monitoring nanostructural transformations during film
TRANSCRIPT
Monitoring nanostructural transformations
during film formation in waterborne coatings
using variable angle X-ray scattering
APOSTOLOS VAGIAS, GIUSEPPE PORTALE
Zernike Institute for Advanced Materials (ZIAM)
Rijksuniversiteit Groningen (RUG)
International Micro Nano Conference, December 12th 2018
“Barrier property” of coatings
❑ Solvents can unavoidably penetrate through structural defects in
applied materials.
❑ Optimal coatings needed to prevent solvent penetration
Features outlining coating quality
https://www.shutterstock.com/de 1Keddie J. et al., ACS Appl. Mater. Interfaces, 2018, 8 (50)
Structural heterogeneities in coatings
Stratification =
“out-of-plane”
heterogeneities
2
Keddie J. et al.,
ACS Appl. Mater. Interfaces,
2016, 8 (50)
Junker P. et al.,
Nature 2011, 476 (308)
Coffee-stain effect = “in-plane” inhomogeneities
https://i.ytimg.com
❑ Latex =aqueous dispersion of polymer colloids
❑ Challenging to realize uniform films (polymer incompatibility)
❑ Defects reported down to micron-sized range (not in nanoscale)
Keddie, J. L. Film Formation of Latex. Mater. Sci. Eng. R Rep. 1997, 21 (3), 101–170.
SubstrateSubstrate Substrate Substrate
Latex suspension Particle packingPacking of
deformed particlesMechanically stable
film
Water content
Stage 1 Stage 2 Stage 3
Polymer Interdiffusion (T > Tg)
Drying time
Waterborne coatings and latex film formation
3
Possibility for defects
Can probe buried nanoscopic objects at interfaces
Grazing Incidence SAXS (GISAXS)
Surface sensitive for structures
at interfaces (minimum
penetration depth, ξp~10 nm)High scattering intensity ideal
for in-situ study
2-D detectors probe at once
lateral & normal order
http://www.gisaxs.de/theory2.html (Andreas Meyer, Uni Hamburg) 4
z
yx
X-rays
ai Substrate
T
R
af
Spreading
direction
kf (= scattered
X-ray wavevector)
0.10 0.15 0.20
10-2
10-1
100
101
p (
m)
a i (
o)
ac (critical angle
of the polymer)
Depth (ξp)-resolution of GISAXS
5
Substrate (glass)
ki (= incident
X-ray wavevector)
Calculations of ξp (αi)
vs. αi, for polyacrylates
(αc ~0.1°)
Polymer Film
kiki
kf kf
Materials (from DSM)Three different polyacrylic (PA) samples investigated
6
Type PA-662 PA-661 PA-660
Hardness hard (Tg ~80° C)
soft (Tg ~4° C)
2 phases:70 % (wt)
soft / 30 % (wt) hard
Solids (%) 39.1 39.1 39.0
pH 8.1 6.8 7.0Particle size (nm), DLS
100 ±3 107 ±1 106±3
PA-662
Non- film forming coating (TFFT < Tg)
PA-660
Film forming coating (TFFT > Tg)
Synchrotron X-rays
Dutch-Belgian Beam Line
DUBBLE-BM26B
(ESRF, Grenoble)
Coating preparation and beamlines
7
MINA: Multipurpose
X-ray Instrument for
Nanostructure Analysis
(University of Groningen)
(T): Transmission(R): Refraction(S): Reflection
