point of the liquid crystal system from the theoretical contrast matching point reference database, which is the theoretical structure model that the liquid crystal system conforms to, and determining the location of the monomer in the liquid crystal system based on the theoretical structure model.

[0020] Preferably, the method of the present invention for locating monomer molecules in a hexagonal phase liquid crystal based on contrast-matched neutron small-angle scattering further includes: (6) Adjust the D2O ratio in the liquid crystal system to the contrast matching point of surfactant / water, and perform neutron small-angle scattering test under this condition. By comparing the scattering spectra under this condition before and after polymerization, determine the monomer distribution state: Before aggregation: If there is no obvious coherent scattering peak under contrast matching conditions, it indicates that the monomer is distributed across two phases. If there are obvious scattering peaks, it indicates that the monomers are concentrated in a single phase; After aggregation: The presence of strong scattering peaks indicates that the monomers have separated from the liquid crystal template phase and formed a bulk polymer.

[0021] Further preferably, the method of the present invention for locating monomer molecules in a hexagonal phase liquid crystal based on contrast-matched neutron small-angle scattering includes: (7) Small-angle X-ray scattering was used to characterize the changes in liquid crystal phase lattice parameters before and after the introduction of monomers, including interplanar spacing, column spacing, and water layer thickness: If the lattice parameter decreases after the introduction of hydrophilic monomers, it indicates that the total interfacial area increases, which corroborates the conclusion that the monomers are located in the hydrophilic head group region. If the lattice parameters increase or the phase behavior changes significantly, the localization model should be re-evaluated in conjunction with small-angle neutron scattering data.

[0022] Preferably, the surfactant is at least one selected from deuterated anionic surfactants, cationic surfactants, nonionic surfactants, amphoteric surfactants, organosilicon surfactants, fluorocarbon surfactants, and amphiphilic polymers; the degree of deuteration of the surfactant is 0%-100%, and the surfactant's SLD is -0.5×10⁻⁶. -6 Å -2 ~6.4×10 -6 Å -2 .

[0023] The anionic surfactant is selected from carboxylate, sulfate, sulfonate, and phosphate surfactants. The cationic surfactant is selected from quaternary ammonium salts and alkylamine salts. The nonionic surfactants mentioned are selected from polyoxyethylene ethers, polyol esters, alkanolamides, and alkyl glycosides. The zwitterionic surfactants mentioned are selected from betaine-type, amino acid-type, and imidazoline-type surfactants; The organosilicon surfactant mentioned is a polyether-modified organosilicon surfactant; The fluorocarbon surfactant is a fluorinated alkyl amphiphilic compound surfactant; The aforementioned amphiphilic polymers are acrylic block copolymers and polyurethane amphiphilic polymers.

[0024] More preferably, the surfactant is selected from at least one of deuterated sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, fatty alcohol polyoxyethylene ether, polyoxyethylene sorbitan fatty acid ester, cocamidopropyl betaine, octadecyltrimethylammonium chloride, polyether modified polydimethylsiloxane, fluorinated alkyl sulfonates, acrylate block dispersants, alkyl glycosides, and glycerol fatty acid esters.

[0025] The monomer contains at least one carbon-carbon unsaturated double bond capable of undergoing free radical polymerization; the carbon-carbon unsaturated double bond is selected from at least one of carbon-carbon double bonds, (meth)acrylate double bonds, vinyl, allyl, maleimide double bonds, and norbornene double bonds.

[0026] More preferably, the monomer is selected from at least one of polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, and 1,6-hexanediol dimethacrylate.

[0027] This invention also includes: screening monomers suitable for lyotropic liquid crystal template polymerization based on monomer positioning results. If the monomer is located in the hydrophilic head group region, it is determined that the monomer is beneficial to stabilizing the curvature of the liquid crystal interface and is suitable for preparing nanoporous materials with structural fidelity. If the monomer is located in the hydrophobic core region, it is determined that the monomer has a negative effect on interface stability and is prone to phase separation during polymerization.

[0028] This invention also provides a method for preparing nanoporous materials, comprising: Different amounts of the monomer to be tested were introduced into a surfactant / water binary matrix, and the intensity changes of the hexagonal phase diffraction peak were monitored by small-angle X-ray scattering to determine the upper limit of the system's stable tolerance to the monomer. The monomer localization results are obtained by combining the method of localizing monomer molecules in hexagonal phase liquid crystal based on contrast matching neutron small-angle scattering, and monomers with strong interface anchoring ability are selected. The selected surfactant / water / monomer composite system was subjected to UV curing polymerization, retaining the hexagonal mesoscopic phase structure, to obtain a nanoporous material with high light transmittance and high strength.

