Intrinsic viscosity Subject

In the present chapter we shall be concerned with quantitative treatment of the swelling action of the solvent on the polymer molecule in infinitely dilute solution, and in particular with the factor a by which the linear dimensions of the molecule are altered as a consequence thereof. The frictional characteristics of polymer molecules in dilute solution, as manifested in solution viscosities, sedimentation velocities, and diffusion rates, depend directly on the size of the molecular domain. Hence these properties are intimately related to the molecular configuration, including the factor a. It is for this reason that treatment of intramolecular thermodynamic interaction has been reserved for the present chapter, where it may be presented in conjunction with the discussion of intrinsic viscosity and related subjects. 

It is now generally accepted that the GPC retention volume is a function of the product M tf, independent of the nature or structure of the polymer 46, 47) though Pannell 45) found that it failed to correlate the elution behaviour of his highly branched polystyrenes, it may be accepted that M rf will be determinable from GPC retention volumes for moderately branched polymers. To estimate branching, it is necessary to separate this product so that M and [rf are both known and the relation between them can then be used, subject to the uncertainties mentioned in Subsection 9.2.2, for this purpose. It is usual to measure rf rather than M in order to make the separation, as it is easier. The combination of GPC and intrinsic viscosity measurements is now the most usual method for studying long branching. 

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. 

On the subject of stars and linear chains, the same authors have employed MC calculations based on Bishop and Clarke s pivot algorithm to study the validity of scaling and group renormalization theories of these interesting molecules. Dimensions and intrinsic viscosities were also calculated. - ... 

The viscoelasticity in polymer solutions has been investigated for some time but the experimental techniques which enabled measurements at high dilutions have been developed since around 1948 (24). When a polymer solution is subject to a sinusoidally varying shearing stress its response can be expressed in terms of a complex intrinsic viscosity [j ], the imaginary part of which is the rigidity ... 

Another interesting result obtained for solutions of PIB in cyclohexane by Tanaka et al. (2,92) is shown in Fig. 3.4. The reduced storage modulus at infinite dilution is close to the prediction of the Rouse theory while the loss modulus is not. This result indicates the existence of an additional contribution to the intrinsic viscosity at high frequency which might be a frequency-independent high frequency limit [in contrast with the results for PMS (94,99) and for PIB in toluene (2,92)]. We will return to this subject in the following chapter. 

PET/PEN blends can be subjected to a solid state polymerization to increase the intrinsic viscosity or to reduce the acetaldehyde generation. In the course of the solid state polymerization, the extent of transesterification is increased. A low level of transesterification of the PEN/PET preform causes poor transparency, while a high level of transesterification prevents strain-induced crystallization and poor mechanical properties. 

The extent of enzymatic destruction of Qins was estimated by the difference between the value of initial intrinsic viscosity of CHT solutions in acetate buffer with pH = 4.5 obtained from dm specimens and that of intrinsic viscosity of solutions from dm specimens subjected to enzymatic destmction for 1 hr. Food collage-nase (Bioprogress, Schelkovo) was used as an enzymatic preparation. The enzymatic preparation concentration on the base was 5% mass of the CHT mass. 

PET/PEN blends can be subjected to a solid state polymerization to increase the intrinsic viscosity or to... 

It is possible to add a second, molecular weight-sensitive detector to an SEC system to provide a direct means of absolute molecular weight calibration without the need to resort to external standards. These detectors represent refinements in classic techniques, such as light-scattering photometry, capillary viscometry (for intrinsic viscosity), and membrane osmometry for on-line molecular weight determination. Yau recently published a review of this subject with comparisons of the properties and benefits of the principal detectors currently in use (22). The present discussion is restricted to lightscattering and viscometry detectors because Yau s osmometry detector is not yet commercially available. The reader is referred to Chapter 4 for a comprehensive discussion of molecular weight-sensitive detectors. 

Continuous viscometer detectors are not subject to the same limitation as LALLS instruments. The reasons for this are as follows. If one represents a polymer molecule in solution as an equivalent hydrodynamic sphere (4), then the intrinsic viscosity of the solution [r ] is defined according to the... 

For the present fluid-mechanical tests a homologous series of polyacrylamide (PAAm) samples was used whose mean weights, of the molar masses were determined by means of a low-angle laser-light-scattering photometer. The PAAm samples exhibit virtually the same molecular weight distribution Myy/Mn = 2.5 the intrinsic viscosity [ 7 1 was deter-minded in a Zimm-Crothers rotational viscometer, since the polymer solutions are subjected to a very low shear rate in this instrument. The porous media flow tests were carried out with the aid of an instrument such as described in Refs. [1, 2]. Reference is also made to these studies as regards the test procedure and evaluation of the measured data. 

There is no doubt that the characterization of chitin and chitosan materials has been the subject of much work and debate. Molecular weight and the degree of acetylation (D.A.) or deacetylation (D.D.) remain the primary properties of interest. Residual protein, other impurities and ash content are some of the other information sought. The use of GPC and intrinsic viscosity measurements for molecular weights persist, while NMR, IR, UV, and elemental analysis have all been used to report on the D.A. and D.D. (Kasaai 2009). It is now clear that where possible, NMR is the method of choice to evaluate D.A. and D.D., while IR, UV, and elemental analysis are still used where the sample mode does not permit easy access for NMR elucidation. 

PET is also sensitive to degradation fi om the additional heat history and exposure to moisture during recychng. This commonly shows up as a decrease in intrinsic viscosity (IV). It is possible to subject the material to solid-stating, much as is done in resin manufacture, to increase... 

In the case of a ternary acrylonitrile-based copolymer, subjected to spinning from a solution, a more pronounced reduction of its intrinsic viscosity is observed, indeed, when working with more diluted solutions (having, nevertheless, a minimum concentration of 10%), Figure 3.280. 

In the case of polystyrene subjected to mechano-destruction, in the presence of DPPH, increase of the solution s concentration causes lower and lower values of intrinsic viscosity [826]. 

According to this model, intrinsic viscosity depends not only on the molecular weight but also on the specific volume of the macromolecule and the shielding ratio, de Gennes considered this a model of porous sponge with uniform density. The monomers inside the sponge are screened from the flow. Only those on the surface are subject to friction. 

Like intrinsic viscosity and diffusion, sedimentation is a frictional property. It is the transport of mass from the surface toward the bottom. In ultracentrifuge sedimentation, which is our major subject in this chapter, macromolecules in solution are forced to sediment by a centrifugal force that is 100,000 times greater than gravitational force. Sedimentation can be described by Pick s two laws with some modification, since sedimentation is often accompanied by diffusion. The modified equation of Pick s first law is... 

By subjecting aqueous solutions of sodium acrylate in concentrations of 25-40 wt.% to high-energy ionizing radiation, polymers were prepared at pHs from 4 to 14. The products were aqueous solutions or gels. The intrinsic viscosities for the product solutions ranged upward from 6 dl/gm at 25°C in 2 A sodium hydroxide [107]. The dosage rate of these polymerizations was less than 200,000 rads/hr for a total of from 1000 rads to that sufficient to convert substantially all of the monomer to polymer. 

Cotton linters have been subjected to acid hydrolysis for various times and the products converted into samples of cellulose tricarbanilate (weight-average mol. wt. 0.21—1.1 X 10 ).Measurements of the intrinsic viscosities of dilute solutions of the derivatives in p-dioxan and butanone showed that the environment is well displaced from the normal 0-state and is closer to that at the lower critical solution temperature (234 °C in / -dioxan). 

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