SUPPORTING INFORMATION
Enhanced Water Barrier Properties of Surfactant-
Free Polymer Films Obtained by MacroRAFT-
Mediated Emulsion Polymerization
Ignacio Martín-Fabiani,1, * Jennifer Lesage de la Haye,2 Malin Schulz,3 Yang Liu,3,4 Michelle
Lee,5 Brendan Duffy,5 Franck D’Agosto,2 Muriel Lansalot2 and Joseph L. Keddie3
1 Department of Materials, Loughborough University, Loughborough LE11 3TU,
Leicestershire, United Kingdom
2 Univ Lyon, Université Claude Bernard Lyon 1, CPE Lyon, CNRS, UMR 5265, Chemistry,
Catalysis, Polymers and Processes (C2P2), 43 Bd du 11 Novembre 1918, 69616
Villeurbanne, France
3 Department of Physics, University of Surrey, Guildford GU2 7XH, United Kingdom
4 Department of Chemistry, University of Toronto, 80 St. George St., Toronto ON, M5S 3H6,
Canada
5 CREST, FOCAS Research Institute, Dublin Institute of Technology, Kevin Street, Dublin 8,
Republic of Ireland
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Polymer Characterization Methods
Nuclear magnetic resonance (NMR). The presence of residual monomer and the final conversion of
PSSNa-1 were determined by 1H NMR spectroscopy in CDCl3 at room temperature (BrukerDRX
300). N,N-dimethylformamide (DMF) was added to the sample as an internal reference. The
conversion was calculated by the relative integration of the proton of the internal reference (DMF) at
8.0 ppm and the vinylic protons of BA (at 5.8, 6.0 and 6.3 ppm).
Size exclusion chromatography (SEC-THF). Measurements were performed in THF at 40 °C at a flow
rate of 1 mL min-1. All the polymers containing MAA units (PMAA-CTPPA macroRAFT agents)
were modified by methylation of the carboxylic acid groups using trimethylsilyl diazomethane. They
were analyzed at a concentration of ~4 mg mL-1 after filtration through a 0.45 μm pore-size
membrane. The separation was carried out on three columns from Malvern Instruments [PLgel Olexis
Guard (300 × 7.5 mm)]. The setup (Viscotek TDA305) was equipped with a refractive index (RI)
detector (λ = 670 nm). The number-average molar mass (Mn), the weight-average molar mass (Mw)
and the dispersity (Đ = Mw/Mn) were derived from the RI signal by a calibration curve based on
poly(methyl methacrylate) standards (PMMA from Polymer Laboratories).
Matrix assisted laser desorption ionization-time of flight mass spectrometry (MALDI-ToF MS). Mass
spectrum of the PSSNa-CTPPA macroRAFT agent was obtained using a MALDI-ToF Voyager-DE
Pro (Sciex) equipped with a nitrogen laser emitting at 337 nm with a 4 ns pulse duration. The
instrument was operated in negative reflector mode. The ions were accelerated to a final potential of
20 kV. The spectrum was the sum of 300 shots and an external mass calibration of mass analyzer was
used (a mixture of peptides, Sequazyme kit (Sciex)). The sample was dissolved in water at a 10 g L -1
concentration and mixed with α-cyano-4-hydroxycinnamic acid at a 10/1 (v/v) ratio. An aliquot of 1
µL of the resulting mixture was spotted on the MALDI sample plate and air-dried.
Dynamic light scattering (DLS). The particle size (intensity-based harmonic mean diameter, Dz) and
the dispersity of highly diluted samples (PDI) were measured by dynamic light scattering (DLS)
(NanoZS from Malvern Instruments). The data were collected at 173° using the fully automatic mode
of the Zetasizer system, and depending on the size distribution, either the monomodal cumulant
analysis or the CONTIN analysis was performed.
pH measurements. The pH values of the aqueous solutions were adjusted with a Mettler Toledo
SevenEasy pH-meter using a InLab Routine Pro electrode. The electrodes were calibrated with 4.01,
7.00, and 10.00 pH buffer solutions from Mettler Toledo.
Differential scanning calorimetry (DSC). Thermal characterizations were performed with a
differential scanning calorimetry, Mettler Toledo DSC 1, equipped with an auto-sampler and a 120
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thermocouples sensor. The temperature and the heat flow of the equipment were calibrated with
indium standard. All samples were accurately weighed (around 10 mg) and sealed in aluminum pans.
They were heated from -70 °C to +120 °C at 20 °C min-1 with an empty aluminum pan as reference.
Two successive heating and cooling were performed and only the second run was considered. Dry
nitrogen with a flow rate set at 30 mL min-1 was used as the purge gas. The glass transition
temperature (Tg) was measured at the midpoint. The STARe thermal analysis software was used for
the calculation.
Film Structure and Barrier Property Characterization
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Figure S1. Simultaneous (a) TGA and (b) DSC thermograms for various latex films after
immersion in water for 72 hours. In the DSC data, the peaks correspond to the temperatures
where there is the greatest rate of water evaporation. There is a corresponding mass loss at
these temperatures.
