facile chain-end modification of raft...

Facile Chain-End Modification of RAFT Polymers

Shelby Shankel

CCS Chemistry, UCSB

Emre Discekici

Read de Alaniz Group, Chemistry and Biochemistry

MARC U-STAR, NIH

Importance of Modification

Br


• Halogens allow for further functionalization of RAFT chain ends for a variety of applications

Br



• Example: block copolymers

ATRP initiator

Br



• Example: block copolymers• Adhesives, rubber

ATRP initiator

Br



• Example: block copolymers• Adhesives, rubber• Micelles

ATRP initiator

Br

Reversible Addition-Fragmentation Chain Transfer (RAFT)

Polymerization


Polymerization• Controlled radical polymerization



• Control of molecular weightsRAFT

Traditional



• Control of molecular weights• Narrow polydispersity index

RAFT

Traditional



• Control of molecular weights• Narrow polydispersity

• Why RAFT?




• Why RAFT?• Tolerance of functional groups




• Why RAFT?• Tolerance of functional groups• Formation of complex structures




• Why RAFT?• Tolerance of functional groups• Formation of complex structures• High conversions




• Why RAFT?• Tolerance of functional groups• Formation of complex structures• High conversions• Water soluble




• Why RAFT?• Tolerance of functional groups• Formation of complex structures• High conversions• Water soluble• Useful in biomedical applications

Current Challenges with RAFT


S

S

ZRR S Z

S

+

Chain Transfer Agent


• Conjugation of chain end

S

S

ZRR S Z

S

+



• Conjugation of chain end• Discoloration

S

S

ZRR S Z

S

+




• Poor retention of chain end

S

S

ZRR S Z

S

+




• Poor retention of chain end• Odor

S

S

ZRR S Z

S

+




• Poor retention of chain end• Odor• Toxicity

S

S

ZRR S Z

S

+


Functionalize RAFT Polymer Chain Ends with Bromides

R S Z

S

R Br


R S Z

S

R Br

R SH


R S Z

S

R Br

R SH

KnownSumerlin, B. S; et al. Polym.

Chem. 2010, 1, 854-859.


R S Z

S

R Br

R SH

Known UnknownSumerlin, B. S; et al. Polym.

Chem. 2010, 1, 854-859.


R S Z

S

R Br

R SH

Known Unknown

Model Systems

Sumerlin, B. S; et al. Polym.

Chem. 2010, 1, 854-859.


R S Z

S

R Br

R SH

Known Unknown

SH

1-Dodecanethiol

Model Systems


Chem. 2010, 1, 854-859.


R S Z

S

R Br

R SH

Known Unknown

SH

SH

1-Adamantanethiol

1-Dodecanethiol

Model Systems


Chem. 2010, 1, 854-859.

Setting Up the Reaction


Reactants


Reactants

R SH


Reactants

R SH

N


Reactants

PBrBr

R SH

N


Reactants

Inert Gas

PBrBr

R SH

N


Reactants

Inert Gas

Stir PlatePBrBr

R SH

N


Reactants

Inert GasHeating Block

Stir PlatePBrBr

R SH

N


Reactants

Inert Gas

Overnight

Heating Block

Stir PlatePBrBr

R SH

N

Purifying and Analyzing the Reaction


Dialysis

Start Equilibrium

Membrane

Solvent

Conc. Solution


Dialysis

or

Precipitation

Start Equilibrium

Membrane

Solvent

Conc. Solution


Dialysis

or

Precipitation

Remove Solvent

Overnight

Start Equilibrium

Membrane

Solvent

Conc. Solution


Dialysis

or

Precipitation

Remove Solvent

Overnight

Start Equilibrium

Membrane

Solvent

Conc. Solution

Analyze


Dialysis

or

Precipitation

Remove Solvent

Overnight

Start Equilibrium

Membrane

Solvent

Conc. Solution

Analyze

Nuclear Magnetic Resonance (NMR)

Spectroscopy

Model System: Dodecanethiol

SH Br

triphenylphosphine dibromidetriethylamine

DCM

Starting material

56% conversion

>99% conversion

Model System: Dodecanethiol

SH Br


DCM

*Conversion determined by 1H-NMR

Eqv. Dodecanethiol

Eqv.Triphenylphosphinedibromide

Eqv.Triethylamine

Solvent Spargedwith argon?

