1. Polymerization Introduction Radical polymerization
Steps
Kinetics
Chain-transfer reaction
Ionic polymerization
Cationic
Anionic
Stereo-specific polymerization
Co-polymerization
Industrial polymerization technologies

2. Polymerization Type Chain Monomers Chain polymerization
Step polymerization
Chain
Radical
Anionic
Cationic
Stereo-selective (coordination)
Monomers
Vinyl
Vinylidene
R1 and R2: Hydrogen, halogen, alkyl, alkenyl, aryl,
Examples: methyl, phenyl, vinyl
The polymerization process determines the structure, properties and stability of the polymer

3. Radical polymerization
The active sites are the free radicals
Radicals react in each steps of polymerization
Initiation (generating the free radicals)
Example: decomposition of peroxides

4. Radical polymerization
Decomposition of azo-derivatives
Redox-initialization
Rate-determinant step

5. Radical polymerization
Propagation
The addition of monomer onto the active site is very fast
Consequently, the concentration of active sites is very small

6. Radical polymerization
Termination (end of propagation)
Interaction of two active sites
Reaction of an active site and a radical from initiator
Reaction with other active molecule
Contamination
Recombination
Disproportion

7. Radical polymerization
The rate of propagation and termination is significantly larger than the rate of initiation
Consequently the lifetime of active sites is extremely short (10-9 s)
The molecular mass is constant during polymerization
The molecular mass can be influenced by the modification of polymerization conditions

8. Radical polymerization
Kinetics
I – initiator, M – monomer, R – active site, k – rate constant and f represents the fraction of radicals formed during initiation that is successful in initiating chains
Assumption: the reactivity of active site is independent on its size
Initiation
Propagation

9. Radical polymerization
Chain-transfer reactions
Monomer, initiator – reaction rate does not change, but polymerization degree decreases
Polymer – polymerization degree does not change, but branching occurs
Solvent – considerable decreased molecular mass
Chain-transfer molecules can influence molecular mass

10. Radical polymerization
Chain transfer molecules
Influencing the molecular mass

11. Radical polymerization
Inhibition and retardation

12. Radical polymerization
Gel-effect
Hindered termination due to diffusion control
Increasing polymerization rate

13. Ionic polymerization - cationic
Catalyst – Lewis acids BF3, AlCl3, TiCl4, SnCl4
Co-catalyst – nucleofil agent: water
Initiation
Propagation
Termination – contaminations, chain transfer
covalent
ion pair
separated ion pair
free ions
Living polymerization, telechelic polymers

14. Ionic polymerization - anionic
Catalyst – possatium-amide, n-butyl lithium, Grignard compound: alkyl-magnesium bromide
Initiation
Propagation – addition to the carbanion
Termination – contamination, chain transfer
Living polymerization

15. Ionic polymerization Factors Contamination Temperature
Polarity of solvent
Character and strength of ionic pair
Resonance
Geometry
Contamination
Temperature
Living polymerization

16. Stereo-specific (coordination) polymerization
Chain structure – regularity, branches etc.
Isomerism – cis- and trans-isomers
Asymmetric monomers – orientation
Head-to-tail, head-to-head and tail-to-tail
Stereo-isomerism

17. Stereo-specific polymerization
May also be occured in ionic polymerization
Requires appropriate substituents
Never occurs in radical polymerization
Coordination polymerization
Heterogeneous catalyst system (AlEt3 – TiCl3, TiCl4)
Amount of atactic polymer, catalyst efficiency
5. Generation – metallocene catalyst system
Regularity, phase structure, properties

18. Stereo-specific polymerization
Mechanism

19. Chain polymerization techniques
Monomer Mechanism of polymerization
Radical Cationic Anionic Coordination
Ethylene – +
Propylene – – – +
Isobutylene – + – –
Diene + – + +
Styrene
Vinyl-chloride + – – +
Vinylidene-chloride + – + –
Vinyl-fluoride + – – –
Tetrafluoro-ethylene + – – +
Acrylates + – + +

20. Copolymerization At least two kind of monomers Types Reactions
Statistic
Alternating
Grafted
Block
Reactions
Mechanism – radical or ionic

21. Copolymerization Kinetics – constant conditions Reactivity of monomers
Alternating r values – different composition
Example (VC-VAC copolymer) wt% solution
r1 = k11/k12 and r2 = k22/k21
Temperature Composition
t :3
t :3
t :3
t :7

22. Copolymerization – reactivity ratio
Monomer 1 Monomer 2 r2 r1 T
(°C)
akryl-nitryl 1,3-butadyene 0,02 0,30 40
methyl-metacrylate 0,15 1,22 80
styrene 0,04 0,40 60
vinyl-chloride 2,70 0,04 60
methyl-metacrylate styrene 0,46 0,52 60
vinyl-acetate 20 0,
vinyl-chloride 10 0,10 68
styrene vinyl-acetate 55 0,01 60
vinyl-chloride 17 0,02 60
vinyl-acetate vinyl-chloride 0,23 1,68 60

23. Copolymerization- composition
1. Ideal polymerization
r1 = r2 = 1
Nearly ideal
r1r2 = 1 and r1 ≠ r2
Alternating
0 < r1r2 < 1
Reality azeotropic
Small conversion, continuous addition of monomers

24. Copolymerization - processing
Statistic, alternating: radical
Block
Radical if r1r2 >> 1
Ionic if the reactivity of monomers is different
Living polymerization (fine regulation of stucture)
Combination of active end-groups
Grafting
From chain
To chain
Mechano-chemical grafting

25. Industrial polymerization techniques
Gas phase
Conditions: High T and p
Initiator: Oxygen
Product struct.: long chain branched
Example: PE
Bulk
Initiator: soluble in the monomer
Product: powder or chunk
Advantage: clean
Disadvantage: gel-effect
Example: PVC, PMMA, PAN
Solution
Product: solution or precipitate
Advantage: heat
Disadvantage: contamination, solvent, chain transfer
Example: ionic, stereo-specific PP
Suspension
Initiator: soluble in the monomer
Medium: water
Product: powder
Advantage: heat transfer
Disadvantage: contamination
Example: PVC, PS, PMMA

26. Industrial polymerization techniques
Emulsion
Initiator: soluble in water
Medium: water
Product: powder
Advantage: diffusion
Disadvantage: contamination
Example: PVC, SBR, PMMA
Monomer droplet
Micelle
Emulgeator
Aqueous media
Polymer droplet