1. www.buffalo.edu
0.8
0.85
0.9
0.95
1
0 500 1000 1500 2000 2500
NormalizedRejection
ppm.h chlorine
Thiol-ene Polymer Networks for Reverse Osmosis
Shawreen Shah, Kaipin Huang, Norman Ng and Haiqing Lin
Department 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 difference
Δ = osmotic pressure difference
Salt Rejection:
C2: salt concentration in the permeate
C1: salt concentration in the feed
)(  pAJW
1001
1
2







C
C
R
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 Membranes
Thin 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
Polymer
Ene
Thiol
Wavenumber (cm
-1
)
Pore-penetration
Increase
viscosity
Decrease
thickness
PEO-
Filler
DCM-
Solvent
Ideal coating
0.8
1
1.2
1.4
1.6
0 500 1000 1500 2000 2500
NormalizedFlux
ppm.h chlorine
• Thiol-ene reactions have fast polymerization rates, high conversion, network
homogeneity and offer versatility in thiol and ene selection.
0
10
20
30
40
50
60
70
80
ContactAngle
T
x
E
y
+ 0.1% PEO
T
x
E
y
+0.35% PEO
+ 50% DCM
T
x
E
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% DCM
Dense 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
0
0.2
0.4
0.6
0.8
1
0 5 10 15 20
Permeance(L/m
2
xhrxbar)
Pressure (bar)
T1E1 + 0.35% PEO + 90% DCM
T1E2 + 0.35% PEO + 90% DCM
0
0.005
0.01
0.015
0.02
0.025
0.03
0.035
0.04
0 5 10 15 20
Permeance(L/m
2
xhrxbar)
Pressure (bar)
T1E1 + 0.35% PEO + 50% DCM
T1E2 + 0.35% PEO + 50% DCM
Lin et al., Ind. Eng. Chem. Res., 2013, 52 (31), 10820