Length of polymer chains

Volume approximation (when the surface contribution to the free energy of a globule is neglected) works the better the farther the system is from the point of the coil-to-globule transition. In the framework of this approximation, it coincides with the -point, whereas under the theoretical consideration where the surface layer is taken into account, a gap appears separating these two points. The less is the length of polymer chain l, the more pronounced is this gap. Hence, the condition, imposed on the thermodynamic and stoichiometric parameters of the system by the equation of the -point,... 

Poly(methyl methacrylate) with a variable degree of polymerization anchored to silica surfaces was synthesized following the room temperature ATRP polymerization scheme described earlier [45,46]. In the main part of Fig. 25 we plot the variation of the PMMA brush thickness after drying (measured by SE) as a function of the position on the substrate. Thickness increases continuously from one end of the substrate to the other. Since the density of polymerization initiators is (estimated to be 0.5 chains/nm ) uniform on the substrate, we ascribe the observed change in thickness to different lengths of polymer chains grown at various positions. 

The involvement of SBM in alkene polymerization is another area of research interest. Although chain growth in Z-N polymerization occurs by 1,2-insertion into an M-C bond, chain termination may involve SBM. For example, H2 is sometimes added to curtail the length of polymer chains. Watson113 observed that H2 reacts with Lu-alkyls according to equation 11.38. The reaction is undoubtedly a SBM and, as such, may provide a good model for what actually occurs when H2 is used to limit polyalkene chain length. 

The lengths of polymer chains obtained in radical polymerization are not monodisperse, even under ideal conditionsIf termination occurs only by radical coupling, M /Mn = 1.5 as a consequence of the statistical distribution of products. If termination occurs by disproportionation,... 

Contour length of polymer chain (cm) in Chapter 4 Onsager coefficient... 

Ionic polymers may be classified according to the type of the bound ion, its position within the structure, and the amount of bound ions present along a given length of polymer chain. They may be further classified according to the nature of the counterion or the nature of the supporting polymeric backbone. 

The type of acid and glycol used will influence other properties such as resistance to chemicals or flame. Polyesters are therefore classified according to the material used in their manufacture (orthophthalic, isophthalic, iso-NPG, bisphenol, etc.). Processing will largely determine the length of polymer chain other influential factors are monomer content and filler addition. 

The degree of polymerization of a polymer is governed by the termination of the addition reaction by statistical accidents, by the type of catalyst or by impurities, etc. Thus, the result will be, in general, a distribution of lengths of polymer chains or a distribution of molecular weights (or, more formally, relative molecular masses). Depending on the type of polymerization and on its rate, the distribution... 

Inhomogeneous length of polymer chains between cross-linking nodes (elastic chains) - Use of controlled/living polymerization methods Very high... 

Number of repeating units in the chain. It is used as a measure of the length of polymer chains. 

FIGURE 1.25. (a) Conductivity of stretched Gaussian coils versus length of polymer chain for various values of the stretch ratio A. (b) Conductivity of a stretched Gaussian coil as a function of the stretch ratio A for various values of the normalized chain length a. (Adapted from Ref. 99.)... 

In the suspension PVC (S-PVC) process, a suspension of PVC particles having a mean particle size of between 50 and 200 pm is produced. Besides particle size, the essential differences between S-PVC grades result from the average length of polymer chains and from the porosity of the particles. Suspension PVC is always produced batch wise in a stirred vessel. 

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