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General Approaches to Polymer Synthesis

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General Approaches to Polymer Synthesis 1. Addition Chain Growth Polymerization of Vinyl Monomers Ring Opening Polymerization Heterocylics Metathesis of Cyclic Olefins – PowerPoint PPT presentation

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Title: General Approaches to Polymer Synthesis


1
General Approaches to Polymer Synthesis
  • 1. Addition Chain Growth
  • Polymerization of Vinyl Monomers

Ring Opening Polymerization Heterocylics
Metathesis of Cyclic Olefins
2. Condensation Step Growth   Polymerization of
A-B or AA/BB Monomers
3. Modification of Preformed Polymers Polysaccha
rides Peptides and Proteins   Synthetic
Precursors
2
Current Strategies in Polymer Synthesis 
  • Objectives Precise Macromolecular Design
  • 1 . Control of Molecular Weight
  • Molecular Weight Distribution
  • Composition
  • Sequence of repeat units
  • Stereochemistry
  • 2.  Versatility

3
Free Radical Initiated Polymerization
  • Classical Free Radical Process
  • Applied to wide range of monomers
  • Broad scope of experimental conditions
  • Molecular weight can be controlled
  • Mw/Mn gt 1.5 ? 2.0 ?
  • Statistical compositions and sequences
  • Little stereochemical control

4
Anatomy of Addition Polymerizations
  • Initiation
  • Generation of active initiator
  • Reaction with monomer to form growing chains
  • Propagation
  • Chain extension by incremental monomer addition
  • Termination
  • Conversion of active growing chains to inert
    polymer
  • Chain Transfer
  • Transfer of active growing site by terminating
    one chain and reinitiating a new chain.

5
Polymerizability of Vinyl Monomers
  • Active Centers must be stable enough to persist
    though multiple monomer additions
  • Typical vinyl monomers

6
Polymerizability of Vinyl Monomers
7
Polymerizability of Vinyl Monomers
8
Types of Vinyl Polymerization
9
Thermodynamics of Polymerization
10
Thermodynamics of Polymerization
11
Suspension Polymerization
  • Equivalent to a "mini-bulk" polymerization
  • Advantages
  • Aqueous (hydrocarbon) media provides good heat
    transfer
  • Good particle size control through agitation and
    dispersion agents
  • Control of porosity with proper additives and
    process conditions
  • Product easy to recover and transfer
  • Disadvantages
  • Suspending Agents contaminate product
  • Removal of residual monomer necessary

12
Suspension (Pearl) Polymerization
13
Suspension Polymerization of Styrene
Monomer Phase 16.6 Kg. Styrene (0.5
kg Methacrylic Acid) 0.012 kg AIBN
0.006 kg Benzoyl Peroxide 0.015 kg
tert-Butyl Perbenzoate
Aqueous Phase 16.6 Kg of H2O 0.24 kg
Ca3PO4 0.14 kg Na Naphthalene sulfonate
0.077 kg. 15 Sodium Polyacrylate
Polymerization Time. Hours
14
EMULSION POLYMERIZATION
  • Advantages
  • High rate of polymerization
  • High molecular weights
  • Few side reactions High Conversion achieved
  • Efficient heat transfer
  • Low viscosity medium Polymer never in solution
  • Low tendancy to agglomerate
  • Emulsified polymer may be stabilized and used
    directly

Disadvantages Polymer surface contaminated by
surface active agents Coagulation introduces
saltsPoor electrical properties
15
Components of Emulsion Polymerization
R.
Water soluble initiator
16
POLYMERS PRODUCED USING EMULSION PROCESSES
17
Major Developments in the 1950-60's
  • 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

18
Ziegler-Natta (Metal-Coordinated) Polymerization
  • Stereochemical Control
  • Polydisperse products
  • Statistical Compositions and Sequences
  • Limited set of useful monomers, i.e. olefins
  • SINGLE SITE CATALYSTS

19
Polyolefins
  • Polypropylene (1954)
  • PP
  • dishwasher safe plastic ware, carpet yarn,
    fibers and ropes, webbing, auto parts

20
Tacticity
  • Isotactic
  • All asymmetric carbons have same configuration
  • Methylene hydrogens are meso
  • Polymer forms helix to minimize substituent
    interaction
  • Syndiotactic
  • Asymmetric carbons have alternate configuration
  • Methylene hydrogens are racemic
  • Polymer stays in planar zig-zag conformation
  • Heterotactic (Atactic)
  • Asymmetric carbons have statistical variation of
    configuration

21
Additional Developments in the 1980's
  • "Immortal" Polymerization (Cationic)
  • Mw/Mn ? 1.05
  • Blocks, telechelics, stars
  • (Controlled molecular architecture)
  • Statistical Compositions and Sequences
  • Severe functional group restrictions

22
Free Radical Initiated Polymerization
  • Controlled Free Radical Polymerization
  • Broad range of monomers available
  • Accurate control of molecular weight
  • Mw/Mn ? 1.05 --Almost monodisperse
  • Blocks, telechelics, stars
  • (Controlled molecular architecture)
  • Statistical Compositions and Sequences

23
Genetic Approaches via Modified Microorganisms
  • Monodisperse in MW
  • Monodisperse in Composition
  • Sequentially Uniform
  • Stereochemically Pure
  • Diverse set of functional groups possible through
    synthesis of novel amino acids

24
Commodity Polyolefins
  • Polyethylene

High Density (1954) HDPE Bottles, drums,
pipe, conduit, sheet, film
Low Density (1939-1945) LDPE Packaging
Film, wire and cable coating, toys, flexible
bottles, house wares, coatings
Linear Low Density (1975) Shirt bags, high
strength films LLDE
25
Commodity Polyolefins
Polypropylene (1954) PP dishwasher safe
plastic ware, carpet yarn, fibers and ropes,
webbing, auto parts
Polyisobutylene (1940) PIB inner
tubes, flexible adhesives, raincoats
26
Commodity Vinyl Polymers
Polystyrene (1920) PS Styrofoam, clear
plastic cups envelop windows, toys
Poly(vinyl chloride) (1927) PVC garde
n hose, pipe, car trim, seat covers, records,
floor tiles
27
Semi-Commodity Polymers
Poly(methyl methacrylate) (1931)
PMMA plexiglas, embedding resin,
resist for X-ray applications
Polytetrafluoroethylene. (1943) teflon, non
stick cookware, no grease bearings, pipe-seal
tape
28
Commodity Condensation Polymers
Nylon 6 / bearings, molded parts carpet
yarn marine rope cooking/boiling bags
Nylon 66 (1939) Fibers, tire cord, fishing line
29
Commodity Condensation Polymers
Polyester (1941) PET, dacron, mylar, kodel
fibers, film-backing, magnetic tapes, soft drink
bottles, tire cord, moldings
Polycarbonate (1957) PC,
Lexan shatter proof glass, cd-disks, car doors
and roofs, appliance housings
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