Chain structure distribution

Polymers which already have a long chain structure may provide a good floe at low mixing rates. Often the turbulence and detention in the clarifier inlet distribution is adequate. 

From the optical absorption of two different hexaphenyl films, one with its chains predominantly standing upright on the substrate, the other with the chains randomly distributed in all orientations, similar structure property relations can be concluded [139]. By comparing the calculated absorption coefficient [139J perpendicular to the chains with the observed optical absorption spectra of both films we see that the optical absorption, plotted in Figure 9-9, in the visible and... 

Usually, crystallization of flexible-chain polymers from undeformed solutions and melts involves chain folding. Spherulite structures without a preferred orientation are generally formed. The structure of the sample as a whole is isotropic it is a system with a large number of folded-chain crystals distributed in an amorphous matrix and connected by a small number of tie chains (and an even smaller number of strained chains called loaded chains). In this case, the mechanical properties of polymer materials are determined by the small number of these ties and, hence, the tensile strength and elastic moduli of these polymers are not high. 

Schlaad H, Smarsly B, Losik M (2004) The role of chain-length distribution in the formation of solid-state structures of polypeptide-based rod-coil block copolymers. Macromolecules 37 2210-2214... 

The statistical distribution of r values for long polymer chains and the influence of chain structure and hindrance to rotation about chain bonds on its root-mean-square value will be the topics of primary concern in the present chapter. We thus enter upon the second major application of statistical methods to polymer problems, the first of these having been discussed in the two chapters preceding. Quite apart from whatever intrinsic interest may be attached to the polymer chain configuration problem, its analysis is essential for the interpretation of rubberlike elasticity and of dilute solution properties, both hydrodynamic and thermodynamic, of polymers. These problems will be dealt with in following chapters. The content of the present... 

Upon applying the calibration constants obtained from the data of one sample to evaluate the SEC data of the other samples, the calculated Mn and values correspond fairly well (within 10-20%) with the absolute MW parameters of the samples. This agreement also suggests that the samples probably have similar chain structures. The distribution functions for samples PN-1 and IL-22 are plotted in Figures 4 and 5. The molecular weight distributions of both polymers are similar to distribution curves reported for derivatized poly(organo)phosphazenes (4-10). 

Techniques were developed for the dilute solution characterization of polydlchlorophosphazene. The purity of the trimer has a significant effect on oligomer formation, polymerization time and polymer MW and MWD. The polymers prepared in this study have high molecular weights and broad molecular weight distributions and probably have similar, if not identical, chain structures. 

A series of structurally characterized di-yttrium(III) complexes bearing alkoxy-derivatized triazacyclononane ligands have been examined as initiators for lactone ROP.886 Both (296) and (297) are active for the polymerization of rac-LA at RT, but little control is afforded over molecular weights. Chain length distributions are broad, (Mw/Mn= 1.5-2.2) and attempts to identify the initiating group via end-group analysis have not been successful. 

From these considerations an important conclusion follows immediately. The structure of a network is insufficiently described if only the number of networks chains and their length distribution is specified. In addition, knowledge of the topography of the chain length distribution or the spatial distribution of the chain length distribution is required. That means that in networks of the same chain length distribution the chains may still be quite differently distributed in space (Fig. 12). 

The accumulation of structural information regarding a network is not an easy task. Direct measurements through optical techniques are often open to various interpretations. Also, their resolving power with respect to factors, important in elasticity, (as, for example, network chain length distribution) is often insufficient. It is, therefore, necessary to obtain structural information through studies of the network formation processes (Chapter II). 

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