Morphology of Polymer/Clay Latex Particles Synthesized by Miniemulsion Polymerization: Modeling and...

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Morphology of Polymer/Clay Latex ParticlesSynthesized by Miniemulsion Polymerization:Modeling and Experimental Results

Matej Micusık, Audrey Bonnefond, Yuri Reyes, Agnes Bogner,Laurent Chazeau, Christopher Plummer, Maria Paulis, Jose Ramon Leiza*

BA/MMA (90:10wt.-%) were copolymerized in the presence of two different organomodifiedclays (C30B and CMA16) and 1.6–2.6wbm.-% surfactants. The effect of the compatibility of theorganoclay in the monomer mixture on the morphology of hybrid polymer/clay particles wasdetermined using TEM. The resulting morphologies were compared with the prediction of aMonte-Carlo simulation that determinedthe equilibriummorphology ofmonomer/clay hybrid miniemulsion droplets. Themodel predicted encapsulated morpho-logies only when the organoclay presentedlow clay/monomer and high clay/waterinterfacial tensions. C30B and CMA16 didnot fulfill these conditions and provideda preferential surface location of theplatelets on the polymer/water inter-phase as predicted by the model.

J. R. Leiza, M. Micusık, A. Bonnefond, Y. Reyes, M. PaulisInstitute for Polymer Materials, POLYMAT, Dpto. de QuımicaAplicada, Facultad de Ciencias Quımicas, University of the BasqueCountry, Joxe Mari Korta zentroa, Tolosa Etorbidea 72, 20018Donostia-San Sebastian, SpainFax: þ34 943 01 7065; E-mail: [email protected]. MicusıkOn leave from Slovak Academy of Sciences, Polymer Institute,Department of Composite Materials, Dubravska cesta 9, 842 36Bratislava, SlovakiaA. Bogner, L. ChazeauMATEIS, INSA-Lyon, 7 avenue Jean Capelle, 69621 Villeurbanne,FranceC. PlummerLaboratoire de Technologie des Composites et Polymeres (LTC),Ecole Federale Polytechnique de Lausanne (EPFL), Station 12, 1015Lausanne, Switzerland

Macromol. React. Eng. 2010, 4, 000–000

� 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Early View Publication; these are NOT the

Introduction

In composite science a huge effort has been devoted to

exfoliate the layered silicate clay on the level of individual

platelets throughout the polymeric matrix,[1–4] and in this

way tune the properties of the polymeric matrix with a low

load of clay, exploiting the enormous interfacial area after

exfoliation. In the last two decades different routes to

prepare polymer/clay nanocomposites (PCNs) have been

developed. In order to synthesize waterborne PCNs emul-

sion polymerization processes have been preferentially

used to incorporate clay platelets into the polymer

matrix.[5–11] Other related techniques such as miniemul-

sion,[12–16] suspension,[17] and microemulsion[18,19] poly-

merization have also been reported. In addition to the

different polymerization techniques employed, several

DOI: 10.1002/mren.200900084 1

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M. Micusık et al.

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types of clays, both synthetic (laponite, hectorite, gibbsite,

etc.), and natural (montmorillonite, hectorite, bentonite,

etc.) have been used with different degrees of modification,

if any. The goal in plenty of the works was just to exfoliate

the clay platelets in the polymer matrix. Other works, in

addition to the exfoliation of the platelets in the polymer

matrix, aimed at controlling the morphology of the hybrid

polymer/clay particles dispersed in water and tried to

achieve encapsulation of the clay platelets inside the

polymer particles.

