PPT Polymer vs Simple molecule

Polymer vs Simple Molecule

• Main Topics:

  • Hydrocarbon molecule/polymer molecule

  • History of development of polymer

  • Chemistry of polymer molecule

  • Classification of polymers

  • Natural vs synthetic polymers

  • Plastics vs Elastomers

  • By – Amal Dissanayake

  • Prepared for I-CHEM: C/CHE31082

  • Date – 05/10/2024

What is Polymer

• The term "Polymer" is derived from Greek words:

  • Poly - meaning many (numerous)

  • Mer - meaning units

• Definition: A polymer is a long-chain molecule made up of many repeating units (mers), typically containing two or more molecules.

• Most common structure: Hydrocarbon backbone, consisting of carbon and hydrogen atoms.

• Examples of hydrocarbon backbone polymers:

  • Polypropylene

  • Polybutylene

  • Polystyrene

• Alternative polymer backbones can include other elements, e.g., Nylon (contains nitrogen).

Polymer Molecules and Monomers

• Polymer Molecules are macromolecules made of large numbers of linked small repeat units called monomers.

• Types of polymers based on monomer composition:

  • Homo-polymers: Composed of one kind of monomer.

  • Copolymers: Composed of several kinds of monomers (e.g., Styrene Butadiene copolymer - SBR).

Monomers and Repeating Units

• The identity of repeat units is critical for polymer classification:

  • Homopolymer: Contains a single type of repeat unit (e.g., Polystyrene).

  • Copolymers: Contain two or more types of repeat units (e.g., Ethylene-vinyl acetate).

  • Terpolymer: A copolymer with three types of repeat units.

• Examples:

  • DNA as a biological polymer contains four types of nucleotide subunits.

Unique Properties of Polymers

• Factors contributing to polymer uniqueness:

  1. Chain Entanglement: Long, flexible chains form complex tangles; affects properties and processing.

  2. Summation of Intermolecular Forces: Stronger intermolecular forces compared to smaller molecules due to size.

  3. Time Scale of Motion: Polymers move slower than small molecules due to their size and entanglement.

Chain Entanglement

• Chain entanglement influences polymer properties:

  • Reticular structures from cross-linking points restrict movement.

  • Can increase toughness but excessive entanglement complicates processing due to high melt viscosity.

Summation of Intermolecular Forces

• All molecules interact via electrostatic forces, but polymers have a cumulative effect:

  • Polar molecules (e.g., water) adhere better than nonpolar ones (e.g., methane).

  • Even weak forces (Van der Waals) become significant in large polymers, enhancing strength.

Time Scale of Motion

• Polymers exhibit slower motion compared to smaller molecules:

  • Influences viscosity in solutions and melts, leading to unique behavior when processed.

Historical Development of Commercial Polymers

• Chronological list of significant polymer developments (up to 1982):

  • Before 1800: Natural fibers (cotton, silk, rubber) and rudimentary materials.

  • 1839: Vulcanization of rubber.

  • Late 1800s: Various cellulose types and early plastics like Bakelite.

  • 1900s: Expansion into synthetic polymers like nylon, polyester, polyethylene.

Classification of Polymers

• Based on origin:

  • Natural, Semi-synthetic, Synthetic

• Based on structure:

  • Linear, Branched, Cross-linked

• Based on molecular forces:

  • Elastomers, Fibers, Thermoplastics, Thermosets

Natural vs Synthetic Polymers

• Natural Polymers: Produced by biological processes (e.g., proteins, cellulose).

• Synthetic Polymers: Man-made through chemical processes (e.g., plastics like Teflon).

Classification Based on Structure

• Linear Polymers: Long straight chains, e.g., high-density polyethylene.

• Branched Polymers: Linear chains with side branches, e.g., low-density polyethylene.

• Cross-linked Polymers: Strong covalent bonds between chains, e.g., bakelite.

Thermoplastics vs Thermosets

• Thermoplastics:

  • Linear structure, softens when heated, recyclable.

  • Example: Polyethylene, PVC.

• Thermosets:

  • Cross-linked structure, turns hard on heating and cannot be remolded.

  • Example: Phenol-formaldehyde resin.

Comparison Between Natural & Synthetic Polymers

Conclusion

• Plastics, derived from polymers, are versatile materials with various classifications.

• Understanding the structure and classification of polymers aids in their application and development in industries.

Polymer vs Simple Molecule

Main Topics:

• Hydrocarbon molecule/polymer molecule

• History of development of polymer

• Chemistry of polymer molecule

• Classification of polymers

• Natural vs synthetic polymers

• Plastics vs Elastomers

By – Amal DissanayakePrepared for I-CHEM: C/CHE31082Date – 05/10/2024

What is Polymer

The term "Polymer" is derived from Greek words:

• Poly - meaning many (numerous)

• Mer - meaning units

Definition:

A polymer is a long-chain macromolecule composed of numerous repeating units called monomers. These monomers are typically composed of two or more molecules and can range widely in size and complexity. Polymers can exhibit varying physical properties based on their molecular structure and the arrangement of their repeating units.

