Irregular polymers

Pomerantz et al. [493] prepared regioregular polymers HHTT-400 and HHTT-401 (Scheme 2.66) and compared them with previously synthesized irregular polymers 400 and 401 (Scheme 2.63) [485]. Regioregular polymers showed blue shifts in absorption for solution and films (23-30 nm and 57-79 nm, respectively Table 2.4), interpreted in terms of shorter conjugation length. Blue shifts in PL and EL were much less-pronounced (10-15 nm) and the PLED showed 2-4 times lower 4>el (Table 2.4) [493]. 

Irregular polymer, the molecules of which are derived from only one species of monomer but which display a variety of structural features more appropriate for description in copolymer terms. 

Note Where appropriate, adjectives specifying the types of copolymer may be applied to pseudo-copolymer. The term statistical pseudo-cqpo/ywer, for instance, may be used to describe an irregular polymer in the molecules of which the sequential distribution of configurational units obeys known statistical laws. 

Block copolymers are named by using dashes (double-length hyphens) for the bonding of bloeks with each other and with junction units. With graft and star polymers, the grafts or the arms, respectively, are eonsidered to be substituents to the main chain, and the structure is named in the same way as a regular or irregular polymer. Table 8 lists some examples. 

The rules of structure-based nomenclature of regular single-strand organic polymers are of fundamental importance in polymer nomenclature. The names of other kinds of polymers such as double-strand [7] and irregular polymers [8] are based on the principles given in this Report. 

Rules for naming irregular polymers Additional examples Referenees... 

Irregular polymers or bloeks are named by placing the prefix poly before the structure-based names of the eonstitutional units, collectively enclosed in parentheses or brackets, with the individual eonstitutional units separated by oblique strokes. A typical name derived from this new system is... 

An irregular polymer derived from vinyl chloride (ehloroethene), the eonstitutional units of whieh are linked both head-to-tail and head-to-head ... 

Irregular polymers with regular or irregular blocks and junction units in a specific sequential arrangement are named by linking the names of the blocks and junction units with dashes ... 

Irregular polymers in which polymer or oligomer chains are attached to the main chain (as in graft copolymers) are named as follows. The attached polymer or oligomer chains are considered to be substituents to the main chain and named in the same way as regular polymers [1] or irregular polymers (cf Rules 1 and 2) but without the suffix -yl. The atom in the attached chains nearest to the point of attachment to the main chain is given the locant 1. 

In irregular polymers in which a central unit is substituted with three or more blocks, i.e., star polymers, the blocks are treated as substituents to a single central unit. A star polymer having identical blocks as its arms is named... 

Names of end groups are prefixed to the name of the polymer and denoted by the Greek letters a and co. When bonding of the end groups to specific constitutional units is unknown, the irregular polymer is named... 

Rule 4.1.2 Pseudoperiodic copolymers, e.g. those in which only some of the constitutional units occur regularly, are treated as irregular polymers (see Ex. 4.1-El) or as unspecified copolymers (see example 4.1-E3). 

Note In cases in which both l-phenylethane-l,2-diyl and 2-phenylethane-1,2-diyl units are present in measurable amounts, the formula for an irregular polymer is used ... 

Rule 4.2.1 Statistical, random and unspecified copolymers are treated as irregular polymers. 

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. 

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... 

Catechol melanin, a black pigment of plants, is a polymeric product formed by the oxidative polymerization of catechol. The formation route of catechol melanin (Eq. 5) is described as follows [33-37] At first, 3-(3, 4 -dihydroxyphe-nyl)-L-alanine (DOPA) is derived from tyrosine. It is oxidized to dopaquinone and forms dopachrome. 5,6-Dihydroxyindole is formed, accompanied by the elimination of C02. The oxidative coupling polymerization produces a melanin polymer whose primary structure contains 4,7-conjugated indole units, which exist as a three-dimensional irregular polymer similar to lignin. Multistep oxidation reactions and coupling reactions in the formation of catechol melanin are catalyzed by a copper enzyme such as tyrosinase. Tyrosinase is an oxidase con-... 

In this connection the formation of irregular polymers (Si BryH R O H with v +x +y +z = 2 is of interest. As a result of steric hindrance566), such compounds will be formed in the reaction of SiBr4 with t-butyl Grignard compound instead of the expected tetrakis (t-butyl)-silane. 

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