Encapsulation of synthetic clay (laponite, gibbsite, and

saponite) has been recently reported.[20–23] Mellon[22] has

doubly modified laponite using a cationic surfactant to

hydrophobize the surface and a reactive silane to modify

the edges. The resulting hydrophobized clay was then

polymerized by miniemulsion polymerization of methyl

methacrylate (MMA)/ butyl acrylate (BA) at relatively low

solids content (SC, �20 wt.-%) to obtain encapsulated

laponite polymer particles. Tong and Deng[23] have also

shown clear evidence of the encapsulation of organosapo-

nite in polystyrene polymer particles synthesized by

miniemulsion polymerization. However, latexes with low

SC and large amounts of nonionic surfactants (9 weight

based on monomer(wbm).-%) were employed to obtain

stable latexes. More recently, Ali et al.[21] have encapsulated

gibbsite clay platelets by starved feed semibatch emulsion

polymerization by adsorbing at the positively charged

surface of the gibbsite platelets amphiphilic living rever-

sible addition/fragmentation chain transfer (RAFT) copo-

lymers of butyl acrylate (BA) and acrylic acid. The process

can be seen as a seeded semibatch polymerization where

the seed particles are the gibbsite platelets stabilized by

negatively charged living copolymers. The drawback of the

approach is that the stability provided by these copolymers

is weak and that the molecular weight of the polymer

synthesized is very low, due to the controlled nature of the

polymerization and hence the mechanical properties would

be strongly affected.

On the other hand, encapsulation of natural montmor-

illonite (MMT) clay in polymer particles by either emulsion

or miniemulsion polymerization has been elusive and in

most of the cases armored or surface location of the clay

platelets have been achieved.[16,24,25] However, Mirzataheri

et al.[26] claimed that MMT platelets were encapsulated

during the miniemulsion polymerization of styrene/butyl

acrylate (S/BA) in the presence of commercial organoclay

Cloisite 30B (C30B) using a mixture of anionic (sodium

dodecylsulfate) and nonionic (Span 80) surfactants. Boua-

nani et al.[27] claimed partial encapsulation of MMT

platelets in the miniemulsion polymerization of the

1,3,5-trimethyl-1,3,5-bis(3,3,3-trifluoropropyl)cyclotrisiloxane

monomer using a mixture of cationic and nonionic

surfactant and KOH as an initiator. In both cases the proofs



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of encapsulation were not sound. Transmission electron

microscopy (TEM) images were at low resolution and

platelet location was hardly recognized. A better example of

encapsulation of MMT was provided by Voorn et al.[28] The

authors modified the MMT platelet by the edges using a

reactive silane providing hydrophobicity and functionali-

zation to the clay. The modified clays were partially

encapsulated in polymer particles by polymerizing MMA

in starved feed surfactant free emulsion polymerization at

very low SC (<8 wt.-%). Although the authors showed clear

TEM evidence of the encapsulation in dumbbell-like

particles, the scanning electron microscopy (SEM) micro-

graph presented a large fraction of particles with no clay

at all.

In order to understand why did MMT clay platelets

preferentially locate at the surface of polymer particles, in

this work we have developed a simulation to predict the

morphology of hybrid monomer/clay miniemulsion

droplets with organoclays of different nature. In addition,

we have synthesized waterborne acrylic polymer/clay

adhesive nanocomposites by miniemulsion polymeriza-

tion using two organically modified clays with different

degrees of compatibility with the comonomer system used

(BA/MMA¼ 90:10). A commercial organomontmorillonite

(C30B) and in-house synthesized Cloisite MA16 (CMA16)

that was produced by cationic exchange of sodium cation in

Cloisite-Na with a cationic long alkyl chain acrylate

monomer were used. The morphologies of the hybrid latex

particles, the morphology of the nanocomposite polymer

films, the microstructure of the polymer and the adhesive

properties were analyzed and the results discussed in terms

of the thermodynamic equilibrium morphologies predicted

from the Monte-Carlo simulation.

