Evgeny Karpushkin, Andrey Bogomolov WSC-9, Tomsk, Feb 2014
description
Transcript of Evgeny Karpushkin, Andrey Bogomolov WSC-9, Tomsk, Feb 2014
Morphology assessment of polymer hydrogels using multivariate analysis
of viscoelastic and swelling properties
Evgeny Karpushkin, Andrey Bogomolov
WSC-9, Tomsk, Feb 2014
What is hydrogel?Large variety of gels, but in this talk
gel = covalently cross-linked 3D (network) polymer swollen in water
Properties:• hydrophilic, swollen, soft materials• biocompatible or biodegradable• responsive to changes of temperature, pH and ionic strength; electrical and magnetic fields
Applications:• artificial implants (contact lens)• supports for enzymes and cells immobilization• sensors, actuators, chemical valves and robots• models of tissues and organs• food industry, cosmetics, …
Examples of hydrogel morphology: polyHEMA
Soft Matter 3 (2007) 1176–1184
Reactive & Functional Polymers62 (2005) 1–9
Macromolecules 40 (2007) 8056-8060
Biomaterials 26 (2005) 1507–1514
Pores generation in HEMA gels:
• phase separation during polymerization• incorporation of soluble particles• cryo (frozen solvent as porogen) • liquid porogen (emulsion polymerization)• introduction of gas generating substances
Journal of Controlled Release102 (2005) 3–12
100 mm
100 mm
100 mm
400 mm
1 mm
Materials science: general aim
Preparation conditions
Structure:porosity,topology,
microphases,…
Utilitarian properties
• How do preparation conditions influence the material structure?• How does structure of material influence its functional properties?• What material structure corresponds to certain measured properties?• How to prepare a material with desired properties?
Measured propertiesComposition
Remarks on microscopyLight microscope:rapid, good for start,but resolution not enough
Electron microscope:for dry samples structure is not always preserved
Electron microscope:for swollen samples observed structure is highly dependent on conditions
Chamber pressure decreasing
dry
swollen
Preparation of samples
CH2
CH3
O
O
OH
CH2
CH3
OOO
CH2
CH3
O O NNCH3
CH3
CH3
CH3
diluent (NH4)2S2O8glass plates
rubber sealing
• diluent content• diluent nature (water, aqueous NaCl, aqueous Mg(ClO4)2)• cross-linker : monomer ratio• swelling medium: water, dimethylsulfoxide, aqueous NaCl
HEMA
DEGDMA TEMED
APS
(0.1M NaCl) 70/1 (DMSO)
diluent type diluent ratio (wt%)
crosslinker to monomerratio (mol%) swelling medium
Sample codeVariable parameters:
> 100 samples
Observed propertiesMorphology type Equilibrium swelling
Shear deformation
Homogeneous Droplets
Interlocking Fused particles
Mixed
• In water, or DMSO, or aqueous NaCl• Sometimes versus temperature
• Forced oscillatory deformation• Creep (constant shear stress in time)
)()()(
swollenmdrymswollenm
Morphology of hydrogels:diluent at preparation = water
Morphology of hydrogels:salting-in diluent at preparation
70/2
(0.05M Mg(ClO4)2)70/2
(0.2M Mg(ClO4)2)70/2
(0.3M Mg(ClO4)2)70/2
More diluent solvating power = less phase separation
Morphology of hydrogels:salting-out diluent at preparation
60/1 (0.2M NaCl)60/1 (0.4M NaCl)60/1 (0.45M NaCl)60/1
(0.475M NaCl)60/1 (0.5M NaCl)60/1 (0.525M NaCl)60/1 (0.6M NaCl)60/1
Fine tuning – never observed before!Less diluent solvating power = more phase separation
Effect of morphology on swelling
0 1 2 3 4 5
0.4
0.6
0.8 homogeneous intermediate interlocking particulate
IWC = 80 wt%
IWC = 70 wt%
IWC = 60 wt%
IWC = 50 wt%
Equ
ilibr
ium
sw
ellin
g (g
/g)
Crosslinker concentration CC (mol%)
IWC = 40 wt%
0.0 0.2 0.4
0.4
0.6
70/2
60/1
Equ
ilibr
ium
sw
ellin
g, g
/g
Mg(ClO4)2 in preparation diluent (mol/L)
40/1
b)
0.0 0.2 0.4 0.6 0.8
0.4
0.6
70/2
60/1
Equ
ilibr
ium
sw
ellin
g, g
/gNaCl in preparation diluent (mol/L)
40/1
d)
Effect of morphology on swelling
Effect of morphology on equilibrium shear modulus
0 1 2 3 4 5
1
10
100
homogeneous intermediate interlocking particulateIWC = 80 wt%
IWC = 70 wt%
IWC = 60 wt%
IWC = 50 wt%
G' a
t 0.1
Hz
(kP
a)
Crosslinker concentration CC (mol%)
IWC = 40 wt%
0.0 0.2 0.40
40
80
120
160
70/2
60/1
G' a
t 0.1
Hz
(kP
a)
Mg(ClO4)2 in preparation diluent (mol/L)
40/1
a)
0.0 0.2 0.4 0.6 0.8
10
100
70/2
60/1
G' a
t 0.1
Hz
(kP
a)NaCl in preparation diluent (mol/L)
40/1
c)
PCA: 35 water-born samples, 19 variables
-0,4 -0,2 0,0 0,2 0,4
-0,4
-0,2
0,0
0,2
0,4
PEWC
G'-0.1G'-1
G'-10
G''-0.1G''-1G''-10
tg-0.1tg-1
tg-10
J-0.04
J-0.1
J-1J-10J-100
CreepGIWC
CC
p1
p 2
PCA: 35 water-born samples, 19 variables
-8 -6 -4 -2 0 2 4 6
-3
-2
-1
0
1
2
3
4
5
40/0.140/0.540/1
40/2
40/3
40/4
40/5
50/0.1
50/0.550/1
50/2
50/3
50/4
50/5
60/0.1
60/0.560/160/2
60/3
70/0.1
70/0.570/1
60/4
60/5
70/2
70/3
70/4
70/580/0.1
80/0.5
80/180/1.5
80/2
t1 (56%)
t 2 (30%
)
PCA: 35 water-born samples, 19 variables
-0,4 -0,2 0,0 0,2 0,4
-0,4
-0,2
0,0
0,2
0,4
PEWC
G'-0.1G'-1
G'-10
G''-0.1G''-1G''-10
tg-0.1tg-1
tg-10
J-0.04
J-0.1
J-1J-10J-100
CreepGIWC
CC
p1
p 2
PCA: 35 samples, 4 variables
-2 0 2 4
-2
-1
0
1
2
3
4
40/0.140/0.540/140/2
40/3
40/4
40/5
50/0.150/0.550/1
50/2
50/3
50/4
50/5
60/0.160/0.560/160/2
60/3
70/0.170/0.5
70/1
60/4
60/5
70/2
70/3
70/470/5
80/0.1
80/0.580/180/1.580/2 t
1 (51%)
t 2 (42%
)
Equilibrium swelling, low frequency modulus, and pair of loss factorsThese variables are important as such, and therefore they are usually determined
Conclusions and perspectives
• PCA approach is promising for indirect morphology assessment.• Fairly reliable• Fast and cheap as compared with the direct ESEM• Uses experimental variables are important as such
• Needs further investigation• Is it possible to exclude swelling data? • Creep curve fitting?• Does the approach work with chemically different materials?