Most Common Structure:

Polymers often have a hydrocarbon backbone, which consists of alternating carbon and hydrogen atoms. This backbone can influence the chemical behavior and properties of the polymer.

Examples of Hydrocarbon Backbone Polymers:

• Polypropylene: Widely used in packaging and textile applications, known for its durability and resistance to chemicals.

• Polybutylene: Used for various applications, including plumbing and gas distribution systems.

• Polystyrene: Commonly used in foam products and insulation.

Alternative polymer backbones can include other elements, such as nitrogen in Nylon, which enhances specific properties like strength and flexibility.

Polymer Molecules and Monomers

Polymer Molecules:

Polymer molecules are defined as macromolecules consisting of vast numbers of linked small repeat units known as monomers. The properties and behaviors of these polymers depend heavily on their monomer composition and arrangement.

Types of Polymers Based on Monomer Composition:

• Homo-polymers: Composed entirely of one kind of monomer, leading to uniform characteristics (e.g., Polystyrene).

• Copolymers: Composed of two or more different types of monomers, which can impart unique properties not found in homo-polymers. An example includes Styrene Butadiene Copolymer (SBR), often used in tires for enhanced durability.

Monomers and Repeating Units:

The specificity of repeat units is crucial for the classification of polymers:

• Homopolymer: Fully contains a single type of repeat unit (e.g., Polystyrene).

• Copolymers: Composed of two or more different repeat units (e.g., Ethylene-vinyl acetate).

• Terpolymer: A type of copolymer featuring three kinds of repeat units, allowing for diverse properties.

Examples:

DNA serves as a biological polymer consisting of four types of nucleotide subunits, showcasing the complexity and functionality of natural polymers.

Unique Properties of Polymers

Several factors contribute to the unique properties of polymers, making them distinct from smaller molecules:

Chain Entanglement:

Polymers tend to have long and flexible chains that can become entangled, forming complex tangles that significantly affect their physical properties and processing capabilities. The degree of entanglement often influences toughness but excessive entanglement can complicate the processing due to increased melt viscosity.

Summation of Intermolecular Forces:

While all molecules interact via electrostatic forces, polymers demonstrate a cumulative effect due to their size:

• Polar molecules (e.g., water) typically adhere better to polar surfaces compared to nonpolar molecules (e.g., methane).

• Even relatively weak intermolecular forces, such as Van der Waals forces, become impactful in large polymers, contributing to enhanced strength and stability.

Time Scale of Motion:

Polymers generally exhibit slower motion than smaller molecules due to their size and mass:

• This property influences viscosity in both solutions and melts, which can lead to unique behaviors during processing and application.

Historical Development of Commercial Polymers

A chronological overview of significant developments in polymers leading up to 1982:

• Before 1800: The use of natural fibers like cotton, silk, and rubber, alongside rudimentary materials, set the foundation for future developments in polymer science.

• 1839: The invention of rubber vulcanization, a crucial technological leap enhancing the durability and utility of rubber products.

• Late 1800s: Development of early plastics, such as Bakelite, marked the shift towards synthetic materials.

• 1900s: The expansion into synthetic polymers during the 20th century, leading to the production of nylon, polyester, and polyethylene, revolutionized multiple industries with new, versatile materials.

Classification of Polymers

Polymers can be broadly classified based on several criteria:

• Based on Origin:

  • Natural Polymers: Produced by biological processes (e.g., proteins, cellulose).

  • Semi-synthetic Polymers: Derived from natural sources but modified through chemical processes (e.g., regenerated cellulose).

  • Synthetic Polymers: Completely man-made through chemical processes (e.g., plastics like Teflon).

• Based on Structure:

  • Linear Polymers: Formed from long, straight chains, exemplified by high-density polyethylene.

  • Branched Polymers: Characterized by linear chains with side branches, e.g., low-density polyethylene, which offers different properties.

  • Cross-linked Polymers: Composed of strong covalent bonds between chains, leading to enhanced structural integrity, like bakelite.

Thermoplastics vs Thermosets

• Thermoplastics:

  • Have a linear molecular structure that allows them to soften and remold when heated, making them recyclable. Examples include Polyethylene and PVC.

• Thermosets:

  • Feature a cross-linked molecular structure that hardens upon heating and cannot be remolded, such as Phenol-formaldehyde resin, making them suitable for applications requiring durability.

Comparison Between Natural & Synthetic Polymers

Conclusion

Polymers serve as the foundational materials for various plastic products. Their diverse classifications and unique properties are vital for their functionality across different industries. A comprehensive understanding of polymer chemistry and its classifications plays a crucial role in advancing applications and innovation in material science.