Tunable Nanoporous Membranes with Chemically Tailored Pore Walls from Triblock Terpolymer Templates

Presented by Jacob L. Weidman1 With research from Ryan A. Mulvenna,2 John A. Pople,3

Bryan W. Boudouris,2 and William A. Phillip1 william.a.phillip.1@nd.edu

1University of Notre Dame, 2Purdue University, 3Stanford Synchrotron Radiation Lightsource

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Filtration is Size-Selective 2  

A New Membrane Material

•  High flux •  Good selectivity •  Mechanical integrity •  Low fouling

Phase inversion

Desired qualities for ultrafiltration membranes:

Self-assembled Track-etched

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Block Copolymers Self-Assemble

Q230 H Q229 fRed

Cochran, E. W. et al. Macromolecules 2006, 39, 2449.

N = number of segments χ = interaction parameter f = polymer volume fraction

L Q230 H Q229 fRed

Red Polymer MINORITY PHASE

Red Polymer MAJORITY PHASE

Theoretical Coil-Coil Diblock Copolymer Phase Diagram

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Membrane Cast by SNIPS

Solvent

Solvent Non-solvent Selective Layer

Support Layer

Evaporate

Precipitate Membrane

Doctor Blade

Polymer Solution

Cast

Glass Slide

Water bath Self-assembly

SNIPS- Self-assembly and Non-solvent Induced Phase Separation

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Prior Efforts Limited by Functionality

Block Function Polyisoprene Increases toughness Polystyrene Forms matrix

Poly(4-vinyl pyridine) pH-responsive, but terminal chemistry

Cast Membrane

Phillip, W. A. et. al. Nano Letters, 2011, 11, 2892-2900.

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Pore Walls Can be Functionalized

Cast Membrane

Block Function Polyisoprene Decreases brittleness Polystyrene Forms matrix

Poly(Dimethylacrylamide) Can be functionalized to specific applications

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Triblock Polymerization by RAFT

Tolerant of atmospheric conditions

Low dispersity

Metal-free

1.3 1.3 1.2

RAFT- Reversible Addition-Fragmentation chain Transfer

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Asymmetric Membrane Produced 9  

A Permeable and Selective Membrane 10  

Membrane Functionalization

Solvent

Solvent Non-solvent

Evaporate

Precipitate

Doctor Blade

Polymer Solution

Cast

Glass Slide

Water bath

6M HCl in Water

Heat to 85ºC React for 2 days

Functionalization

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Functionalization Alters Pore Chemistry

Pore walls can be reacted to a variety of functional groups (pink dots).

“Click” Chemistry

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Porous Structure Retained Parent Functionalized

Less than 4% deviation in average pore size and porosity

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A Selective pH-responsive Membrane 14  

Parent Functionalized

Parent Functionalized Parent

How  Pore  Wall  Groups  Affect  Pore  Size  

Dry state (SEM) PDMA Wet State (MWCO) Parent Membrane

Average- 52 nm Water soluble Estimated- 8.1 nm

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Parent Functionalized

Parent

•  AFM to compare wet/dry pore sizes •  New functional to line pore walls •  Transport tests for targeted applications

Functionalized Estimated -2.6 nm

Conclusions

This material produces robust selective membranes with a high density of monodisperse pores in the self-assembled selective layer.

Pore walls have been successfully deprotected to a functionalizable polyacrylic acid group, lending itself to a variety of applications by simple chemical conversion.

Controlled radical polymerization allows for a scalable production method of terpolymer with tunable block lengths and low dispersity. I D

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Acknowledgements

             As  well  as:  

–  Center  for  Environmental  Science  and  Technology  (CEST)  

–  Notre  Dame  Integrated  Imaging  Facility  (NDIIF)  

 THANK  YOU!!  

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Special  thanks  to:    Professor  Bryan  W.  Boudouris  Ryan  A.  Mulvenna  

 

         Professor  William  A.  Phillip              John  Pople