Temp.(℃)

Time (hr)

Conversion

1.00 3.00 3.00 DCM yes room 18 >99%

Model System: AdamantanethiolSH


DCM

Br

>99% conversion

67% conversion

Starting material

Model System: AdamantanethiolSH


DCM

Br

*All conversions determined by H-NMR

Eqv. Adamantanethiol

Eqv. Triphenylphosphinedibromide

Eqv.Triethylamine

Solvent Spargedwith argon?

Temp.(℃)

Time (hr)

Conversion

1.00 5.00 5.00 DCM yes 45 5 100%

1.00 5.00 5.00 DCM yes room 5 85%

1.00 10.00 10.00 DCM yes 45 26 100%

Bromination on Polymers


In-Hwan Lee

Polystyrene


In-Hwan Lee

Polystyrene

S

S

SC12H25

n

NC

hexylamine (50 eq.)tributylphosphine (5 eq.)

DCMroom temp SH

n

NC


In-Hwan Lee

Polystyrene

S

S

SC12H25

n

NC


DCMroom temp SH

n

NC

SHn

NC

triphenylphosphine dibromide (5 eq.)

DCMroom temp Br

n

NC


+In-Hwan Lee

Polystyrene

S

S

SC12H25

n

NC


DCMroom temp SH

n

NC

SHn

NC


DCMroom temp Br

n

NC NC

n-1

2:1


+In-Hwan Lee

Polystyrene

Poly(methyl acrylate)

S

S

SC12H25

n

NC


DCMroom temp SH

n

NC

SHn

NC


DCMroom temp Br

n

NC NC

n-1

2:1


+In-Hwan Lee

Polystyrene


S

S

SC12H25

n

NC


DCMroom temp SH

n

NC

SHn

NC


DCMroom temp Br

n

NC

S

S

SC12H25

n

NCO

SHn

NCOOhexylamine (25 eq.)

tributylphosphine (5 eq.)

DCMroom temp

O

NC

n-1

2:1


+In-Hwan Lee

SHn

NCOO

Brn

NCOO

triphenylphosphine dibromide (10 eq.)triethylamine (10 eq.)

DCMroom temp

Polystyrene


S

S

SC12H25

n

NC


DCMroom temp SH

n

NC

SHn

NC


DCMroom temp Br

n

NC

S

S

SC12H25

n

NCO

SHn



DCMroom temp

O

NC

n-1

2:1


+In-Hwan Lee

SHn

NCOO

Brn

NCOO

triphenylphosphine dibromide (10 eq.)triethylamine (10 eq.)

DCMroom temp

Not complete conversion

Polystyrene


S

S

SC12H25

n

NC


DCMroom temp SH

n

NC

SHn

NC


DCMroom temp Br

n

NC

S

S

SC12H25

n

NCO

SHn



DCMroom temp

O

NC

n-1

2:1

Future Work:Further Optimization on

Polymers Systems

• Solvent• Temperature• Equivalents• Reagents

R S Z

S

R Br

Thank you!The Read de Alaniz Group:

Javier Read de AlanizLes BurnettKyle ClarkYvonne DiazEmre DiscekiciDavid FisherJames HemmerSaemi Oh Poelma

Andrey SamoshinJamie ShaumAndre St. AmantNicolas TreatGabby HammersleyEllia LaLandon MillsJoseph Sanz

Research reported here was supported by the National Institute of General Medical Sciences of the National Institutes of Health under Award Number T34GM113848

References1. Willcock, H.; O’Reilly R. K. Polym. Chem. 2010, 1, 149-157.2. Pissuwan, D.; Boyer, C.; Gunasekaran, K.; Davis, T. P.; Bulmus, V. Biomacromolecules. 2010, 11

(2), 412–420.3. Sigma-Aldrich. RAFT: Choosing the Right Agent to Achieve Controlled Polymerization.

http://www.sigmaaldrich.com/united-states.html4. Stories of Australian Science. Star-shaped polymers boost engine performance.

http://stories.scienceinpublic.com.au/subject/plastics/.5. Carnegie Mellon: the Matyjaszewski Polymer Group. Graft Copolymers with Complex

Architecture. http://www.cmu.edu/maty/materials/Polymers_with_Specific_Architecture/densely-grafted-linear-copolymers.html.

6. Carlmark, A.; Hawker, C.; Hult, A.; Malkoch, M. Chem. Soc. Rev. 2009, 38, 352-362. 7. Cobo, I.; Li, M.; Sumerlin, B. S.; Perrier, S. Nature Materials. 2015, 14, 143–159. 8. School Work Helper. Selective Permeability of Dialysis Tubing Lab: Explained.

http://schoolworkhelper.net/selective-permeability-of-dialysis-tubing-lab-explained/.

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