www.buffalo.edu

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Thiol-ene Polymer Networks for Reverse OsmosisShawreen Shah, Kaipin Huang, Norman Ng and Haiqing LinDepartment of Chemical and Biological Engineering, University at Buffalo (SUNY), Buffalo, NY 14260, USA

Overview

Conclusion and Future Work

Drawback of Current RO Membranes

Approach: Thiol-Ene Based Polymer Networks

Conclusion: Highly crosslinked thiol-ene polymers and thin film composite membranes based on these polymers have been successfully prepared and characterized.

Future Work: • Optimize composite membranes and evaluate salt rejection using a dead-end

filtration system and a crossflow filtration system.

Laboratory of InNovative

Membranes at UB

Composition

Density(g/cm3)

Fractional Free Volume

Water Sorption Sol-Gel Percent

Without solvent*

With solvent*

Without solvent*

With solvent*

Without solvent*

With solvent*

Without solvent*

With solvent*

T1+E1 1.2 1.2 0.16 0.16 2.4% 2.6% 1.6% 0%

T1+E2 1.3 1.3 0.12 0.12 2.2% 2.3% 1.2% 0%

T2+E1 1.3 1.3 0.12 0.12 2.8% 2.7% 1.6% 0%

T2+E2 1.3 1.3 0.15 0.15 1.9% 2% 0.2% 0%

Reverse Osmosis (RO) system(Δp > Δ)

Δp = pressure differenceΔ = osmotic pressure difference

Salt Rejection:

C2: salt concentration in the permeateC1: salt concentration in the feed

)( pAJW

10011

2

CCR

Current RO membranes are subjected to chlorine oxidation, leading to higher water flux and lower salt rejection.

Thiol monomers T1: T2:

Ene monomers E1: E2:

Objective: To design and develop thiol-ene polymer based reverse osmosis membranes and study structure/property correlation.

Advantage of Thiol-Ene Polymers: • Highly crosslinked and homogenous• Versatile with many choices of monomers• Easy to prepare and immune from oxygen inhibition

Approach: • Novel polymers are prepared using multifunctional thiols and enes. • Polymers are characterized using FTIR-ATR, density and fractional free

volume measurements, and water sorption measurements.• Thin film composite membranes are prepared on commercial microporous

substrates for reverse osmosis applications.

Flux evaluation:

• Thiol-ene polymer networks are immune to oxidation, and hence chlorine is not expected to degrade the membrane.

A series of thiol-ene polymers were synthesized by UV photopolymerization.

Monomers used:

The reaction is initiated by exposure to UV light and proceeds via free radical polymerization.

Thin Film Composite MembranesThin film composite membranes were prepared by coating prepolymer solution on commercial microporous supports such as polyacrylonitrile (PAN).

A dead end membrane filtration system was designed and built to test pure water flux across thin film composite membranes.

Acknowledgement

The selective layer of commercial RO membranes is comprised of highly crosslinked aromatic polyamide.

We thank School of Engineering and Applied Sciences at University at Buffalo for their financial support.

• Greenlee, Lawler, Freeman, Marrot, Moulin, Water Res., 43 (2009) 2317-2348..• Ju, McCloskey, Sagle, Wu, Kusuma, Freeman, J. Membr. Sci., 307 (2008) 260-267

Characterization of Polymer Films

Photo of a thiol-ene polymer film

Fundamental of Reverse Osmosis

1000 1500 2000 2500 3000

PolymerEneThiol

Wavenumber (cm -1)

Pore-penetrationIncrease viscosity

Decrease thickness

PEO-Filler

DCM-Solvent

Ideal coating

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• Thiol-ene reactions have fast polymerization rates, high conversion, network homogeneity and offer versatility in thiol and ene selection.

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tact

Ang

le

TxE

y + 0.1% PEO

TxE

y+0.35% PEO

+ 50% DCMT

xE

y+0.35% PEO

+ 90% DCM

T1E2T1E1 T2E1 T1E1 T1E2 T2E1T1E2T2E1 T1E1PAN 30

Increasing the solvent content in the prepolymer solution increases the water permeance in the thin film composite membranes.

SEM image of T1E2 + 0.35% PEO + 90% DCMDense polymer structure on the surface.

Membranes of thiol-ene polymers show hydrophilicity.

Polymer network formation

Salt

* 50% Solvent content in prepolymer solutions

* Lowe, Poly. Chem., 2010, 1, 17-36

* Wu, Liu, Yu, Liu, Gao, J. Membr. Sci., 352 (2010) 76-85

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T1E2 + 0.35% PEO + 50% DCM

Lin et al., Ind. Eng. Chem. Res., 2013, 52 (31), 10820