Experimental Part

Materials

Commercial natural and organomodified clay, Cloisite-Na and

C30B [where methyl-bis-2-hydroxyethyltallow(�65% C18; �30%

C16; �5% C14)ammonium chloride was used as organomodifier]

were provided by Southern Clay Products Inc. (Texas, USA). Cloisite-

Na has a cationic exchange capacity of 92.6 mequiv. per 100 g clay

and its X-ray diffraction (XRD) analysis shows that the interlayer

space is 1.15 nm. MMA and BA (Quimidroga, Spain) were used as

monomers. As anionic surfactant Dowfax2A1 (Dow, USA) and as

nonionic surfactant Disponil AFX 4060 (Cognis, Germany), were

used. Stearyl acrylate (SA, Sigma-Aldrich) was used as a co-

stabilizer. Azoisobutyronitrile (AIBN), potassium persulfate (KPS),

and 4,4’ azobis(4-cyanopentanoic acid) (V501, Sigma-Aldrich,

Germany) were used as initiators. (2-Methacryloylethyl)hexade-

cyldimethylammonium bromide (MA16) was synthesized as

shown elsewhere.[16] All materials were used as received.

DOI: 10.1002/mren.200900084

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Morphology of Polymer/Clay Latex Particles Synthesized by Miniemulsion . . .

Table 1. Formulation to prepare miniemulsions containing30wt.-% SC.

Component Amount Content

g wbm.-%

oil phase

BA 135 90

MMA 15 10

SA 4.5 3

organoclay 1.5–4.5 1–3

aqueous phase

anionic surfactant 1.5–3 1–2

nonionic surfactant 0–0.9 0–0.6

total surfactant 2.4–3.9 1.6–2.6

H2O 350 233.3

Miniemulsion Polymerization with Organically

Modified Clays

Preparation of Cloisite MA16 (CMA16) Organoclay

1.1 mequiv. of MA16 per gram of Cloisite-Na were used for cationic

exchange with Naþ. MA16 was dissolved in distilled water, and

then continuously added dropwise to the clay dispersion that was

being stirred at 25 8C. The cationic exchange was carried out at 25 8Cfor 6 h. Afterward, the CMA16 clay was filtrated and washed several

times with distilled water (until the conductivity of the filtrated

solution reached the conductivity of distilled H2O) in order to wash

off the possible adsorbed MA16, and then dried in a vacuum oven at

room temperature for 24 h.

Miniemulsion Polymerization

The miniemulsions were prepared using 500 mL agitated glass

reactors. A typical formulation employed in the polymerization is

displayed in Table 1. The oil phase was prepared by dissolving the

costabilizer SA and the organically modified clay in the monomers

(BA/MMA¼ 90:10 wt.-%). This mixture was stirred for 15 min at

1 000 rpm with a magnetic stirrer. The aqueous phase was prepared

by dissolving the emulsifier in water. As emulsifier anionic Dowfax

2A1 or the combination of nonionic Disponil AFX4060 and Dowfax

2A1 was used. Both phases (aqueous and oil phase) were brought

together and mixed for 15 min at 1 000 rpm. The dispersion was

sonicated using a Branson Sonifier 450 (operating at amplitude

�118mm and 80% duty cycle) for 15 min in an ice bath and under

magnetic stirring. The latexes, with SC of 30 wt.-% were synthesized

batchwise. The miniemulsion prepared as above was charged into

the jacketed reactor and the temperature rose to 70 8C. Water

soluble KPS, V501, or oil-soluble AIBN initiators were used.

Characterization Techniques

The organic content of organomodified clay was studied by

thermogravimetric analysis (TGA). To perform the TGA analysis the




sample was heated from 0 to 800 8C with a heating rate of

10 8C �min�1 in the nitrogen atmosphere using a Thermogravi-

metric Analyzer model Q500 (TA Instruments).

The static contact angle (CA) measurements were performed on

pressed organoclay disks with distilled water, using a goniometer

OCA 20 (DataPhysics Instruments GmbH), in air under controlled

environment (23 8C and 55% humidity).

The dispersion state of organoclays in monomer mixture was

studied by absorption at l¼ 401 nm using UV-Vis spectrometer

Spectronic Genesys 5 (Milton Roy Comp.)

Polymer particle and monomer droplet size distributions were

measured by dynamic light scattering (DLS) using a Zetasizer Nano

Series (Malvern Instruments Ltd.). For this analysis, a fraction of the

latex (or miniemulsion) was diluted with deionized water

(saturated with monomers in the case of miniemulsion droplet

size measurement). The reported average particle size (droplet size)

values represent an average of two repeated measurements.

