Molecular weight, relationship

The molecular weight of SAN can be easily determined by either intrinsic viscosity or size-exclusion chromatography (sec). Relationships for both multipoint and single point viscosity methods are available (18,19). Two intrinsic viscosity and molecular weight relationships for azeotropic copolymers have been given (20,21) ... 

Fig. 2. Glass-transition temperature—molecular weight relationship for poly(ethylene oxide) (-) represents classical T —mol wt relationship Q, data from...

Fig. 15. Polymerization rate vs molecular weight relationship for spontaneous bulk styrene polymerization under neutral and acidic conditions.

The dilute solution properties of copolymers are similar to those of the homopolymer. The intrinsic viscosity—molecular weight relationship for a VDC—AN copolymer (9 wt % AN) is [77] = 1.06 x 10 (83). The characteristic ratio is 8.8 for this copolymer. 

Intrinsic viscosity—molecular weight relationships have been obtained for copolymers in methyl ethyl ketone. The value for a 15 wt % ethyl acrylate (EA) copolymer is [77] = 2.88 x 10 . ... 

Table 3. Intrinsic Viscosity—Viscosity Average Molecular Weight Relationships as a Function of Hydrolysis...

The study of the peak temperature sensitivity to the reactor operating parameters and the construction of sensitivity boundary curves for stable reactor operation were previously reported ( l). This paper presents a computer study on conceptual relationships between the conversion-product properties and the reactor operating parameters in a plug flow tubular reactor of free radical polymerization. In particular, a contour map of conversion-molecular weight relationships in a reactor of fixed size is presented and the sensitivity of its relationship to the choice of initiator system, solvent system and heat transfer system are discussed. 

This work particularly emphasizes the importance of selecting the initiator system for optimum reactor operation and reveals general concepts which specify the desired properties and operational modes of an optimum initiator system. In addition, the effects of the system heat transfer and the CTA (chain transfer agent) level on the conversion-molecular weights relationships are presented. 

Equation (8) provides a general relationship between the reactor temperature profile and the operating parameters. In relating the system heat transfer to the conversion-molecular weights relationship for a reactor of fixed size, the heat transfer coefficient emerges as the correlating parameter. 

Fig. 50.—Intrinsic viscosity-molecular weight relationship for polyisobutylene in diisobutylene (DIB) at 20° and in cyclohexane at 30°C. Open circles from Ref. 7 filled circles, Ref. 8.

The viscosity average molecular weight depends on the nature of the intrinsic viscosity-molecular weight relationship in each particular case, as represented by the exponent a of the empirical relationship (52), or (55). However, it is not very sensitive to the value of a over the range of concern. For polymers having the most probable distribution to be discussed in the next chapter, it may be shown, for example, that... 

We, therefore, propose an indirect method for obtaining the variation of the intrinsic viscosity and number average molecular weight across the chromatogram. First the intrinsic viscosity-molecular weight relationship for a polymer with long chain branching (LCB) is assumed to be expressable in a form similar to that used by Ram and Milts (6),... 

Kurata, M., Tsunashima, Y., Iwama, M., and Kamada, K., Viscosity-molecular weight relationships and unperturbed dimensions of linear chain molecules, in Polymer Handbook, 2nd ed., Brandrup, J. and Immergut, E. H., Eds, John Wiley Sons, New York, 1975, iv, 1-60. 

Figure 2 shows the time-conversion and time-molecular weight relationships in the photopolymerization of St and MMA with 13 at 30°C [16, 76,157]. The yields and molecular weight of the polymer increased with polymerization time. From the analysis of the end groups of the polymer chain, it was confirmed that the number of the DC groups remained at two during polymerization (Table 2) [76,156]. 

The time-conversion and time-molecular weight relationships in the photopolymerization of St with 7 and 8 are shown in Fig. 3, in which the concentration of the DC group as an iniferter site in these iniferters was identical, i.e., [7]/2-[8]. 

Fig Intrinsic viscosity-Molecular weight relationships for polyisobutylene in disobutylene and cyclohexane. 

Kurata, M. and Tsunashima, Y., Molecular weight relationships and unper-turbated dimensions of linear chain molecules, In Polym. Handbook, 4th Edn, Wiley-Interscience, New York, 1999, p. VII-35. 

The original poly(vinyl alcohol) was studied in both aqueous and DMSO solutions. Viscosity-molecular weight relationships have been reported for each of these solutions at 30°C as shown in Equations 19 and 20 (3). 

Intrinsic viscosity molecular weight relationship. The values of two constants appearing in the above relation, determined when fractions of a polymer of molecular weights 34000, 61000 and 130000 dissolved in an organic solvent gave the intrinsic viscosities as 1.02,1.60 and 2.75 respectively at 25°C... 

Table II. The covolume factor-molecular weight relationship for the major detonation species.

A more appropriate equation (3) for CTPB viscosity-molecular weight relationship which appears to apply over a wider molecular weight range is ... 

Fig. 24. Intrinsic viscosity-molecular weight relationships for typical polypeptides in helicogenic solvents (O) PELG in TFE (57), ( ) PBLA in m-cresol at 15° C (22% (3) PCBL in DMF at 25° C (23% ( ) PCBL in DMF at 20° C (58)...

Gupta,D., Forsman,W.C. Newtonian viscosity-molecular weight relationship for concentrated solutions of monodisperse polystyrene. Macromolecules 2, 304-306... 

The polydispersity factor p is evaluated with the aid of any of the well-known viscosity-molecular weight relationships. From eq. (3.60) a proportionality of the intrinsic viscosity to the half power of the molecular weight is expected, as this theory holds for 0-solvents. However, based on the conclusion of Section 3.5, viz. that the reduced steady-state compliance of a monodisperse polymer is insensitive to the excluded... 

However, the square root of this denominator controls the viscosity-molecular weight relationship [cf. eq. (3.37)]. This means that any increase of JeR corresponds to a decrease of the viscosity below the value... 

As the scope of the present chapter is to stress limits and background for the Gaussian theory, a discussion of the said viscosity-molecular weight relationships is omitted. Some general remarks will be made in the discussion of the next section. 

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