Materials- Polymers Intro

Question 1

Name some natural polymers

Answer 1

Wood, rubber, wool, leather, silk

Question 2

Name some synthetic polymers

Answer 2

Plastics, some rubbers, fibre materials

Question 3

What does polymer mean?

Answer 3

A class of macromolecule consisting of a set of regularly repeated chemical units of the same type, or possibly a very limited number of different types to form a chain molecule.

Question 4

Describe how a polymer is arranged

Answer 4

Long, linear, thread-like molecules of variable length, composed of small definable molecular units, covalently bonded to one another to form a macromolecule.

Question 5

Describe the molar mass of polymers

Answer 5

Large

Typically 10^4-10^6

Question 6

What is ethylene also known as?

Answer 6

Ethene

Question 7

Describe acetylene

Answer 7

Two carbon triple bonded together both attached to a H.

Question 8

What is an unsaturated molecule?

Answer 8

A molecule that has double or triple covalent bonds. Each carbon is not bonded to four other atoms and it is possible for another atom or group of atoms to become attached to the original molecule.

Question 9

What is a saturated molecule?

Answer 9

All bonds are single ones and no new atoms may be joined without the removal of others that are already bonded.

Question 10

Structure of formaldehyde

Answer 10

Methanal

Question 11

What is isomerism?

Answer 11

When compounds have the same composition but different atomic arrangements

Question 12

Do physical properties depend on isomeric state?

Answer 12

Yes

Question 13

What is a monomer?

Answer 13

The small molecule from which a polymer is synthesised

Question 14

What is the angle between carbon atoms in a polymer?

Answer 14

109°

Question 15

What is an isotactic polymer?

Answer 15

Where all of the monomers are joined in the same orientation. This makes the polymer more crystalline.

Question 16

What is a syndiotactic polymer?

Answer 16

Where the monomers alternate between one orientation and the opposite orientation

Question 17

What is an atactic polymer?

Answer 17

Where the orientation of the monomers in the chain is random

Question 18

How does melting temperature change with molecular mass?

Answer 18

It increases for up to about 100,000g/mol

Question 19

Typical molecular mass of liquid, waxy solid and solid polymers at room temperature

Answer 19

About 100 is liquid. About 1000 is waxy solid. Solid range from 10,000 and several million.

Question 20

Graph of distribution for number of molecules with each molar mass after polymerisation.

Answer 20

Steep line up with ever-decreasing gradient. Then curves back down like exponential decay.

Question 21

Formula for total mass of polymer

Answer 21

W=ΣNi

Where Ni is the total mass of each fraction which is number of moles of polymer with molar mass Mi

Question 22

What are two sources of monomers?

Answer 22

Coal and crude oil

Question 23

What is polymerisation?

Answer 23

The process where monomers are linked together to generate long chains composed of repeat units

Question 24

What is the process for addition polymerisation?

Answer 24

Monomer units are attached one at a time to form a linear macromolecule. Has three stages of initiation, propagation and termination. Rapid process with molecule consisting of 1000 repeat units in the order 10^-2 to 10^-3 seconds

Question 25

Initiation step of addition

Answer 25

There is an initiator with a free radical that attacks the monomer (with a C=C). The free radical moves onto carbon the initiator doesn’t join into because the double bond is broken. This carbon is the active centre of propagation.

Question 26

Propagation step of addition

Answer 26

Linear growth of the polymer chain by the sequential addition of monomer units to this active growth chain molecule in the same mechanism as initiation step

Question 27

Termination step of addition

Answer 27

Combination: the active ends of two propagating chains may link together to form one molecule.
Disproportionation: two growing molecules react to form two separate “dead chains”, one of which has a double bond at the end.

Question 28

What is condensation polymerisation?

Answer 28

The formation of polymers by stepwise intermolecular chemical reactions that may involve more than one monomer species. There is usually a small molecular weight by-product such as water that is eliminated.
Generally longer reaction times than for addition.

Question 29

For nylon classification, what does each number mean?

Answer 29

The first one is number of carbons between nitrogens. Second one is number of carbons between oxygens.