Lecture 4 - polymers Flashcards
(32 cards)
What is a polymer?
A polymer is a substance that consists of very large molecules made from repeating subunits derived from monomers.
Non-metallic materials that are composed of monomers to form large molecules.
Define monomer.
A monomer is a molecule that can be bonded to other identical molecules to form a polymer.
Monomers are the building blocks of polymers.
What is polymerization?
Polymerization is the process in which monomers chemically bond together to form a polymer chain or network.
What does polydispersity refer to?
Polydispersity refers to the degree of variation in molecular weight among the polymer chains in a sample.
What is a homopolymer?
A homopolymer is a polymer made from one type of monomer repeated multiple times.
What is a copolymer?
A copolymer is a polymer made from two or more different types of monomers.
List the types of copolymers.
- Random
- Alternating
- Block
- Graft
Define bifunctional monomer.
A bifunctional monomer has two active bonds that form a one-dimensional molecule.
What is a trifunctional monomer?
A trifunctional monomer has three active bonds that form branches or a two- or three-dimensional network molecule.
What is cross-linking in polymers?
Cross-linking is the method by which one polymer chain is connected to another, typically by a covalent or ionic bond.
What is vulcanization?
Vulcanization is the process of converting natural rubber into more durable materials via the addition of sulfur.
What is isomerism?
Isomerism refers to substances having the same composition but different atomic arrangements.
Define stereoisomerism.
Stereoisomerism is when atoms are linked together in the same order but differ in their spatial arrangement.
What is geometrical isomerism?
Geometrical isomerism involves double bonds between carbon atoms and different arrangements of side groups.
What does Tg stand for?
Tg stands for glass transition temperature.
What happens to polymers below Tg?
Below Tg, amorphous polymers tend to be brittle, hard, and glassy.
What is the melting temperature (Tm)?
Tm is the temperature at which crystalline polymers transition from a crystalline state to a liquid.
What are thermoplastics?
Thermoplastics are polymers that are hard at room temperature but become softer when heated, allowing for a reversible process.
What are thermosets?
Thermosets are polymers that do not become softer when heated and are cross-linked.
What are elastomers?
Elastomers are natural or synthetic polymers that can stretch and retract rapidly.
Define stress in materials.
Stress refers to the intensity of the force acting on a material.
Define strain in materials.
Strain refers to the resulting deformation of the material.
What are the stages of addition polymerization?
- Initiation
- Propagation
- Termination
What is condensation polymerization?
Condensation polymerization is when monomers are joined with the release of a small molecule like water.
