Intrinsic viscosity , decrease

Equation (4) shows that the dose-rate exponent of the degree of polymerization agrees with the theory Eq. (2). However, the degree polymerization and the intrinsic viscosity decrease with increasing dose rate is probably due to increased termination reactions caused by the increasing radical population at high dose-rate [22]. 

For poly electrolyte solutions with added salt, prior experimental studies found that the intrinsic viscosity decreases with increasing salt concentration. This can be explained by the tertiary electroviscous effect. As more salts are added, the intrachain electrostatic repulsion is weakened by the stronger screening effect of small ions. As a result, the polyelectrolytes are more compact and flexible, leading to a smaller resistance to fluid flow and thus a lower viscosity. For a wormlike-chain model by incorporating the tertiary effect on the chain... 

Although shear rate effects are more pronounced in good solvents, the intrinsic viscosity decreases with shear rate even in 0-solvents, where excluded volume is zero (317,318). The Zimm model employs the hydrodynamic interaction coefficients in the mean equilibrium configuration for all shear rates, despite the fact that the mean segment spacings change with coil deformation. Fixman has allowed the interaction matrix to vary in an appropriate way with coil deformation (334). The initial departure from [ ]0 was calculated by a perturbation scheme, and a decrease with increasing shear rate in 0-systems was predicted to take place in the vicinity of / = 1. 

It is observed that the reduced steady-state compliance is more sensitive to chain branching than the intrinsic viscosity. Whereas the intrinsic viscosity decreases with increasing degree of branching due to the fact that the values of the longest relaxation times are decreasing, the reduced steady-state compliance decreases as a consequence of the fact that the lines of the spectrum of relaxation times come closer together [cf. Ham]. 

Here kH is the Huggins coefficient. The intrinsic viscosity decreases and the Huggins coefficient increases, as micelles become smaller. On micellization, ijsp/c has been observed to increase for some systems but to decrease for others, and unfortunately there are no firm rules governing which case will prevail for a given block copolymer solution. The viscosities of polymer solutions are measured in capillary flow viscometers, which are described in detail by Macosko (1994). 

After having reached the equilibrium ratio polymer/monomer the intrinsic viscosity shows its maximum value, depending on the temperature, concentration and sort of catalyst (29, 49, 94). By prolonged heating the intrinsic viscosity decreases and after a very sharp decrease during the first stage the viscosity approaches a certain limiting value which depends on the m temperature and on the sort and concentration of j- 7 catalyst (fig. 2). This decrease is a result of... 

Subjected to the same irradiation as the control samples, the breaking strength of the dialdehyde celluloses decreased almost linearly by 10-15% each week within the same oxidation level and no distinct accelerating effect of the introduced groups could be observed. After four weeks exposure, the intrinsic viscosity decreased by about 50-60% with respect to the nonexposed counterpart and by 70 to 80% with respect to the nonexposed unoxidized control. 

The conversion of dextran with 1,2-epoxy-3-phenoxypropane, epoxyoctane or epoxydodecane may be exploited for the preparation of amphiphilic dextran derivatives. Polymeric surfactants prepared by hydrophobic modification of polysaccharides have been widely studied, starting with the pioneering work of Landoll [261]. Neutral water-soluble polymeric surfactants can be obtained by reaction of dextran with 1,2-epoxy-3-phenoxypropane in 1 M aqueous NaOH at ambient temperature (Fig. 35, [229,233]). The number n of hydrophobic groups per 100 Glcp units varies between 7 and 22 depending on the reaction conditions. 2-Hydroxy-3-phenoxy propyl dextran ethers (DexP) behave like classical associative polymers in aqueous solution. In dilute solution, the intrinsic viscosity decreases significantly whereas... 

The results showed that the DLTDP-PPP formulation has the best over-all stability as measured by both intrinsic viscosity change and meter-gram torque (melt viscosity) readings. All formulations suffered torque decreases as well as intrinsic viscosity decreases (Figure 2). 

