Part 9 Formation and Structure of Polymers MELC

Summary

This video lesson covers the fundamentals of organic compounds and polymers, explaining their structure, formation, and types. It introduces the concept of monomers and their role in polymer chains, which can be natural or synthetic. The lesson explores various polymerization methods, such as chain growth and step growth, and explains copolymers and their classifications. Key polymer types, like isotactic, senjotactic, and atactic, are discussed, along with examples like polypropylene and Nylon 66. Understanding these concepts helps in recognizing how polymers are created and applied in real-world products, from plastics to textiles.

Takeaways

• 😀 Polymers are large molecules formed by chains of repeating units called monomers, linked by covalent bonds.
• 😀 Natural polymers are found in living organisms like humans, animals, and plants, while synthetic polymers are man-made and found in various commercial products.
• 😀 Polymers can be classified based on their origin into natural and synthetic types.
• 😀 Homopolymers are made from only one type of monomer, while heteropolymers are made from two or more types of monomers.
• 😀 Copolymers can have alternating or random monomer arrangements, and can be formed in controlled conditions for specific applications.
• 😀 Chain growth polymerization involves a radical or ionic initiator that reacts with alkenes to form reactive species that continue to polymerize until all monomers are used up.
• 😀 Chain growth polymerization includes three main steps: initiation, propagation, and termination, with possible branching under certain conditions.
• 😀 The properties of chain growth polymers are influenced by the groups attached to the alkene monomer, which can determine if the polymer is isotactic, senjotactic, or atactic.
• 😀 Isotactic polymers have pendant groups on the same side of the backbone, while senjotactic polymers have alternating pendant groups, and atactic polymers have random orientations.
• 😀 Step growth polymerization occurs through addition or condensation reactions, where polymer chains grow separately and may merge, as seen in the formation of polyurethanes and Nylon 66.

Q & A

What is a polymer?

A polymer is a large molecule consisting of chains of repeating units called monomers, which are linked by covalent bonds.

What are the two major classifications of polymers based on their origin?

Polymers can be classified as natural polymers, which are found in living organisms, and synthetic polymers, which are man-made and used in products like plastics and fabrics.

What is the difference between homopolymers and heteropolymers?

Homopolymers consist of only one type of monomer, while heteropolymers (or copolymers) are made from two or more types of monomers.

How do copolymers differ in structure?

Copolymers can have monomers arranged in an alternating or random pattern. They can also have block or graft structures, where different monomers are introduced at specific stages of polymerization.

What is chain growth polymerization?

Chain growth polymerization is a process in which a radical or ionic initiator reacts with a monomer, usually an alkene, to produce a reactive species that adds more monomers to form a polymer.

What are the key steps in chain growth polymerization?

The key steps are initiation (where an initiator starts the reaction), propagation (where monomers are added to the growing chain), and termination (where the reaction stops).

How does the presence of different groups attached to alkene monomers affect polymer properties?

The groups attached to the alkene monomers, referred to as pendant or dependent groups, affect the polymer's properties by influencing its structure and behavior, such as in the isotactic, syndiotactic, and atactic classifications.

What is the difference between isotactic, syndiotactic, and atactic polymers?

Isotactic polymers have pendant groups arranged on the same side of the polymer backbone. Syndiotactic polymers have alternating pendant group positions, while atactic polymers have pendant groups arranged randomly.

What is step growth polymerization?

Step growth polymerization occurs when monomers with two different functional groups react to form a polymer chain, without depending on other growing chains. This process involves addition or condensation reactions.

Can you provide an example of a step growth polymer?

An example of a step growth polymer is Nylon 66, which forms through a condensation reaction between hexamethylenediamine and adipic acid.