CH3A4, Polymer Chemistry20022003 - PowerPoint PPT Presentation

Title: CH3A4, Polymer Chemistry20022003


1
CH3A4, Polymer Chemistry 2002/2003

• www.warwick.ac.uk/polymers

2
CH3A4, Polymer Chemistry 2002/2003

• Copolymers
• Ionic Polymerisation
• Statistical Copolymers

3
CH3A4, Polymer Chemistry Dave Haddleton 2002/2003
Lecture 1 Introduction
Discussion of polymers in everyday use
structure/property correlation
Brief description of copolymers statistical,
block, graft copolymers
4
Books Principles of
Polymerisation
G Odian Polymer Synthesis
P
Rempp and E W Merrill Polymers Chemistry
Physics of Modern Materials J M G Cowie
Polymer Chemistry An Introduction
G Challa Introduction to
Polymers R J Young and P A Lovell

• Mayo Equation

5
Need to Know from Year 2

• Viscosity equations
• Mark-Houwink equation
• Scheme for Free radical Polymerisation

6

• Plastics
• Paint
• Adhesives
• Fibres/Fabrics
• Tyres

• Mobile phones
• Shampoo
• Cosmetics
• Optics
• CD,s

7
Copolymers

• Statistical
• Block
• Graft
• Alternating
• Terpolymers

8
When the two monomers are arranged in an
alternating fashion, the polymer is called, of
course, an alternating copolymer
-A-B-A-B-A-B-A-B-A-B-
In a random copolymer, the two monomers
may follow in any order
-A-A-B-A-B-B-B-A-B-A-A-B-
In a block
copolymer, all of one type of monomer are
grouped together, and all of the other are
grouped together. A block copolymer can be
thought of as two homopolymers joined together
at the ends A-A-A-A-A-A-A-B-B-B-B-B-B-B-B-

9
(No Transcript)
10
Lecture 2 Revision of polymers in
solution viscosity equations, Mark-Houwink
equations Polymers in the solid
state, Tg and Tm, physical meaning of Tg
Tg of copolymers, calculation of Tg
with respect to polymer composition
Revision of free radical homopolymerisation
11
Polymers in Solution

• When we add a polymer to a solvent
• A) Polymer swells to a gel
• B) Dissolves to a viscous solution
• Usually into a random coil or sometimes more rod
  like

12
(No Transcript)
13
(No Transcript)
14
(No Transcript)
15
Polymers in the solid state

• Crystalline
• Glassy
• Not all polymers can crystallise
• None are 100 crystalline
• (look at USM web page for movie)

16
(No Transcript)
17
(No Transcript)
18
(No Transcript)
19
(No Transcript)
20
(No Transcript)
21
(No Transcript)
22
(No Transcript)
23
(No Transcript)
24
(No Transcript)
25
Copolymerisation

• If we have 50 mol MMA and 50 mol Styrene and
  leave the reaction to 50 conversion.
• What is the composition of the polymer?
• What is the composition of the monomer?
• What is the Tg of the polymer produced?

26
(No Transcript)
27
(No Transcript)
28
(No Transcript)
29
Statistical Copolymerization

• RM1? M1 ? RM1M1?
• Rate k11RM1?M1
• RM1? M2 ? RM1M2?
• Rate k12RM1?M2
• RM2? M1 ? RM2M1?
• Rate k21RM2?M1
• RM2? M2 ? RM2M2?
• Rate k22RM2?M2

30
The rate of monomer disappearance is given
by -dM1/dt k11M1M1
k21M2M1 -dM2/dt k12M1M2
k22M2M2 Steady state approximation k12M1
M2 k21M2M1 M1/ M2 k21M1
k12M2
31
The relative rates of comonomer incorporation
then reads dM1/dM2 k11M1M1
k21M2M1 k12M1M2
k22M2M2 divide both by M2 and
rearrange dM1/dM2 M1 k11/ k12 M1
M2 M2 k22/ k21 M2 M1
32

• Reactivity ratios
• r1 k11 k12
• r2 k22 k21

33
Statistical Copolymerization

• r1 characterizes the reactivity of the 1 radical
  with respect to the two monomers 1 and 2
• If r1 gt 1 then homopolymerization growth is
  preferred
• If r1 0 then only reaction with 2 will occur

34
Statistical Copolymerization

• Fa is the amount of monomer A in the POLYMER
• fa is the amount of monomer A in the monomer feed
• Fa Fb 1 fa fb 1

