Polymer Chemistry: Step-Growth Polymers

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Questions and Answers

What is the primary characteristic of step growth polymerization?

Oligomers react together to give longer chains (correct)

Chain growth is associated with addition polymerization

It forms highly crystalline polymers

It involves the gradual depletion of monomers

What is the primary reason for the reduced density of a polymer?

Presence of substituents or branches (correct)

Short chain length

Strong Van der Waals forces

High degree of crystallinity

What type of polymerization is associated with chain growth?

Step growth polymerization

Condensation polymerization

Addition polymerization (correct)

Free radical polymerization

What is the term for regions of a polymer with highly ordered chains?

Crystallites Signup and view all the answers

What is the primary function of Van der Waals forces in polymers?

To hold the individual chains together Signup and view all the answers

What is the result of having highly ordered polymer chains?

An increase in density, hardness, and resistance to heat Signup and view all the answers

What type of polymer has short branches connected to the main chain?

Branched polymer Signup and view all the answers

What is the primary characteristic of a cross-linked polymer?

Covalently bonded linking units between chains Signup and view all the answers

What is the mechanism by which epoxides are polymerized when the initiator is a Lewis acid?

Cationic mechanism Signup and view all the answers

What is the main problem with natural and most synthetic rubbers?

They are too soft and sticky Signup and view all the answers

What type of polymerization reaction is involved in the formation of condensation polymers?

Step-growth polymerization Signup and view all the answers

What is the purpose of vulcanization in rubber production?

To create a harder and more flexible material Signup and view all the answers

What type of copolymer has a random distribution of monomers?

Random copolymer Signup and view all the answers

What is the main difference between homopolymers and copolymers?

Homopolymers are formed from one monomer, while copolymers are formed from two or more monomers Signup and view all the answers

What is the result of heating rubber with sulfur in the vulcanization process?

The formation of a harder and more flexible material Signup and view all the answers

What is the name of the process by which a polymer is formed from a single compound with two different functional groups?

Condensation polymerization Signup and view all the answers

What is the primary characteristic of a step-growth polymer?

It is formed from a monomer with two different functional groups Signup and view all the answers

What is the reaction mechanism involved in the synthesis of nylon 6?

Condensation reaction Signup and view all the answers

What is the starting material for the synthesis of nylon 6?

ε-caprolactam Signup and view all the answers

What is the primary characteristic of epoxy resins?

They are extensively cross-linked systems and can adhere to almost any surface Signup and view all the answers

What is the reaction mechanism involved in the synthesis of Dacron?

Transesterification reaction Signup and view all the answers

What is the primary characteristic of polyurethanes?

They contain a urethane group, which is a compound with an OR group and an NHR group bonded to the same carbonyl carbon Signup and view all the answers

What is the primary difference between nylon 6 and nylon 66?

Nylon 6 is formed from a single monomer, while nylon 66 is formed from two different monomers Signup and view all the answers

What is the primary application of epoxy resins?

They are used as adhesives and coatings Signup and view all the answers

Study Notes

Step-Growth Polymers

Contain two functional groups (A and B) in each monomer
Examples: Polyamides, Polyesters, Epoxy Resins, Polyurethanes

Polyamides

Formed from monomers with different functional groups (carboxylic acid and amino)
Nylon 6: formed from 6-aminohexanoic acid (contains six carbons)
Nylon 66: formed from adipoyl chloride and 1,6-hexanediamine (each with six carbons)

Polyesters

Contain many ester groups
Dacron: formed by transesterification of dimethyl terephthalate with ethylene glycol
Kodel polyester: formed by transesterification of dimethyl terephthalate with 1,4-di(hydroxymethyl)cyclohexane

Epoxy Resins

Strong adhesives with extensive cross-linking systems
Can adhere to almost any surface and resist solvents and high temperatures
Formed by reacting a low-molecular-weight prepolymer with a hardener

Polyurethanes

Contain urethane (carbamate) groups
Formed by reaction of isocyanate and alcohol groups

Addition Polymers

Ring-Opening Polymerizations: epoxides polymerize through cationic mechanism
Polymerization of Dienes: natural rubber is a polymer of 2-methyl-1,3-butadiene (isoprene)
Synthetic rubbers: made by radical polymerization of dienes other than isoprene
Vulcanization: heating rubber with sulfur causes cross-linking of polymer chains through disulfide bonds

Copolymers

Formed from two or more different monomers
Types: alternating, block, random, and graft copolymers

Condensation Polymers (Step-Growth Polymers)

Formed by intermolecular reaction of molecules with functional groups at each end
Can be formed by reaction of a single compound with two different functional groups or two different compounds

Classification of Polymers

Structure

Linear polymers: continuous chain of repeating units
Branched polymers: short branches connected to the main chain
Cross-linked polymers: covalently bonded linking units between chains

Physical Properties

Physical properties result from arrangement of individual chains
Chains held together by Van der Waals forces
Crystallites: regions of highly ordered polymer chains
Amorphous regions: randomly oriented chains between crystallites
Density, hardness, and heat resistance increase with crystallinity

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Description

This quiz covers the characteristics and examples of step-growth polymers, including polyamides, polyesters, epoxy resins, and polyurethanes.