Physical Chemistry of Foods
of mass, is now given by rg¼ rm H 6 ¼ 0 : 41 Ln^0 :^5 ð 6 : 2 Þ The volume that the random coil occupies, including entrapped so ...
more tenuous (rarefied, expanded) for a largerMorn. It also implies that the viscosity of a polymer solution of a given concentr ...
be described as a random chain ofn^0 ‘‘statistical chain elements’’ of average lengthb, wheren^0 b¼nL. Any statistical chain ele ...
valid, since the helix now is a flexible chain, albeit shorter and of larger diameter. Excluded volume and solvent quality. Up ...
self-avoiding random walk. Most water-soluble polymers have 04b4 1 ð 0 : 5 5w5 0 Þ. This implies that for a linear homopolymer r ...
Polydispersity. As mentioned, most polymers show a range in degree of polymerization or molar mass. This means that suitable av ...
mass are available,nandn^0 , and thus the length of a statistical chain element b, can be established. These data can then be us ...
It should be noticed that the results obtained would greatly depend on conditions, such asM,b/L, andb. For instance, ifM¼ 105 , ...
relation, ½Z 0 ¼KhMia¼KhMi^3 n^1 ð 6 : 6 Þ whereMis expressed in daltons. The relation between the exponentsaandn follows from ...
diffusion time of a solid sphere of radiusris given by trot¼ 4 pr^3 Zs kBT ð 6 : 7 Þ whereZsis the viscosity of the solvent. The ...
the molecule or particle. Because of the random variation in conformation, some of the polymer molecules will always be nonspher ...
Question For a solution of (a certain type of) locust bean gum in water at room temperature, the Mark–Houwink parameters areK¼ 8 ...
6.3.1 Description A polymer containing electrically charged groups is called a polyelectrolyte or a macroion. Three types can be ...
Figure 6.7a gives titration curves of a sample of poly(methacrylic acid). We will first consider the curve for low ionic strengt ...
at the prevailing ionic strength; pKavis the average pKaof all groups andfis a constant>1. It is seen in Figure 6.7a that the ...
The polyelectrolyte itselfcontributes to the ionic strength. Recall thatI¼ð 1 = 2 ÞSðmiz^2 iÞ. For a high polymermis very small ...
6.3.2 Conformation and Viscosity Electric charges on a polymer greatly affect its conformation in aqueous solution, because like ...
if k is in nm^1 and the ionic strengthI in mol?L^1. It follows from Eq. (6.10a) thatcis reduced toc 0 =eð& 0 :37 timesc 0 ...
radius of gyration thus is relatively large. If the molecule is not very long, it will attain an almost rodlike conformation at ...
counterion. The association of counterions generally decreases in the order Kþ>Naþ>Liþ, following the Hofmeister series (S ...
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