Molecular weight entanglement

Since pc 1/2, we observe that Me 2Mg, as commonly observed. Mg is determined from the onset of the rubbery plateau by dynamic mechanical spectroscopy and Me is determined at the onset of the highly entangled zero-shear viscosity law, T) M. This provides a new interpretation of the critical entanglement molecular weight Mg, as the molecular weight at which entanglement percolation occurs while the dynamics changes from Rouse to reptation. It also represents the... 

Hergenrother W.L. and Doshak J.M., Determination of entanglement molecular weight of thermoplastic elastomers by tensile retraction measurement, J. Appl. Polym. Sci., 40, 989, 1990. 

The new information necessary to make this approach quantitative is the dependence of the effective entanglement molecular weight on the concentration, (j) of unrelaxed segments. This is known from experiments on dilution of polymer melts by theta-solvents to be approximately which corre-... 

Fig.9. Predictions of parameter-free theory for G (co) with 0(1) corrections to Gq and Tg as for Fig. 8 and data for a range of 3- and 4-arm star polyisoprenes from [5]. Arm molecular weights in 10 g mol are 11.4,17, 36.7,44,47.5, 95 and 105. The entanglement molecular weight has been taken as 5000 g mol" ...

The mathematical treatment that arises from the dynamic dilution hypothesis is remarkably simple - and very effective in the cases of star polymers and of path length fluctuation contributions to constraint release in Hnear polymers. The physics is equally appealing all relaxed segments on a timescale rare treated in just the same way they do not contribute to the entanglement network as far as the unrelaxed material is concerned. If the volume fraction of unrelaxed chain material is 0, then on this timescale the entanglement molecular weight is renormalised to Mg/0 or, equivalently, the tube diameter to However, such a... 

The critical molecular weight, Mc is related to the entanglement molecular weight, Me, as Me = Mc/2. The entanglement molecular weight specifies the length of a polymer that is required to cause interpenetration of the chains. If solvent is added to the melt, the... 

A/, M c e Critical molecular weight, entanglement molecular weight, (7.65). 

The entanglement molecular weight Me of SAN copolymers at melt temperatures falls from about 18 [30,34] to 5.0kg/mol [34] as wAn rises from 0.0... 

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