[0029] Preferably, the surfactant is a reactive amphiphilic surfactant, which has the dual functions of a surfactant and a polymerizable monomer.

[0030] Reactive amphiphilic surfactants include hydrophobic and lipophilic segments, hydrophilic polar head groups, and polymerizable active double bonds. The reactive amphiphilic surfactant is at least one of sodium acryloyloxyalkyl sulfonate, allyl polyoxyethylene ether, and allyl quaternary ammonium salt. Preferably, the reactive amphiphilic surfactant is 2-(methacryloyloxy)ethyl dodecyl dimethyl ammonium bromide.

[0031] Preferably, the monomer is polyethylene glycol dimethacrylate or polyethylene glycol diacrylate.

[0032] In a further preferred embodiment, the mass ratio of surfactant, water, and monomer in the surfactant / water / monomer composite system is 75:19-22:3-6.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) Quantitative accuracy: By comparing the experimental CMP with the CMP of various theoretical models, the subtle positioning differences in the head base region of homologous monomers (such as PEGDA575 and PEGDMA550) with only slight differences in hydrophilicity / hydrophobicity can be distinguished, thus solving the problem of insufficient resolution of qualitative methods such as NMR. (2) Non-destructive in situ: The neutron has strong penetrating power and does not need to damage the liquid crystal sample. The same sample can be tracked throughout the process before and after polymerization. (3) Clear signal separation: The matrix cloaking strategy enables the monomer scattering signal to be completely separated from the background, realizing direct verification of the location of monomers in different regions of micelles; (4) Guiding material optimization: After clarifying the monomer positioning, monomer structures that can effectively stabilize the surfactant / water interface can be screened to improve the fidelity polymerization ability of the liquid crystal mesophase and obtain nanoporous materials with high mechanical strength and high order. Attached Figure Description

[0034] Figure 1 The diagram shows the structure of the monomers and surfactants used in the embodiments of the present invention, as well as the structure and cross-sectional view of the hexagonal liquid crystal phase. Figure 2 This invention utilizes SAXS and2 H NMR confirmation of phase behavior in binary and ternary systems, (A) is SAXS, (B) is 2 H NMR; Figure 3 To obtain the matching point of the d-DTAB / water binary system through contrast matching SANS in this invention, (A) is the neutron SANS scattering spectrum of the d-DTAB / water (60 / 40, v / v) system with different H2O / D2O mixing ratios; (B) is the fitting relationship graph of the square root of the scattering peak intensity as a function of the volume fraction of D2O in the sample; (C) is the contrast matching point obtained by intersecting the fitted line with the x-axis. Figure 4 The matching points of different ternary systems obtained by contrast matching SANS in this invention (using the scattering intensity of the primary peak) are: (A) d-DTAB / water / PEGDA575, (B) d-DTAB / water / PEGDMA550, and (C) d-DTAB / water / HDDMA. Figure 5 This invention uses the matching points obtained through comparative experiments and simulations to determine the distribution model diagram corresponding to PEGDA575. Figure 6 This is a diagram showing the changes in the lattice parameters of the system before and after the introduction of the hydrophilic monomer, as confirmed by SAXS in this invention. Figure 7 This invention determines the distribution model corresponding to PEGDMA550 by comparing the matching points obtained from experiments and simulations. Figure 8 This invention uses SANS to compare the water solubility of PEGDA575 and PEGDMA550; Figure 9 The present invention obtains the matching point of the DTAB / water / HDDMA ternary system through contrast matching SANS (based on the scattering intensity of the secondary peak). (A) is the fitting relationship diagram of the square root of the scattering peak intensity as a function of the volume fraction of D2O in the sample. (B) is the contrast matching point obtained by intersecting the fitted line with the x-axis (y=0). Figure 10 This invention determines the distribution model corresponding to HDDMA by comparing the matching points obtained from experiments and simulations. Figure 11 In this invention, after precisely matching d-DTAB with aqueous SLD, the distribution of monomers before and after polymerization of the DTAB / water / monomer ternary system was evaluated by SANS. (A) is the DTAB / water / PEGDA575 system, (B) is the DTAB / water / PEGDMA550 system, and (C) is the DTAB / water / HDDMA system. Figure 12To evaluate the changes in phase behavior of the DTAB / water / monomer ternary system before and after polymerization using SAXS, (A) is the DTAB / water / PEGDA575 system, (B) is the DTAB / water / PEGDMA550 system, and (C) is the DTAB / water / HDDMA system. Figure 13 This invention uses (A) SANS and (B) SAXS to evaluate the changes in phase behavior of the AOE / water binary system before and after polymerization; Figure 14 This invention utilizes SAXS and 2 ¹H NMR was used to assess the maximum capacity concentrations of monomers PEGDA575 and PEGDMA550 in the AOE / water binary system. (A) shows the SAXS spectra of the AOE / water / PEGDMA550 and AOE / water / PEGDA575 systems, and (B) shows the AOE / water / PEGDMA550 and AOE / water / PEGDA575 systems. 2 H NMR spectrum; Figure 15 The following is a comparison of the performance of the AOE / H2O / PEGDA575 system and the AOE / H2O / PEGDMA550 system after polymerization. (A) is the degree of structure retention of the AOE / water / monomer ternary system after polymerization, evaluated by SAXS; (B) is the transparency evaluation of the AOE / water / monomer ternary system; (C) is the tensile property evaluation of the AOE / water / monomer ternary system; and (D) is the water absorption performance evaluation of the AOE / water / monomer ternary system. Detailed Implementation

