Hydrodynamic radius of the polymer

Hydrodynamic radius of the polymer is also dependent on the analyte interaction with the solvent. Polymer conformation and degree of the solvation varies with the variation of the solvent properties. Detailed discussion of all aspects of size exclusion chromatography is given in Chapter 6. 

The success of Swislow et al. (1980) stems from their use of very high molecular weight polymer (2-7 x 10 ) at exceedingly low concentrations (of order 1 x 10 g cm ). They exploited the high sensitivity of photon correlation spectroscopy to measure the hydrodynamic radius of the polymer as a function of temperature. Their results are presented in Fig. 6.5,. These show clearly the collapse of the hydrodynamic radius from 125 nm to 50 nm at 32 °C (this corresponds to a 04). The transition is relatively sharp, its width being about 5 °C. 

Figure 31 displays the influence of sodium hydroxide concentration on the power-law index for each of the polymer solutions examined in Figure 30. At a given polymer concentration, the power-law index significantly increased as sodium hydroxide concentration was increased to 1 wt%. The rate of change of the power-law index with sodium hydroxide concentration was greatly reduced at sodium hydroxide concentrations greater than 1 wt%. These results indicate, considering the rod-like shape of xanthan chains, that the hydrodynamic radius of the polymer is significantly...

While SEC and CZE are capable of physically resolving components, and FIA is not, the point made in Table I is that at a given Mi the reliability of a molecular weight determination improves with increasing resolution per time, Rs/t (equations 1 and 2). In addition, SEC is limited by pore size for the molecular weight resolution of analytes, as well as polymer/solvent interactions that will affect the hydrodynamic radius of the polymer, while CZE experiences the artifact of non-ideal flow rate. However, FIA-based methods operate at zero back pressure, with a lower probability of clogging than most sample modulated analyzers such as S. Further, IA with G detection provides a means for the analysis of mixtures using multivariate statistical techniques (24). 

There are two kinds of electric birefringence techniques, the FEBS and the transient electric birefringence (TEB) method [171, 173]. The TEB method was applied to the solution of polydiacetylene to investigate the rod-coil conformational transition of the polymer chains [174]. The FEBS, on the other hand, has the advantage of giving us the mobility of the carriers along the polymer chain separately from the hydrodynamic radius of the polymer chain (usually referred to as the polymer conformation) [149]. Shimomura et al. [175] have recently applied the FEBS technique to the solutions of dilutely doped PHT to study the intrachain conduction in the conducting polymer and its relation to the main-chain conformation. 

The preceding sections have demonstrated that dendrimers of lower generation are akin to branched polymeric structures. It is therefore to be expected that their flow behavior in dilute solution may be described in terms of the well-known concepts of dilute polymer solutions [14, 15]. Hence, dissolved dendrimers should behave like non-draining spheres. From an experimental comparison of and the immobilization of solvent inside the den-drimer can be compared directly since in this case the dendrimer may be approximated by a homogeneous sphere. Therefore R = 3/5 Rl where Ry, denotes the hydrodynamic radius of the dendrimer. This has been found experimentally [19]. 

In polymer solutions, DLS is used to determine the hydrodynamic radius of the constituent particles using the Stokes-Einstein equation... 

Many foods contain high-molecular weight polymers, such as proteins, pectins, and others. Often, they contribute significantly to the structure and viscosity of foods. In dilute solutions, the polymer chains are separate and the intrinsic viscosity, denoted as [ ], of a polymer in solution depends only on the dimensions of the polymer chain. Because [ ] indicates the hydrodynamic volume of the polymer molecule and is related to the molecular weight and to the radius of gyration, it reflects important molecular characteristics of a biopolymer. The concentrations of polymers used should be such that the relative viscosities of the dispersions are from about 1.2 to 2.0 to assure good accuracy and linearity of extrapolation to zero concentration (Morris and Ross-Murphy, 1981 da Silva and Rao, 1992). Intrinsic viscosity can be determined from dilute solution viscosity data as the zero concentration-limit of specific viscosity (ijsp) divided by concentration (c) ... 

Temperature dependence as the temperature increases, the hydrodynamic radius of the free polymer decreases (due to dehydration) and hence more polymer will be required to achieve the same effect at lower temperatures. 

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