StarShaped Polymers by CuII Living Radical Polymerisation

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Star-Shaped Polymers by Cu(II) Living Radical
Polymerisation

• Benjamin Wong and Prof. David Haddleton
• Dept. of Chemistry, University of Warwick
• Coventry CV4 7AL, UK.
• www.warwick.ac.uk/polymers

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Star-Shaped Polymers

• Interesting Physical Properties
• Hydrodynamic Volumes
• High Chain End Functionality
• Different Spatial Shapes
• 3-dimensional
• Core first
• Synthetic Challenge

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Star Polymers Based on b-Cyclodextrin

• 3-D Cone Shape
• D-Glucopyranose Units
• a-1,4-linkages
• 21-hydroxyl groups
• Molecular Recognition
• Inclusion Complexes
• Non Polar Cavity

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Star Polymeric Architectures Based on
b-Cyclodextrin
21 arms
14 arms
7 arms
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Cyclodextrin Star PMMA with 21 arms
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Cyclodextrin Star PMMA with 14 arms
5h, 13 60,000 (96,000) 1.063
7h, 16 83,000 (116,000) 1.064
3h, 7.5 36,000 (57,000) 1.063
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Hydrolysis Of Star Polymers
Before Hydrolysis Mw 130 000 gmol-1
After Hydrolysis Mn 10 000 gmol-1
Arms are of Uniform Size
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Synthesis of a 7-arm Multifunctional Initiator by
Selective Modification of b-Cyclodextrin
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LRP of MMA Using 7-arm Multifunctional Initiator
MMAICu(I)Brligand500148 _at_ 600C in
toluene
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Synthetic Strategy for Diblock Copolymer Formation
Deactivation of chain ends
Deprotection of TBDMS groups
Initiator formation
Star polymer with 14 arms
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Honeycomb Formation Using Star Polymers
Humidity Chamber gt70 humidity 18-20 0C
Air flow meter
Air Flow
Glass slide
Water Reservoir
Water reservoir to Saturate air flow
Polystyrene Solution in CS2
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Honeycomb/Membrane Formation
Film Formation on Glass Slide
Mount on stub and Splutter with Gold for
conductance
Scanning Electron Microscope
Pore Formation Hexagonal Distribution Homogeneous
in size Diameter 1mm
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Modification of Pores
Defects are observed when the temperature and
humidity are too low
Hexagonal array is disrupted when CH2Cl2 is used
in place of CS2
Hydrophilicity is introduced via 1 of a
polyethylene glycol copolymer
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Proposed Mechanism for Membrane Formation
1. Flow of moist air over cold surface
2. Water condensation
3. Water droplets form close packed array
4. Array cools and sinks into solution
6. New close packed array templated by underlying
layer
5. New generation of water droplets
7. Solvent and water evaporated to leave scaffold
Srinivasarao et al. Science, 2001
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Conclusions

• Selective Modification of Cyclodextrin using
  Protection/deprotection Chemistry
• LRP of Cyclodextrin Initiators to form well
  defined star polymers with 21, 14, and 7 arms
• Synthetic Route to Hydrophobic-Hydrophilic Di
  Block Copolymers
• Highly ordered Membrane Structures Using Star
  Polymers

Acknowledgements
Professor David Haddleton Dr. Kohji Ohno
EPSRC