[0035] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be noted that the embodiments described below are intended to facilitate the understanding of the present invention and do not limit it in any way.

[0036] A method for locating monomer molecules in a liquid crystal phase based on contrast-matched small-angle neutron scattering includes the following steps: Step 1: Constructing a ternary liquid crystal system of deuterated surfactant / water / monomer A deuterated amphiphilic molecule (such as deuterated dodecyltrimethylammonium bromide, d-DTAB) was selected as the liquid crystal matrix component. A binary liquid crystal matrix was prepared using deionized water or heavy water (D₂O) as the solvent at a predetermined volume ratio (e.g., 60 / 40, v / v). Subsequently, the analyte monomer was introduced into the system at a ratio not exceeding the upper limit of system stability (e.g., replacing an equal volume of binary matrix with 10 vol%). A homogeneous hexagonal ternary liquid crystal sample was prepared using vortex mixing and centrifugation, and then equilibrated overnight.

[0037] Step 2: Theoretical calculation of the scattering length density (SLD) of each component and the contrast matching point (CMP) of the system. Based on the chemical structure, molecular weight, and density of each component, the scattering length density (SLD) is calculated using the following formula: ; in, Let Avogadro's constant be 1. For sample density, molar mass For the first The coherent scattering length of each atom. It can also be calculated directly using the SLD calculator tool in SasView software.

[0038] Based on the SLD and volume fraction of each component, the theoretical volume fraction of D2O required for overall system contrast matching (i.e., theoretical CMP) is calculated as a benchmark for subsequent experimental data comparison. The theoretical volume fraction of D2O is calculated using the following formula. : ; in, The scattering length density of the monomer to be tested. The scattering length density of H2O The scattering length density of D2O This represents the volume fraction of H2O.

[0039] Step 3: Prepare a series of contrast variation samples and conduct SANS tests. With the liquid crystal system composition unchanged, a series of samples with different neutron scattering contrasts (D2O volume fraction gradient covering 0%–100%, which is the volume fraction of D2O in the aqueous phase) were prepared by gradually replacing H2O with D2O in the aqueous phase. SANS tests were performed on these samples, and the integral area of ​​the primary scattering peak (and secondary scattering peaks, if applicable) in each scattering spectrum was extracted. The square root value was then calculated, and a graph showing the relationship between the square root of the peak intensity and the D2O volume fraction was plotted. This linear relationship was fitted, and the D2O fraction corresponding to the intersection of the fitted line and the x-axis (y=0) is the experimental contrast matching point (experimental CMP) for the system.

[0040] Step 4: Construct theoretical structural models for various monomer localization hypotheses and calculate the corresponding theoretical CMP. Based on the geometric characteristics of the hexagonal columnar liquid crystal phase (assuming a circular cross-section), and according to the SLD and volume fraction of each region, the following representative structural models were constructed using Mantid software. The SANS spectra corresponding to each structural model were simulated and calculated, and the theoretical CMP corresponding to each theoretical structural model was also calculated: Model 1 (Two-Region Model): The deuterated surfactant as a whole and the continuous aqueous phase are regarded as two uniform regions, and the monomer is set to be entirely located in the surfactant region or entirely located in the aqueous phase region, respectively. Model 2 (Three-Region Model): The surfactant is further subdivided into a hydrophobic tail chain region and a hydrophilic head group region, plus a continuous aqueous phase, for a total of three regions. The monomer is respectively set to be located in the tail chain region, the head group region, or the aqueous phase region. Model 3 (Special Hydrophobic Core Model): For hydrophobic monomers, four regions are set up: aqueous phase, head-base region, tail-chain region, and monomer enrichment region located in the core, to simulate the situation where monomers are concentrated in the micelle hydrophobic core.

