Electrospun PCL nanomembranes, polymer blends and surface modifications – physical
characterization and comparison
Daniela M.P. Rodrigues*, A. Jorge Guiomar, Jorge M.S. Rocha and M. Helena Gil
NYMembrains 14 – London, 2012
Summary
1. Objectives 2. Electrospinning 3. Nanofiber Modification 4. Nanofiber Characterization 5. Conclusion 6. Acknowledgements
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1. Objectives
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• NanoBioCats
Separation membranes with
improved biocatalytic
performance
Enzyme carriers
Nanofiber membranes
1. Objectives
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Protein
Nanofiber Membrane
Protease
Peptides/ Aminoacids Nanomembranes
Reactor 1 Reactor 2
Nanomembranes
Protein Peptides/ Aminoacids
2. Electrospinning
• Specificities – High voltage is applied to a liquid droplet; – Electrostatic repulsion counteracts the surface
tension and the droplet is stretched; – Formation of uniform fibers with nanometer-scale
diameters.
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Figure 1 - Electrospinning apparatus.
2. Electrospinning
• Advantages and Disadvantages
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Disadvantages Advantages
2. Electrospinning
• Applications
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Polymer nanofibers
Filtration
Tissue Engineering
Wound Healing
Release Control
Catalysts and
Enzyme Carriers
Sensors
Energy Conversion
and Storage
2. Electrospinning
• Factors that influence electrospinning success
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Polymer
• Molecular weight • Concentration • Crosslinking • Isomeric structure
Solution
• Solvent • Viscosity • Electrical
conductivity • Surface tension
Process
• Voltage • Distance • Flow rate • Solvent
evaporation rate • Collection
technique • Relative Humidity • Temperature
2. Electrospinning
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Figure 2 - Beading
Figure 3 – Beading and fiber disruption
• Common problems
2. Electrospinning
• Polymer solution – Polymer: Polycaprolactone (PCL) (Mw= 50 000), 15% (w/v) – Solvent: Acetone
• Processing Conditions
– Voltage: 20 kV – Tip-collector distance: 80 mm – Flow-rate: 10mL/h – Needle diameter: 0.41mm – Temperature: RT
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Figure 4 – Electrospun fibers.
3.Nanofiber modification – pellets modification
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O (CH2)5 C
O
n
PCL Nanofiber
+ UV Radiation
Plasma
+ O
OH
ELECTROSPINNING
COOH COOH
COOH
COOH COOH COOH COOH
COOH
COOH COOH COOH
PCL MAA
or
3.Nanofiber modification – nanofiber modification
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O (CH2)5 C
O
n
PCL nanofiber mat
+ UV Radiation
Plasma
+ O
OH
PCL nanofiber mat
COOH COOH
COOH COOH
COOH COOH
COOH
COOH
COOH COOH
MAA
or
3. Nanofiber modification
• UV Radiation – 30 min photoinitiator; – 30 min monomer MAA;
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Figure 5 – UV chamber.
Figure 6 – PCL surface modified by UV radiation
3. Nanofiber modification
• Plasma – 6 min – Argon at 0.6 mbar – 3 cm from the electrode – 100W – 24h at room temperature in MAA 10% (V/V)
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Figure 7 – PCL surface modified by Plasma.
Figure 8 – Plasma equipment.
3. Nanofiber modification
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O (CH2)5 C
O
n+
O
OOH +
O
OH
• Copolymerization
PCL Nanofiber
ELECTROSPINNING
COOH COOH
COOH
COOH COOH COOH COOH
COOH
COOH COOH
MAA HEMA
3. Nanofiber modification
• Blending Polylactic Acid (PLA) – PLA(a) Mw=67 000 Da – PLA(b) Mw=53 000 Da – PLA(c) Mw=43 000 Da
– PCL+PLA at 15% (w/v) in acetone; – PCL/PLA 1:1.
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Different ramification degrees
Figure 9 – PLA samples.
4. Nanofiber characterization
• SEM
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(a (b (c
(d (e (f
a) b) d) c)
e) f) g) h) a)PCL nanofibers; b) PCL+PLAa; c)PCL+PLAb; d) PCL+PLAc ;
e) PCL UV; f) PCL Plasma; g) PLC+HEMA+MAA.
g)
4. Nanofiber characterization
• Porosity and fiber diameter
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Sample Largest Pore Area (µm)2
Smallest Pore Area
(µm)2
Largest Diameter
(µm)
Smallest Diameter
(µm)
PCL 8.04 ± 1.61 0.08 ± 0.02 1.56± 0.43 0.35±0.04 PCL UV 18.68 ± 2.82 0.1 ± 0.02 2.18± 0.97 0.62±0.10
PCL Plasma 20.75 ± 2.34 0.22 ± 0.02 1.3± 0.22 0.17±0.03 PCL+PLAa 19.82 ± 4.21 0.04 ± 0.01 0.5± 0.08 0.06±0.01 PCL+PLAb 25.15 ± 3.05 0.04 ± 0.01 0.67± 0.12 0.07±0.01 PCL+PLAc 7.12 ± 2.37 0.01 ± 0.00 1.56± 0.41 0.11±0.01
PCL+HEMA+MAA 4.14 ± 0.85 0.01 ± 0.00 0.49±0.09 0.02±0.00
4. Nanofiber characterization
• Water absortion capacity
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0
20
40
60
80
100
120
% o
f wat
er a
bsor
ved
4.Nanofiber characterization
• Dynamic Contact Angle
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50 60 70 80 90
100 110 120 130 140 150
0 5 10 15 20 25 30
Cont
act a
ngle
(º)
time (min)
PCL+PLAb PCL PCL Plasma PCL+PLAa PCL UV PCL+PLAc PCL+HEMA+MAA
4.Nanofiber characterization
• ATR-FTIR
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PCL
PCL
PCL
PLA
PLA
PCL+PLA
PCL+PLA
PCL PLA
PCL+PLA
4.Nanofiber characterization
• ATR-FTIR
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4.Nanofiber characterization
• TGA
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PLA Different forms of PCL
Blends of PCL and PLA
4.Nanofiber characterization
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• DSC
PCL
PLA
4.Nanofiber characterization
• Tensile tests
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0
50
100
150
200
250
Youn
g's M
odul
us (M
Pa)
170.45 MPa
211.87 MPa
4.Nanofiber characterization
• Trypsin immobilised by adsorption
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0 5
10 15 20 25 30 35
% o
f Try
psin
ads
orbe
d
32.96% 34.57%
5. Conclusions
• The blend of PCL with PLA(a) (Mw=67 000 Da) yields a good nanofiber membrane with enzyme carrier capability due to: – Large pores and thinner fiber diameters, which provide a good
water absortion ability;
– High contact angle, which allows the occurrence of a fluid retention time, required for an efficient protein enzymatic hydrolysis.
– High mechanical resistance, which allows resistance to pressure differentials.
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6. Acknowledgements
• FCT (Fundação de Ciência e Tecnologia) for financial support of the project NanoBioCats – PTDC/CTM-POL/112289/2009;
• Polylactic acid kindly provided by the project SFRH/BD/42245/2007.
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