-0.15 -0.10 -0.05 0.00 0.05 0.10 0.15
I(q
y)
(a.u
.)qy (nm-1)
(ai =0.1o)
GISAXS data analysis
8
qy*= 2·π/d* (=0.08 nm -1)
Intensity cuts I(qy) vs. qy at qz=constant
kf
ki αi
z
yx
d* (~80 nm) : heterogeneity spacing
Depth-resolved GISAXS (PA-660)
❑(Strong) Scattering is lost at ξp ~15 μm
❑Crossover transition at ξp ~10 μm (𝛼𝑖 = 0.15°) from
structure (heterogeneities) to structure-less region
𝛼𝑖= 0° 𝛼𝑖 = 0.1°(ξp ~0.5 μm)
𝛼𝑖 = 0.2°(ξp ~15 μm)
𝛼𝑖 = 0.35°(ξp ~ 28 μm)
𝛼𝑖 = 0.15°(ξp ~10 μm)
𝛼𝑖 = 0.5°(ξp ~ 42 μm)
9
Tqy
qz RRT T
𝛼𝑖
RT
R
T
S
SR
T
S
S
Vagias A. et al, submitted to ACS Applied Polymer Materials (under review)
Depth-resolved GISAXS patterns
10
PA-661
PA-660
❑(Strong) Scattering
lost at ξp ~10-15 μm
❑Top film layer with
heterogeneities
❑Lower film layer:
no heterogeneities
❑PA-662: Control case
with strong contrast (non
film-forming) PA-662
Vagias A. et al, submitted to ACS Applied Polymer Materials (under review)
GISAXS I(qy) vs. qy cuts: proposed nanostructures
11
Sideview
-0.30 -0.15 0.00 0.15 0.300.0
2.0x10-4
4.0x10-4
6.0x10-4
8.0x10-4
I(q
y)
(a.u
.)
qy (nm-1)
ai=0.10o
ai=0.15o
ai=0.21o
ai=0.37o
glass (ai=0.37o)
increasing ai
q*
PA-660 (multiphase) PA-661 (soft) PA-662 (hard)
-0.45 -0.30 -0.15 0.00 0.15 0.30 0.45
10-3
10-2
10-1
q*
q*
I(q
y)
(counts
/s)
qy (nm-1)
ai=0.10o
ai=0.17o
ai=0.29o
ai=0.43o
ai=0.43o (S)
increasing ai
q*
-0.30 -0.15 0.00 0.15 0.300.0
2.0x10-4
4.0x10-4
6.0x10-4
8.0x10-4
I(q
y)
(a.u
.)
qy (nm-1)
ai=0.1o
ai=0.16o
ai=0.22o
ai=0.37o
glass (ai=0.37o)
increasing ai
q*
Quantifying GISAXS analysis:
nanostructural heterogeneities
12
Sideview
Topview
d*(~80 nm)
d*(~80 nm)
ddomain(~5-10 nm)ddomain(~20 nm)
PA-660 (multiphase) PA-661 (soft) PA-662 (hard)
ddomain(~60 nm)
Vagias A. et al, submitted to ACS Applied Polymer Materials (under review)
0 5 10 15 20 25 30 35 40
0.02
0.04
0.06
Film
weig
ht
(g)
time (min)
In-situ GISAXS (𝛼𝑖 = 0.15°):PA-660
At tdrying =4’ : “colloidal suspension”-like (4’)
At tdrying > 9’: partially coalesced particles
Insets: time after slot die coating (tdrying)
13
T
qz
qy
t drying= 4’ 8’
RT
S
9’
RT
S
20’
RT
S
z
yx
Macroscopic drying kinetics
Vagias A. et al. (in preparation)
0 2 4 6 872
76
80
84
88 PA-660
PA-661
PA-662
d* (
nm
)
tdrying (min)
Nanostructural transformations during drying
❑ (d*) decreases with tdrying more strongly for PA-660
❑ Nanostructural evolution during drying can be quantified 14
0 5 10 15 2010-6
10-5
10-4
10-3 PA-660
PA-661
PA-662
<a
ve
rag
e p
ixe
l in
ten
sit
y (
a.u
.)>
tdrying (min)
Vagias A. et al. (in preparation)
Conclusions GISAXS is an optimal technique to probe:
❑Rich unexplored nanostructural transformations during film drying
❑The quality of (dry) waterborne coatings at the nanoscale
(submicrometric heterogeneities)
