Critical degree of polymerization

The analysis of the reaction serum (the continuous phase without polymer particles) at the end of polymerization led to the conclusion that the molecular weight of the soluble oligomers of styrene and PEO macromonomer varied from 200 to 1100 g mol-1. This indicates that the critical degree of polymerization for precipitation of oligomers in this medium is more than ten styrene units and only one macromonomer unit per copolymer chain. Several reasons for the low molecular weight of the soluble copolymers were proposed, such as the thermodynamic repulsion (or compatibility) between the PEO chain of the macromonomer and the polystyrene macroradical, the occurrence of enhanced termination caused by high radical concentration, and, to a lower extent, a transfer reaction to ethanol [75]. 

Hydrodynamic average molecular weight degree of polymerization critical degree of polymerization depolarization of luminescence... 

In polyionic complexes, formed by polymeric amines and sodium oligophosphates, an sigmoid dependence of the effective constant of binding on oligomer length is observed (Fig. 24). The critical degree of polymerization of is equal to 792 for the system sodium polyphosphate-poly(dimethylaminoethyl methacrylate). It should be... 

Thus, a cooperative interaction of the growing daughter chain with the mac-romolecular matrix is possible only when a critical degree of polymerization n. of the... 

The critical degree of polymerization N, above which phase separation is expected for a mixture containing equal volume fractions of components of equal N, increases from 830 to over 10,000 as the 1,2- content of the PBD increases from 8 to 97%. Actually, phase separation has never been observed in blends of PIP with high 1,2-PBD, with 10,000 representing a lower limit for N [4]. Only the miscible region of the phase diagram has been accessible for this system. 

Flory-Huggins interaction parameter critical degree of polymerization (= 2/X) phase separation not observed... 

Frequently the complexation of the monomer is weak, and only oligomers exceeding a critical degree of polymerization can become complexed to the template-chain (Figure 39). Because the polymerization simultaneously proceeds in the solution and along the template complex, a lower over-all rate enhancement is observed. If the number of monomer molecules exceeds the available complexation sites, the reaction rate is decreased. Virtually all investigated template polymerizations seem to obey this mechanism [484]. 

Coombes and Katchalski [29] have considered a slightly more complex version of this mechanism in which a second propagation coefficient operates above a critical degree of polymerization. Katchalski et al. [30] calculated the molecular weight distribution obtained in a system following scheme (12) but also including a bimolecular termination step. Various authors have analysed more complex systems in which the initiator is a polymeric species. Thus Gold [31] has shown that initiation by a poly a-amino acid with a Poisson distribution leads to a polymeric product with an over-all Poisson distribution, and Katchalski et al. [32] demonstrated that in multichain polymers synthesized from polyfunctional initiators Poisson distributions also arise. 

Aqueous phase concentration of oligomeric radicals of degree i (mol/L) Critical degree of polymerization for homogenous nucleation Rate of propagation (volume growth per particle) (L/sec)... 

Volume of water in the system (L) Critical degree of polymerization for entry van der Waals radius of a monomer unit (dm)... 

They may also undergo further propagation (usually only significant if no micelles are present) to a critical degree of polymerization at which they precipitate . These events comprise micellar and homogeneous nucleation. 

Above this point, the conversion curves obtained with the two models differed significantly from each other, as shown in Figure 10, where the conversion plots as a function of time are reported for the three cases. Two important effects can be observed when the critical degree of polymerization is reached (open circles), the conversion rate accelerates as a result of the diffusion limitations. At the same time, the conversion curves predicted by the complete model (dashed curves) start differing significantly from the simplified model (solid curves), where the CLD... 

Xco critical degree of polymerization for the entanglement of polymerchains ( >p volume fraction of polymer... 

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