![]() ![]() For bidisperse polymers containing long chains that are not or barely entangled with other long chains (i.e., long chains are self-unentangled), all the entanglements along the probe chains can be considered as short-long entanglements and the entanglement segments have a similar relaxation time, τ o b s, which mostly depends on the relaxation time of the short chains. It has been modelled by different approaches, such as the “self-consistent CR”, the “dynamic Tube dilation”, or the “Double reptation” models. This relaxation mechanism takes place all along the probe chains and is called Constraint Release (CR). Several mechanisms have been proposed to describe the relaxation of the long chains, among which the periodical loosening and reformation of the long chain entanglements involving a short chain (called short-long entanglements), which allows the long chains to further explore their surroundings and relax faster than in the monodisperse case. However, the relaxation process of a long linear polymer moving in a shorter linear matrix is still under discussion. The processes involved in the relaxation of the orientation of a monodisperse linear polymer are well identified and understood, based, for example, on the molecular tube picture proposed by Doi, Edwards and de Gennes. The accurate description of the experimental data obtained provides a good starting point to extend this approach to self-entangled binary blends. Finally, we propose a new description of τ o b s, which is implemented in a tube-based model. While this slight change in the power law exponent does not strongly affect the values of the constraint release times, the results obtained suggest the universality of the CRR process. Based on this large set of data, it is found that with respect to the molar mass of the short chain matrix, τ o b s follows a power law with an exponent close to 2.5, rather than 3 as previously proposed. Therefore, the first objective of the present work is to discuss the different approaches proposed to determine this time and compare them to a large set of experimental viscoelastic data, either newly measured (poly(methyl-)methacrylate and 1,4-polybutadiene blends) or coming from the literature (polystyrene and polyisoprene blends). In particular, while it has been shown that the relaxation of self-unentangled long chains diluted in a short chain matrix is well approximated by a Constraint Release Rouse (CRR) mechanism, there is no consensus on the value of the average release time of their entanglements, τ o b s, which fixes the timescale of the CRR relaxation. This distance and angular rotation are related by the radius of curvature.Despite a wide set of experimental data and a large number of studies, the quantitative description of the relaxation mechanisms involved in the disorientation process of bidisperse blends is still under discussion. The arc length is the distance traveled by the object in rotational motion. While doing rotational motion, the object does a circular motion. The angle of rotation is defined by the angle covered by the body. While working on rotational motion problems, we try to draw similarities between translatory and rotational motion and use similar variables. Rotational motion is the circular motion around a fixed axis. For example, angular velocity and velocity in the translatory motion are analogous and so are torque-force and mass-moment of inertia. These bodies in rotation motion often exhibit behaviors that are similar to the behaviors exhibited by them during translatory motion. Rotational Motion is concerned with the bodies which are moving around a fixed axis. It is defined as the change in position over a period. ![]() In terms of physics and mechanics, this is called velocity. Motion is described as a change in position over a period of time. ISRO CS Syllabus for Scientist/Engineer Exam.ISRO CS Original Papers and Official Keys.GATE CS Original Papers and Official Keys. ![]()
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