What does esterification crosslinking mean? What is a crosslinker

Cross-linked enzyme crystals provide a combination of enzymes (high activity, high selectivity, easy handling, mild reaction conditions) and solid-phase catalysts (highly adaptable to the environment and can be recycled). It has outstanding advantages in terms of stability, activity and mechanical strength. Cross-linking enzyme crystals are very useful in organic synthesis, such as chiral compound resolution, peptide synthesis, and carbon-carbon bond formation.

Cross-linking, enzymatic hydrolysis or cross-linking, esterification, enzymatic hydrolysis of modified maltodextrin, and its preparation and application, belong to the field of starch modification deep processing. The present invention adopts cross-linking modification to starch or cross-linking modification and esterification modification at the same time, and then enzymatic hydrolysis to prepare modified maltodextrin. The product of the present invention is a modified maltodextrin with low hygroscopicity and certain emulsifying effect, and the product can be used as a functional factor and a sustained-release agent in the food and pharmaceutical industry, and is convenient for popularization and application.

The present invention is to organically combine cross-linking, esterification two modification methods, can be carried out on the traditional maltodextrin production line, does not need to add too much equipment, the process design is scientific, practical, easy to realize industrial production.

Two meanings. 1. Esterification. Acids and alcohols react to form esters, which is an esterification reaction.

2. Cross-linking. Both reactants have 2 functional groups, so that the product of this reaction is a linear macromolecule. If one of them has 3 functional groups, then the reaction product will be a macromolecule with a three-dimensional network structure, like a network.

The latter reaction is the cross-linking reaction.

In summary, esterification cross-linking is a cross-linking reaction in which the reaction functional groups are alcohol hydroxyl groups and carboxyl groups.

Crosslinkers, also known as bridging agents, are an important part of polyhydrocarbon photoresists.

The photochemical curing effect of this photoresist relies on the crosslinker with double photosensitive functional groups to participate in the reaction, and the crosslinker produces double free radicals after the crosslinker**, which reacts with the polyhydrocarbon resin phase to form a bridge bond between the polymer molecular chains and becomes an insoluble substance with a three-dimensional structure.

Crosslinkers are mainly used in polymer materials (rubber and thermosetting resins). Because the molecular structure of polymer materials is like a long line, the strength is low when there is no cross-linking, easy to break, and there is no elasticity, the role of the cross-linking agent is to produce chemical bonds between the first-class molecules, so that the linear molecules are connected to each other to form a network structure, so as to improve the strength and elasticity of the polymer material, the cross-linking agent used in rubber is mainly sulfur, and an accelerator should be added.

NHS ester reaction chemistry.

NHS esters are reactive groups formed by carbodiimide activation of carboxylate molecules (see Carbodiimide Crosslinker Chemistry). NHS ester-activated crosslinkers and labeled compounds react with primary amines under physiological to weakly alkaline conditions (pH to 9) to form stable amide bonds. The reaction releases N-hydroxysuccinimide (NHS).

NHS ester hydrolysis competes with primary amine reactions. The rate of hydrolysis increases with the pH of the buffer, and the crosslinking efficiency decreases in low concentration protein solutions. At pH and 0°C, the hydrolysis half-life of NHS-ester compounds is 4 to 5 hours.

At pH and 4°C, this half-life is reduced to 10 minutes. The degree of NHS ester hydrolysis in aqueous solutions without primary amines can be measured at 260 to 280 nm because NHS by-products absorb peaks in that range.

NHS-ester crosslinking reactions are most commonly performed at room temperature or 4°C in phosphate, carbonate-bicarbonate, HEPES, or borate buffer at pH ( hours). Not compatible with primary amine buffers (e.g., TRIS, TBS) as they compete for reactions. However, in some steps, tris or glycine buffer can be added at the end of the binding step to quench (stop) the reaction.

Low concentrations of sodium azide ( 3 mM or or thimerosal ( mm or Usually do not significantly interfere with the NHS-ester reaction, but do occur at higher concentrations. Impure glycerol and high concentrations of glycerol (20-50) can also reduce reaction efficiency.

