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Surface Properties of Graft-Copolymers Possesing Oppositely Charged Groups:Oppositely Charged Groups:
Mitigation of Microbial Biofilm Formation, mechanisms and applications
קו עם המושתלים שטח פני מטעןתכונות מנוגדות קבוצות בעלי פולימרים פולימרים בעלי קבוצות מנוגדות מטען-תכונות פני שטח המושתלים עם קו:ומניעת גידול ביופילם מיקרוביאליאפשריים ושימושים םמנגנונים ם אפשר מוש ם וש מנגנונ
Moshe HerzbergZuckerberg Institute for Water ResearchBlaustein Institutes for Desert Research,,Sede Boqer CampusBen Gurion University of the Negev
Contamination of water treatment and distribution systems
Phil Stewart / Peg Dirckx – The Center for Biofilm Engineering - MSU Phil Stewart / Peg Dirckx – The Center forPhil Stewart / Peg Dirckx The Center for
Biofilm Engineering - MSUPaper machine biofilms
Phototrophic biofilms on ship hullshulls
Marko Kolari, Helsinki University, Finland http://phobia.itqb.unl.pt/
Microbial biofilms
Bacteria form aggregates in a self produced EPS on membranes
Bulk Side
Membrane Side
Main antifouling strategy: Increased surface hydrophilicityhydrophilicity
Charged surfaces: Less favorable;
N h d h d hili tiNon-charged hydrophilic coatingSagle, Freeman et al., J Memb Sci (2009)Bryers et al., Biomaterials (2004)
Polyethylene-glycol
“Modern antifouling” – net charge = 0S Jiang et al Advanced Materials (2008)
glycol
S. Jiang et al., Advanced Materials (2008)Cheng et al., Angew Chem (2008)
An attractive method for fabrication of antifouling surface:Redox-initiated graft polymerization using hydrophilic monomers
Polymer brushes
K2S2O8, K2S2O5
S hi B lf d h k A t P l i 1998 J M b S i 1998
Benefits:
Sophia Belfer and her coworkers, Acta Polymerica 1998; J Memb Sci 1998
In aqueous solutions, room temperature Short reaction times (~ 30 mins) C i ll il bl d h t Commercially available and cheap reagents
Possible modification inside membranes used for water treatment (Belfer et al., 2004)
Generation of free radical in solution by the redox couple:couple:
Potassium persulfate
Potassium metabisulfitep metabisulfite
Bamford and K. Al-Lamee, Polymer (1994)
Disadvantages:Disadvantages:
• Grafting occurs on the surface as well as in solution
• Slow reaction time and high concentration is required•
Our approach:
Polymer surface
Co-grafting
ZwiterionicZwiterionic monomer
SPESPE(sulfo-betaine)
Objectives1 Fabricating anti-fouling polyamide or PVDF surfaces having1. Fabricating anti-fouling polyamide or PVDF surfaces having
increased wettability with minimal change in surface charge
2. Surface characterization, swelling, and reduced EPS adsorption f fof modified membranes
SPMSulfopropyl methacrylate
MOETMAMethacryloyloxy ethyl trimethylammonium
Polymer surface
Co-graft-polymerization
MOETMA + SPM modification
K2S2O8K S O
MOETMA
SPM
SO3N+ CH
CH3
K2S2O5SPM
ATR-FTIR spectrum:
C=O esterN+ CH3
CH3
Achieve high grafting yields of sulfo and ammonium !
Hydrophilicity – by water drop t t lcontact angle
MOETMA + SPM
Achieve dramatic increase in hydrophilicity (wettability) in all concentrations used!!
Electrostatic repulsions between negatively-charged sulfo and RO polyamide membrane:sulfo and RO polyamide membrane:
SSPM only:
RO Polyamidemembrane
MOETMA + SPM:SPM:
RO Polyamideymembrane
Zeta-potential of RO membrane surface after grafting
MOETMA + SPM
MOETMA only
+2 eV
-19 eV-19 eV
Graft Copolymerization On PVDF-coated surface using SPM + MOETMAusing SPM MOETMA
Polyvinylidene fluoride - PVDF Ultrafiltration membranes Hydrophobic polymer
K S OK2S2O8K2S2O5PVDF
PVDF-coated graft co-polymer
Graft Copolymerization On PVDF-coated surface using SPM + MOETMAusing SPM MOETMA
Polyvinylidene fluoride - PVDF Ultrafiltration membranes Hydrophobic polymer
1) Surface characterization of the grafted PVDF surface
2) Antibiofouling properties and involved mechanisms
K2S2O8K S OPVDF K2S2O5PVDF
PVDF-coated graft co-polymer
ATR-FTIR and water drop contact angle of PVDF-surface grafted with MOETMA and SPMsurface grafted with MOETMA and SPM
62 º ± 3 º
90º ± 4º
Structural, viscoelastic properties and mass changes in real-time using quartz crystalchanges in real time using quartz crystal
microbalance with dissipation technology (QCM D)dissipation technology (QCM-D)
.
