Carbon nanoparticle containingresponsive hydrogel composites
Barbara Berke
Supervisors: Orsolya Czakkel (ILL)
Krisztina László (BME)
All You Need Is Neutrons – 17/05/2016
Polymer Hydrogels
IUPAC: Non-fluid polymer network that is expanded throughout its whole volume by a fluid.
• Solid, three dimensional polymer network filled by air (aerogels) or liquids (liogels) water (hydrogel)
• Amphiphilic polymer chains must be kept together
first order bonds: chemical gels (monomer + cross-linker are needed)
second order bonds: physical gels
2
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High absorption capacity and soft character
3
Non-linearchange upon
environmentalstimuli.
Introduction Synthesis Macroscopic Responsivity Neutrons Summary
Stimuli-responsive (intelligent) hydrogelsControlled drug delivery
Tissue engineering
Actuators
Microfluidics
Sensors
Intelligent polymer
4
Problems: weak mechanical properties, fracture upon repetitive usage, etc.
tuned response is needed
• Collapsing near human body temperature
Volume phase transition temperature (VPTT) (~34 °C)
• Excellent swelling properties (~30-40 times of dry weight)
• Almost completely reversible deformation
• Biocompatible ?!
Possible solution: Composite preparation
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Poly(N-isopropylacrylamide) – PNIPA
http://brm.technion.ac.il/gallery/
5
Multi-walled
carbon nanotubes (CNT) Graphene oxide(GO)Good mechanical properties
IR sensitivity
Potentially tunable electrical
and thermal conductivity,
magnetic sensitivity
Dispersibility
functionalisation
Toxicity ?
Oxidised by cc. HNO3 Improved Hummers method
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Carbon nanoparticles (CNP)
graphene
Keresztkötő-sűrűség:
6
150molNIPA
mol BA
Nomenclature:
X mg GO/ g monomer –
GOX@PNIPA
Introduction Synthesis Macroscopic Responsivity Neutrons Summary
CNT and GO@PNIPA compositesNIPA BA
N-isopropylacrylamide N,N’ methylenebisacrylamide
N,N,N’,N’ –
tetramethylethylenediamine
ammonium persulfate
water
Filler-free gel
GO suspension
Gel synthesis
GO@PNIPA
CNT suspension - aggregates
Gel synthesis
CNT@PNIPA
CNT
containing
composite
GO
containing
composite
Cross-linking density:
Keresztkötő-sűrűség:
7
150molNIPA
mol BA
Nomenclature:
X mg GO/ g monomer –
GOX@PNIPA
Introduction Synthesis Macroscopic Responsivity Neutrons Summary
CNT and GO@PNIPA compositesNIPA BA
N-isopropylacrylamide N,N’ methylenebisacrylamide
N,N,N’,N’ –
tetramethylethylenediamine
ammonium persulfate
water
Filler-free gel
GO suspension
Gel synthesis
GO@PNIPA
CNT suspension - aggregates
Gel synthesis
CNT@PNIPA
CNT
containing
composite
GO
containing
composite
Cross-linking density:
8
• Macroscopic lengthscale:
• Swelling degree
• Elastic modulus
• Microscopy
• Responsivity:
• Differential scanning calorimetry
• Temperature induced deswelling kinetics
• Microscopic lengthscale - Neutrons
• Small angle neutron scattering (SANS)
• Neutron spin-echo spectroscopy (NSE)
Introduction Synthesis Macroscopic Responsivity Neutrons Summary
Characterisation
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Microscopy
Digital optical
microscope
(DOM)
Scanning electron
microscope
(SEM)
CNT@PNIPA GO@PNIPAPNIPA
50 mm
10
[1] B. Berke et al.: Static and dynamic behaviour of responsive graphene oxide - poly(N-isopropyl acrylamide) composite gels. Submitted
[2] K. László et al. Macromolecules 2004, 37, 10067-10072; Chetty et al. – eXPRESS Polymer Letters Vol.7, No.1 (2013) 95–105
GO@PNIPA1 PNIPA from literature2
0 5 10 15 20 250
2
4
6
8
10
Ma
ss s
wel
lin
g d
egre
e (-
)
Mo
du
lus
(kP
a)
mg GO/g NIPA
20
25
30
35
40
200 150 100 500
2
4
6
8
10
Mass
sw
elli
ng d
egre
(-)
Mod
ulu
s (k
Pa)
Cross-linking density (mol/mol)
20
25
30
35
40
0 5 10 15 20 250
2
4
6
8
10
Ma
ss s
wel
lin
g d
egre
e (-
)
Mo
du
lus
(kP
a)
mg CNT /g NIPA
20
25
30
35
40
CNT@PNIPA
Introduction Synthesis Macroscopic Responsivity Neutrons Summary
Swelling degree (at 20 °C) and elastic modulus
What kind of interactions are formed?
11
VPT did not change
The relative swelling degree does
not depend on the quality and
quantity of the filler.
20 25 30 35 40 45 500
20
40
60
80
100
CNT20@PNIPA
CNT5@PNIPA
GO5@PNIPA
GO20@PNIPAPNIPA
Rela
tiv
e s
well
ing
deg
ree (
%)
Temperature (°C)
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Equillibrium responsive properties
Relative swelling degree (%):
𝑆𝑤𝑒𝑙𝑙𝑖𝑛𝑔 𝑑𝑒𝑔𝑟𝑒𝑒 𝑎𝑡 𝑇
𝑆𝑤𝑒𝑙𝑙𝑖𝑛𝑔 𝑑𝑒𝑔𝑟𝑒𝑒 𝑎𝑡 20 °𝐶× 100
12
0 5 10 15 20 25
50
55
60
65
70
En
thalp
y (
J/g
)
mg GO / g NIPA
200 150 100 50
50
55
60
65
70
En
thalp
y (
J/g
)
Cross-linking density (mol/mol)
[1] B. Berke et al.: Static and dynamic behaviour of responsive graphene oxide - poly(N-isopropyl acrylamide) composite gels. Submitted
[2] K. László et al. Macromolecules 2004, 37, 10067-10072;
VPTT: 33.8 °C
The enthalpy depends on the GO content.