Sulfo(sulfo)-NHS esters are identical to NHS esters except that they contain a sulfonate group (SO3) on an N-hydroxysuccinimide ring. This charged group has no effect on the entire chemical reaction and is mainly used to increase the water solubility of the decaying and relieving residual coupling agent containing them. In addition, charged groups prevent sulfo-nhs crosslinkers from crossing the cell membrane, making them usable for cell surface starvation surface crosslinking.

Crosslinker refers to a substance that acts as a bridge between the most advanced molecules, so that multiple linear molecules bond and cross-link into a network structure. Crosslinkers are called differently in different industries. In the rubber industry, it is customary to call it "vulcanizing agent"; In the plastic industry, it is called "curing agent", "curing agent", "hardener"; In the adhesive or coating industry, it is called "curing agent", "hardener", etc.

Although the names are different, they reflect the same chemical nature. Crosslinker is mainly used in polymer materials, because the molecular structure of polymer materials is like a long line, low strength when there is no crosslinking, easy to break, and no elasticity, the application of crosslinker makes the polymers connected together to form a network structure, and the strength and elasticity have been greatly increased.

Uses: 1. Cross-linking and modification of a variety of thermoplastic plastics (polyethylene, polyvinyl chloride, chlorinated polyethylene, EVA, polystyrene, etc.). The general addition amount of thermal crosslinking is 1-3%, plus cumene peroxide (DCP) is; The amount of irradiation crosslinking added is, and DCP can be added.

After cross-linking, it can significantly improve the heat resistance, flame retardancy, solvent resistance, mechanical strength and electrical properties of the product. It significantly improves product quality than peroxide crosslinking alone and is odor-free. Typical for polyethylene, polyethylene, chlorinated polyethylene, polyethylene, EVA cross-linked cables and polyethylene high and low foaming products.

2. Ethylene propylene rubber, various fluorine rubber, CPE and other special rubber vulcanization (used in combination with DCP, the general dosage is, which can significantly shorten the vulcanization time, improve the strength, wear resistance, solvent resistance and corrosion resistance.

3. Cross-linking of acrylic acid and styrene ion exchange resins. It is less than divinylbenzene crosslinker, has high quality, and can prepare ion exchange resin with excellent performance such as anti-fouling, high strength, large pore size, heat resistance, acid and alkali resistance, and oxidation resistance. This is a new type of ion-exchange resin that has been newly developed at home and abroad and has excellent prospects.

4. Modification of polyacrylate, polyalkyl acrylate, etc. It can significantly improve heat resistance, optical properties, and process performance. Typical for the heat resistance modification of ordinary plexiglass.

5. Modification of epoxy resin and DAP (polyalllyl rephthalate) resin. It improves heat resistance, adhesion, mechanical strength and dimensional stability. Typically used for the modification of epoxy potting and encapsulating materials.

6. Cross-linking and modification of unsaturated polyester and thermoplastic polyester. It can significantly improve heat resistance, chemical resistance, dimensional stability, weather resistance and mechanical properties. It is typically used to improve the heat resistance of hot-pressed unsaturated polyester FRP products, and the service temperature of the modified products can reach more than 180.

7. The homopolymer of TAIC itself - polyallyl isotrimelanate is a transparent, hard, heat-resistant, and electrically insulating resin, which can also be used to bond glass and ceramics. Typically used in the manufacture of multi-layer safety glass.

8. The internal plasticization of polystyrene, styrene and TAIC and other copolymerization modifications can be used to make transparent and brittle-resistant products.

Suzhou China Resources.

Generally speaking, cross-linking agents are in polymers. It is mainly the cross-linking of two macromolecular chains. Turning linear polymer crosslinking into a body shape, e.g., for rubber crosslinking.

In life science research, the clever use of crosslinkers can lead to many breakthroughs. Crosslinkers have been widely used in cell membrane structure studies, protein structure studies, protein-protein interaction studies, and biological missiles.