[0041] By systematically changing the H2O / D2O ratio in the theoretical structural model system, the theoretical CMP at the primary and secondary peaks of each model was calculated, establishing a theoretical CMP reference database. The calculation process for the theoretical CMP of the theoretical structural model is consistent with that of the experimental CMP: the square root of the integrated area of ​​the scattering peaks in the SANS spectrum of each simulated sample is extracted, the simulated D2O volume fraction is plotted and linearly fitted, and the intersection of the fitted line with the x-axis is the theoretical CMP corresponding to the theoretical structural model.

[0042] Step 5: Compare experimental CMP with theoretical CMP to determine monomer localization. The experimental CMP obtained in step three is quantitatively compared with the CMP of each theoretical model in step four: If the experimental CMP is close to that of the binary matrix system (the difference in SLD between the contrast matching point of the liquid crystal system and the contrast matching point of the surfactant / water binary matrix system is less than or equal to 0.4 × 10⁻⁶), then... -6 Å -2 If the result is consistent with the theoretical prediction of the three-region model (Model 2) in which the monomer is located in the head group region of the surfactant, then the monomer is determined to be located in the hydrophilic head group region of the surfactant. If the experimental CMP is significantly lower (the difference between the SLD at the contrast-matching point of the surfactant / water binary matrix system and the SLD at the experimental contrast-matching point of the liquid crystal system is greater than 0.4 × 10⁻⁶), then... -6 Å -2 If the experimental CMP values ​​of the primary and secondary peaks are consistent with the four-region model (Model 3) in which the monomer is concentrated in the hydrophobic core, then the monomer is determined to be located in the micelle hydrophobic core.

[0043] Step Six (Verification Step): Directly observe single-cell signals using matrix stealth strategy. The D2O ratio in the system was precisely adjusted to a value that perfectly matched the deuterated surfactant with the aqueous SLD (i.e., the surfactant / water matrix contrast matching point). Under these conditions, the matrix is ​​"transparent" to the neutron beam, and the measured scattering signal originates entirely from the hydrogen-containing monomer itself. By comparing the SANS scattering spectra before and after polymerization under these conditions, it can be directly determined that: If there is no obvious coherent scattering peak (the integral area of ​​the scattering peak is 0) under the contrast matching condition, it indicates that the monomer is distributed across the two phases (located at the head-base interface), making the SLD in each region tend to be uniform, and the scattering contrast is canceled out. If there are obvious diffraction peaks (the integral area of ​​the scattering peaks is greater than 0), it indicates that the monomers are concentrated in a single phase (such as a hydrophobic core) and retain an obvious SLD gradient. If a strong scattering peak (the integral area of ​​the scattering peak is greater than 0) appears after polymerization, it indicates that the monomer has separated from the liquid crystal template phase and formed a bulk polymer.

[0044] Step 7 (Auxiliary Verification): Characterizing lattice parameter changes using SAXS. Small-angle X-ray scattering (SAXS) was used to characterize the changes in lattice parameters (interface spacing, column spacing, and water layer thickness) of the liquid crystal phase before and after the introduction of the monomer. If the lattice parameters decreased after the introduction of the hydrophilic monomer, it indicated an increase in the total interfacial area, consistent with the conclusion that the monomer is embedded in the surfactant head region; if the lattice parameters increased or the phase behavior changed significantly, the localization model needed to be re-evaluated in conjunction with SASX data.

[0045] Please refer to the chemical structures of the substances used in each embodiment. Figure 1 .

[0046] Example 1 Positioning of hydrophilic monomer PEGDA575 (polyethylene glycol diacrylate (Mn=575)) in d-DTAB / water hexagonal phase (1) System preparation and behavior verification Deuterated dodecyltrimethylammonium bromide (d-DTAB, deuteration rate approximately 88%, molecular weight 338.8 g / mol, density 1.14 g / mL, SLD ≈ 6.14 × 10⁻⁶) was used. -6 Å -2 A binary hexagonal phase matrix was prepared by mixing PEGDA575 with deionized water at a ratio of 60 / 40 (v / v), and 10 vol% PEGDA575 (see structure) was added. Figure 1 (Molecular weight 565.99 g / mol, density 1.12 g / mL, SLD≈0.91×10) -6 Å -2Ternary liquid crystal samples were prepared by replacing an equal volume of the binary matrix (d-DTAB, water, and PEGDA575 in a 55 / 35 / 10 volume ratio) with a vortex mixer, centrifugation, and overnight equilibration. SAXS analysis confirmed that the samples exhibited hexagonal phase characteristic diffraction peaks (peak position ratio...). ), 2 ¹H NMR shows a single hexagonal phase line, confirming the homogeneity and stability of the system. Please refer to [link / reference]. Figure 2 .

