The basic principle of determining the molecular weight of cellulose by terminal group analysis is to quantify specific functional groups at the end of the polymer chain through chemical or physical methods, and then calculate the average molecular weight. The terminals of cellulose often contain groups such as hydroxyl groups (-OH), so molecular weight can be estimated by detecting the concentration of these terminal groups. Detailed steps: 1. Sample preparation Dissolve the cellulose sample in an appropriate solvent to ensure complete dissolution. Cellulose molecules are not easy to dissolve, and a suitable solvent system is required to choose, such as dimethylacetamide-lithium chloride system (DMAc/LiCl), or alkaline aqueous solution. 2. The commonly used methods for calibration of terminal groups in chemical reactions include esterification or acylation reaction, which modify the hydroxyl group (-OH) at the terminal of cellulose molecules. For example, acetylation reaction is used to react with the terminal hydroxyl group to form an acetate. The product generated after the reaction is then determined by titration or other quantitative analysis techniques, thereby indirectly calculating the concentration of the terminal hydroxyl group.

Gel Permeation Chromatograph (GPC), also known as size exclusion chromatography (SEC), is an analysis method based on molecular volume differential separation of polymers. It is widely used to determine the molecular weight and molecular weight of polymers. distributed. GPC is suitable for determining the molecular weight of polymer materials such as cellulose. The following are the steps and detailed principles for determining the molecular weight of cellulose using GPC. 1. Basic Principle GPC separates molecules of different sizes by using a chromatographic column with porous fillers. Since macromolecules cannot enter small pores, they will pass through the column first, while small molecules can enter pores, thus delaying their outflow. By analyzing the retention time of the molecules in the chromatographic column, the molecular weight of the molecules can be calculated. Results of GPC usually include: • Number average molecular weight (Mn): Indicates the average molecular weight of all molecules in the sample. • Weight average molecular weight (M

Nuclear magnetic resonance (NMR) spectroscopy can be used to determine the molecular weight of cellulose, but this process is more complicated because the structure of cellulose is large and complex. Here are the general steps for determining cellulose molecular weight using NMR method: 1. Sample preparation • Purify the sample: Make sure the cellulose sample is as pure as possible and remove other impurities. • Dissolved sample: Cellulose is not easily dissolved in water and therefore requires dissolving with a suitable solvent system, such as sodium dihydrogen phosphate solution (e.g., 6% sodium phosphate solution) or other solvent systems. 2. NMR Experiment • Select the appropriate NMR frequency: Use high-field NMR instruments, such as instruments with a frequency of 300 MHz or higher, to obtain a clear spectrum. • Obtain spectra: Perform a solid or solution NMR experiment, and obtain a ¹³C-NMR or ¹H-NMR spectrum of cellulose according to the experimental settings. ¹&su

The viscosity method is a simple and effective method to determine the molecular weight of polymers, and is often used to determine the relative molecular weight of polymers such as cellulose. The specific process is based on the relationship between the intrinsic viscosity of the solution and the molecular weight of the polymer. The following are the general steps and principles for determining the molecular weight of cellulose by using the viscosity method: 1. Basic Principle In the viscosity method, by measuring the viscosity of cellulose solution and combining empirical formulas (such as Mark-Houwink equation), the average cellulose can be calculated. Molecular weight. The viscosity measurement method depends on the relationship between the viscosity and molecular weight of the polymer solution, i.e.: [η]=K⋅Mva where: • [η] is the intrinsic viscosity of cellulose (unit: dL/g) and is from the solution. A dimensionless value derived from the viscosity data. • Mv is the viscosity average molecular weight of cellulose. • K and

Determining the molecular weight of cellulose using ultracentrifugation is not a standard method, but the following steps can be tried. The basic idea of ​​this method is to use the settlement behavior of cellulose in the centrifugal field to infer its molecular weight. 1. Prepare sample and solution sample preparation: Dissolve cellulose in a suitable solvent. Commonly used solvents include amino acid salt solutions, ionic liquids or other solvents that can dissolve cellulose. The solubility of cellulose is usually low, so it may be necessary to choose suitable solvents and conditions. Solution preparation: Dissolve cellulose into a solution of a certain concentration and ensure that the solution is uniform. The complete dissolution of the cellulose can be ensured by ultrasonic treatment or other methods. 2. Ultracentrifuge experimental equipment settings: Use an ultracentrifuge (such as a liquid centrifuge) and select the appropriate rotor and speed as needed. Common speed ranges are hundreds of thousands to millions (centrifugal acceleration). Centrifugal conditions: Select the appropriate centrifugal conditions (transfer