35
Mole fraction of monomer A in feed fa
M1/M1 M2
36

• Reactivity ratios
• r1 k11 k12
• r2 k22 k21

37
Copolymer equation

• Incorporate reactivity ratios and use mole
  fractions
• F1 r1f12 f1f2
• r1f12 r2f22 2f1f2

Reactivity ratios are monomer pair dependant I.e.
they are always the same for each monomer pair
38
Assumptions

• Long Chain assumption i.e. initiation and
  termination reactions can be ignored in the
  calculation of copolymer composition
• Equal reactivity i.e rate is independent of chain
  size
• Reactivity ratios are independent of dilution
• Reactivity ratios are independent of rate and
  conversion

39
Assumptions continued

• Reactivity ratios are independent of inhibitors,
  retarder CTAs and solvents

40
We now need to look at the effect of
the reactivity ratios on the copolymerisation proc
ess. We plot the composition of the polymer as a
function of the composition of the monomer feed.
41
Ideal Copolymerization

• ra rb 1
• A and B exhibit the same relative reactivity
  towards B
• equation becomes
• Fa rafa
• rafa fb

42
Ideal Copolymerization

• Plot is around the diagonal

43
Alternating copolymer

• rb 0

44
Ideal copolymer
45
Alternating Copolymer
46
Rich in one monomer
47
Quite typical copolymerisation
48
Determination of reactivity ratios

• Copolymerise at different monomer feed ratios
• Obtain Fa vs fa data (E.g. 0.2, 0.4, 0.6)
• Interpret data by a lineraization method
• Kelen-Tudos
• Fineman-Ross

49
Linearization method

• Fineman Ross
• (see transparency)
• ra and rb not treated symmetrically
• Kelen-Tudos method probably most common

50
Factors that affect copolymer reactivites

• Steric Factors
• Resonance stabilization of radical
• Polarity of the double bond

51
Qe scheme

• Attempt to predict the reactivity of a monomer
  towards a radical
• Use resonance and polarization parameters
• Similar to Hammett plots
• Rather Qualitiative

52
Penultimate effects
53
(No Transcript)
54
(No Transcript)
55
Living/Ionic Polymerisation

• Anionic Polymerisation
• Cationic Polymerisation
• Ring Opening Polymerisation
• Living Radical Polymerisation
• Group transfer Polymerisation

56
Living Polymerisation

• Method to prepare polymers with predetermined Mn
• DP Monomer/Initiator
• Narrow PDi (lt1.20)
• Controlled functionality
• Block copolymers by various strategies
• No termination
• No Chain Transfer

57
Anionic Polymerisation

• More selective than radical polymerisation
• Need electron withdrawing group attached to vinyl
  group
• e.g. -CO2R, -CN, -Ph, -vinyl
• Invented in 1956 by Swarzc (Nobel Prize)
• Industrial use limited
• Blocks, stars, grafts
• Usually an organometallic initiator

58
(No Transcript)
59
Anionic Polymerisation of Styrene
60
Anionic Polymerisation of dienes
61
Aggregation of Butyl Lithium
62
Ion-Pair formation
63
Solvents

• Aprotic to prevent transfer to solvent and
  termination
• Free of electrophilic impurities which will react
  with ionic sites
• Dissolve both monomer and polymer allowing
  heterogeneous polymerisation

64
Solvents can vary in polarity

• e.g.
• alkanes
• cyclohexane
• benzene
• toluene
• thf, dimethoxyethane

65
Additives can be used to increase polarity
66
(No Transcript)
67
Anionic Polymerisation of Acrylics
E.g.
Initiation
68
Anionic Polymerisation of MMA
Propagating end is an enol
69
Problems with Propagation
70
(No Transcript)
71
(No Transcript)
72
(No Transcript)
73
(No Transcript)
74
(No Transcript)
75
Calculate Mn for Psty with BuLi
76
Calculate PDi
77
(No Transcript)
78
Propagation

• Dependant on ion-pair
• Anion
• Cation (or Gegen-ion)
• Solvent polarity

79
Effect of solvent polarity on stereochemistry
80
(No Transcript)
81
Termination
82
(No Transcript)
83
Termination with protic impurities
84
Termination to functioanl polymers
85
Block copolymers

