Дисперсный состав полиметилметакрилатных суспензий и молекулярные массы полимеров, полученных суспензионной полимеризацией в присутствии акриловых сополимеров в качестве ПАВ

The dispersion composition of polymer suspensions and molecular weights of polymers obtained by suspension polymerization of MMA in the presence of polymer surfactants – methylmethacrylate and methacrylic acid copolymers – were studied. It is shown that a highly dispersed fraction of particles with diameters of 0.02–2.0 µm and a fraction of particles with large diameters (up to 1000 µm) are always present in the polymer suspension. After fractionation of polymer suspensions 3 fractions of particles with different diameters were obtained. For each particle fraction the molecular masses of polymers were determined by viscometry. A significant difference in the values of the molecular masses of polymers obtained as particles of small and large diameters – 105 and 106 Da, respectively – is shown. The presence of a highly dispersed fraction of particles in which a polymer of high molecular weight is formed has a noticeable effect on the average molecular weight of the polymer. In particles of small diameter polymerization takes place according to a mechanism close to the emulsion, due to the fact that the volume of such particles contains a small amount of radicals. The high rate of polymerization leads to the formation of a polymer of high molecular weight, the appearance of a gel effect and a decrease in the termination constant. In most particles, polymerization proceeds by a mechanism close to the solution polymerization, and polymers of low molecular weight are formed. This makes it possible to synthesize polymers of a given molecular weight in drops of certain dispersity.Изучены дисперсный состав полимерных суспензий и молекулярные массы полимеров, полученных суспензионной полимеризацией метилметакрилата в присутствии полимерных ПАВ – сополимеров метилметакрилата и метакриловой кислоты. Показано, что в составе полимерной суспензии всегда присутствуют высокодисперсная фракция частиц с диаметрами 0.02–2.0 мкм и фракции частиц с большими диаметрами (до 1000 мкм). После фракционирования полимерных суспензий получены 3 фракции частиц с различными диаметрами и для каждой фракции частиц определены молекулярные массы полимеров методом вискозиметрии. Показано существенное различие в значениях молекулярных масс полимеров, полученных в частицах малого и большого диаметров – 106 и 105 Да соответственно. Наличие высокодисперсной фракции частиц, в которых образуется полимер высокой молекулярной массы, оказывает заметное влияние на среднюю молекулярную массу полимера. В частицах малого диаметра протекает полимеризация по механизму, близкому к эмульсионной полимеризации, что обусловлено тем, что в объеме таких частиц содержится небольшое количество радикалов. Высокая скорость полимеризации приводит к образованию полимера высокой молекулярной массы, появлению гель-эффекта и уменьшению константы обрыва цепи. В больших частицах полимеризация протекает по механизму, близкому к растворной полимеризации, и образуются полимеры невысокой молекулярной массы. Таким образом, появляется возможность синтеза полимеров заданной молекулярной массы в каплях определенной дисперсности

The Dispersion Composition of Polymethylmethacrylate Suspensions and Molecular Weights of Polymers Obtained by Suspension Polymerization in the Presence of Acrylic Copolymers as Surfactants

The dispersion composition of polymer suspensions and molecular weights of polymers obtained by suspension polymerization of MMA in the presence of polymer surfactants – methylmethacrylate and methacrylic acid copolymers – were studied. It is shown that a highly dispersed fraction of particles with diameters of 0.02–2.0 µm and a fraction of particles with large diameters (up to 1000 µm) are always present in the polymer suspension. After fractionation of polymer suspensions 3 fractions of particles with different diameters were obtained. For each particle fraction the molecular masses of polymers were determined by viscometry. A significant difference in the values of the molecular masses of polymers obtained as particles of small and large diameters – 105 and 106 Da, respectively – is shown. The presence of a highly dispersed fraction of particles in which a polymer of high molecular weight is formed has a noticeable effect on the average molecular weight of the polymer. In particles of small diameter polymerization takes place according to a mechanism close to the emulsion, due to the fact that the volume of such particles contains a small amount of radicals. The high rate of polymerization leads to the formation of a polymer of high molecular weight, the appearance of a gel effect and a decrease in the termination constant. In most particles, polymerization proceeds by a mechanism close to the solution polymerization, and polymers of low molecular weight are formed. This makes it possible to synthesize polymers of a given molecular weight in drops of certain dispersity