Investigation of the mechanism of photo- and photooxidative destruction has shown [141, 154 158] that intrinsic viscosity decreases at photodestruction of cellulose acetate, content of combined acetic acid also decreases and accumulation of carbonyl groups takes place. There have been identified six main volatile products CH2=C=0 CO CO2 H2 H2O CH3COOH, moreover acetic acid is the main product [159]. In some authors opinion, break of acetal bond 1-4 and opening of pyranose cycle according to C1-C2 happen at photodestruction of cellulose acetate. 

Studying mechanism of photo- and photooxidative destruction Ibishkovitch and others [243] have shown that during PETP photodestruction intrinsic viscosity decreases, carboxyl groups contain increases, sample density rises, optical density increases at 373 and 632 cm ... 

Figure 10 shows a plot of intrinsic viscosity versus hydrophobe level for two HMHEC samples that have different hydrophobes. As the hydrophobe content at fixed molecular weight increases, the intrinsic viscosity decreases. This behavior is even more striking for CieHMHEC. In dilute solutions, the HMHEC molecules are separate and untangled, and no intermolecular association occurs. However, to minimize the disruption of water structure, hydrophobes on the same chain tend to cluster. This clustering results in a much reduced hydrodynamic volume, and a lower viscosity is observed. Therefore, the dilute solution properties of HMHEC are consistent with intramolecular hydrophobic association (10). Because of intramolecular association and incomplete solubility, the intrinsic viscosity of HMHEC cannot be appropriately correlated with its molecular weight. Hence, to obtain meaningful intrinsic viscosity data, intramolecular association must be com-... 

It is obvious from Table 5.1 that with the increase in exposure time (1-4 minutes), the percentage grafting increased up to 3 minutes (which is optimized) after which it decreased. This may be because of the fact that, beyond an exposure time of 3 minutes, the prolonged exposure to microwave irradiation may have degraded the polysaccharide backbone. Hence, the percentage grafting and intrinsic viscosity decreased. 

Figure 12.1.6 shows two different behaviors for unassociated and associated block copolymers. The first type has a linear relationship between viscosity and concentration whereas with the second there is a rapid increase in viscosity as concentration increases. This is the best described as a power law function. Two polymers in combination have different reactions when dissolved in different solvents (Figure 12.1.7). In MEK, intrinsic viscosity increases as polymer concentration increases. In toluene, intrinsic viscosity decreases as polymer concentration increases. The polymer-solvent interaction term for MEK is very small (0.13) indicating a stable compatible system. The interaction term for toluene is much larger (0.58) which indicates a decreased compatibility of polymers in toluene andlowers viscosity of the mixture. Figure 12.1.8 explicitly shows that the behavior of...

Thus the intrinsic viscosity decreases in proportion to k. On the other hand, rigorous asymptotic analysis and the numerical calculation show that the intrinsic viscosity decreases as... 

The intrinsic viscosity as a function of the sonification time in Table 6.3 shows a similar progression as the molar mass. The intrinsic viscosity decreases exponentially with time and reaches the minimum value of 140 ml/g for this polymer and the chosen energy input. The polydispersity MJM also decreases sUghtly with the sonification time. 

In the situation in which only the thermal factor acts, the relations given in Figure 3.268 would be obtained. The extudates intrinsic viscosity decreases with the increase of the inhibitor s concentration and temperature. 

At 300°C, in the absence of inhibitor, the extrudate intrinsic viscosity decreases with the increase of total - both thermal and mechanical - degradation, (Figure 3.270). 

Comparable results have also been reported for EPDM rubbers [28, 29]. The intrinsic viscosity decrease with mastication temperature (Fig. 3.9) shows three different regions the first (for 20-65°C), where the intrinsic... 

The intrinsic viscosities of the SPPO polymer with an lEC value of 1.93 meq/g in different solvent mixtures are given in Table 14. The data show that the intrinsic viscosity decreased with an increase in chloroform content. Thus, as the chloroform content in the solvent mixture is increased, the intra-molecular SPPOH interactions become more favorable than the SPPOH-solvent interactions. The stronger polymer-polymer interactions lead to tighter... 

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