Introduction to Macromolecular Chemistry
aka polymer chemistry
Mondays, 8.15-9.45 am, NC 02/99
Dr. Christian Merten, Ruhr-Uni Bochum, 2019 www.ruhr-uni-bochum.de/chirality Polymerization reactions: Summary
STEP GROWTH REACTION CHAIN GROWTH REACTION
. Monomer with 2 . Monomer has one polymerizable groups polymerizable group
. Multiple reactive chain . Active chain end, i.e. ends growth in one direction
. Molecular weight increases slowly
. High molecular weight Different mechanisms: only at high conversion . Radical polymerization . Cationic polymerization . Anionic polymerization . Coordinative polym.
Macromolecular Chemistry | Dr. C. Merten, 2019 72 Free radical polymerization
Typical examples
monomer polymer
Ethylene
Vinyl chlorid Cl
Acrylo nitrile C N
Three step reaction: . Initiation Vinyl acetate . Chain growth . Termination Methyl acrylic acid
Styrene
Macromolecular Chemistry | Dr. C. Merten, 2019 73 Free radical polymerization: Initiation
Photochemical activation of initiator
Thermal activation of initiator
Thermal initiation of polymerization
Macromolecular Chemistry | Dr. C. Merten, 2019 74 Free radical polymerization: Initiation
Important: Initiator radical lifetime at polymerization temperature
Isopropyl percarbonate Azobisisobutyro nitrile Dibenzoyl peroxide Di-tert-butyl peroxide Cumolhydro peroxide
Macromolecular Chemistry | Dr. C. Merten, 2019 75 Free radical polymerization: Growths and termination
Chain growths
Termination mechanisms a) Combination
b) Disproportionation
Macromolecular Chemistry | Dr. C. Merten, 2019 76 Free radical polymerization: Kinetics
Initiation: In-In 2 In
Chain start: In + M In-M
Initiation is much slower than chain start: ≫