• Sequential Monomer Addition
• Multi-functional Initiators

86
Calculate Mn for Block Copolymer
87
GTP

• Initiator

88
Group Transfer Polymerisation

• Polar Solvent
• eg thf, glymes
• (Will not work in non polar solvents eg toluene,
  MWD is 2)
• Catalysts
• Nucleophiles
• eg F-, HF2-, AcO-, CN-
• Gegen-ions
• large eg Bu4N, Et4N

89
Mechanism of GTP

• Associative
• Dissociative

90
GTP Associative Mechanism
91
GTP Irreversible Dissociative Mechanism
92
(No Transcript)
93
(No Transcript)
94
(No Transcript)
95
Cationic Polymerisation

• Over 20 yrs old
• Industrial use in butyl rubber manafacture
• Copolymer of
• Active sites are carbenium or oxonium

Need electron donating groups to stabilise the
cation
96
Cationic polymerisation

• Usually reactive enough to make polymers at very
  low temperatures
• However, inherently unstable, side reactions
• in particular ?-proton elimination from active end

97
Monomers for Cationic Polymerisation
98
Cationic polymerisation

• Usually no real molecular weight control
• Living cationic polymerisation would yield
  controlled polymer geometries not available from
  other methods.

99
Cationic Initiation
Protonic acids with bulky anions e.g. H2SO4,
HClO4, FSO3H, etc, etc
Lewis Acids e.g SnCl4, AlCl3, BF3 when reacted
with a nucleophile
100
Cationic Propagation
101
Termination in Cationic Polymerisation
See http//www.psrc.usm.edu/macrog/index.htm
102
Living cationic polymerisation

• 1980's Sawamoto and Higahimura theorised that if
  the charge on the cation could be decreased by a
  specific nucleophilic interaction it may be
  stabilised towards ?-proton elimination.
• 1984 1st example of living cationic polymerisation

103
Living cationic polymerisation

• using HI/I2
• shortly afterwards HI/ZnX2 X I, Br, Cl
• Mn ? M/I
• Block copolymer by sequential addition
• Mn increases linearly with conversion

104
Ring Opening Metathesis
Metathesis of alkenes
105
Ring Opening Metathesis
106
Ring Opening Metathesis
107
Ring Opening MetathesisCatalysts

• Normally made in-situ
• WCl6/AlEt3
• MoCl5/AlEt3

108
Ring Opening Metathesis
109
Living ROMP
Good ROMP catalyst W or Mo Bulky ligands M-O and
MN ligands
110
Living ROMP

• Metal needs to be in high oxidation state
• 4-coordinate alkylidene with bulky ligands
• this allows small substrates to attack
• change alkoxide to (CF3)2MeC.O increase turnover
  for pentene from 2 to 1000 turnovers per minute

111
Commercial use of ROMP

• Poly(norbornene)
• MoO3/alumina
• production for 20 years
• PDCP
• Reaction injection moulding
• 2 reactant streams
• high density of crosslinks

112
ROMP in water
113
(No Transcript)
114
Overview of course

• Radical Copolymerization
• Living Polymerization
• Anionic Polymerization
• Cationic Polymerization
• ROMP

115
Control of Polymer Structure

• Block copolymers
• Telechelic polymers
• Graft copolymers
• Star copolymers
• Narrow PDi polymers

116
When the two monomers are arranged in an
alternating fashion, the polymer is called, of
course, an alternating copolymer
-A-B-A-B-A-B-A-B-A-B-
In a random copolymer, the two monomers
may follow in any order
-A-A-B-A-B-B-B-A-B-A-A-B-
In a block
copolymer, all of one type of monomer are
grouped together, and all of the other are
grouped together. A block copolymer can be
thought of as two homopolymers joined together
at the ends A-A-A-A-A-A-A-B-B-B-B-B-B-B-B-

117
Equations

• Instantaneous copolymer equation
• Fa vs fa plots
• Mn in living polymerisation
• PDi in living polymerisation
• Mn for block copolymers
• Molecular weight equations
• Viscosity equations
• Tg for copolymers

118
(No Transcript)
119
Copolymer equation

• Incorporate reactivity ratios and use mole
  fractions
• F1 r1f12 f1f2
• r1f12 r2f22 2f1f2

Reactivity ratios are monomer pair dependant I.e.
they are always the same for each monomer pair
120
(No Transcript)
121
(No Transcript)
122
Characterisation methods

• GPC
• NMR
• FTIR
• DSC
• MALDI MS
• Gravimetry