Synthetic Polymers

Order the following monomers concerning their expected reactivity toward anionic polymerization, and explain your answer:

H₂C = CHCH₃, H₂C = CHC $\equiv$N, H₂C = CH-C₆H₅

Polystyrene is produced commercially by the reaction of styrene with butyllithium as an anionic initiator. Using resonance structures, explain how the chain-carrying intermediate is stabilized.    

Vinylidene chloride, H₂C = CHCl, does not polymerize in isotactic, syndiotactic, and atactic forms. Explain.

Polymers such as polypropylene contain a large number of chirality centers. Would you therefore expect samples of isotactic, syndiotactic, or atactic polypropylene to rotate plane-polarized light? Explain.

Irradiation of poly (1,3-butadiene), followed by the addition of styrene, yields a graft copolymer that is used to make rubber soles for shoes. Draw the structure of a representative segment of this styrene-butadiene graft copolymer.

Poly(ethylene terephthalate), or PET, is a polyester used to make soft-drink bottles. It is prepared by reaction of ethylene glycol with 1,4-benzenedicarboxylic acid (terephthalic acid). Draw the structure of PET.

Show the mechanism of the nucleophilic addition reaction of an alcohol with an isocyanate to yield a urethane.

Look at the structures of Vestenamer and Norsorex and show how they might be made by olefin metathesis polymerization.

Draw a three-dimensional representation of segments of the following polymers:

 (a) Syndiotactic polyacrylonitrile

 (b) Atactic poly (methyl methacrylate)

 (c) Isotactic poly (vinyl chloride)

Draw the structure of Kedol, a polyester prepared by heating dimethyl 1,4- benzene dicarboxylate with 1,4- bis (hydroxymethyl) cyclohexane.

Show the structure of the polymer that results from heating the following diepoxide and diamine:

Nomex, a polyamide used in such applications as fire-retardant clothing, is prepared by reaction of 1,3-benzenediamine with 1,3-benzenedicarbonyl chloride. Show the structure of Nomex.

Nylon 10, 10 is an extremely tough, strong polymer used to make reinforcing rods for concrete. Draw a segment of nylon 10, 10, and show its monomer units.

1,3-Cyclopentadiene undergoes thermal polymerization to yield a polymer that has no double bonds in the chain. Upon strong heating, the polymer breaks down to generate cyclopentadiene. Propose a structure of the polymer.

When styrene, ${\mathbf{C}}_6{\mathbf{H}}_5\mathbf{CH}\mathbf{=}{\mathbf{CH}}_2$  , is copolymerized in the presence of a few percent p-divinylbenzene, a hard, insoluble, cross-linked polymer is obtained. Show how this cross-linking of polystyrene chains occurs.

Poly (vinyl butyral) is used as the plastic laminate in the preparation of automobile windshield safety glass. How would you synthesize this polymer?

What is the structure of the polymer produced by the anionic polymerization of $\mathbf{\beta }$  -propiolactone using   $\mathbf{NaOH}$ as catalyst?

Glyptal is a highly cross-linked thermosetting resin produced by heating glycerol and phthalic anhydride (1,2-benzenedicarboxylic acid anhydride). Show the structure of a representative segment of glyptal.

Melmac, a thermosetting resin often used to make plastic dishes, is prepared by heating melamine with formaldehyde. Look at the structure of Bakelite shown in Section 31-6, and then propose a structure for Melmac.

Epoxy adhesives are cross-linked resins prepared in two steps. The first step involved the SN2 reaction of the disodium salt of bisphenol A with epichlorohydrin to form a low molecular weight prepolymer. This polymer is then cured into a cross-linked resin by treatment with a triamine such as 

1. What is the structure of prepolymer?
2. How does addition of the triamine to prepolymer result in cross-linking?

The smoking salons of the Hindenburg and other hydrogen-filled dirigibles of the 1930s were insulated with urea–formaldehyde polymer foams. The structure of this polymer is highly cross-linked, like that of Bakelite (Section 31-6). Propose a structure.

2-Ethyl-1-hexanol, used in the synthesis of di(2-ethylhexyl) phthalate plasticizer, is made commercially from butanal. Show the likely synthesis route.