Precipitation titration is a method of calculating the molecular weight of the polymer by reacting the terminal groups of the polymer with a specific reagent, and calculating the amount of precipitate produced by titration. For cellulose, titration assays are usually performed for terminal hydroxyl or carboxy groups. The following are the detailed steps: 1. Sample preparation Sample dissolution: Cellulose dissolves in the solvent to ensure uniform dispersion. For cellulose, solvent systems such as DMAc/LiCl can be used. 2. Select a suitable titrator for chemical reactions: Select a suitable precipitant according to the properties of the terminal groups of the cellulose. The titrator commonly used for carboxyl groups is silver ion solution (AgNO₃), which reacts with terminal carboxyl groups to form an insoluble precipitate (such as AgCl). 3. Titration step Mix the cellulose solution with the reaction reagent (such as AgNO₃) to observe the process of producing precipitation. Add AgNO₃ dropwise until no new precipitation is generated (end point can be passed by indicator

Light scattering is an analysis technology based on the interaction between light and matter, and is widely used to determine the molecular weight and molecular size of polymers (such as cellulose). The light scattering method is mainly divided into two types: static light scattering (SLS) and dynamic light scattering (DLS). Among them, static light scattering is used to measure the weight average molecular weight (Mw), root mean square rotation radius (Rg) and second veri coefficient (A2) of the polymer; dynamic light scattering is used to measure the diffusion coefficient and hydrodynamics of particles. Radius (Rh). The following will describe in detail how to determine the molecular weight of cellulose using light scattering method. 1. Basic Principle 1.1 Static Light Scattering (SLS) When a monochromatic, parallel light is irradiated into a polymer solution, the polymers in the solution will cause light scattering. The intensity of scattered light is related to parameters such as molecular weight, concentration and molecular size of the polymer. According to Rayleigh scattering theory, for small particles (particle size is much smaller than the wavelength of light), the scattered light intensity and molecules

Determination of cellulose molecular weight is a key step in cellulose chemistry research. Since cellulose is a linear polymer and different sources and treatment methods will affect its molecular weight, scientific determination of its molecular weight is crucial for the processing and application of cellulose materials. Commonly used cellulose molecular weight measurement methods include viscosity method, gel permeation chromatography (GPC), light scattering method and terminal group analysis. The following describes these methods in detail: 1. Viscosity method The viscosity method is the most commonly used indirect method to determine the molecular weight of cellulose. This method is based on the empirical relationship between the viscosity of a polymer solution and its molecular weight. • Basic principle: By measuring the intrinsic viscosity [η] of the cellulose solution and combining with the Mark-Houwink equation, the viscosity average molecular weight Mv of cellulose is calculated: [η]=K⋅Mva where K and a are solvent and polymer systems. empirical constants. • Steps: 1. Dissolve cellulose in appropriate dissolution

Compared with commonly used lithium-ion batteries of organic electrolytes, rechargeable batteries of water electrolytes are receiving increasing attention due to their low manufacturing cost and high safety. Metal zinc has high electrochemical stability in water electrolytes and can be used directly as the anode of zinc and zinc. Zinc can achieve two electrons participating in electrochemical reactions, with a higher theoretical specific capacitance (820 mAh g−1 and 5855 mAh cm−3) and a lower redox potential (−0.763 V vs standard hydrogen electrode). Zib has the advantages of safety, low cost, high energy density, etc., and is expected to become a high-efficiency energy storage device for the next generation of portable electronic devices. 1. The flexible electrode was prepared with zinc-grown graphite paper as the anode and nanopolyaniline-cellulose paper as the cathode. CNF-based flexible gel electrolytes have high ionic conductivity. When the power density is 0.16 W g−1,

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