Mean degree of polymerization

Polymerization of e-CL and (L- or D,L-)LA is perfectly living when initiated with any of the aforementioned functional aluminum alkoxides in toluene at 25 and 70 °C, respectively. This is supported by the close agreement between the mean degree of polymerization (DP) at total monomer conversion and the mon-omer-to-initiator molar ratio, the narrow molecular weight distributions (PDI=... 

Table 3.1 Mean degree of polymerization (mDP) of GSE fractions determined by phlorogluci-nolysis...

Molecular-mass characteristics of these polymers are very interesting I4,20,136, i54. ns. i58) oligomer with a mean degree of polymerization equal to ca. 5 has been formed by polymerization of phenylglycidyl ether. Its molecular-mass characteristics are extremely insensitive either to monomer conversion (Table 9) or to variations of polymerization conditions (Table 10). 

Figure 4 Mean degree of polymerization as a function of the mass action variable X for the isodesmic and the self-catalyzed nucleated polymerization models. N is the value averaged over all the monomers in the solution, Na that averaged over the active material only. Activation constant of the nucleated polymerization Ka — 10-4.

Pc mean degree of polymerization at critical polymer concentration... 

By means of the latter relations, kinetic schemes can be completely solved, mean degrees of polymerization can be derived, as well as the polydispersity coefficients of polymers terminated by disproportionation (= Sf +1 V p) and of macroradicals or inactive macroradicals after transfer (= S + 1 /S l). For the number, weight, and z average, k = 0, 1, and 2, respectively. 

The situation is considerably complicated by transfer in the polymerizing medium. The mean degree of polymerization is reduced... 

Now the ratio A p(M)//c<(M-) = fcp(M)(M-)//c (M-) can be seen to be the ratio of the rate at which monomer is converted into polymer to the rate of termination of radical chains. If termination occurs by recombination, then this ratio is just one-half the average number of monomer units per final polymer chain, which we may represent by n, the mean chain length, or mean degree of polymerization. This permits us to write for the stationary radical concentrations... 

The CCI3 radical usually goes on to start a new chain, so that there is no loss of radicals in the system, nor even any appreciable change in the rate of polymerization. The chief effect of such transfer reactions is found in the mean degree of polymerization. Since each transfer stops one chain and starts a new one, it will lower the mean chain length. Since the mean degree of polymerization n is the ratio of number of monomer units polymerized —d A)/dt to the number of polymer chains formed, we must modify our previous c(iuation (XVI. 10.9) to include chain transfer. If we assume termination by recombination... 

This last equation tells us that, in the absence of transfer agents other than M, the reciprocal mean degree of polymerization is a linear function of / 1V(M). Rt can, of course, be varied at constant (M) by using photoinitiation, whence Rtoz lay the absorbed light intensity. Alternatively, where chemical initiation is used, R cc (In), the initiator concentration. In this last case, transfer to initiator must be investigated separately in order to distinguish this effect from monomer transfer. 

There are discordant reports regarding the distribution of the molecular weights (MW) of proanthocyanidins in the seeds. Nevertheless, it has been reported that their mean degree of polymerization (mDP) is lower than 10 and that they are mainly constituted of (+)-catechin and (—)-epicatechin with a minor extent of (—)-epicatechin gallate. (+)-Catechin, (—)-epicatechin and (—)-epicatechin gallate are the terminal monomers (Kennedy and Jones, 2001 Downey et al., 2003 Pastor del Rio and Kennedy, 2006) (—)-epigallocatechin is absent in the seed proanthocyanidins. 

Gonzalez-Manzano, S., Santos-Buelga, C., Perez-Alonso, J.J. Rivas-Gonzalo, J.C. and Escribano-Bailon, M.T. (2006) Characterization of the mean degree of polymerization... 

A mean degree of polymerization of 42 and a molecular weight of approximately 1200 g mol can be estimated from the quantitative end group determination in the given example. 

Proportional composition of proanthocyanidins (in moles), and with the following subunit abbreviations EGC-P (-)-epigallocatechin extension subunit C-P (+)-catechin extension subunit EC-P (-)-epicatechin extension subunit C (+)-catechin terminal subunit ECG-P (-)-epicatechin-3-0-gallate extension subunit EC (-)-epicatechin terminal subunit ECG (-)-epicatechin-3-0-gallate terminal subunit Conversion yield (by mass) in the conversion of proanthocyanidin fraction to known subunits Mean degree of polymerization... 

Table 2. Hyperchromic effect (measured at 523 nm) of grape seed tannin fraction on MaIvidin-3-Glucoside in tartrate buffer (pH 3.5). mOP is the mean degree of polymerization measured by diioacidolysis. r the molar ratio between tannin and anthocyanin (a fixed concentration of 1 g/1 of tannin was used). T is the absorbance of tannin solution (control) at 523nm.

The oldest paper we know dealing with the polymerization of a molecule nowadays named as a sur ner is the work of Bistline et al. [4]. They obtained sur ce active polymers with a mean degree of polymerization of about 10 by polymerization erf allylic esters erf sexlium salts of a-sulfe>-stearinic acid and 0E-sulfe)-paImitinic acid. 

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