Polymerization product distribution

The primary polymerization product ia these processes has a relatively wide molecular weight distribution, and a separate step is often used to narrow the polydispersity. Such a narrowkig step may consist of high vacuum stripping to remove volatile polymer chains, often followed by a solvent fractionation step (35,36), sometimes a solvent fractionation step alone (37,38), or a fractional precipitation from organic solvent (32). The molecular weight distribution can also be narrowed by depolymerization at elevated temperatures ia the presence of a depolymerization catalyst (217—220). 

The FTS mechanism could be considered a simple polymerization reaction, the monomer being a Ci species derived from carbon monoxide. This polymerization follows an Anderson-Schulz-Flory distribution of molecular weights. This distribution gives a linear plot of the logarithm of yield of product (in moles) versus carbon number. Under the assumptions of this model, the entire product distribution is determined by one parameter, a, the probability of the addition of a carbon atom to a chain (Figure 4-7). ... 

Finally, it has been reported that carbon electrodes modified with thin polymeric films of polypyridyl metal complexes containing a dispersion of metal particles (Rh° or Pd°) can be used as electrocatalyst for reduction of C02 to hydrocarbons in MeCN. Apparently CH4 is the dominant reduction product (up to 18% of faradaic efficiency).123,124 It should be noted that the product distribution is reminiscent of a Fischer-Tropsch process since C2, C3, and C4 hydrocarbons are also formed. 

The product distribution frcm the Fischer-Tropsch reaction on 5 is shown in Table I. It is similar but not identical to that obtained over other cobalt catalysts (18-21,48, 49). The relatively low amount of methane production (73 mol T when compared with other metals and the abnormally low amount of ethane are typical (6). The distribution of hydrocarbons over other cobalt catalysts has been found to fit the Schulz-Flory equation [indicative of a polymerization-type process (6)]. The Schulz-Flory equation in logarithmic form is... 

Starting from equations 7.3-3 to -6 applied to a constant-volume BR, for polymerization represented by the step-change mechanism in Section 7.3.2, show that the product distribution can be calculated by sequentially solving the differential equations ... 

After polymerization, PET is processed to final products, distributed to consumers and eventually ends up in a waste treatment system. Manual sorting or various automated methods can be applied to separate the PET fraction from a waste stream [HI]. 

The number, size and distribution of the formed particles depend on the number of nuclei, the probability of particles becoming stable, and the aggregation of the particles. The amount and quality of the stabilizer used are related to these terms. Before discussing the qualitative analysis of number and size of the particles, we discuss the stabilizer, which has the greatest influence on the state of polymerization products. 

Anionic polymerization of -caprolactone has been studied in several laboratories and it was found that considerable amounts of oligomers were found as by-products.— — We have studied the formation of oligomers in the anionic polymerization of 6-capro-lactone by gpc technique.A In view of the very facile intra- and intermolecular transesterification reactions in this system- -, the product distribution seems very interesting to check the validity of the thermodynamic equilibrium. 

The reaction mixture remained living after reaching equilibrium, because addition of monomer, dilution with solvent shifted the product distribution to a new equilibrium. The equilibrium concentration of each oligomers as a function of total monomer unit concentration is shown in Figure 2. It is evident that equilibrium formation of oligomers cannot be neglected even in bulk polymerization and oligomer can consist more than one third of the products in solution polymerization.4... 

Figure 4. Change oj product distribution (GPC) with polymerization time [ML = 0.24 , [/] = 4.4 X 3 (9).

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