Length of unit chain

Amylose Content, and Average Length of Unit Chain, of Amylovectins... 

Starch source Amyloset % Average length of unit chain References... 

Table I shows the results of periodate oxidation and methylation applied to amylopectins from various sources. If the percentage of amylose in a whole starch is known, the length of unit chain of the amylopectin component can be calculated from the results of periodate oxidation of the whole starch (see Table II). The length of unit chain appears to depend on the botanical species, but not the variety, from which the starch wras isolated. In the case of tapioca and corn amylopectins, sub-fractionation of these by precipitation with methanol, followed by periodate oxidation, showed the sub-fractions had the same degree of branching as the original amylopectins.71 The action of periodate on whole starches and amylopectins is now so well established and accurate, that it may well completely supersede the methylation technique for pure starches, in view of its many advantages.

Species and/or cultivar differences are also observed in other starch properties and in the properties of isolated amylose and amylopectin. To illustrate, purified amylose samples have been shown to differ in (3-amylolysis limit and average DP.64,67,124 Purified amylopectin samples have also been shown to differ in (3-amylolysis limit, average length of unit chains and viscosity.64,66 67 124,125 Campbell et al.121 observed a range of amylose content from 22.5% to 28.1% in 26 maize inbreds selected for maturity, kernel characteristics and pedigree. Starches from these non-mutant genotypes also differed in thermal properties (DSC), paste viscosities and gel strengths. 

Fig. 61). Specifically, a chain is defined as that portion of a molecule between two branch units, or between a branch unit and a terminal unreacted functional group (e.g., OH or COOH). The lengths of the chains will vary, but for the present this variation is unimportant.

These results confirm that the tendency for an alternating arrangement of the comonomer units increases with the length of alkyl chains at the tin atom. 

Telechelic polymers rank among the oldest designed precursors. The position of reactive groups at the ends of a sequence of repeating units makes it possible to incorporate various chemical structures into the network (polyether, polyester, polyamide, aliphatic, cycloaliphatic or aromatic hydrocarbon, etc.). The cross-linking density can be controlled by the length of precursor chain and functionality of the crosslinker, by molar ratio of functional groups, or by addition of a monofunctional component. Formation of elastically inactive loops is usually weak. Typical polyurethane systems composed of a macromolecular triol and a diisocyanate are statistically simple and when different theories listed above are... 

The doubling or amplification that is inherent in dendrimer chemistry is the dominant process that controls the dendrimer shape [1], With each generation, the number of terminal units usually doubles. Each shell (generation) enhances at approximately a constant value, whereas the total molecular mass approximately doubles with each generation as does the number of branch points. While the dendrimer mass doubles with generation, the space to fit the units increases at a much slower rate. The contour length of any chain from the core to the terminal units is proportional to the number of chemical bonds and hence the number of... 

At low concentrations, when uncharged polymers are dissolved in a solvent in which they do not crosslink or entangle, they possess a viscoelastic response through hydrodynamic and entropic effects. We can begin by considering an isolated chain in its quiescent state. The chain will be in constant motion. In the absence of any specific interactions, the chain will evolve to its maximum entropy state. We can represent the chain as N links or submolecules each with a length b. These links are formed from a few monomer units of the chain. The root mean square end-to-end length of the chain is... 

The polyamides differ by the nature and lengths of the units between amide groups and by the arrangement of these amide groups. Certain properties are clearly affected by the length of the chains. 

Here N is the number of chains in unit volume of the rubber and T is the absolute temperature. Note that the chain is defined here as part of a long polymer molecule between neighboring cross-linking points. The fundamental assumptions made in deriving Eq. (28) are that all chain ends are displaced to new positions by affine transformation when the rubber is deformed, that there are no intermolecular interactions, and that the end-to-end distance of each chain is much smaller than the contour length of the chain. 

Here a0 is a constant called the effective bond length of the chain, and as(z) is a dimensionless quantity called the linear expansion factor of the chain. The latter depends on long-range interactions between pairs of monomer units and chain length through the so-called excluded-volume parameter z. For details of these quantities characterizing the dimensions of random-coil polymers, the reader is referred to a recently published book by Yamakawa (40). At this place we simply note that as tends to unity in the absence of excluded-volume effect. 

The spectra and redox potentials of the binuclear bismacrocyclic Ni(II) complexes, 17-19 and 20, are similar to those of the corresponding mononuclear complexes of 9 and 3a, respectively. That is, the ligand field strength of the complexes is only slightly affected by the type or the length of bridging chain that links the two macrocyclic units. 

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