Термометричні дослідження полімеризації 2-гідроксіетилметакрилату в присутності полівінілпіролідону з одночасним відновленням йонів нікелю

The kinetics of heat release during the processes of 2-hydroxyethyl methacrylate (HEMA) polymerization in the presence of polyvinylpyrrolidone (PVP) and the copolymerization of HEMA with PVP with simultaneous reduction of Ni2+ has been investigated. Nickel sulphate/sodium hypophosphite redox system in alkaline medium was used for Ni2+ reduction. The kinetic regularities of polymerization have been evaluated by thermometric method. The temperature change of the reaction medium during polymerization has been investigated by means of developed equipment, based on the reactor with properties like adiabatic one. The characteristic parameters that correspond to the time of gel formation, the time of exothermic maximum temperature reach, the range of gel effect and maximum temperature of the exotherm are identified on the obtained thermometric curves. It is determined that in the case of HEMA/PVP compositions, polymerization in the presence of benzoyl peroxide occurs with high rate already at 50 °C. The time of the gel effect start and maximum exothermic temperature mainly depend on the initial composition formula, solvent content, initial polymerization temperature, and also the simultaneous reduction of Ni2+ in the polymerization process. The presence of even a small content of oxidizing agent and reducing agent causes an increase of the time of gel formation start, time of maximum exothermic temperature reach and a decrease of the maximum exothermic temperature. It is determined that use of benzoyl peroxide in combination with iron (II) sulfate for initiating of HEMA copolymerization with PVP enables the process to be performed at room temperature and with a maximum exothermic temperature, which provides chemical reduction of Ni2+. The time and temperature parameters of polymerization determined in the work, as well as the main factors on which these parameters depend, will provide an opportunity to substantiate the technological parameters of metal-filled HEMA/PVP copolymers obtaining.За допомогою термометричного методу досліджено кінетику виділення тепла під час полімеризації композицій на основі 2-гідроксіетилметакрилату (ГЕМА) та полівінілпіролідону (ПВП), ініційованої пероксидом бензоїлу з одночасним відновленням Ni2+. Для відновлення Ni2+ використано окисно-відновну систему нікелю сульфат натрію гіпофосфіт у лужному середовищі. Оцінено вплив складу вихідної композиції, вмісту розчинника, початкової температури полімеризації, концентрації окисника та відновника на кінетичні параметри полімеризації – час початку гелеутворення, час досягнення максимальної температури екзотермії, область гель-ефекту та максимальну температуру екзотермії. Встановлено, що у випадку ГЕМА/ПВП композицій полімеризація у присутності пероксиду бензоїлу відбувається з високою швидкістю вже за температури 50°С. Доведено, що використання комплексного ініціатора, який складається з сульфату заліза (ІІ) та пероксиду бензоїлу, дає можливість здійснювати полімеризацію ГЕМА/ПВП композицій за кімнатної температури та з максимальною температурою екзотермії, яка забезпечує хімічне осадження металу. Виявлено, що температура, до якої нагрівається реакційне середовище, може бути достатньою для перебігу хімічної реакції відновлення Ni2+

Technological Features in Obtaining Highly Effective Hydrogel Dressings for Medical Purposes

The new technology of formation of hydrogel dressings for medical purposes, containing particles of silver was developed. To obtain metal-containing composite hydrogels, we proposed a high-tech single-stage method, which involves polymerization of polymer-monomer compositions based on polyvinyl-pyrrolidone and 2-hydroxyethylmethacrylate with simultaneous chemical reduction of silver ions from its nitrate by ethanol. It was found by the thermometric research that the temperature conditions needed for chemical reduction of silver ions are achieved due to the heat, which is released at the exothermic polymerization reaction. The temporal and temperature parameters of polymerization depending on the composition of the original polymer-monomer composition, the content of solvent and of the initiator, and silver nitrate concentration were determined. They include the initial temperature of polymerization, maximum exothermic temperature, the time of reaching the maximum exothermic temperature, and duration of effect gel. The use of combined initiating system of iron (II) sulfate + benzoyl peroxide makes it possible to implement the process of obtaining hydrogels, containing silver particles, at room temperature, in the open air. The synthesis is technologically simple and is executed without complicated apparatus design. The authors proposed a new technology of formation of hydrogel films with the use of the centrifugal method. Polymerization with silver deposition occurs in the centrifugal form simultaneously with film formation, which allows obtaining the materials with predictable properties that have a uniform distribution of the filler with equal thickness and high quality surfaces in the polymer matrix. The film products obtained as a result of the developed technology can swell in water and other polar solvents, are characterized by durability, elasticity, bactericidal and antifungal properties. The results of the clinical studies showed sufficient clinical effectiveness of using the developed hydrogel dressings for medical purposes based on hydrogels, containing silver particles. Such materials in combination with the integrated therapy help to increase the speed and intensity of treatment of trophic venous ulcers of lower limb