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Differential scanning microcalorimetry (DSC) – GO@PNIPA
20 25 30 35 40 45 50
0.2 mW
5GO@PNIPA
PNIPA
10GO@PNIPA
Hea
t fl
ow
(m
W)
Temperature (°C)
exo
20GO@PNIPA
GO@PNIPA1 PNIPA from literature2
Minta𝒎
𝒎𝟎 𝒇𝒊𝒏A1
t1
(min)p1 A2 t2 (min) p2
PNIPA 5.49 82.6 12.1 1.33 - - -
5GO@PNIPA 3.64 51.8 4.90 0.69 44.2 13301 0.53
10GO@PNIPA 7.14 33.6 3.56 0.50 59.1 4369 0.59
20GO@PNIPA 7.85 42.9 5.04 0.57 49.1 1317 0.70
13
21
1 2
( ) ( )
1 2
0 0
( )
ppx x
t t
fin
m mA e A e
m m
0.1 1 10 100 1000 10000 1000000
20
40
60
80
100
Rel
ati
ve
ma
ss (
%)
Time (min)
0 5 10 15 20 250
5000
10000
15000
t 2 (
min
)
mg GO / g NIPA
𝒎
𝒎𝟎 𝒇𝒊𝒏:final relative mass
A: preexponential constant
t: time constant
p: exponent
20 °C 50 °C
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Time-dependent responsive behaviour – GO@PNIPA
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0.1 1 10 100 1000 10000 1000000
20
40
60
80
100PNIPA
5GO@PNIPA
10GO@PNIPA
20GO@PNIPA
Rel
ati
ve
mass
(%
)
Time (min)
20 °C 50 °C
Introduction Synthesis Macroscopic Responsivity Neutrons Summary
Time-dependent responsive behaviour
1 10 100 1000 10000 100000
40
60
80
100
PNIPA
3CNT@PNIPA
6CNT@PNIPA
12CNT@PNIPA
24CNT@PNIPA
Rel
ati
ve
dia
met
er
(%)
Time (min)
CNT@PNIPAGO@PNIPA
15
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From macroscopic to microscopic lengthscales
(almost) all you need is neutrons
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Introduction Synthesis Macroscopic Responsivity Neutrons Summary
Small-angle neutron scattering- SANS
http://www.mirrotron.kfkipark.hu/images/SANS-concept.png
2 2
(0)( )
1
II Q B
Q
Ornstein-Zernike model
I(Q): intermediate scattering function
Q: scattering vector
I(0) and B: Q-independent constants
ξ: correlation length
ρ: fractal dimension of polymer coils
Component
Neutron scattering
cross-section
(10-6/Å2)
PNIPA, (C6H11NO)n 0.825
GO, C65O35 5.993
D2O 6.364
Samples swollen in D2O
at 25 °C
Measured on D22
17
Dynamic processes from 1 ps to ~100 ns
Diffusion, polymer solutions, gels, membranes, etc
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Neutron spin-echo spectroscopy - NSE
Measured on IN11
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NSE in swollen state (25 °C) - PNIPA
Simple exponential fit
Dynamics ~q2
Full decay (baseline=0)
Diffusive motion
( , )exp( )
( ,0)
I Q
I Q 2
diffD Q
6
Bdiff
H
k TD
𝐼(𝑄,𝜏
𝐼(𝑄,0: intermediate scattering function
G: relaxation rate
t: time constant
Ddiff: diffusion coefficient
kb: Boltzmann constant
T: absolute temperature
h: viscosity of the medium
ξH: hydrodynamic correlation length
19
CNT@PNIPA
Sample Ddiff1011 (m2/s) ξH (Å) ξ (Å)
PNIPA 7.03±0.14 28.4±0.01 92.0±1.09
5GO@PNIPA 7.41±0.24 26.9±0.08 90.0±1.11
20GO@PNIPA 8.10±0.30 24.6±0.90 66.7±0.67
GO20@PNIPA
Baseline ≠ 0
~2% 0.05
Summary of neutron results so far…
Introduction Synthesis Macroscopic Responsivity Neutrons Summary
NSE in swollen state (25 °C) - composites
GO5@PNIPA
Baseline = ?
~0.5% ~0.005 - 0.01?
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Introduction Synthesis Macroscopic Responsivity Neutrons Summary
Summary
Regular PNIPA
cross-links
PNIPA cross-links
+ GO hypernodes
Effects on: CNT@PNIPA GO@PNIPA
Swelling, elasticity
Aggregations
Interactions weak strong
Response
VPTT
Enthalpy
Kinetics
Time constant
Architecture of the polymer matrix
21
• NMR interactions between CNP and polymer?
• Mechanical tests
• Temperature-dependent structure & dynamics (SANS, NSE, SAXS, XPCS).
Other systems:
• Modification of the surface chemistry of the nanoparticles to influence the
interactions in the composites
• Pre-planned, application-oriented composite-preparation by tuning the quality and the
quantity of the nanoparticles.
Introduction Synthesis Macroscopic Responsivity Neutrons Summary
Next steps
Acknowledgement
ILL PhD program
George Olah Doctoral School (BME)
OTKA K101861
TÁMOP-4.2.1/B-09/1/KMR-2010-0002
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Surface Chemistry Group
Dávid Kun
József Hári
Lionel Porcar
Dimitri Renzy
Mark Jacques
Krisztina László Orsolya Czakkel
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