Monomeric base unit, defined

To pursue the problem it is convenient to introduce some terminology. Instead of a phrase "a favorable arrangement of a number of consecutive base units" we shall use the name compact bundle it is relatively more rigid. Other arrangements of monomeric units will be called extended bundles. Thus we have two kinds of units constituting a polymer chain, to be denoted by symbols c and e. We introduce the symbol Nce for the number of pairs of nearest neighbor bundles such that one of them is compact and the other extended. Ncc and Nee are defined analogously. 

Similarly to homopolymers, source-based nomenclature has been applied to copolymers [4]. The principal problem is to define the kind of arrangement in which various types of monomeric units are related to each other. Seven types of separate arrangements have been defined, which are shown in Table 1, where A, B and C represent the names of monomers. The monomer names are linked either through an italicized qualifier or connective (infix), such as -CO- , to form the name of the copolymer, as in poly(styrene-co-acrylonitrile). The order of citation of the monomers is arbitrary. 

Therefore a detailed study of the influence of dimerization of well-defined synthetic lipids seems to be the most direct approach to achieve an understanding of the role of these complex amphiphilic molecules in living cells. In addition, new lipidic materials based on dimerization might be of practical value. Based on these expectations, several reports describing the design, synthesis and characterization of a number of new dimeric lipids have appeared in recent literature. Most of these lipids are made up of two identical monomeric lipid moieties connected at the level of the head groups or very close to these by a spacer unit, which can be either hydrophilic or hydrophobic, or even be either rigid or flexible. 

Both physical and technological properties of copolymers are influenced by the sequence distribution in the macromolecular chains. The mathematical relationships governing the distribution, first developed by Alfrey and Goldfinger (7), are based upon kinetic and statistical considerations implying three fundamental assumptions a) steady state copolymerization, b) terminal effect only (i.e. influence of the last, but not of the penultimate unit of a growing chain on the addition of the next monomeric unit), and c) constant monomer feed. Under these assumptions, which may be defined as a first order approximation, the copolymers are described by two quantities, the ratio / of the molar fractions of the two monomers and the product of reactivity ratios... 

To estimate compositional inhomogeneity of synthesised copolymers, integral curves of the distribution by composition estimated by the Laury-Mayer method are calculated based on values of copolymerisation constants obtained, which confirmed that the compositional inhomogeneity decreased on approaching the azeotropic composition of the initial monomeric mixture [52, 65]. Based upon the previously mentioned data it is found that MMA-4FMA copolymers are the most homogeneous as defined by both structure of the macromolecules and type of units distribution in the chains and create compositionally homogeneous polymeric materials with the best optical characteristics [3]. 

Specifically, the copolymer mechanism expressed in Fig. 1.3.4 is the so-called terminal model, because identification and reactivity of copolymer radicals are solely based on which monomeric unit contains the radical site. Based on the rate coefficients shown above the reaction arrows, the following reactivity ratios are defined ... 

The model shortly reviewed in the previous section will be the base for the simulation of the NMR spectrum. A sequence of three specified diads Xi and four well-defined dihedral angles will be necessary for the simulation (vide infra). As we want to investigate a high molar mass polymer and not a low molecular compound, we concentrate on a small sequence within an extended polymer chain of several hundred monomeric units (Fig. 15.b). We are interested in the probability distribution of the four dihedral angles t 2> if the configuration Xi, X2, Xs of the three central diads is given and... 

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