Alternating units, polymer

Thus, because -O—CH2— is senior to —S — CH2 —, it would be named first in a polymer that contained both —O—CH2— and —S—CH2— segments. Further, a polymer containing these alternating units would not be poly(thiomethyleneoxymethylene) but would be named poly (oxymethylenethiomethylene). 

The trans-poly-1,4-butadiene isomer is a harder and less soluble rigid crystalline polymer than the cis isomer. As shown by the skeletal structures for the trans isomer (Figure 1.11), chain extensions on opposite sides of the double bonds allow good fitting of adjacent polymer chains, and this, results in a rigid structure. In contrast, the os-poly-1,4-butadiene isomeric polymer units do not permit such interlocking of alternate units. Even so, chain... 

Lysozyme catalyzes the hydrolysis of a polysaccharide that is the major constituent of the cell wall of certain bacteria. The polymer is formed from /3( 1 —> 4)-linked alternating units of IV-acetylglucosamine (NAG) and N-acetyl-muramic acid (NAM) (Figure 1.25). The solution of the structure of lysozyme... 

After the first amide is formed, one end of the new molecule is nucleophilic and the other electrophilic so that it can grow at both ends. The polymer is made up of alternating -NH(CH2)6NH-and -(CH2)4CO- units, each having six carbon atoms, and is called nylon 6.6 . Another and much simpler way to make nylon is to polymerize caprolactam. This monomer is a cyclic amide and the polymer does not have alternating units—instead, each unit is the same. 

In this chapter, stable polyyne-type compounds and materials are surveyed with regard to their synthesis, properties, and possible applications. They are classified into end-capped polyynes with or without metals and alternating co-polymers having a polyyne unit with or without metals. In order to determine the possible application of polyynes, the detailed chemical and physical properties in solution, and in the liquid, and solid states, must be known. 

In the different classes of ordered polymers discussed above mesogenic behaviour is best explained on the basis that either the [A] or [B] repeat unit comprises the structure [(CH2)m-Ar-(CH2)n] where the MI is the sum of the contributions of the aromatic and linking polar parts. The alkylene units are not scored, but the contributions of the apparently isolated conjugated units in the A and B units are summed to find the Mesogenic Index. In this respect they are treated just like an alternating AB polymer. 

Appropriate telechelic polymers produced from a variety of monomers may be incorporated as reactive components in a variety of applications such as sealants, elastomers, foams, and fibers. Such telechelic polymers may impart almost any desired characteristic such as hydrophilic properties, elastomeric properties, dyeability, and solvent resistance. A dihydroxy telechelic polymer may be reacted with a telechelic polymer containing two carboxylic acid groups to produce a condensed polyester. Accordingly, from these telechelic entities one may produce block copolymers that will have alternating addition polymer residues of like or unlike repeat units. In addition, block copolymers can be produced by modifications of this procedure in which addition polymers are alternated with condensation polymer units. 

As the accompanying structure shows, the carbohydrate portion of the peptidoglycan is a polymer of alternating units of two modified glucose molecules called N-acetylglucosamine and N-acetylmuramk acid. These two unusual monosaccharides... 

Chondroitin sulfates (Figure 9.23) are molecules classified as glycosaminoglycans.Two common chondroitin sulfates are chondroitin-4-sulfate and chondroitin-6-sulfate. Each is a polymer of alternating units of D-glucuronate and N-acetyl-D-galactosamine-sulfate linked in a 1-3 linkage. 

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