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Ma ME523: Polymer And Polymer Composites > L1: Intro and Solid State > Flashcards

L1: Intro and Solid State Flashcards

1
Q

Define polymer

A

Many units of monomers covalently bonded together to form a long chain (a macromolecule)

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2
Q

Give the 3 conventional classifications of polymer

A
  • Natural
  • Semi-synthetic
  • Synthetic
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3
Q

What are the subdivisions of natural polymers?

A

Organic and inorganic

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4
Q

What are semi-synthetic polymers? Give an example

A

Naturally occurring polymers chemically modified to make their properties desirable
Vulcanisation of rubber

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5
Q

What are synthetic polymers?

A

Human made polymers, made from monomers derived from petroleum

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6
Q

Give the key characteristic of organic synthetic polymers. How do inorganic synthetic polymers differ?

A

Backbones have C-C bonds

No C in backbone

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7
Q

What are the two main categories of polymerisation reaction and the sub-types for each?

A 
Chain-growth 
-Free radical
-Coordination 
-Cationic 
-Anionic 
Step-growth 
-Polycondensation 
-Polyaddition
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8
Q

When are brackets used in nomenclature?

A

When the monomer name consists of more than one word - eg poly(vinyl chloride)

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9
Q

What feature must monomers have in order to carry out chain-growth polymerisation?
What must happen to ethylene to create this feature?

A

Carbon-carbon double bonds ( C=C )

One or more hydrogen atoms in the ethylene monomer must be replaced by other elements or organic groups

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10
Q

Give an overview of free-radical polymerisation

A
  1. Initiation. A free radical initiator reacts with the monomer, opening the C=C bond. One electron from the double bond is left alone - a larger free radical has been made
  2. Propagation. Monomers are added to the chain one at a time
  3. Termination. Two large free radical chains meet to form dead chains. Dead chain length is random
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11
Q

What is the requirement for monomers used in step-growth polymerisation?

A

Monomers must have 2 different functional groups (can have 2 different monomers or 1 monomer with 2 different groups)

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12
Q

Give an overview of step-growth polymerisation

A

Difunctional group monomers react, potentially forming H2O as a byproduct.
Intermediate medium-sized oligomers form

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13
Q

Give an overview of condensation polymerisation

A

An ester linkage is formed between two monomers when the -COOH and -OH groups react (can have two different monomers or a difunctional monomer). A water molecule is produced as a by-product
Chain grows from both ends of the chain

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14
Q

What does an ester linkage look like?

A

O
ll
- O - C -

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15
Q

Give an overview of condensation polymerisation

A

The hydrogen from an amine group reacts with the hydroxyl group from another monomer to form a water molecule as a by-product, linking the two monomers by an amide bond

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16
Q

What does an amide bond look like?

A

H O
l ll
N - C

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17
Q

What are the key features of polyaddition polymerisation?

A
  • Difunctional groups are required

- No small molecules are formed as byproducts

18
Q

Describe the change when a thermoplastic polymer is heated

A

It melts into a viscous liquid. This is a reversible change

19
Q

Describe how heat affects liquid thermoset polymers

A

They are ‘cured’ into a hard solid. They become hard and rigid due to inter-chain cross-linking reactions

20
Q

What is the result of polymers being polydispersed, and what must therefore be measured?

A

No unique molecular weight

Need to measure Molar Mass Distribution

21
Q

Give the formula relating mass, moles and molecular mass

A

Mass = moles x molecular mass

22
Q

Define degree of polymerisation (both words and equation)

A
  • Mean number of monomer units per polymer chain

- (Molar mass of chain)/(Molar mass of monomer)

23
Q

Why is molar mass important?

A
  • Higher MM gives better mechanical properties due to increased chain entanglement and interaction
  • More difficult to process due to increased melt viscosity
24
Q

Give names for polymer architecture with the following structures (2 is the group of i, ii, iii):

  1. -A-A-A-A-A-A
  2. i) -A-B-A-B-A-B-A-
    ii) -A-A-A-A-B-B-B-B-
    iii) -A-B-A-A-A-B-B-A-B
A
  1. Homopolymer
  2. Copolymer
    i) Alternating
    ii) Block
    iii) Statistical
25
Q

Give the names for polymers:

  1. Consisting of identical monomers
  2. Consisting of different monomers
A
  1. Homopolymer

2. Copolymer

26
Q

Describe branched polymers

A

Long chains of identical monomers with shorter branching chains of identical monomers

27
Q

Describe graft polymers and give their nomenclature

A

Long chains of identical monomers with shorter branching chains of
different identical monomers
poly(A-g-B)

28
Q

Describe cross-linked polymers

A

A 3D network of polymer chains

29
Q

Give the 3 spatial arrangements of tacticity and a basic description

A
  1. Isotactic - same orientation
  2. Syndiotactic - Alternating orientation
  3. Atactic - No regularity
30
Q

Why can’t atactic polymers crystallise?

A

There are steric clashes so the molecules cannot arrange themselves in an ordered fashion

31
Q

How do synthetic polymers crystallise?

A

They form regular helices, which are straight and periodic

32
Q

What are lamellar stacks?

A

Alternating crystallise and amorphous layers

33
Q

How does pinning work in lamellar stacks?

A

Macromolecules pass from one phase to another many times. The longer the chains, the more effective the pinning

34
Q

Describe spherulites

A

Spherical aggregates, 1micrometer to 1mm in size.

They crystallise from a nucleation point & grow radially in 3D until impinged on

35
Q

What effect do spherulites have on mechanical strength?

A

They degrade it, as cracks appear along their boundaries

36
Q

How does density change with crystallinity?

A

More dense with higher crystallinity

37
Q

How does young’s modulus change with crystallinity?

A

Increases linearly with degree of crystallinity

38
Q

How does strength change with crystallinity and molar mass?

A

Increases

39
Q

How does toughness change with crystallinity and molar mass?

A

Increases with molar mass, decreases with crystallinity

40
Q

What is changing in the ductile-brittle transition?

A

Molar mass and density (ie crystallinity)

Ma ME523: Polymer And Polymer Composites (3 decks)

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