epubs.surrey.ac.ukepubs.surrey.ac.uk/845996/2/Enhanced Water Barrier... · Web viewSUPPORTING INFORMATION Enhanced Water Barrier Properties of Surfactant-Free Polymer Films Obtained

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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