[0047] (2) SLD calculation and theoretical CMP determination According to the SLD calculation formula, the values ​​of H2O (SLD = -0.56 × 10⁻⁶) were determined. -6 Å -2 D2O (SLD = 6.38 × 10⁻⁶) -6 Å -2 ), d-DTAB as a whole (SLD ≈ 6.14 × 10) -6 Å -2 ) and PEGDA575 (SLD ≈ 0.91×10 -6 Å -2 The scattering length density of d-DTAB / water binary system is calculated. Theoretical calculations show that the contrast matching of the d-DTAB / water binary system with a D2O volume fraction of 96.54% (SLD = 6.14 × 10⁻⁶). -6 Å -2 For the calculation process of D2O, please refer to step two in the specific implementation steps.

[0048] (3) Series contrast SANS test and experimental CMP extraction A series of d-DTAB / (H2O-D2O) (60 / 40, v / v) samples with D2O volume fractions of 70%, 80%, 85%, 90%, 95%, and 100%, and corresponding samples containing 10 vol% PEGDA575 were prepared. SANS analysis was performed on a neutron scattering apparatus. The square root of the integrated area of ​​the primary scattering peak in the SANS spectrum of each sample was extracted, plotted against the D2O volume fraction, and linearly fitted. The intersection of the line with the x-axis is the experimental CMP. (See [reference needed]). Figure 3 .

[0049] The results showed that the experimental CMP value for the d-DTAB / water binary system corresponded to a D2O volume fraction of 96% (SLD ≈ 6.11 × 10⁻⁶). -6 Å -2 The result is highly consistent with the theoretical value of 96.54% (the deviation stems from minor errors in sample preparation); the experimental CMP value for the d-DTAB / water / PEGDA575 (55 / 35 / 10) ternary system corresponds to a D2O volume fraction of 95.9% (SLD ≈ 6.10 × 10⁻⁶). -6 Å-2 (This is almost identical to the binary system; please refer to...) Figure 4 (A)

[0050] (4) Multi-model comparison and judgment positioning Eight theoretical models (including two-region and three-region models) were constructed, and the theoretical CMP of each model under different D2O ratios was simulated and calculated (please refer to step four for the calculation process). Figure 5 The comparison results show that the experimental CMP (SLD=6.10×10) -6 Å -2 The predicted values ​​are consistent with the three-region model where the monomer is located in the hydrophilic head region of the surfactant, but deviate significantly from the predicted values ​​of the model where the monomer is uniformly dispersed throughout the system or located in the hydrophobic tail region.

[0051] (5) SAXS-assisted verification Comparison of SAXS lattice parameters before and after the introduction of PEGDA575: After the introduction of the monomer, the q value of the primary peak increased from 0.169 Å. -1 Increased to 0.192 Å -1 The corresponding interplanar spacing d decreases from 37.16 Å to 32.71 Å, and the column spacing d inter The water layer thickness d decreased from 42.91 Å to 37.77 Å. W The decrease from 7.42 Å to 6.53 Å indicates an increase in the total interfacial area, which corroborates the SANS conclusion regarding the PEGDA575 embedding head base region. Please refer to [link to relevant documentation]. Figure 6 .

[0052] Conclusion: PEGDA575 is located in the hydrophilic head region of d-DTAB micelles.

[0053] Example 2 Positioning of hydrophilic monomer PEGDMA550 (polyethylene glycol dimethacrylate (Mn=550)) in d-DTAB / water hexagonal phase PEGDMA550 (molecular weight 533.99 g / mol, density 1.10 g / mL, SLD ≈ 0.80 × 10⁻⁶) -6 Å -2 The main structural difference between PEGDMA550 and PEGDA575 lies in the terminal groups: PEGDMA550 has a methacrylate group at the end, while PEGDA575 has an acrylate group at the end. The former is slightly more hydrophobic.

[0054] Following the same procedure as in Example 1, the experimental CMP of the d-DTAB / water / PEGDMA550 (55 / 35 / 10) ternary system corresponded to a D2O volume fraction of 91.3% (SLD ≈ 5.78 × 10⁻⁶). -6 Å-2 The SLD level was lower than that of the PEGDA575 system (SLD = 6.10 × 10⁻⁶). -6 Å -2 However, this is higher than that of hydrophobic monomer systems; please refer to [link / reference]. Figure 4 (B)

[0055] The experimental CMP was compared with various theoretical models, and the results also fell within the prediction range of the model with the monomer located in the three-region head-base region (model e). Please refer to [link to model e]. Figure 7 The lattice parameters after introducing PEGDMA550 are (q=0.188Å). -1 d = 33.40 Å, column spacing d inter =38.57Å, water layer thickness d W The evolution pattern of PEGDMA550 (=6.67Å) is consistent with that of Example 1, further confirming that PEGDMA550 is also located in the head-base region. Please refer to [link to relevant documentation]. Figure 6 .

