General Approaches to Polymer Synthesis
1. Addition
Chain Growth
Polymerization of Vinyl Monomers
2. Ring Opening Polymerization
Heterocylics
Methathesis of Cyclic olefins
3. Condensation
Step Growth
Polymerization of A-B or AA/BB Monomers
4. Modification of Preformed Polymers
Polysaccharides
Peptides and Proteins
Synthetic Precursors
Current Strategies in Polymer Synthesis
Objectives: Precise Macromolecular Design
1. Control of:
Molecular Weight
Composition
Sequence of repeat units
Stereochemistry
2. Versatility
Synthetic Methods
1.
Step-growth (Condensation) Polymerization
Mw/Mn  2
Statistical compositions and sequences
2.
Chain-growth (Addition) Polymerization
Mw/Mn > 1.5  2.0 
Statistical compositions and sequences
Little stereochemical control
Major Developments in the 1950-60's
3. Living Polymerization (Anionic)
Mw/Mn  1
Blocks, telechelics and stars available
(Controlled molecular architecture)
Statistical Stereochemical Control
Statistical Compositions and Sequences
Severe functional group restrictions
4. Ziegler-Natta (Metal-Coordinated)
Polymerization
Stereochemical Control
Polydisperse products
Statistical Compositions and Sequences
Limited set of useful monomers, i.e. olefins
Additional Developments in the 1980's
5. "Immortal" Polymerization (Cationic)
Mw/Mn  1.05
Blocks, telechelics, stars
(Controlled molecular architecture)
Statistical Compositions and Sequences
Severe functional group restrictions
Under Development in the 1990's
6. "Living" Free Radical Polymerization
Mw/Mn  1.05
Blocks, telechelics, stars
(Controlled molecular architecture)
Statistical Compositions and Sequences
Broad range of monomers available
7. Genetic Approaches via Modified
Microorganisms
Monodisperse in MW
Monodisperse in Composition
Sequentially Uniform
Stereochemically Pure
Diverse set of functional groups possible
Structural Complexity of Polymers
Homopolymers
Head to Tail vs. Head to Head Adducts
1,2- vs 1,4 Adducts
Tacticity of Enchainments
Branching
Copolymers
Identity and Number of Comonomers
Ratio and Distribution of Comonomers
Statistical
Alternating
Blocks
Grafts
Molecular Weight
Mn, Mw, Mz, Mv Averages
Molecular Weight Distribution
Crosslinking
Density
Length of Crosslinks
Morphology
Impurities
Additives
Structural Complexity of Polymers
Time Dependent Changes
Chemical Reactions
Hydrolysis
Dehydrohalogenation
Photodegradation
Oxidation
Thermal Degradation
Processing
Aging
Crystallization
Changes in Polymorphism
Weathering
Plasticizer Loss -- Imbrittlement
Types of Intermolecular Forces
Type of
Force
Relative
Strength
Low
Molecular
Analog
Polymer
Dispersion
or Van der
Waals
Weak
Methane
Hexane
Polyethylene
Polypropylene
DipoleDipole
Medium
CH3Cl
PVC
CH3CO2CH3 PMMA
Hydrogen
bonding
Strong
H2O
CH3CONH2
Proteins
Cellulose
Polyamide
Electrostatic Very Strong NaCl
Ionomers
+
or Ionic
CH3CO2 Na
Vinyl Monomers
CH2=CH
X
X
H
Polymer
Polyethylene
Abbreviation
PE
CH3
Polypropylene
PP
Cl
Poly(vinyl
chloride)
PVC
Phenyl
Polystyrene
PSt
CN
Polyacrylonitrile
PAN
COOCH3
Poly(methyl
acrylate)
PMA
O-COCH3
Poly(vinyl acetate) PVAc
Vinylidene Monomers
X
CH2=C
Y
X
CH3
Y
CH3
Polymer
Polyisobutylene
Abbreviation
PIB
Cl
Cl
Poly(vinylidene
chloride)
PVDC
F
F
Poly(vinylidene
fluoride)
PVDF
Phenyl
CH3
Poly(-methyl
styrene
CH3
COOCH3
Poly(methyl
methacrylate)
CN
COOR
Poly(alkyl cyanoacrylate
PMMA
Tacticity
Isotactic
H
H
H
X
X
X
X
X
X
All asymmetric carbons have same configuration
Methylene hydrogens are meso
Polymer forms helix to minimize substituent interaction
Syndiotactic
H
X X
X X
X X
Asymmetric carbons have alternate configuration
Methylene hydrogens are racemic
Polymer stays in planar zig-zag conformation
Heterotactic
(Atactic)
H
XX
X
X
X X
Asymmetric carbons have alternate configuration