Different molecular weights

In RNA the sugar is ribose and uracil replaces thymine. Different varieties of RNA exist with widely different molecular weights. Messenger RNA conveys information in the form of the sequence of bases from DNA to RNA on the ribosomes, where proteins are... 

A series of polyvinylpyridine standards of different molecular weight were analyzed by size-exclusion chromatography, yielding the following results. 

The first and second columns of Table 1.4 give the number of moles of polymer in six different molecular weight fractions. Calculate and for this polymer and evaluate a using both Eqs. (1.7) and (1.18). 

At 200°C the Newtonian viscosities of polystyrene samples of different molecular weights were studied by Spencer and Dillont and the following results were reported ... 

Shultz and Floryf measured the critical temperature for precipitation for polystyrene fractions of different molecular weight in cyclohexane. The following results were obtained ... 

Table 9.3 lists the intrinsic viscosity for a number of poly(caprolactam) samples of different molecular weight. The M values listed are number average figures based on both end group analysis and osmotic pressure experiments. Tlie values of [r ] were measured in w-cresol at 25°C. In the following example we consider the evaluation of the Mark-Houwink coefficients from these data. 

For a polydisperse system containing molecules in different molecular weight categories which we index i, we can write (m,), =, and... 

Fig. 7. Shear viscosity at 180°C of polypropylene of different molecular weight and distribution vs shear rate (30) see Table 4 for key. Pa-s = 0.1 P...

Processes for HDPE with Broad MWD. Synthesis of HDPE with a relatively high molecular weight and a very broad MWD (broader than that of HDPE prepared with chromium oxide catalysts) can be achieved by two separate approaches. The first is to use mixed catalysts containing two types of active centers with widely different properties (50—55) the second is to employ two or more polymerization reactors in a series. In the second approach, polymerization conditions in each reactor are set drastically differendy in order to produce, within each polymer particle, an essential mixture of macromolecules with vasdy different molecular weights. Special plants, both slurry and gas-phase, can produce such resins (74,91—94). 

The properties of PVC may also he expected to depend on the molecular weight distribu n. Most commercial polymers, however, appear to have similar values for MJM and in any case there is little published information on effects of altering the parameter. It is perhaps rather surprising that there appears to be little work reported on the effect of blends of polymers of differing molecular weight on mechanical and rheological properties. 

Although not apparent at this time, it will become clear that two adjacent peaks from solutes of different chemical type, or significantly different molecular weight, are not likely to have precisely the same peak widths (i.e., exhibit the same efficiency). Nevertheless, in most cases, the difference will be relatively small and, in fact, likely to be negligible. As a consequence, the widths of closely adjacent peaks will, at this time, be assumed to be the same. 

This could occur if the separation ratio of another solute pair, although larger, was very close to that of the critical pair but contained solutes, for example, of widely different molecular weight (and, consequently, very different diffusivities). Fortunately, the possibility of this situation arising is remote in practice, and will not be considered in this discussion. It follows that the efficiency required to separate the critical pair, numerically defined, is the first performance criterion. 

Fig. 6. Variation of interface toughne.ss with area den.sity of copolymer for a range of different molecular weight PS-PMMA copoly mens between PMMA and PPO (or PPE) [39J.

Fig. 10. The variation of 6, with E for three different molecular weight polyisoprene tethered chains in a cross-linked polyisoprene lens [23].

Solution and peel properties of polychloroprenes with fast crystallizing characteristics but different molecular weight... 

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