11 Polymer Synthesis

Question 1

what is a polymer?

Answer 1

macromolecules made covalently bonded repeating subunits (monomer)

Question 2

what does a monomer need?

Answer 2

2 (bifunctional) or more (polyfunctional) bonding sites

Question 3

bi/polyfunctional produce

Answer 3

bi: linear
poly: branched

Question 4

2 types polymer

Answer 4

Homopolymer: one species of monomer

Copolymer: two or
more monomers.

Question 5

4 types copolymers

Answer 5

• Statistical copolymer. Two + monomers
  randomly distributed.
  – Alternating copolymer: alternate
  throughout the chain.
  – Block copolymer: Blocks of one monomer
  followed by a second monomer.
  – Graft copolymer: One monomer is grafted on to
  the backbone of another polymer.

Question 6

how to draw polymers

Answer 6

• repeat unit in square brackets, n
  repeat units
  – end group is
  known/relevant, it can be
  shown bonded to the repeat
  unit

Question 7

how to name a polymer

Answer 7

bad standardized

use poly(monomer) or hypothetical monomer

Question 8

2 ways to grow polymers

Answer 8

• step growth: add to growing chain, can combine chains, free for all
• chain growth: monomers add to growing chain

Question 9

chain growth mech

Answer 9

initiation
propagation
termination

Question 10

Initiation

Answer 10

• monomer react with initiator

types initiators: radical, anionic, cationic

Question 11

Propogation

Answer 11

initiator monomer react with monomer

Question 12

Termination

Answer 12

2 radicals recombine
random process
reason why broad MW distribution

Question 13

disproportionation

Answer 13

type termination
involves transfer of H ?

Question 14

Chain transfer

Answer 14

• active and chain attacks another chain that NOT unsaturated
• original chain terminated new chain activated

Question 15

Free radical initiator

Answer 15

• makes azo cmpd can decompose under mild/moderate conditions
• AIBN, VAZO
• characteristic of rad polymerization
• accelerate as T increases
• generally need heating/UV

Question 16

anionic initiators

Answer 16

n-bu li or naphthalide

Question 17

characteristic of anionic initiators

Answer 17

need to cool rxn
- can’t touch water
- said to be living: w/o terminating all chains active even if all monomers consumed

Question 18

Living polymerization

Answer 18

chain polymerization with no transfer or termination

Question 19

characteristic of living polymerization

Answer 19

1) chains similar lengths
2) length depends on amount initiator
3)can make block co-polymers
4)can add funtional groups

Question 20

Narrow MW
distribution
because rate of
__________&raquo_space; rate of ___________

Answer 20

initiation, propagation

Question 21

Characteristic of living polymerization

Answer 21

• need to suppress chain transfer
• no termination until add a terminating species (work up)
• rate initiation&raquo_space; propagation
• polymer chain length can be increase by adding more monomer
• can form block copolymers
• can add functional group

Question 22

cationic initiator

Answer 22

Strong acid/ some Lewis acid
HCl, H2SO4, BF3, TiCl4

• can result in living chains
• stabilized by EWG in chains

Question 23

Step growth polymerization

Answer 23

• NO 3 steps
• Polymerization from polyfunctional monomers
• producing repeating units connected by
  ester, amide, urethane, sulfide, and ether
  linkages.
• Upon reaction, a small molecule
  (generally water) is produced.

Question 24

structure polymer classification

Answer 24

• Condensation polymers: Contain ester, ether,
  urethane, sulfide linkages.
  – Addition polymers: Do NOT contain linkages
  above

Question 25

polymerization clasification

Answer 25

• Step growth: A small molecule is released.
  Reactivity of monomers is the same as that of
  polymers.
  – Chain growth: No small molecule is released.
  Monomers are added to growing chain.

Question 26

What is PET

Answer 26

polyethylene terephthalate: made from terephthalic acid
and ethylene glycol.

in water bottles

Question 27

characterization of condensation polymerization

Answer 27

1. Removal water/ another small
   molecule drives the reaction forward.
2. Broad molecular weights
3. Chain length controlled by adding
   monofunctional reagents.
4. Highest molecular weights
   when equimolar amounts of reagents
   used.
5. Chain branching is possible if for example
   triols or triamines are used.

Question 28

Step growth polymerization & chain length

Answer 28

Broad size distribution
Low MW until close to
completion

Question 29

Secondary reactions – Modifying polymer structure

Answer 29

• modifying side groups.
• used when polymerization with unsuitable side group

Question 30

secondary rxn - crosslinking

Answer 30

-Two polymer chains can bond along their length
- can
occur via covalent bonding between
neighbouring chains, or via ionic bonding where
a single counter ion links two charged groups on
neighboring chains.
- helps reduce
solubility, improve strength, and increase
thermal stability.

Question 31

Types of crosslinking

Answer 31

1) Between polymers with unsaturated side groups. Or between polymers with saturated
side-groups which undergo hydrogen radical
abstraction using peroxides or UV-light.

2) Between polymers that produce water or
other stable by-products and form a covalent
bond between chains.

3) Between polymers that have monovalent
cations upon exposure to divalent and
trivalent cations. (weaker)

Question 32

Secondary reactions – Surface reactions

Answer 32

Sometimes the chemical properties of a solid
polymer surface must be different than the bulk.