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Interfacial tension measurement and interfacial analysis of a reactive polymer blends
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The synthesis of a new polymer with outstanding chemical and mechanical properties has both commercial and economic disadvantages. Hence, existing polymers are modified, or two or more polymers are blended to obtain a material with desirable properties. However, due to entropy loss, most of blends is unstable upon further processing and shaping. So we usually use some additive - compatibilizer
Specially, reactive blending of two or more immiscible polymers with in situ reactive compatibilizers has been extensively employed for developing new materials with desirable physical and mechanical properties.
In this study, we proposed a rheological method to observe the reaction kinetics in the reactive blending system and correlated morphological change at the interface with rheological properties. According to rheological results as well as interfacial morphological changes measured by AFM and TEM, three distinct stages can be considered for reactive blends with planar geometry.
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Figure 1. Plot of etha*
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In stage I, a coupling reaction starts, and the copolymers formed by in situ reaction cover the interface. Because of the increase of interface adhesion by this reaction, the modulus increases. During very short reaction time until the interface is not roughened, the reaction is also characterized by the second-order reaction in addition to the first-order reaction. However, as the reaction continues (t > ttran), the interface becomes saturated and then corrugated. During this time interval, the first order is suitable to analyze the kinetics.
In stage II, the reactive chains near the interface are totally consumed. Thus, chains should move through the brushlike graft copolymer layer. We found that e* does not change with reaction time during the second stage, which suggests that incubation time exists. This incubation time was longer than the value calculated by the self-diffusion coefficient because the diffusion of homopolymer through the copolymer is slower than the self-diffusion.
In stage III, since chains can diffuse through the brushlike layer, the reaction can occur again. The interface is more corrugated and becomes large; thus, e* increased again. When the corrugation of interface was enough (or t > tmic), the copolymer began to pinchoff, which finally became microemulsions (and micelles). Changes of interfacial morphologies during the reaction are schematically drawn in Figure.
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Figure 2. AFM images of PS-mCOOH/PMMA-GMA roughness
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Figure 3. TEM images of PS-mCOOH/PMMA-GMA
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Related Journals
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(1) H. K. Jeon and J. K. Kim, "The Effect of the Amount of In-situ Formed Copolymers on the Final Morphology of Reactive Polymer Blends with an In-situ Compatibilizer", Macromolecules, Vol.31, pp.9273-9280 ACS (1998.12).
(2) Hwang Yong Kim, Unyong Jeong, and Jin Kon Kim, "Reaction Kinetics and Morphological Changes of Reactive Polymer-Polymer Interface" Macromolecules, Vol 36(5), pp.1594-1602.
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