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Table S1. Geometric parameters obtained for the particles in the latex films through analysis
of the AFM images in Figure 3
Sample Dz
(nm)
Peak-to-
peak
distance,
a (nm)
Average
roughness
Ra (nm)Ra/ Dz Ra/a Strain,
(Dz – a)/Dz
m m/(1 – ) rPB
(nm)
PMAA-1 196 174 ± 15 69.2 0.35 0.40 0.112 0.64 0.72 89
PMAA-1.5 149 112 ± 23 6.1 0.04 0.05 0.248 0.64 0.85 50
MAA-1 742* 628 ± 10 45.1 0.06 0.07 0.154 0.74 0.87 229
MAA-1.5 630 542 ± 18 26.5 0.04 0.05 0.140 0.74 0.86 202
PSSNa-1 192 180 ± 15 33.6 0.17 0.19 0.062 0.64 0.68 93
* Number average, Dn, obtained via analysis of cryoTEM images (n = 50 particles), as
particle size is on the edge of the detection range of DLS instrument
(a) (b)
Figure S2. Definition of geometric parameters in latex films for (a) packed spherical particles
and (b) sintered particles.
Analysis of atomic force microscopy images. For close-packed hard spheres, the ratio of the
peak-to-valley height to the sphere diameter will be 0.5 and will fall toward zero over time
during sintering. In latex films, the ratio of the average surface roughness, Ra, over the z-
average particle size, Dz, can be used as an indicator of the extent of particle deformation in a
close-packed array of particles.1 Analysis of the AFM images in Figure 3 is presented in
Table S1. The Ra/Dz fraction is low (0.04-0.06) for the two MAA films and the PMAA-1.5
film. It is particularly high (0.40) for the PMAA-1 film. In this film, the particles are
randomly packed, which contributes to the film’s surface roughness.
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Dz
aao
In a packed array of mono-size spheres, the centre-to-centre spacing, a, for two
spheres in contact will be exactly the particle diameter. (See Figure S2a.) As the particles
deform under the action of surface energy reduction and capillary forces, the value of a will
decrease (Figure S2b). The unidirectional strain, , between the spheres is obtained from the
decrease in a divided by the initial distance of ao = Dz. That is, = (Dz – a)/Dz. From this
analysis, we see in Table S1 that the PMAA-1.5 particles have strained to a greater extent
than the other particles. Conserving volume and invoking a mean-field approach,2 the strain
in a packed bed of spheres can be related to the volume fraction of space filled as ϕ=ϕm
1−ε.
Here, m represents the volume fraction of spheres when they are first close-packed.
Crowley et al.3 have described the space-filling of deforming close-packed spheres
using a model of a polyhedral foam structure. The planes between neighboring particles meet
to form the Plateau borders with a radius of curvature of rPB. Spheres in an FCC close-packed
array will fill space by deforming into dodecahedra. The value of rPB approaches 0 as the
spheres deform into dodecahedra. In close-packed viscoelastic latex spheres, the deformation
takes an exceedingly long time to fill space. Most of the unfilled space is found in the voids
created by the Plateau borders where the edges of the dodecahedra meet. The volume of these
voids is proportional to rPB.
Following the derivation of Crowley et al.,3 it can be seen that for a given volume fraction of
filled space, spheres of a greater size will have a greater radius of curvature:
r PB=Dz
2 √(1−ϕ )0.34
Despite the approximations, we can use this equation to estimate the rPB in each latex film and
hence have some indication of the relative sizes of the intraparticle void size. From an
observation of the particle packing in the AFM images, we describe the MAA films as having
FCC packed particles, and hence we use m = 0.74. The particles in the PMAA and PSSNa
films appear randomly-packed, and we take m = 0.64.
The estimates of rPB are listed in Table S1. The calculations are not exact but provide
an indication of the differences in structures within the film. Although the amount of space
filling for the MAA-1 particles is the highest, because the original particles are the largest,
the size of the interparticle voids is estimated to be greatest. The PMAA-1 and the PSSNa-1
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films both have lower values of rPB, and the PMAA-1.5 presents the lowest value of all
studied samples.
The AFM images were obtained one day after film-casting, and their particle
deformation is incomplete. It will continue over time, and the deformation is accelerated at
higher temperatures.
References
Perez, E.; Lang, J. Flattening of Latex Film Surface: Theory and Experiments by Atomic
Force Microscopy. Macromolecules, 1999, 32, 1626-36.2 Routh, A.F.; Russel, W.B. A Process Model for Latex Film Formation: Limiting
Regimes for Individual Driving Forces. Langmuir, 1999, 15, 7762-7773.3 Crowley, T.L.; Sanderson, A.R.; Morrison, J.D.; Barry, M.D.; Morton-Jones, A.J.; Rennie,
A.R. Formation of Bilayers and Plateau Borders during the Drying of Film-Forming Latices
As Investigated by Small-Angle Neutron Scattering. Langmuir, 1992, 8, 2110-2123.
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Figure S3. Water sorption isotherms showing the experimental data points and their fitting using the GAB (red line), BET (green line) and ENSIC (blue line) models for various latex films: (a) MAA-1, (b) PMAA-1, (c) PMAA-1.5, (d) MAA-1.5, and (e) PSSNa-1.
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Figure S4. Digital photographs of formulated paints made with the PSSNa surfactant-free latex (a) during accelerated weathering test after 100 h of exposure; and (b) at the end of the weathering test after 750 h of exposure. Small corrosion spots (appearing as the brown specks) developed within the first 100 h of accelerated weathering.
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