[0056] SANS tests on the mixtures of PEGDMA550 / D2O and PEGDA575 / D2O separately showed that the scattering curve of PEGDMA550 exhibited more pronounced micellar characteristics, indicating that its water solubility was lower than that of PEGDA575. This drives its deeper interfacial penetration in the head group region, stronger interaction with reactive surfactant (AOE) head groups, and better interfacial stabilization. Please refer to [link to relevant documentation]. Figure 8 .

[0057] Conclusion: PEGDMA550 is located in the hydrophilic head region of d-DTAB micelles, and due to the presence of terminal methyl groups, its interfacial anchoring ability should be superior to that of PEGDA575.

[0058] Example 3 Positioning of the hydrophobic monomer HDDMA (1,6-hexanediol dimethacrylate) in the d-DTAB / water hexagonal phase HDDMA (1,6-hexanediol dimethacrylate, molecular weight 254 g / mol, density 0.995 g / mL, SLD ≈0.80 × 10⁻⁶) -6 Å -2 It is a strongly hydrophobic bifunctional monomer. The d-DTAB / water / HDDMA (55 / 45 / 10) system was prepared according to the same procedure.

[0059] (1) Primary peak CMP The experimental CMP corresponds to a D2O volume fraction of 67.8% (SLD ≈ 4.15 × 10⁻⁶). -6 Å -2 The SLD (sulfate-to-active liquid concentration) was significantly lower than that of the binary matrix system (96%), indicating that the component with a significantly lower SLD than the surfactant was distributed within the micelles. Please refer to [link to relevant documentation]. Figure 4 (C)

[0060] (2) The necessity of secondary peak CMP A significant change in the relative intensity ratio of the primary and secondary peaks was observed in the HDDMA-containing system during contrast variations (a phenomenon not observed in the hydrophilic monomer system), indicating that the introduction of the monomer altered the micelle shape factor P(q). Therefore, the experimental CMP of the secondary peak needs to be analyzed simultaneously: the experimental CMP of the secondary peak corresponds to an SLD ≈ 8.2 × 10⁻⁶. -6 Å -2 Please see Figure 9 .

[0061] (3) Validation of the four-region model Simulations were performed using a three-region model (aqueous phase / head-base / tail chain) and a four-region model (aqueous phase / head-base / tail chain / single-phase HDDMA core). Comparison results show that the experimental primary peak CMP (4.15) and secondary peak CMP (8.2) are closest to the predicted values ​​(4.3 and 10.1) of the four-region model, clearly confirming that HDDMA molecules are concentrated and encapsulated within the hydrophobic core of d-DTAB micelles. Please refer to [link to relevant documentation]. Figure 10 .

[0062] Conclusion: HDDMA is located in the hydrophobic core region of d-DTAB micelles, which has a negative effect on interface stability.

[0063] Example 4 Tracking monomer distribution before and after polymerization – a matrix stealth strategy The D2O volume fraction was adjusted to 96.54% (d-DTAB precisely matched to the aqueous SLD). SANS tests were performed before and after polymerization on ternary systems containing PEGDA575, PEGDMA550, and HDDMA, respectively. Please refer to [link to relevant documentation]. Figure 11 .

[0064] Before aggregation: (1) The sample containing PEGDA575 and PEGDMA550 did not show obvious coherent scattering peaks under the contrast matching condition, indicating that the two monomers are distributed across the two phases in the head base region, making the SLD of each region tend to be uniform and the scattering contrast is canceled. (2) The sample containing HDDMA showed obvious diffraction peaks, indicating that HDDMA was concentrated in the hydrophobic single phase and retained obvious SLD gradient, which is consistent with the conclusion of Example 3.

[0065] After aggregation: (1) Strong scattering peaks were observed in all three monomer systems, indicating that the monomers had separated from the hexagonal mesoscopic template and formed a bulk polymer, and were no longer uniformly distributed in the liquid crystal structure. (2) Analysis based on SAXS results: Hexagonal phase diffraction peaks are still visible in the SAXS spectra after polymerization (and the lattice parameters are somewhat enlarged). This does not originate from the polymer network itself, but rather from the hexagonal liquid crystal phase that spontaneously reorganizes after the separation of the residual surfactant phase. Please refer to [link to relevant documentation]. Figure 12 This indicates that the monomer alone is insufficient to lock the hexagonal phase structure through polymerization.

