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Chapter 26: Q35P (page 1343)

The polyester named LactomerRis an alternating copolymer of lactic acid and glycolic acid. Lactomer is used for absorbable suture material because stitches of Lactomer hydrolyze slowly over a two-week period and do not have to be removed. The hydrolysis products, lactic acid and glycolic acid, are normal metabolites and do not provoke an inflammatory response. Draw the structure of the Lactomer polymer.

Short Answer

Expert verified

Polymers whose repeat units are derived from two or more types of monomers are known as copolymers. Some examples of copolymers are polyesters, bakelite, Buna-S etc.

Step by step solution

01

Copolymers

Polymers whose repeat units are derived from two or more types of monomers are known as copolymers. Some examples of copolymers are polyesters, bakelite, Buna-S etc.

02

Lactomer polyester

It is a copolymer formed from monomers lactic acid and glycolic acid.

03

Structure of lactomer polymer

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Most popular questions from this chapter

Draw the important resonance forms of the stabilized anion formed in the anionic polymerization of methyl acrylate.

Polyoxymethylene (polyformaldehyde) is the tough, self-lubricating DelrinR plastic used in gear wheels.

(a) Give the structure of polyformaldehyde.

(b) Formaldehyde is polymerized using an acidic catalyst. Using H+ as a catalyst, propose a mechanism for the polymerization as far as the trimer.

(c) Is Delrin an addition polymer or a condensation polymer?

The mechanism given for cationic polymerization of isobutylene (Mechanism 26-2) shows that all the monomer molecules add with the same orientation, giving a polymer with methyl groups on alternate carbon atoms of the chain. Explain why no isobutylene molecules add with the opposite orientation.

Plywood and particle board are often glued with cheap, waterproof urea-formaldehyde resins. Two to three moles of formaldehyde are mixed with one mole of urea and a little ammonia as a basic catalyst. The reaction is allowed to proceed until the mixture becomes syrupy, and then it is applied to the wood surface. The wood surfaces are held together under heat and pressure, while polymerization continues and cross-linking takes place. Propose a mechanism for the base-catalyzed condensation of urea with formaldehyde to give a linear polymer, and then show how further condensation leads to cross-linking. (Hint: The carbonyl group lends acidity to the N - Hprotons of urea. A first condensation with formaldehyde leads to an imine, which is weakly electrophilic and reacts with another deprotonated urea.)

One of the earliest commercial plastics was BakeliteR, formed by the reaction of phenol with a little more than one equivalent of formaldehyde under acidic or basic conditions. Bayer first discovered this reaction in 1872, and practical methods for casting and molding. Bakelite were developed around 1909. Phenol-formaldehyde plastics and resins (also called phenolics) are highly cross-linked because each phenol ring has three sites (two ortho and one para) that can be linked by condensation with formaldehyde. Suggest a general structure for a phenol-formaldehyde resin, and propose a mechanism for its formation under acidic conditions. (Hint: Condensation of phenol with formaldehyde resembles the condensation of phenol with acetone, used in Problem 26-17, to make bisphenol A.)

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