Real-time monitoring of graft polymerization on PVDF using quartz crystal microbalance with dissipation
DDW Monomers
0z
Monomers
-100
Shi
ft, H
Monomers+
-200
ency
S Initiators
Washing stages
-300Freq
ue
g g
0 50 100 150Ti Mi tTime, Minutes
Characterizing swelling with QCM-D
2
100 mM NaCl
DDWDDW 100 mM NaCl
0
1
Fact
orEPS
-2
-1
0
issi
patio
n Cl -
0 20 40 60 80-3
2
Time, Minutes
Di
8
Unmodified PVDF
ONa+
0
1
2
Fact
or
4
6
8
Shift
, Hz Graft polymerized PVDF
PVDF-coated Graft co-polymers
-2
-1
0
Dis
sipa
tion
F
0
2
Freq
uecy
S
0 20 40 60 80-3
T im e, M inutes
D
-2
F
Characterizing swelling with atomic force microscopy
Modified Surface in DDW Modified Surface in NaCl
How swelling affects force interactions ith d l f l t?with model foulant?
30
20
30Unmodified crystal in 100 mM NaCl
Modified crystal in 100 mM NaCl
10
mN
/m) Unmodified crystal in DDW
Modified Crystal in DDWEPS
10
00 0.1 0.2 0.3 0.4 0.5
adiu
s (m
CC
O
O
CH3 O
EPS
Cl -
-20
-10
orce
/Ra3
CC
C
O
O
CH3 Na+
-30Separation Distance (µm)
Fo
PVDF-coated Graft co-polymers
-40Separation Distance (µm)
Force interactions with model foulant
100
100 Modified, DDWNon-modified, DDW
60
80
Avg: 29.9 mN/mStd: 3.74 mN/m
ency
, % 60
80 Avg: 3.5 mN/mStd: 2.38 mN/m
ency
, %
0
20
40
Freq
ue
0
20
40
Freq
ue
0 5 10 15 20 25 30 35 400
Force/Radius, mN/m0 5 10 15 20 25 30 35 40
0
Force/Radius, mN/m
100 100 Modified NaClNon-modified, NaCl
60
80
100
Avg: 4.3 mN/mStd: 5.5 mN/m
y, % 60
80
100
Avg: 0.1 mN/mStd: 0.4 mN/m
y, %
Modified, NaClNon modified, NaCl
20
40
Freq
uenc
y
20
40
Freq
uenc
y
0 5 10 15 20 25 30 35 400
Force/Radius, mN/m0 5 10 15 20 25 30 35 40
0
Force/Radius, mN/m
The source of foulant:Extracellular Polymeric Substances (EPS) fromExtracellular Polymeric Substances (EPS) from
MBR system
Carriers
EPS Page 22
EPS Extraction MethodEPS extraction is carried out by formaldehyde- NaOH method:
Formaldehyd NaOH10 mL sample + 0.06 mL formaldehyde(37 %), 1 h, 4 °
Formaldehyde
NaOH
sample + 4 mL 1 N NaOH, 3 h, 4°C
centrifugation 3500rpm 30 min
filtration the supernatant with Nylon membrane Filter (0.45um 47mm)
centrifugation 3500rpm, 30 min
dialysis against deionized water overnight
freeze-drying(−80°C for 48 hours)
Di l i L hili tiDialysisFiltration
Lyophilization
Effect of surface modification on adhesion of EPS
Time, MinutesTime, Minutes
20 20 40 60 80 100 120
A2
0 20 40 60 80 100 120
ADDW
2
0
ft, H
z
A BDC E
2
0
ft, H
z
A BDC E
DDW NaCl
DDWNaClEPS
-4
-2
ncy
Shif
-4
-2
ncy
Shif
8
-6
Freq
uen
Modified Crystal8
-6
Freq
uen
Modified Crystal
-10
-8 Non-Modified Crystal
-10
-8 Non-Modified Crystal
ATR FTIR t fNon-modified
ATR-FTIR spectrum of
fouled QCM-D sensors
with EPS
Modified
Concluding Remarks
• We successfully co-grafted MOETMA and SPM on y gpolyamide and PVDF surfaces.
• Copolymer grafted layer possessing oppositely chargedCopolymer grafted layer possessing oppositely charged groups is reducing fouling due to increased hydrophilicity and swelling.
• The significant reduced adsorption of MBR-originated EPS to modified PVDF surface has strong anti-biofouling g gimplications.
Acknowledgments
• Sophia Belfer• Roza Feinstein• Slava Freger• Gideon Oron• Gideon Oron
• Amer Sweity• Matan Brami• Yair Kaufman
• Funding: BMBF 2010
Thanks for the attention!Thanks for the attention!
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