Molecular weights anomalous

Using both condensation-cured and addition-cured model systems, it has been shown that the modulus depends on the molecular weight of the polymer and that the modulus at mpture increases with increased junction functionahty (259). However, if a bimodal distribution of chain lengths is employed, an anomalously high modulus at high extensions is observed. Finite extensibihty of the short chains has been proposed as the origin of this upturn in the stress—strain curve. 

For PVA and PCP the dependences on V of log(MyJ)v and log (My)y (Figures 2a, 2b and 4) show similar trends as for SRM 706. Noticeable downward curvature of log(M,y)y at low molecular weight occurs in each case, in contrast to relatively linear behavior of log(MjJ)y. Anomalously large values of g result (Figures 3 and 5). In the highest molecular weight region, a sharp downturn in the log (My)y dependence on V is apparent which is accompanied by very Tow g values. 

A quite different approach to rheo-NMR was taken by Xia and Callaghan [12], in an NMR microscopy measurement of the velocity profile of a high molecular weight polymer solution flowing through a capillary. In this study anomalous polymer diffusion was found at a radius within the pipe at which the local shear rate exceeded... 

Moleeular weight sal 19. Molecular volume anomalous I i I I. 1 litre weight 79 4 eritht. 

The Friedel-Crafts alkylation of ferrocene with ethylene chloride has been the subject of considerable investigation. It was initially reported by Nesmeyanov and coworkers that the reaction produced diferrocenylethane and appreciable amounts of polymeric material (55). Rinehart and coworkers later proved that the low molecular weight product was l,l -diferrocenylethane (XVII) instead of the expected 1,2-isomer (103). The anomalous product is postulated to result... 

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