Intro to Polymers

Question 1

Isomerism

Answer 1

Spatial arrangement of reactive groups on a Monomer, where different orientations yield different properties

Question 2

Isotactic

Answer 2

All reactive groups on the same side

Question 3

Syndiotactic

Answer 3

Alternating side reactive groups

Question 4

Metallic bonding

Answer 4

Sea of delocalized electrons

Question 5

Ionic bonding

Answer 5

Transfer of electrons

Question 6

3-D sharing of electrons

Answer 6

Covalent bonding (thermosets and crosslinking)

Question 7

1-D sharing of electrons

Answer 7

Covalent bonding, thermoplastics

Question 8

Hydrogen bonding

Answer 8

Covalent primary, Van der Waals secondary

Question 9

Dipole to dipole

Answer 9

Van der waals bonds, secondary e sharing

Question 10

Amorphous Polymers

Answer 10

1-D chains-covalent bonding with van der Waals between chains.
Glassy, amorphous, and brittle at room temp.
Example is PMMA

Question 11

Semi-Crystalline Polymers (Thermoplastics)

Answer 11

1-D chains, covalently bonded with van der Waals between chains.
Both crystalline and amorphous regions.
Tg is typically below 0 deg C, leathery, rubber at room temp.
High ductility and toughness, with good chemical resistance
Examples: PE, PETE, PP, PVC, Nylon, Teflon

Question 12

Elastomers

Answer 12

3-D covalently bonderd, lightly crosslinked, long chain.
Irreversible Curing.
Lower modulus but moderate tensile strength.
Tg below 0 deg C, leathery/rubbery at room temp.
Examples: Vulcanized rubber, silicones

Question 13

Thermosets

Answer 13

3-D covalently bonded, highly cross-linked.
Reactive elements added between adjacent chains, covalent bonding between polymer chains.
Cannot be recycled.
Brittle fracture: high modulus and minimal plastic deformation.
Highest Tg due to curing reactions and highly crosslinked chains.
Examples: Epoxy, cynate ester, bakelite.

Question 14

Free radical

Answer 14

Atom or group with a dangling covalent bond

Question 15

Addition polymerization

Answer 15

Initiation: Free radical attaches to monomer
Propagation: Free radical monomer combines with additional monomers
Termination: Free radicals combine or transfer to other chains

Question 16

Condensation (stepwise) polymerization

Answer 16

Two molecules combine and leave behind a condensate, such as H20
Requires heat, pressure, and time (bakelite)