DM.5

Question 1

What are the following:

a) Homopolymer
b) Regular copolymer
c) Block Copolymer

Answer 1

a) (one monomer)
b) repeating pair or sequence of monomers
C) alternating segments of different polymer compositions,

Question 2

What type of reaction forms copolymers?

Answer 2

condensation polymerization

Question 3

What is formed by condensation polymerization?

Answer 3

copolymers

Question 4

What type of reaction forms homopolymers?

Answer 4

addition polymerization

Question 5

What is formed by addition polymerization?

Answer 5

homopolymers

Question 6

How many products are there in an addition reaction?

Answer 6

1

Question 7

How many products are there in an condensation reaction?

Answer 7

Condensation reactions system have a bi-product e.g. water, CO, CO2, H2.,

Question 8

1) what are the distinctive reaction stages of addition polymerisation?
2) what is required for it to occur?

Answer 8

1) activation, initiation, propagation, termination

2) active species such as an ion or radical (molecule with a spare electron)

Question 9

What properties is required of the free radicals we use:

Answer 9

1. must be activated by something e.g. energy, , light

2. reasonable stable, can be stored for a certain amount of time

Question 10

Why don’t we use heat to activate free radicals?

2) What do we do instead?

Answer 10

we would possible have to heat to 60 degrees.

2) Instead we use light. We can also use another chemical to activate with a benzene ring e.g. N, N dimethyl-p-toluidine

Question 11

What type of bond to we break usually when activating a free radical?

Answer 11

ones with low bond enthalpy. O-O,

Question 12

What safety issues are there with polymerisation:

Answer 12

heat produced,

monomers can be toxic when not in polymer form

Question 13

what happens in the activation step of polymerisation?

Answer 13

free radical formed

Question 14

What happens in the initiation step of polymerisation?

Answer 14

free radical reacts with monomer (added to it)

Question 15

What happens in the propagation step of polymerisation?

Answer 15

monomer bonded to radical reacts with another monomer

Question 16

What happens in the termination step of polymerisation?

Answer 16

monomer bonded to radical reacts with monomer bonded to radical, or radical with radical

Question 17

What happens when you mix the monomers?

2) Why do we have to be careful no to over add initiator?

Answer 17

1) polymer is formed and viscocity increases. eventually reaction will terminate as no frequency of collisions decreases
2) initiator will react with itself

Question 18

What sort of monomer forms cross-links when polymerised?

2) are polymers that are cross-linked the same as polymers that are not? (if made up of same monomer)
3) do we want linear or non-linear polymers in dentiistry?

Answer 18

1) di or tri-functional monomer
2) properties change
3) Linear polymers flow apart in lquid, like spaghetti in water. Therefore, liner polymers will soften and aren’t useful in the mouth. The solution joining the chains together.

Question 19

1) Give an example of a bulking agent used in dentures:
2) what do bulkers do?
3) What properties does it give the material?
4) What would happen if too much was added?

Answer 19

1) Ethylene Glycol dimethacylate, is added to the bulk polymer (methy methacrylate) making up dentures,
2) act as cross-linkers to form a copolymer.
3) harder to deform
4) brittle.

Question 20

What is Bis-GMA?

2) What is it used in?
3) what are its properties and what about it gives it this property?

Answer 20

1) bulking agent
2) Bis-GMA is used in composite filling materials,
3) viscous due to large size (it has aromatic rings)
naturally forms cross-links (mathymathacrylate group)