❑depth-dependent stratification in the films
15
Perspectives
To expand the successful ex-situ/ in-situ options:
❑ couple with laser speckle imaging (structure-dynamics) (Prof. J. Sprakel, WUR) / environmental effects (airflow, humidity, aging)
❑ different chemistries (also polyurethanes, blends) / substrates (metal, wood) successfully assessed
❑ Biomedicine: polyhydroxyurethane
(PHU-QAS) dental coatings
(UMCG, P. Sharma group) 16
Untreated Ion-exchanged
Acknowledgements
• DPI for funding INCOAT (914ft16)
• DSM Coating Resins (sample synthesis, cross-sectional AFM)
• D. Hermida-Merino (DUBBLE BM26B@ESRF)
• Gert H. ten Brink (RUG)
• ALL OF YOU for your attention! 17
Monitoring nanostructural transformations
during film formation in waterborne coatings
using variable angle X-ray scattering
APOSTOLOS VAGIAS, GIUSEPPE PORTALE
Zernike Institute for Advanced Materials (ZIAM)
Rijksuniversiteit Groningen (RUG)
18
SAXS in suspensions: NP shape/size
19
SAXS modeling
𝐼 𝑞 = Δ𝜌2𝑉න𝑅1
𝑅2
𝑆 𝑞 𝑃 𝑞, 𝑅 𝐷 𝑅 𝑑𝑅
❑ Polydisperse ensemble of spheres
❑ S(q): local monodisperse approximation
20
10-3
10-2
10-1
100
0.1 1
0
0.05
0.1
0.2
0.4
I(q
)
q (nm-1
)
q-4
~q-4
Dense colloidal suspensions
S(q) simulations for liquid-
like systems at different
volume fractions φ
The peak (q*=2·π/d*) accounts
for spatial correlation between
particles (=spacing d*)
𝐼 𝑞 =𝑁
𝑉𝑉𝑝𝑎𝑟𝑡2 𝑃 𝑞 𝑆(𝑞)
q (nm-1)
(φ)
q*
d*
21
SAXS structure factor (S(q))
0.1 1
10-5
10-4
10-3
10-2
10-1
40% wt
I(q
)
q (nm-1)
5% wt
1% wt
water
dilution
SAXS in PA suspensions
❑ PA-660: (dSAXS~96nm, dDLS~106 nm)
PA-660
qmin· RNP= 4.48
(RNP , NP radius)
q* (from S(q))
22
SAXS in aqueous PA-660 suspensions
23
Appendix-
Modeling of SAXS curves in suspension
0.1 0.2 0.3 0.4 0.5 0.60.70.810-5
10-4
10-3
10-2
10-1
100
101
I*(q
) (c
ou
nts
/s)
q (nm-1)
PA-660
PA-661
PA-662
PA-661, PA-662: Polydisperse particle model
PA-660: (Polydisperse) Core-shell particle model
Monodisperse model
❑ Particle radii: PA661 (45nm) > PA662 (41nm) > PA660 (40nm)
❑ Very different nanostructure morphology in films vs. suspensions
for PA660 and PA661. PA662 shows absence of deformability!
-0.6 -0.4 -0.2 0.0 0.2 0.4 0.610-6
10-5
10-4
10-3
10-2
10-1
I(q
y)
(a.u
.)
qy (nm-1)
PA660
PA661
PA662
10-8
10-7
10-6
10-5
10-4
10-3
10-2
10-1GISAXS
PA660
PA661
PA662
SAXS
0.1 0.2 0.3 0.410-5
10-4
10-3
10-2
10-1
SAXS in aqueous suspensions
q*
q*
PA660
PA661
PA662
I* (q)
(counts
/s)
q (nm-1)
q*
Suspensions (left) vs. coatings (right)
24
25
Appendix- Features on GISAXS patterns
Depth-resolved GISAXS (PA systems)
❑ Peak intensity: PA-662> PA-660 > PA-661
❑ Different form factor and nature of scattering in hard PA-662 coating 26
-0.30 -0.15 0.00 0.15 0.300.0
2.0x10-4
4.0x10-4
6.0x10-4
8.0x10-4
I(q
y)
(a.u
.)
