Introduction to Polymers Flashcards
What are Polymers?
Large molecules composed of many repeating subunits (called monomers)
How does the melting point of a polymer change as the number of chains in the backbone increase?
Melting point increases
(chemical, physical, and thermal properties have a relationship with polymer length)
When does a chain become a polymer?
When the loss of a couple carbons no long significantly changes the properties of the molecule
How can we determine the Polymers are long chains? (ex. how can we quantify the polymer length?)
- Look at bulk properties
(ex. viscosity changes with polymer length) - Characterization techniques
- Atomic force microscopy
Molecular weight and a mixture?
Molecular weight is a distribution for polymers and the skinnier the distribution the closer the dispersity is to 1
What is dispersity?
- a value that tells us about the width/breadth of the molecular weight distribution
calculated as Mw/Mn
Thermoplastics vs Thermosets
Thermoplastics: reversible between solid and liquid
Thermosets: obtained by irreversible crosslinking, thus permanent transform from liquid to solid (once in shape does not want to change - must break links to do so)
Structures of Polymers
- Amorphous - does not form crystals
- Semi-crystalline polymers - have crystalline regions intersperses between amorphous regions
(cannot have crystalline because of how the polymers form - solids cannot move)
Chain Structure of Polymers
- homopolymers - made up of a single repeating monomer
- copolymers - made up of 2 or more repeating monomers
- these can be in Random, Alternating, Block, of graft
What is tacticity
How pendant groups are arranged along the main backbone
- isotacic - all on 1 side
- syndiotatic - ordered on both sides
- actactic - random side of pendant group
