Tailoring Copolymer Properties by Gradual Changes in the Distribution of the Chains Composition Using Semicontinuous Emulsion Polymerization

Abstract

Abstract:To design the properties of a copolymer using free radical polymerization, a semicontinuous process can be applied to vary the instantaneous copolymer composition along the conversion searching for a specific composition spectrum of copolymer chains, which can be termed as weight composition distribution (WCD) of copolymer chains. Here, the styrene-n-butyl acrylate (S/BA) system was polymerized by means of a semicontinuous emulsion process, varying the composition of the comonomer feed to obtain forced composition copolymers (FCCs). Five different feeding profiles were used, searching for a scheme to obtain chains rich in S (looking for considerable modulus), and chains rich in BA (looking for large deformation) as a technique to achieve synergy in copolymer properties; the mechanostatic and dynamic characterization discloses the correspondence between WCD and the bulk properties. 1 H-nuclear magnetic resonance ( 1 H-NMR) analysis enabled the determination of the cumulative copolymer composition characterization, required to estimate the WCD. The static test (stress-strain) and dynamic mechanical analysis (DMA) were performed following normed procedures. This is the first report that shows very diverse mechanostatic performances of copolymers obtained using the same chemical system and global comonomer composition, forming a comprehensive failure envelope, even though the tests were carried out at the same temperature and cross head speed. The principles for synergic performance can be applied to controlled radical copolymerization, designing the composition variation in individual molecules along the conversion.

A Methodology Towards Mechanical Properties Optimization of Three-Component Polymers by the Gradual Variation of Feed Composition in Semi-Continuous Emulsion-Free Radical Polymerization

“…In fact, the aforementioned referred composition variation has already been demonstrated, using the styrene/n-butyl acrylate system (70/30 wt %), where a considerably higher damping capacity was obtained with this type of copolymeric materials, compared to a traditional core-shell type polymer [6]; furthermore, for the same chemical system, using a 50/50 wt % global composition, much higher Young's modulus and toughness values were obtained with these forced composition copolymers (FCC), compared to equivalent statistical and two-stage polymeric materials [7]. The evolution of chains' composition along conversion (for the FCC) was followed by proton nuclear magnetic resonance ( 1 H NMR).…”

“…The evolution of chains' composition along conversion (for the FCC) was followed by proton nuclear magnetic resonance ( 1 H NMR). In those works, the structure-properties relationship was clearly disclosed, "building histograms" of the distribution of copolymer chain's composition contained in each polymer system [6][7][8]. In fact, the great potential to design the properties of a copolymer using that method was demonstrated, disclosing the different types of stress-strain behavior that can be obtained by variations in the feeding profiles while maintaining constant the global copolymer composition [7].…”

“…In those works, the structure-properties relationship was clearly disclosed, "building histograms" of the distribution of copolymer chain's composition contained in each polymer system [6][7][8]. In fact, the great potential to design the properties of a copolymer using that method was demonstrated, disclosing the different types of stress-strain behavior that can be obtained by variations in the feeding profiles while maintaining constant the global copolymer composition [7]. Briefly, the high modulus along with significant values in ultimate deformation that can be obtained denote that a synergistic performance can be achieved with that methodology [8,9].…”

“…For the mechanical performance rationalization of this type of copolymer system [7], the principles explained previously also apply to copolymers synthesized by RDRP, where a gradient in composition is formed in each chain [10,11], and optimal synthesis procedures for linear gradient copolymers have been proposed [12]. Reviews with that technique have shown subsequent advances in that field [13][14][15].…”

The Multirole of Modified Natural Gums for Multicomponent Polymers: As Coupling Agents for Polymers Reinforced With Cellulosic Fibers or Compatibilizers for Biodegradable Polymer Blends

“…Such phenomenon was reported time ago for blends 36 and interpenetrating polymer networks, 37,38 and recently for copolymers also looking for synergic mechanical performance. 39,40…”