Abstract
AbstractIn this work, for a semicontinuous emulsion polymerization reaction, it is shown that using a redox initiation system at 40°C, substantial modifications in copolymer chain composition with conversion can be easily obtained. To test controllable trajectories for comonomer feeding, linear and parabolic profiles were chosen to get different types of chain composition variations for the 50/50 w/w styrene/n-butyl acrylate system. For the “forced composition copolymers,” the molecular weight averages and distribution were obtained by size exclusion chromatography. The composition along conversion was followed by proton nuclear magnetic resonance to determine the weight composition distribution (WCD) of the copolymer chains. Mechanodynamic (dynamic-mechanical analysis), tensile, and hardness tests exhibited consistent results depending on the WCD that outcomes from the respective feeding profile. The results confirm that this methodology is of great potential for industrial applications when looking for synergy in copolymer properties, and low-cost processes.
Highlights
In this work, for a semicontinuous emulsion polymerization reaction, it is shown that using a redox initiation system at 40°C, substantial modifications in copolymer chain composition with conversion can be obtained
The average Mn’s are >105, and the ĐM’s present reasonable values for semicontinuous reactions [26], which shows the stability of the system about the relation that exists between the comonomer mass flow and the generated radicals with the redox initiation system
No gel formation was observed for the reactions, which sometimes occurs in redox emulsion polymerization reactions [27]
Summary
Abstract: In this work, for a semicontinuous emulsion polymerization reaction, it is shown that using a redox initiation system at 40°C, substantial modifications in copolymer chain composition with conversion can be obtained. Improved results have been obtained with block or graft copolymers of uniform composition, varying size and number of blocks, or graft density for example [1,2] Their industrial production has been limited due to reaction complexities, as well as the difficulties to obtain well-defined structures (affecting the desired properties), and/or the long reaction times, along with the use of costly catalysts or high synthesis temperature, which increases energy costs [3]. A distribution of composition for the copolymer chains is formed within the polymer bulk, and its properties are determined by the whole weight composition distribution (WCD) Such gradient principle has been reported for copolymers “forcing their composition” to make forced composition copolymers (FCC) through the reaction time by variations in the feed composition of the comonomers using semicontinuous emulsion polymerization in free-radical polymerization [10]. Redox initiation in semicontinuous polymerization 615 modulus, as well as deformation and toughness/energy dissipation capacity) is expected, having as main aim to demonstrate that the synthesis of copolymers with a predetermined combination of properties is feasible using redox initiation in a semicontinuous polymerization process
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