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Questions and Answers
What is the reason why an alkene does not readily undergo nucleophilic attack?
What is the reason why an alkene does not readily undergo nucleophilic attack?
- Alkenes have a high molecular weight
- Alkenes have a low molecular weight
- Alkenes are electron poor
- Alkenes are electron rich (correct)
What type of initiator is required for anionic polymerization of an alkene?
What type of initiator is required for anionic polymerization of an alkene?
- A strong acid
- A very good nucleophile (correct)
- A strong base
- A moderately good nucleophile
What is the reason why living polymers are common in anionic polymerization?
What is the reason why living polymers are common in anionic polymerization?
- Chains can be terminated by chain combination
- Chains cannot be terminated by proton loss (correct)
- Chains can be terminated by disproportionation
- Chains can be terminated by proton loss
What is the monomer of Super Glue?
What is the monomer of Super Glue?
What is the purpose of polymers similar to Super Glue in medical applications?
What is the purpose of polymers similar to Super Glue in medical applications?
What type of polymerization occurs when an epoxide is polymerized?
What type of polymerization occurs when an epoxide is polymerized?
What is the mechanism of anionic polymerization of epoxides?
What is the mechanism of anionic polymerization of epoxides?
What is the requirement for an alkene to undergo anionic polymerization?
What is the requirement for an alkene to undergo anionic polymerization?
What is the primary method of preparing polyurethanes?
What is the primary method of preparing polyurethanes?
What is a distinctive feature of Dyneema?
What is a distinctive feature of Dyneema?
How do microorganisms degrade biodegradable polymers?
How do microorganisms degrade biodegradable polymers?
What is the byproduct of lactic acid polymerization?
What is the byproduct of lactic acid polymerization?
What is the primary mechanism of PHA degradation?
What is the primary mechanism of PHA degradation?
What is the most common PHA?
What is the most common PHA?
What is the characteristic of oriented polymers?
What is the characteristic of oriented polymers?
What is the advantage of Dyneema compared to steel?
What is the advantage of Dyneema compared to steel?
What is the estimated amount of synthetic polymers manufactured annually in the United States?
What is the estimated amount of synthetic polymers manufactured annually in the United States?
What is the process of linking monomers together to form a polymer called?
What is the process of linking monomers together to form a polymer called?
What is the more widely used system for naming polymers?
What is the more widely used system for naming polymers?
How are polymer formulas typically written?
How are polymer formulas typically written?
What is the term for polymers synthesized by cells?
What is the term for polymers synthesized by cells?
What is the name of the polymer commonly known as Teflon?
What is the name of the polymer commonly known as Teflon?
What are examples of biopolymers?
What are examples of biopolymers?
How can polymers be broadly classified?
How can polymers be broadly classified?
Study Notes
Urethanes
- Urethanes can be prepared by treating an isocyanate with an alcohol in the presence of a catalyst such as a tertiary amine.
- The most common polyurethanes are prepared by the polymerization of toluene-2,6-diisocyanate and ethylene glycol.
Oriented Polymers
- Polymer chains obtained by conventional polymerization can be stretched and packed together again in a more ordered, parallel arrangement than originally, resulting in polymers that are stronger than steel.
- Dyneema is an oriented polyethylene polymer with a molecular weight 100 times greater than that of high-density polyethylene.
- Dyneema is lighter than Kevlar and at least 40% stronger.
- A rope made of Dyneema can lift almost 119,000 pounds, whereas a steel rope of similar size fails at 13,000 pounds.
Biodegradable Polymers
- Biodegradable polymers can be degraded by microorganisms such as bacteria and fungi.
- Polylactide (PLA) is a biodegradable polymer of lactic acid, widely used.
- Lactic acid is converted to a cyclic dimer, which can form a polymer without loss of water by ring-opening polymerization.
- Polyhydroxyalkanoates (PHAs) are also biodegradable polymers.
- PHAs are condensation polymers of 3-hydroxycarboxylic acids.
- The most common PHA is PHB, a polymer of 3-hydroxybutyric acid; it can be used as polypropylene.
- PHAs are degraded by bacteria to CO2 and H2O.
Anionic Polymerization
- Nucleophilic attack on an alkene does not occur readily because alkenes are electron-rich.
- The initiator must be a very good nucleophile, such as sodium amide or butyllithium, and the alkene must contain electron-withdrawing substituents to decrease the electron density of the double bond.
- Living polymers are most common in anionic polymerization because the chains cannot be terminated by proton loss from the polymer.
- Examples of anionic polymerization include the polymerization of methyl α-cyanoacrylate, which is used in Super Glue.
Ring-Opening Polymerizations
- Some compounds can polymerize more readily than ethylene and substituted ethylenes in chain-growth polymerizations.
- Epoxides undergo chain-growth polymerization, which can occur by an anionic mechanism.
Synthetic Polymers
- Synthetic polymers are a multibillion-dollar industry, with over 50 trillion pounds manufactured each year in the United States alone.
- A polymer is a large molecule made by linking together repeating units of small molecules called monomers.
- The process of linking them together is called polymerization.
Polymer Nomenclature
- Polymers can be named according to their structure, but an alternative source-based system is more widely used.
- Source-based names are generated by adding the prefix poly- to the name of the monomer.
- When the name of the monomer consists of two words, both words are enclosed in parentheses following poly-.
- The polymer formulas are written by enclosing the repeating unit within brackets, followed by the letter n to indicate that the number of repeating units is not specified.
Classification of Polymers
- Polymers can be divided into two broad groups: synthetic polymers and biopolymers.
- Synthetic polymers are synthesized by scientists, whereas biopolymers are synthesized by cells.
- Examples of biopolymers include DNA, RNA, proteins, and polysaccharides.
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Description
This quiz covers the preparation and properties of polyurethanes, including their synthesis, polymerization, and strength.