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Constraint Release Mechanisms for H-Polymers Moving in Linear Matrices of Varying Molar Masses
Lentzakis, Helen,Costanzo, Salvatore,Vlassopoulos, Dimitris,Colby, Ralph H.,Read, Daniel Jon,Lee, Hyojoon,Chang, Taihyun,van Ruymbeke, Evelyne American Chemical Society 2019 Macromolecules Vol.52 No.8
<P>We investigate the influence of the environment on the relaxation dynamics of well-defined H-polymers diluted in a matrix of linear chains. The molar mass of the linear chain matrix is systematically varied and the relaxation dynamics of the H-polymer is probed by means of linear viscoelastic measurements, with the aim to understand its altered motion in different blends, compared to its pure melt state. Our results indicate that short unentangled linear chains accelerate the relaxation of both the branches and the backbone of the H-polymers by acting as an effective solvent. On the other hand, the relaxation of the H-polymer in an entangled matrix is slowed-down, with the degree of retardation depending on the entanglement number of the linear chains. We show that this retardation can be quantified by considering that the H-polymers are moving in a dilated tube at the rhythm of the motion of the linear matrix.</P> [FIG OMISSION]</BR>
Architectural Dispersity in Model Branched Polymers: Analysis and Rheological Consequences
Snijkers, Frank,van Ruymbeke, Evelyne,Kim, Paul,Lee, Hyojoon,Nikopoulou, Anastasia,Chang, Taihyun,Hadjichristidis, Nikos,Pathak, Jai,Vlassopoulos, Dimitris American Chemical Society 2011 Macromolecules Vol.44 No.21
<P>We combine state-of-the-art synthetic, chromatographic, rheological, and modeling techniques in order to address the role of architectural polydispersity in the rheology of model branched polymers. This synergy is shown to be imperative in the field and leads to several important results. Even the best available synthesis is prone to “contamination” by side-products. The exact targeted macromolecular structure can be analyzed experimentally and statistically and eventually fractionated. Temperature-gradient interaction chromatography proves to be an indispensible tool in this process. All techniques are sensitive to the various macromolecular structures, but in different ways. In particular, the presence of side-products may or may not influence the linear rheology, due to competing contributions of the different relaxation processes involved, reflecting different structures at different fractions. Hence, combination of all these techniques is the key for fully decoding the architectural composition of branched polymers and its influence on rheology.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/mamobx/2011/mamobx.2011.44.issue-21/ma2013805/production/images/medium/ma-2011-013805_0019.gif'></P>