qy (nm-1)
ai=0.10o
ai=0.15o
ai=0.21o
ai=0.37o
glass (ai=0.37o)
increasing ai
q*
-0.30 -0.15 0.00 0.15 0.300.0
2.0x10-4
4.0x10-4
6.0x10-4
8.0x10-4
I(q
y)
(a.u
.)qy (nm-1)
ai=0.1o
ai=0.16o
ai=0.22o
ai=0.37o
glass (ai=0.37o)
increasing ai
q*
-0.30 -0.15 0.00 0.15 0.30
10-3
10-2
10-1
q*
q*
I(q
y)
(a.u
.)
qy (nm-1)
ai=0.10o
ai=0.17o
ai=0.29o
ai=0.43o
increasing ai
q*
PA-660 PA-661 PA-662
Depth-resolved GISAXS (PA-660)
❑(Strong) Scattering is lost at ξp ~10-15 μm
❑Top layer with heterogeneities 27
0.1 0.2 0.3 0.4
75
80
85
90
95
(a)
30m, PA660
7m, PA660
30m, PA661
d*(a
i) (
nm
)
ai (o)
0.1 0.2 0.3 0.4
0.0
2.0x10-6
4.0x10-6
6.0x10-6
8.0x10-6
0.0
2.0x10-5
4.0x10-5
6.0x10-5
8.0x10-5
30um, PA660
7um, PA660 30um, PA661
A (a
i) (
a.u
.)ai (
o)
I pix
el (a
i) (
co
un
t/ [
pix
els])
(b)
Cross-sectional AFM (at DSM)
Cross-sectional AFM corroborates stratification!
Rq = 3.0 nm
1 μm
Rq = 7.5 nmRq = 3.0 nmglass air
5 μm
28
GISAXS simulations
29
Randomly packed
cylinder model
Randomly packed
hard sphere model
-0.4 -0.2 0.0 0.2 0.40.0
2.0x10-2
4.0x10-2
6.0x10-2
8.0x10-2
1.0x10-1
qy (nm-1)
PA662
fit
(a)
-0.4 -0.2 0.0 0.2 0.40.0
5.0x10-5
1.0x10-4
1.5x10-4
2.0x10-4
(b)
qy (nm-1)
PA661
fit
-0.4 -0.2 0.0 0.2 0.40.0
1.0x10-4
2.0x10-4
3.0x10-4
4.0x10-4
5.0x10-4
6.0x10-4
(c)
qy (nm-1)
PA660
fit
Randomly packed
cylinder model
Object shape I(0) Dy (nm) dy h
PA662 (hard) Sphere 1.1 x 10-4 60 70 0.45
PA661 (soft) Cylinder 3.0 x 10-5 8 72 0.40
PA660 (multiphase) Cylinder 1.0 x 10-7 16 70 0.40
The local monodisperse approximation was used to take into account for the object size polydispersity described by
a log-normal distribution function. The structure factor was in all cases a Percus-Yevick function.9 The fits were
achieved using the FitGISAXS program.10
-0.4 -0.2 0.0 0.2 0.4
1000
2000
3000
4000
5000
I(q
y)
(a.u
.)
qy (nm-1)
fresh
aged (1 year)
T-annealed
after 1year aging
❑ Tannealing (= 150 °C) > Tg,DMTA,hard (~105 °C)
❑ Annealing smears out nanostructural
heterogeneities
Aging effects (𝛼𝑖 = 0.1°)
30
Fresh, non-annealedAged, non-annealed Aged, annealed
❑ T-annealing at 150 °C> Tg,DMTA,hard (~105 °C)
❑ T-annealing smears out the nanostructure
(heterogeneities evidenced by GISAXS)
Edge effects (𝛼𝑖 = 0.2°)
qz
31
qy