Cross Linked PVP Polyvinylpyrrolidone

The PVP Aqueous Solution Was Treated With Persulfates Such As NaZSZO:, KZSZO
To generate cross-linked PVP gel. In order to obtain a gel with moderate strength, the required persulfate concentration is very high, generally twice the concentration of PVP. The exact mechanism of persulfate cross-linking PVP is still unclear. The possible explanation is that persulfate is thermally decomposed into sulfate ion radicals and hydroxyl radicals in aqueous solution, which can capture a hydrogen atom from the polymer molecule to generate macromolecular free radicals. These macromolecular free radicals diffuse and move through molecules or chain segments, and can form stable covalent cross-links with each other.

In The Presence Of Peroxide, a-Diene Is Used To Cross-Link The PVP Solution
The cross-linking reaction is to prepare a reaction solution of 1 mol PVP and 0.02-0.3 mol of a certain α-diene such as 1,7-octadiene with an organic solvent, wherein each mol of α-diene contains 0.5-1.0 mol of peroxide, and react at a constant temperature of 100-200 ° C for 1-30 hours, and then remove the organic solvent by vacuum distillation to obtain a cross-linked product. The reaction solvent should be a common solvent for α-diene and PVP, and various alcohols such as methanol, ethanol and 1,4-butanediol can be used. Due to the high reaction temperature, if a low-boiling organic solvent is used, the reaction needs to be pressurized. Any α-diene with a molecular weight between 68 and 280 can be used as a cross-linking agent. By changing the relative concentration of α-diene and the reaction time, various products with different solubility can be obtained, from cross-linked PVP with

different solubility to PVP gel that is completely insoluble in water.

Cross-linked PVP Can Also Be Prepared By Copolymerization Of Nvp Monomer And Cross-Linking Agent
NVP and an appropriate amount of crosslinking agent and free radical initiator are subjected to precipitation polymerization in an aqueous electrolyte solution. The resulting product is a porous granular NVP crosslinked polymer after filtration, washing and drying. Commonly used crosslinking agents in the polymerization system include the following multifunctional compounds: alkylene bisacrylamide such as N, N'-methylene bisacrylamide, etc.; divinyl aromatic compounds such as divinylbenzene, divinylethylbenzene, etc. Free radical initiators commonly used in vinyl polymerization reactions are suitable for this reaction, including peroxide initiators such as diphenylphthalide peroxide, ditert-butyl peroxide, etc., and azo compounds such as azobisisobutyronitrile, etc. Since NVP monomers can only be partially dissolved in aqueous electrolyte solutions, when the amount of NVP exceeds its saturation in aqueous electrolyte solutions, a heterogeneous polymerization system can be maintained by mechanical stirring. Buffer solutions such as disodium hydrogen phosphate are often added to the reaction system to make the reaction solution neutral or weakly alkaline.