Irregular macromolecule

Graphic representations (chemical formulae) of macromolecules are used extensively in the scientific literature on polymers including lUPAC documents on macromolecular nomenclature. This document establishes rules for the unambiguous representation of macromolecules by chemical formulae. The rules apply principally to synthetic macromolecules. Insofar as is possible, these rules are consistent with the formulae given in lUPAC documents [2-4] and they also cover the presentation of formulae for irregular macromolecules [5], copolymer molecules [1, 6] and star macromolecules. 

An irregular polymer is a substance composed of irregular macromolecules, the structure of which essentially comprises the repetition of more than one type of constitutional unit, or of macromolecules, the structure of which comprises constitutional units not all connected identically with respect to directional sense. 

Depending on the fraction of anomalous units, metal-containing polymers can be divided into several types. According to the lUPAC nomenclature, when the content of these emits is low, the polymers can be classified as regular macromolecules, which consist mostly of identical repeating units linked to one another in the same way. When the content of rmit variability is relatively large, they are called irregular macromolecules. 

Irregularly hyperbranched grafts provide a useful way to modify surfaces. A variety of chemistry can be used and a wide variety of grafts can be prepared. The hyperbranched grafts can serve as supported membranes, as catalyst supports or as substrates for further covalent graft chemistry. Functional groups within these interfaces can be readily modified by solution-state chemistry. The interfaces themselves can be used as media for further chemistry within the interface or as substrates in molecular recognition and self assembly of other macromolecules. 

Note 1 A crystallite may have irregular boundaries and parts of its constituent macromolecules may extend beyond its boundaries. 

The concept of a unique hydrodynamic volume for all rodlike polymers was derived from examination of the Mark-Houwink constants, K and a, of the equation [rj ] = KMa. Macromolecules with values of a greater than unity are commonly accepted to be stiff or rigid rods. However, it was also found that such molecules (even for values of a less than unity) obey a relation illustrated by close concordance with the curve in Fig. lb (13) flexible, branched or otherwise irregular polymers, on the other hand, show dispersion around the upper part of the curve. The straight line curve in Fig. lb implies that the constants K and a are not independent parameters for the regular macromolecules to which they apply. Poly (a- and polyQJ-phenylethyl isocyanide) fall on this line the former has a value of a > 1 while the latter has a value a < 1 (14) both polymers give linear concentration dependence of reduced specific viscosity for fractionated samples... 

Crystallization is a consequence of molecular symmetry. A macromolecule with a precise, regular sequence of side groups arrayed along the chain will be more prone to pack tightly with neighboring molecules than will a polymer that has an irregular disposition of side groups. 

These two branching processes decrease the regularity of the polyethylene macromolecules. Individual polymer chains may have long branches or butyl branches that occur at random positions. As we will see shortly, this irregularity in the structure dramatically affects the physical properties of the polymer. 

As discussed earlier, solid polymers can be distinguished into amorphous and the semicrystalline categories. Amorphous solid polymers are either in the glassy state, or - with chain cross linking - in the rubbery state. The usual model of the macromolecule in the amorphous state is the "random coil". Also in polymer melts the "random coil" is the usual model. The fact, however, that melts of semi-crystalline molecules, although very viscous, show rapid crystallisation when cooled, might be an indication that the conformation of a polymer molecule in such a melt is more nearly an irregularly folded molecule than it is a completely random coil. 

A very versatile approach to the formation of multilayer films has been developed by Decher, based on polyelectrolytes. If a solid substrate with ionic groups at the surface is dipped into a solution of a complementary polyelectrolyte, an ultrathin, essentially monomolecular film of the polyion is adsorbed [340]. The adsorption is based on pairing of surface bound ionic sites with oppositely charged ions, bound to the macromolecule. The polymers adsorb in an irregular flattened coil structure and only part of the polymer ions can be paired with the surface ions (Figure 29a). Ionic sites which remain with small counterions provide anchor points for a next layer formed by a complementary polyelectrolyte [342,343]. This way multilayer polyelectrolyte films can be prepared layer-by-layer just by dipping a suitable substrate alternately in an aqueous solution of polyanions and polycations. The technique can be employed with nearly all soluble charged polymers and results in films with a... 

As a matter of fact, structures (XVI) and (XVII) represent only a minor fraction of polymer molecules. Due to the great number of irregular structures which may be incorporated into the polymer molecules (Section 4.3), a great variety of types of macromolecules can be present in anionic polymers [95]. The nature of irregular structures formed during anionic lactam polymerization is primarily determined by the type and concentration of catalytic species and temperature, as well as by ring size and substitution of the lactam. Only polymers of o ,a-disubstituted lactams are free of irregular structures, and should be composed only of macromolecules of type (XVI) and (XVII). 

Polymers derived from other lactams contain irregular units such as indicated in the schemes (45) and (52) so that both linear and branched macromolecules are present [134, 151, 152]. Structures (XVIII)—(XXII) containing substituted keto amide units will prevail at lower temperatures, viz. 

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