24 Questions
What is the primary characteristic of step growth polymerization?
Oligomers react together to give longer chains
What is the primary reason for the reduced density of a polymer?
Presence of substituents or branches
What type of polymerization is associated with chain growth?
Addition polymerization
What is the term for regions of a polymer with highly ordered chains?
Crystallites
What is the primary function of Van der Waals forces in polymers?
To hold the individual chains together
What is the result of having highly ordered polymer chains?
An increase in density, hardness, and resistance to heat
What type of polymer has short branches connected to the main chain?
Branched polymer
What is the primary characteristic of a cross-linked polymer?
Covalently bonded linking units between chains
What is the mechanism by which epoxides are polymerized when the initiator is a Lewis acid?
Cationic mechanism
What is the main problem with natural and most synthetic rubbers?
They are too soft and sticky
What type of polymerization reaction is involved in the formation of condensation polymers?
Step-growth polymerization
What is the purpose of vulcanization in rubber production?
To create a harder and more flexible material
What type of copolymer has a random distribution of monomers?
Random copolymer
What is the main difference between homopolymers and copolymers?
Homopolymers are formed from one monomer, while copolymers are formed from two or more monomers
What is the result of heating rubber with sulfur in the vulcanization process?
The formation of a harder and more flexible material
What is the name of the process by which a polymer is formed from a single compound with two different functional groups?
Condensation polymerization
What is the primary characteristic of a step-growth polymer?
It is formed from a monomer with two different functional groups
What is the reaction mechanism involved in the synthesis of nylon 6?
Condensation reaction
What is the starting material for the synthesis of nylon 6?
ε-caprolactam
What is the primary characteristic of epoxy resins?
They are extensively cross-linked systems and can adhere to almost any surface
What is the reaction mechanism involved in the synthesis of Dacron?
Transesterification reaction
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
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
What is the primary application of epoxy resins?
They are used as adhesives and coatings
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
This quiz covers the characteristics and examples of step-growth polymers, including polyamides, polyesters, epoxy resins, and polyurethanes.
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