The chain effect

The chain effect deserves further study. It is strange that it appears only in polysarcosine, since Bamford s explanation suggests that a similar mechanism may also operate for other polypeptiees. 

Intrinsic viscosity measurements on polymers isolated after the chain-effect reactions showed that the materials were true block copolymers, their viscosities being identical with those of copolymers prepared by... 

More recently Ballard [73] has reported that poly-L-proline does not show the chain-effect with DL-phenylalanine NCA. He has also studied a number of block copolymers of L-proline and sarcosine as initiators with results shown in Table 5. The complex behaviour observed is discussed by Ballard in terms of availability to peptide sites for NCA adsorption. It is concluded that poly-L-proline does not adsorb the NCA. The existence of a chain effect with the initiators (Sarc)j o(Pro), qX and (Sarc)5 (Pro), qX requires explanation it may be connected with the occurrence of conformations of the proline chain in which the terminal base group X is not far removed from the sarcosine tail . 

A phenomenon related to the chain-effect has been observed [76] when polymeric catalysts containing basic units in the chain are employed to initiate the polymerization of DL-j3-phenylalanine-, 4-nitro-DL- 3-phenylalanine- and 2,4-dinitro-DL-j3-phenylalemine-NCAs. The enhance-... 

Comparison of Eqs (8.16) and (8.25) reveals that the Zimm time is shorter than the Rouse time in dilute solution. In principle, a chain in dilute solution could move a distance of order of its size by Rouse motion, by Zimm motion, or some combination of the two. The chain could simply move its monomers by Rouse motion through the solvent without dragging any of the solvent molecules with it, or it could drag all of the solvent in its pervaded volume with it, thereby moving by Zimm motion. In dilute solution, Zimm motion has less frictional resistance than Rouse motion, and therefore, the faster process is Zimm motion. The chain effectively moves as though it were a solid particle with volume of order of its per-... 

The chain effect in complexation consists of a change in macromolecular... 

According to equipment damage probability, the expansion probability of the chain effect introduced by tank G613 is shown in Table 2. 

When studying template systems, it is important to compare the template process and products of the reaction with conventional polymerization carried out under the same conditions but in a system in which the template is replaced by a low molecular nonpolymerizable analogue (blank reaction). The influence of the template on the process and on the product is usually called the template effect or the chain effect (3-6). The template effects can be expressed as follows ... 

Thus, in the intermediate time domain the root mean square displacement of a bead increases more slowly with time ( than ordinary diffusion. The physical reason for this is clear The fact that a given bead is connected to other beads in the chain effectively slows down its diffusive motion [41]. To complete the picture, we also consider the displacement of a bead under the influence of an external force, see Eq. 50 in the same domain of intermediate times (to [Pg.192]

Imanishi and his colleagiKs have studied the influence of chain-flexibility of the initiator on the chain-effect, - extending their studies to initiation by block copolymers containing sarcosine (c/. Ballard ). Imanishi et a/. further demonstrated that macromolecules carrying tertiary base residues can give rise to the chain-effect and that in appropriate systems charge-transfer interactions contribute to bonding of the NCA to the template. 

Consistent with the chain effect, which can be added to the neighboring group effect, the Avc=o V tie is strongly affected by the molecular weight of a macroligand. For example, for C0CI2 complexes with poly(vinylpyrrolidone) with polymerization degrees of n = 100, 200, 360, and 6300 and Avc=o values of 54, 49, 48, and 43 cm , respectively, were found. ... 

These types of interactions were confirmed by IR analysis by examination of the N-H stretching vibrations in monomer end C=0 stretching vibrations of tbe polysarcosine groups. In any step of the reaction, the monomer molecule was adsorbed onto polysacrosine. It was proved by tbe autbors tbat tbe rate of tbe reaction depended on tbe typ>e of solvent used. The smaller tbe interaction, for instance, in N,N-DMF, the smaller the chain effect. 

In continuation of the investigation on the chain-effect polymerization, stereoselectivity of this process was examined. The set of polymerizations were conducted with polypeptide initiator with similar composition but different chiral stmeture. Obtained results indicated that the activated NCA-typ>e polymerization is stereoselective. 

F. is the total effective electric force on the chain (effective means projected onto the primitive path) and R, is the projection of the end-to-end vector onto the field direction. For long chains and practically useful fields, this drift rapidly dominates over reptation, so that the disengagement time t fe is obtained as ... 

In spite of this, the failure envelopes are normal. Thus Figure 1 shows the envelopes for several Solithane 113-300 compositions (lO), These envelopes can be fitted by the inverse Langevin approximation (ll) to the stress-strain curve, and from the curve fit both the number of effective chains per cm and the niimber of equivalent random links N can be determined (l2). The fit for two compositions is shown in Figure l8 and the results of such an analysis (13) are given in Table II. It can be seen that the chain concentration is almost constant but N increases, i.e, the chains effectively become stiffer as the concentration of prepolymer is increased. 05iis is -ttie only elastomer system we are aware of in which such a change can be effected at constant Ye ... 

At the photochemical initiation of the chain effect, after the light was switched on, some time period passes until the stationary radical concentration and constant reaction rate are established. This is used for measuring the rate constant of chain termination. If chains terminate linearly, then after switching-on the light... 

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