[0066] Example 5 Enhancing the fidelity of reactive surfactant (AOE) architecture (1) AOE / D2O binary system The reactive amphiphilic molecule AOE possesses dual functions as both a surfactant and a polymerizable monomer. The AOE / D₂O (73 / 27, mass ratio) system was cured under UV light (365 nm, 2650 µW / cm²). 2 (20 min), both SANS and SAXS retained hexagonal phase characteristic diffraction peaks before and after polymerization ( (For evidence demonstrating that the AOE system effectively maintains its hexagonal mesoscopic phase structure after polymerization, please refer to...) Figure 13 .

[0067] (2) AOE / H2O / monomer ternary system Different amounts of PEGDMA550 and PEGDA575 were introduced into the AOE / H2O system, respectively. (See [link to relevant documentation]). Figure 14 : ①The intensity of the SAXS primary peak in the AOE / H2O / PEGDA575 (75 / 20 / 5, mass ratio) system decreased significantly after the introduction of 5wt% PEGDA575, indicating that the hexagonal phase structure was significantly damaged. ②The AOE / H2O / PEGDMA550 system only showed a similar peak intensity decrease when the dosage exceeded 6wt%, indicating that the AOE / water matrix has a higher upper limit for PEGDMA550.

[0068] ③ 2 1H NMR analysis showed that the sample containing PEGDMA550 exhibited a clear hexagonal phase line, while the sample containing PEGDA575 showed a significant isotropic signal, further confirming that PEGDMA550 has a better effect on improving interface stability.

[0069] (3) Comparison of final material properties A performance comparison was performed after polymerization of AOE / H2O / PEGDA575 (75 / 21 / 4) and AOE / H2O / PEGDMA550 (75 / 20 / 5). Please refer to [link to relevant documentation]. Figure 15 : AOE / H2O / PEGDMA550 (75 / 20 / 5) has higher light transmittance than AOE / H2O / PEGDA575 (75 / 21 / 4), indicating better structural uniformity; it also has higher Young's modulus and tensile strength; and its water absorption rate is 3% higher, indicating higher porosity.

[0070] The AOE / PEGDMA550 system effectively stabilizes the curvature of the surfactant / water interface during polymerization due to the precise anchoring of its monomers at the interface, resulting in nanoporous materials with uniform structure, high strength, and high light transmittance.

[0071] The embodiments described above provide a detailed explanation of the technical solutions and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, additions, and equivalent substitutions made within the scope of the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for locating monomer molecules in a hexagonal phase liquid crystal based on contrast-matched neutron small-angle scattering, characterized in that, Includes the following steps: (1) Construct a surfactant / water / monomer ternary liquid crystal system, wherein the liquid crystal system has a regular mesoscopic ordered structure; (2) Calculate the scattering length density of each component in the liquid crystal system theoretically, and calculate the theoretical volume fraction of D2O required for overall contrast matching of the liquid crystal system based on the scattering length density and volume fraction of each component. (3) With the liquid crystal system composition unchanged, a series of samples with different neutron scattering contrasts were prepared by gradually replacing H2O in the aqueous phase with D2O. Neutron small-angle scattering tests were performed on the series of samples to solve the experimental contrast matching point of the liquid crystal system. (4) Based on the geometric characteristics of the liquid crystal phase, computer software is used to construct theoretical structural models under various single-unit positioning assumptions, simulate and calculate the theoretical contrast matching points corresponding to each theoretical structural model, and establish a theoretical contrast matching point reference database. (5) Quantitatively compare the experimental contrast matching points obtained in step (3) with the contrast matching points of each theoretical structural model in step (4), and determine the theoretical structural model that the liquid crystal system conforms to based on the comparison results, thereby determining the positioning of the monomer in the liquid crystal system.

2. The method for locating monomer molecules in a hexagonal phase liquid crystal based on contrast-matched neutron small-angle scattering according to claim 1, characterized in that, In step (3), the experimental contrast matching points of the liquid crystal system are determined as follows: The integral area of ​​the scattering peaks in the scattering spectrum of each sample was extracted, and the relationship between the square root of the scattering peak intensity and the volume fraction of D2O in the sample was plotted and linearly fitted. The volume fraction of D2O corresponding to the intersection of the fitted line and the x-axis is the experimental contrast matching point of the sample.

