Multichain polymers

Fig. 56.—Molecular weight distributions for multichain polymers for the several values of / indicated, as calculated from Eq. (22 ). Number averages for the different distributions are identical. (Schulz. )...

Whiteway S. G, Smith I. B. and Masson C. R. (1970). Theory of molecular size distribution in multichain polymers. Can. Jour. Chem., 48 33-45. 

It was shown that in multichain polymers the molecular weight distribution, Xw/Xn, is equal to 2 when chain transfer is taking place. When, however, chain transfer is absent, Xw/Xn = 1.5. In actual practice, typical Xw/Xn values for vinyl polymers prepared to high conversion seldom exceed 5. Special cases like autoacceleration are exceptions where values as high as Xw/Xn = 10 were reported (5). 

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. 

Tacryl . Acrylic fiber of a specific multi chain type. The structure conld he described as a Spider molecule with up to siit long straight linear legs which can orient independently and build up a fibrous structure. The molecular structure is built up by a controlled cross-linking process, so that Tacryl is like wool as it has a specific chain molecular interlinking which contributes to its mechanical and elastic properties. Synthesis of multichain polymers Schaefgen,... 

Schaefgen JR, Flory PJ (1948) Synthesis of multichain polymers and investigation of their viscosities 1. J Am Chem Soc 70 2709-2718... 

Very large model systems, which are often necessary to track the morphological characteristics responsible for the peculiar properties of polymers, also present a great challenge in polymer simulations. Detailed atomistic multichain polymer models used today seldom contain more than a few thousands of atoms, although domain decomposition strategies on parallel machines offer the possibihty of going up to millions of atoms. 

Fig. 2.5. Structure of a multichain polymer containing a backbone of polylysine and an external random copolymer of tyrosine and glutamic acid (molar ratio, Lys Tyr Glu D,L-Ala= 1 1.8 3.7 24). The average molecular weight of the polymer used as antigen in the experiments discussed in the text is 35,000. From Fuchs and Sela (27,28).

Simulating the Dynamic and Equilibrium Properties of a Multichain Polymer System... 

More specific polymer-surfactant interactions can be obtained if the polymer chain is modified to introduce more hydrophobic groups along the chain. Such modifications provide more opportunity for hydrophobic interactions between the surfactant tail and the polymer. In addition, they may result in increased intra- and interchain polymer interactions, producing more compact chain conformations in aqueous solution or multichain polymer aggregates or micelles (Figure 7.9). 

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