Entanglement of chains

In the Eqs. (3.1) and (3.3), a second term can be introduced to account for the average molecular mass 1V1E between entanglements of chains [5, 29] ... 

Studies of preparation and properties of the so-called Simultaneous Interpenetrating Networks (SIN) occupy a special position among these works. SIN is a complex system of two or more three-dimensional network polymers which are chemically not bonded but are inseparable due to mechanical entanglement of chains. A detailed description of the preparation and properties of SIN is given by Lipatov and Ser-geeva . ... 

Figure 11.6 Entanglement of chain molecules increases with chain length. (Reproduced with permission from L. H. Sperling, Introduction to Physical Polymer Science, 3rd edition, p. 5. Wiley, New York, 2001.)...

Adhesion is a surface phenomenon due to entangling of chains at the surface. Adhesion of different elastomers before (tack) and after vulcanization (co-cure) can often be obtained only through the blending of the dissimilar elastomers with a single component. However, the composition of the surface and thus the adhesion characteristics can be altered without using a high concentration of a particular elastomer in the blend. 

However, ESI mass spectrometry occupies only a small, but valuable, segment in the analysis of synthetic polymers. It is better suited for the analysis of nearly monodisperse biopolymers, because of complications arising from the formation of multiply charged ions. Furthermore, for synthetic polymers the entanglement of chains prevents obtaining ESI spectra at high masses, also posing a limit to its utilization. ... 

X index corresponding to crosslinking chemical bonds (and to entanglement of chains) h index corresponding to interchain physical bonds V volume of swollen sample, (Vj/V ),j( )2 = (yJ V. ... 

The pseudo-cross-link model was proposed by several authors [30-33]. The model is constructed of cross-links caused by the entanglement of chains. 

This observed system-dependence of the value of [t/Jc is to be expected, because the average chain conformations, and therefore the entanglement of chains, depends on solvent quality. Poly(ethylene glycol) (PEG) electrospun from solutions of [iq]c 10 but made up in different solvents yielded very different average fiber diameters, partly because the solvent characteristics also play a role in determining fiber quality (Son et al. 2004d). 

Regardless of the reasons, however, the theoretical calculation usually gives the lower limit, or most conservative value, for the gel-point conversion, giving a margin of safety in practice. An apparent exception can sometimes occur. In concentrated solutions, physical entanglements of chains can cause a polymer to behave as a crosslinked gel at conversions lower than that predicted by this theory. Also, in the preparation of unsaturated polyester... 

Several important problems involving polymer systems depend on a characterization of the interpenetration of chain molecules. These concern (a) the compatibility of polymers in bulk, (b) the entanglement of chain molecules in semidilute solution and (c) the interdiffusion of polymers above the glass transition temperature. Studies carried out over the last few years have shown that emission spectra from systems containing polymers tagged with two fluorescent labels can yield information concerning each of these problems. 

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