Electrospun PCL nanomembranes, polymer blends and surface...

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

*[email protected]

NYMembrains 14 – London, 2012

Summary

1. Objectives 2. Electrospinning 3. Nanofiber Modification 4. Nanofiber Characterization 5. Conclusion 6. Acknowledgements

2 NYMembrains14 - London 2012

1. Objectives

3 NYMembrains14 - London 2012

• NanoBioCats

Separation membranes with

improved biocatalytic

performance

Enzyme carriers

Nanofiber membranes

1. Objectives

NYMembrains14 - London 2012 4

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.


Figure 1 - Electrospinning apparatus.

http://en.wikipedia.org/wiki/Voltage

http://en.wikipedia.org/wiki/Nanometer

2. Electrospinning

• Advantages and Disadvantages


Disadvantages Advantages

2. Electrospinning

• Applications


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


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


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


Figure 4 – Electrospun fibers.

3.Nanofiber modification – pellets modification


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


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;


Figure 5 – UV chamber.

Figure 6 – PCL surface modified by UV radiation


• Plasma – 6 min – Argon at 0.6 mbar – 3 cm from the electrode – 100W – 24h at room temperature in MAA 10% (V/V)


Figure 7 – PCL surface modified by Plasma.

Figure 8 – Plasma equipment.



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


• 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.


Different ramification degrees

Figure 9 – PLA samples.

4. Nanofiber characterization

• SEM


(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)


• Porosity and fiber diameter


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


• Water absortion capacity


0

20

40

60

80

100

120

% o

f wat

er a

bsor

ved

4.Nanofiber characterization

• Dynamic Contact Angle


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


• ATR-FTIR


PCL

PCL

PCL

PLA

PLA

PCL+PLA

PCL+PLA

PCL PLA

PCL+PLA


• ATR-FTIR



• TGA


PLA Different forms of PCL

Blends of PCL and PLA



• DSC

PCL

PLA


• Tensile tests


0

50

100

150

200

250

Youn

g's M

odul

us (M

Pa)

170.45 MPa

211.87 MPa


• Trypsin immobilised by adsorption


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.


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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