3. The method for locating monomer molecules in a hexagonal phase liquid crystal based on contrast-matched neutron small-angle scattering according to claim 2, characterized in that, The scattering peaks include primary scattering peaks and / or secondary scattering peaks; the integral areas of the primary scattering peaks and / or secondary scattering peaks are extracted respectively, and the relationship between the square root of the peak intensity and the volume fraction of D2O is plotted to obtain the experimental contrast matching points of the primary peaks and / or secondary peaks respectively.

4. The method for locating monomer molecules in a hexagonal phase liquid crystal based on contrast-matched neutron small-angle scattering according to claim 3, characterized in that, For hydrophobic monomer liquid crystal systems, it is also necessary to extract the integral area of ​​the secondary scattering peak and calculate its experimental contrast matching point, which is then used in conjunction with the experimental contrast matching point of the primary peak for monomer localization.

5. The method for locating monomer molecules in a hexagonal phase liquid crystal based on contrast-matched neutron small-angle scattering according to claim 1, characterized in that, In step (4), the theoretical structural model includes: Two-region model: includes two uniform regions: the surfactant whole and the continuous aqueous phase. The monomer is set to be entirely located in the surfactant region or entirely located in the continuous aqueous phase region. The three-region model includes three regions: the hydrophobic tail chain region, the hydrophilic head group region, and the continuous aqueous phase region of the surfactant. The monomer is set to be located in the hydrophobic tail chain region, the hydrophilic head group region, or the continuous aqueous phase region. The four-region model includes the hydrophobic tail chain region of the surfactant, the hydrophilic head group region, the continuous aqueous phase region, and the hydrophobic monomer enrichment region located in the core of the column. The hydrophobic monomers are concentrated in the micelle hydrophobic core.

6. The method for locating monomer molecules in a hexagonal phase liquid crystal based on contrast-matched neutron small-angle scattering according to claim 5, characterized in that, Step (5) includes: selecting the theoretical structure model corresponding to the theoretical contrast matching point that is closest to the experimental contrast matching point of the liquid crystal system from the theoretical contrast matching point reference database, which is the theoretical structure model that the liquid crystal system conforms to, and determining the location of the monomer in the liquid crystal system based on the theoretical structure model.

7. The method for locating monomer molecules in a hexagonal phase liquid crystal based on contrast-matched neutron small-angle scattering according to claim 1, characterized in that, Also includes: (6) Adjust the D2O ratio in the liquid crystal system to the contrast matching point of surfactant / water, and perform neutron small-angle scattering test under this condition. By comparing the scattering spectra under this condition before and after polymerization, determine the monomer distribution state: Before aggregation: If there is no obvious coherent scattering peak under contrast matching conditions, it indicates that the monomer is distributed across two phases. If there are obvious scattering peaks, it indicates that the monomers are concentrated in a single phase; After aggregation: The presence of strong scattering peaks indicates that the monomers have separated from the liquid crystal template phase and formed a bulk polymer.

8. The method for locating monomer molecules in a hexagonal phase liquid crystal based on contrast-matched neutron small-angle scattering according to claim 1, characterized in that, Also includes: (7) Small-angle X-ray scattering was used to characterize the changes in liquid crystal phase lattice parameters before and after the introduction of monomers, including interplanar spacing, column spacing, and water layer thickness: If the lattice parameter decreases after the introduction of hydrophilic monomers, it indicates that the total interfacial area increases, which corroborates the conclusion that the monomers are located in the hydrophilic head group region. If the lattice parameters increase or the phase behavior changes significantly, the localization model should be re-evaluated in conjunction with small-angle neutron scattering data.

9. The method for locating monomer molecules in a hexagonal phase liquid crystal based on contrast-matched neutron small-angle scattering according to claim 1, characterized in that, Monomers suitable for lyotropic liquid crystal template polymerization were selected based on monomer localization results: If the monomer is located in the hydrophilic head group region, it is determined that the monomer is beneficial to stabilizing the curvature of the liquid crystal interface and is suitable for preparing nanoporous materials with structural fidelity. If the monomer is located in the hydrophobic core region, it is determined that the monomer has a negative effect on interface stability and is prone to phase separation during polymerization.

10. A method for preparing a nanoporous material, comprising: Different amounts of the monomer to be tested were introduced into a surfactant / water binary matrix, and the intensity changes of the hexagonal phase diffraction peak were monitored by small-angle X-ray scattering to determine the upper limit of the system's stable tolerance to the monomer. The monomer localization result is obtained by combining the method of localizing monomer molecules in hexagonal phase liquid crystal based on contrast matching neutron small-angle scattering as described in any one of claims 1-9, and monomers with strong interface anchoring ability are selected. The selected surfactant / water / monomer composite system was subjected to UV curing polymerization, retaining the hexagonal mesoscopic phase structure, to obtain a nanoporous material with high light transmittance and high strength.

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