The goal of the present work is to study hybrid poly(ethylene oxide), PEO, silica nanoparticle systems. The effect of the Silica nanoparticle on the structural and conformational properties of PEO is highlighted through both experiments and simulations. The effect of the polymer molecular weight and the confinement are also addressed.

1. in
nanocomposites
than in the bulk
Vyron Sotirios Petrakis,1 Anastassia N. Rissanou,2, Vagelis Harmandaris,3
Hellen Papananou,1,4 Kiriaki Chrissopoulou,4 and Spiros H. Anastasiadis1,4
1Department of Chemistry, University of Crete, Heraklion, Greece.
2Crete Center for Quantum Complexity and Nanotechnology (CCQCN), Department of Physics, University of Crete, Heraklion, Crete, Greece.
3Department of Mathematics and Applied Mathematics, University of Crete, GR-71409, Heraklion, Crete, Greece.
4Institute of Electronic Structure and Laser - Foundation for Research and Technology Hellas, Heraklion, Greece.
The goal of the present work is to investigate
the effect of silica nanoparticles, SiO2, on the structural and conformational properties of poly(ethylene oxide), PEO in PEO / SiO2 systems. The study is highlighted
both through experiments and simulations whereas the effects of the polymer molecular weight and the confinement are addressed, as well.
Acknowledgements
PROENYL research project, Action
KRIPIS,
Structural and Conformational Properties of PEO/Silica
Nanocomposites through Simulations and Experiments
Simulations
PEO : 10-50 Monomeric units
PEO : Mw=100.000SiO2: R~2nm
SiO2: R~7nm
METHOD
Differential Scanning
Calorimetry (DSC)
Infrared Spectroscopy (ATR-FTIR)
280 300 320 340 360 380 400
1.00
1.02
1.04
1.06
1.08
1.10
1.12
1.14
10mer
50mer
10mer experiment
(g/cm
3
)
T(K)
Materials
280 300 320 340 360 380 400
15
16
17
18
50mer
Ree
T(K)
Rg
T(K)
280 300 320 340 360 380 400
35
40
45
Bulk Polymer
Hybrid System
10 20 30 40 50 60
0.0
0.5
1.0
1.5
(gr/cm
3
)
r(Å)
10mer 95%PEO - 5%SiO2
(wt)
20 25 30
0.96
1.04
1.12
1.20
1.28
1.36
1.44
1.52 T=285K
T=300K
T=318K
T=330K
T=400K
10 20 30 40
0.0
0.5
1.0
1.5
50mer at T=400K
30 % wt
57 % wt
(gr/cm
3
)
r(Å)
-200 -100 0 100 200
0.0
0.4
0.8
1.2
1.6
2.0
distributionofOCCO

o
50mer 43%PEO-57%SiO2
(wt) OCCO
-200 -100 0 100 200
0.0
0.4
0.8
1.2
1.6
2.0
COCC330K
350K
370K
400K
distributionofCOCC

o
0.78
0.81
0.84
0.87
0.90
50mer 67% PEO-33% SiO2
(wt)
50mer 57% PEO-43% SiO2
(wt)
Bulk
Gauche/Total
300 325 350 375 400
0.15
0.18
0.21
0.24
0.27
COCC
T(K)
Gauche/Total
OCCO
300 325 350 375 400
0.87
0.90
0.93
0.96
0.99
50mer 67% PEO-33% SiO2
(wt)
50mer 57% PEO-43% SiO2
(wt)
Rg
/Rgbulk
T(K)
Inhomogeneous
density profile.
Bulk regime is not
reached in
strongly confined
systems.
Density higher
close to the SiO2
surface.
Gauche population
OCCO
COCC
as T
Gauche population
1200 1220 1240 1260 1280 1300 1320 1340 1360 1380
100% PEO
T=393 K
T=383 K
T=373 K
T=363 K
T=353 K
T=343 K
Intensity(a.u.)
27% PEO-73% SiO2
(wt)
C-C
trans
C-C
gauche
Wavenumbers (cm
-1
)
-50 0 50 100
PEO Content
% (wt)
18%
Temperature (
o
C)
Cp
(calgr
-1o
C
-1
)
100%
27%
Polymer chains confined between SiO2
particles or close to its surfaces
crystallize differently than the bulk
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
0
20
40
60
80
100
%ofPEOvolumewhichisin
a1nmshellaroundtheparticle
PEO (wt)
Why?
Large amount of chains are very
close to the inorganic walls
and confined between them and
have no space to crystallize
Crystalline
region
Analysis
70 80 90 100 110 120
0.4
0.5
0.6
0.7
0.8
0.9
1.0
Temperature (
o
C)
I
gauce
/I
total
100% PEO
86% PEO (vol)
43% PEO (vol)
31% PEO (vol)
Gauche population
in
nanocomposites
than in the
bulk
No effect of
temperature
DSC
FTIR-ATR
High polymer contents behave like the bulk
Low polymer contents behave differently due to confinement
Crystalline
regions
Amorphous
region
Are the confined
amorphous regions the same
as the amorphous bulk?
Polymer more
dense near
the SiO2 surface
C-C Conformations
Gauche population
in nanocomposites
than in the bulk
Decrease of Rg-values of polymer in
the nanocomposite compared to the
corresponding bulk values. Indication
of helical conformations!
Experimental
METHOD
Atomistic Molecular Dynamics simulations (MD). PEO was
represented by a united atom model and interactions were
described by a slightly modified TraPPE force field.
Degree of
Confinement
Degree of
Confinement
d/Rg = 0.2-20
d
d
d/Rg = 0.2-0.8
Temperature dependence of density. Temperature dependence
of chain dimensions.
Gauche increase
degree of confinement
both in simulation
and experiment.