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DS1102 > Week 2 - Intro Polymers > Flashcards

Week 2 - Intro Polymers Flashcards

1
Q

What is a polymer

A

macromolecules which are high molecular weight molecules resulting from linking together many simple low molecular weight units (monomers) using covalent bonds. Polymers are substantially cross linked covalently often in a 3D network.

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2
Q

What is polymerisation

A

the chemical reaction which bring about joining of monomers

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3
Q

What is a resin

A

raw, semi liquid reasonably dense material used in a chemical reaction to make a polymer (often used in composite)

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4
Q

What is a plastic

A

a polymer that can be formed into various shapes by the use of heat ( and or pressure)

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5
Q

What is a thermoplastic

A

plastic which can be heated to a liquid and reshaped - over and over again

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6
Q

What is a thermosetting plastic

A

plastic which is fixed into shape by an irreversible reaction. - heat drives this reaction or it may be exothermic which fixes it into shape.

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7
Q

What are the different ways which polymers are classified

A
  • Based on origin
  • Thermal behaviour
  • Structure of polymer
  • Chemistry of monomer structural unit
  • Number of monomers involved in the chemistry
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8
Q

How does origin classify polymers

A
  • Biopolymers (carbohydrates, proteins, DNA) - Natural polymers

Polymers that occur in nature and can be extracted from plants or animals. Most biopolymers are formed by a condensation process eliminating H2O

Alginate is naturally derived biopolymer used in synthesis of dental impression materials.

  • Synthetic polymers (LDPE, PVC, nylon)

Polymers chemically synthesized in laboratories or industries. Mainly they are synthesised through these two roots

  1. addition polymerization (LDPE)
  2. Condensation polymerisation (Nylon)
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9
Q

How does thermal behaviour classify polymers

A
  • thermoplastic (nylon, PMMA, LDPE)

Polymer that can be melted and reshaped multiple times. They soften on heating and harden on cooling.

  • Thermoset

Polymers that undergo permanent chemical change when heated and cannot be remelted or reshaped.

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10
Q

How does the structure of the polymer classify polymers

A

Polysaccharides built form glucose with different structure that relate to their physiological and biochemical functions. Most synthetic polymers have structures that are linked to function.

  • Linear

Polymers with long and straight chains

  • Branched

Polymers with side chains or branches attached to the main chain. Often have lower density and melting points in comparison to linear polymers.

  • Hyperbranched

Branches stemming from other branches

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11
Q

How does the chemistry of monomer structural units classify polymers

A
  • Acrylic resins
  • Epoxy resins (not important)
  • Polyamide resins
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12
Q

How does the number of monomers involved in the chemistry classify polymers

A

The number of different types of monomers

Homopolymers - Only 1 monomer

Copolymer- 2 or more different monomers

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13
Q

How are synthetic polymers classified

A
  • Addition polymerisation
  • Condensation polymerisation
  • Chain growth
  • Step growth
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14
Q

What is addition polymerisation

A

Monomers add together without losing any atoms.

The whole monomer becomes part of the polymer

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15
Q

What is condensation polymerisation

A

Monomers join together with the loss of small molecules like water

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16
Q

What is chain growth

A

Monomers are added one at a time to the growing polymer

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17
Q

What is step growth

A

The polymer may grow from both ends. Growing polymer, monomers and oligomers (n>10) may all react with each other

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18
Q

What are the 3 mechanisms which addition polymerisation can occur

A
  1. Radical chain growth polymerisation
  2. Ionic chain growth: anionic and cationic (not important)
  3. Ring opening polymerisation: polar (not important)
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19
Q

What is a radical

A

a species with a single unpaired electron which are highly reactive e.g. Cl-

20
Q

What is an initiator

A

something which triggers polymerisation by generating reactive species such as free radicals, cations, or anions which interact with the monomers to begin the chain reaction leading to polymer formation

21
Q

What are common initiators

A
  • Thermal production of radicals from initiator (heat cure)
  • Visible light production of radicals from photo initiator system - light cure (explained in the 3rd lecture)
    -Benzoyl peroxide
22
Q

Explain the 3 steps in addition polymerisation via radical mechanism

A
  1. Initiation - generate a radical species (I. = R.). the radical is then join onto a monomer which produces a monomer radical
  2. Propagation - where monomers are added to the monomer radical forming a live polymer (has a radical at the end)
  3. Termination - addition of a radical to a live polymer or adding two live polymers together which causes polymerisation to stop
23
Q

What are co-monomers

A

precursor to a copolymer aside from the base monomer

24
Q

What is a copolymer

A

polymer with more than 1 different types of monomers

25
Q
A

Acrylate

26
Q
A

Methyl Acrylate (MA)

27
Q
A

Methyl Methacrylate (MMA)

28
Q
A

bisGMA = Bisphenol A glycidylmethacrylate

29
Q
A

UDMA = urethane dimethacrylate

30
Q
A

TEGDMA = triethylene glycol dimethacrylate

31
Q

What is the structure of acrylate

A
32
Q

What is the structure of methyl acrylate (MA)

A
33
Q

What is the structure of methyl methacrylate (MMA)

A
34
Q

What is chain transfer of polymer

A

Where the active radical site is transferred somewhere else on the chain or jump from one polymer to another resulting in branching

35
Q

What is degree of branching affected by

A
  • steric hinderance (bulky groups)
  • flexibility of polymer
  • synthesis conditions
36
Q

What is a dead polymer

A

polymer with no free radicals

37
Q

What is a live polymer

A

polymer with a free radical on it

38
Q

What is crosslinking

A

a way of introducing stiffness into a polymer by bonding chains together.

39
Q

What is a plasticizer

A

low molecular weight compounds added to a polymer to soften it. Plasticizer molecules keep chains separate inhibiting crystallinity. —> a monomer which doesn’t react and lies in between the polymer - this lubricates the polymer

40
Q

What type of polymerisation process produces polycarbonate

A

step-growth condensation polymer - involving the condensation of phenol (removal)

41
Q

What is the reaction which forms polycarbonate

A

condensation of bisphenol A and diphenyl carbonate - removing phenol in the process

42
Q

What polymerisation reaction forms Nylon 66

A

step growth polymerisation where the condensation of water occurs

43
Q

What are lactomer sutures and what type of polymerisation forms it

A

they are sutures which are biodegradable and absorbable and do not need to be removed
- condensation polymerisation reaction between glycolic acid and lactic acid producing water
- it is a copolymer ABAB type
- sutures dissolve as hydrolysis of ester linkages occur

44
Q

What type of chemical reaction radical addition polymerisation

A

usually - photochemical

45
Q

What type of chemical reaction is condensation polymerisation

A

metathesis - since precipitation drives the reaction

46
Q

What molecule facilitates the polymerisation of composite resin under blue light

A

Camphorquinone

DS1102 (30 decks)

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