Unfractionated polymer

Figure 8.5 Theoretical plots of weight fraction n-mers versus n for unfractionated polymer (A), the dilute phase (B), and the concentrated phase (C) (drawn with R = 10 ). (Adapted from Ref. 1.)...

Calculate Mn and Mvv the ratio M /Mn for the original polymer. Also evaluate the ratio Mw/Mn for the individual fractions. Comment on the significance of Mvv/Mn for both the fractionated and unfractionated polymer. 

The use of the HIXCO methodology for the NMR tacticity data of whole (unfractionated) polymers is straightforward.(16)... 

The early characterizations were carried out on unfractionated polymer samples of poly(d,/-a-phenylethyl isocyanide) of two origins ... 

In the case of poly-menthyl-methacrylate, an evaluation of the type and degree of stereoregularity of the unfractionated polymers, obtained by different polymerization processes, has been made by converting poly-menthyl-methacrylate into polymethyl-methacrylate and then determining the stereoregularity of the methyl derivative thus obtained by N. M. R. analysis (135). 

Figure 9 Temperature dependence of topochemical photodimerization of films of polymer, 23a. (a) HMW polymer, (b) LMW polymer, (c) Unfractionated polymer. Relative reactivities were obtained by monitoring the change in absorbance (A0 — At) of the C=C stretching band at times t relative to t = 0 (/Iq). (Reprinted with permission from Ikeda et al. [54]. Copyright 1990 American Chemical Society.)...

Polyacrylonitrile and polymethacrylonitrile make a fifth pair of this kind, but the viscosity relations for the latter are based on osmotic measurements for only four unfractionated polymers with molecular weights lying between 180,000 and 500,000 [Fuhrman and Mesrobian (115a)], so that only a crude estimate of a can be made for this polymer. Nevertheless, the effect of the methyl group is about the same as in the other, better established cases. 

Thermogravimetric analysis of the polymer was carried out under very nearly the same conditions as previously reported for permethylpolysilane and polysilastyrene (17, 18) (Figure 5). Unfractionated polymer 2 lost 35% of its weight upon heating under nitrogen at a 10 °C/min rise in temperature, up to 800 C. The theoretical loss according to equation 4 or 5 is 27 or 40%, respectively, and the results indicate that practically no volatile silicon compounds have been driven off. 

The weight-average molecular weight is of particular significance in this study because it can be compared with values measured by static LALLS on unfractionated polymer. 

However, the detectors currently in use in commercial MALDI-TOF instruments (see Section 10.2.6) do not meet this crucial condition. Mass discrimination effects at high masses are observed, and therefore MALDl spectra of unfractionated polymer samples may not produce the correct MM estimate. ... 

Great caution is therefore needed in estimating MM and MMD of unfractionated polymers by MALDl-TOF, with accurate estimates being limited to nearly monodisperse polymer samples. Since the great majority of synthetic pol57mers show a marked polydispersion, this conclusion has raised some concern about the general applicability of the MALDl-TOF method for the determination of MM in polymers. This concern, in turn, has stimulated several studies devised to test these results and to ascertain tire reasons why MALDl spectra have shown such a limitation. ... 

For an unfractionated polymer also, strength depends on the size of the molecules of which the specimen is composed. But in this case, because there is a distribution in RMM, it is necessary to state how the average for the specimen is to be defined. Consider a specimen of total mass W to be made up of a series of closely spaced fractions (see Figure 1.10) of which the mass of the ith is w,-. Then... 

In the classic light-scattering experiment one solves the Debye equation over a wide range of angles and concentrations for unfractionated polymer samples. The data are plotted in a rectilinear grid known as a Zimm plot in which the ordinate and abscissa are Kc/AR and sin 0/2 -i- kc, respectively, where k is an arbitrary constant used to adjust the spacing of the data points (27). The Zimm plot yields parallel lines of either equal concentration or angle. The slope... 

It has been known for many years that an increase in molecular weight results in a decrease in growth rate for unfractionated polymers [12-15] however, definitive data is available for few commercially significant polymers. A thorough understanding of molecular weight effects requires a detailed evaluation of fractions. Few such smdies are available. 

Data similar to those in Fig. 4 were obtained for the two PAM s, and each of these samples was also examined by SEC/LALLS and static LALLS on the unfractionated polymer. The SEC/LALLS setup included 3 60-cm columns [TSK 6000 PW, TSK 6000 PW, and TSK 5000 PW], a Chromatix CMX-100 LALLS, an Altex 156 DRI detector, and Chromatix data-acquisition and software systems. 

MALDI spectral quality is important, and thus, many authors have collected SEC fractions, recorded their MALDI spectra, and compared them with the spectra of the unfractionated polymer. To the best of our knowledge, there are no reports that quality worsens when using SEC. Vice versa, very often quality increases. For instance, the MALDI spectra of SEC fractions of Poloxamer407 (see above) possess a better spectral quality than the unfractionated sample. Moreover, a poly(bisphenol-A-carbonate) sample [64] with a poly-dispersity index of around 2 was analyzed by SEC and fractions were collected. Figure 45.11 contains the MALDI spectrum of PCF22 corresponding to the SEC... 

A series of low molecular weight PS and PMMA polymers were produced by free-radical polymerization with a monoacylphosphine oxide,more specifically (2,4,6-trimethylbenzoyl) diphenylphosphine oxide (TPO), as a photoinitiator [65]. The MMD of the PS and PMMA samples was broad, with polydispersities of 1.81 and 2.81, respectively. SEC fractionation yielded improved MALDI spectra with respect to the unfractionated polymers. 

Figure 3.223. Variation of the molecular weight and of the split bonds number (Z) as a function of ultrasonic treatment duration of PVC in aqueous suspension. 1) in unfractionated polymer 2) in the 80 pm fraction 3) in the 200 pm fraction 4) in the 40 pm fraction 5) Z in the unfractionated polymer 6) Z in the 80 pm fraction 7) Z in the 200 pm fraction 8) - Z in the 40 pm fraction.

From the size distribution viewpoint, superior mechanical properties are to be noted for the more homogeneous fraction, as compared to the unfractionated polymer. 

Fig. 2.3 Specific volume-temperature relation for linear polyethylene samples. Samples initially crystallized at 131.3 °C for 40 days. Unfractionated polymer, Marlex-50 fraction M = 32 000 O. (From Chiang and Flory (5))...

Fig. 4.3. Specific-volume-temperature relations for the melting of linear polyethylene. Key , unfractionated polymer o, fraction M = 32000. (Reprodnced from [4], copyright 1961, American Chemical Society.)...

The boiling heptane insoluble fractions of PP gave similar spectra to PP produced with a large amount of external donor. The amount of non-isotactic defects in the boiling heptane insoluble fraction is clearly varies with the isotactidty of the unfractionated polymer as Figure 6 shows, the lower the isotacticity of the unfractionated polymer, the greater the amount of nonisotactic defects or sequences in the boiling heptane insoluble fraction. 

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