The stability of miniemulsions was studied by measuring the

backscattering light at 60 8C using a Turbiscan Lab expert device

(Formulaction SA).

The morphology of latex particles and films was studied by

means of a TEM. The latex samples were analyzed by negative

staining with Tecnai G2 20 Twin device at 200 kV (FEI Electron

Microscopes). Latexes were diluted up to 5 mL in deionized water to

predetermined concentration depending on particle size, and

stained with 0.5 mL of a 4 wt.-% aqueous solution of phospho-

tungstic acid. Samples were allowed to react during 7 d with the

stain. The dried films were cryosectioned with a Reichert-Jung

Ultracut E cryoultramicrotome at �70 8C with a Diatome 458diamond knife, and the observations were made with a Philips

CM10 TEM operated at 80 kV.

Wet-STEM experiment was performed in an environmental

scanning electron microscope (ESEM) FEG XL 30 (FEI Electron

Microscopes) operating at 30 kV in low-vacuum mode. The detector

usually used for backscattered electrons collection is placed just

below the sample, and in such a way that it collects scattered

electrons with both of the diodes, resulting in a kind of annular

dark-field mode. Schematically, it corresponds to brighter areas for

high atomic number elements and high thickness, i.e., an inverse

mass-thickness contrast. Wet-STEM is a recent imaging mode

developed in ESEM: operating with the STEM mode in ESEM enables

the observation of samples in water in its liquid state in

transmission imaging conditions. This new imaging mode is

described in details in ref.[29]

Wide-angle X-ray diffraction (WAXD) analyses were performed

on a D8 Advance (Bruker) (Cu Ka radiation with l¼0.154056 nm) at

room temperature. The range of the diffraction angles was 2u¼2–

128at a scanning rate of 0.018 � (5 s)�1. The (001) basal spacing of the

clay (d) was calculated using the Bragg equation.

The films used for the adhesive tests were made on a treated

poly(propylene) substrate.

The shear tests were done using a Binder oven (Sneep Industries),

at a temperature of 30 8C. The tack tests were carried out using the

rolling ball technique.[30] Each measurement was repeated eight

times for each latex.

The gel fractions of the samples were measured via conventional

Soxhlet extraction, using tetrahydrofuran (THF) as the solvent and

calculated as shown elsewhere.[31]

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M. Micusık et al.

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Results and Discussion

Predicting the Morphology of Hybrid Monomer/ClayMiniemulsion Droplets

As discussed in the introduction, there is already plenty of

experimental evidence showing that armored polymer

particles are preferentially achieved when organically

modified clays are used in in situ emulsion or miniemulsion

polymerization. Encapsulation of MMT platelets has shown

to be elusive no matter the type of hydrophobization or

modification of the clay employed.

The equilibrium morphology of clay platelets dispersed

in a polymer melt has been widely studied experimentally

and also by theoretical approaches. The model developed by

Lyatskaya and Balazs[32] has been employed to determine

the phase behavior of PCNs, under different conditions.

However, as far as the authors are aware there are no

reports addressing the equilibrium morphologies of mono-

mer (polymer)/clay hybrid droplets (particles).

The particle morphology depends on the interplay

between thermodynamic and kinetics. Thermodynamic

determines the particle morphology at equilibrium, accord-

ing to the minimum surface free energy. Kinetic factors

control whether the particle reaches the equilibrium

morphology or remains at a metastable (kinetically stable)

morphology. Since miniemulsion polymerization is the most

appropriate technique to incorporate hydrophobic species

into polymer particles[33] and organically modified clay

platelets are considered (hydrophobic in nature), the predic-

tion of the equilibrium morphology of monomer/organoclay

platelets miniemulsion droplets was considered in this work.

A standard canonical Monte-Carlo simulation was

carried out[34] to determine the morphology of hybrid

monomer/clay droplets. The simulation was carried in two-

dimensions for better visualization of the results and

because of computational efficiency. The three components

in the system were water (W), monomer (M), and clay (C).

The water and monomer phases were simulated by a

collection of individual disks of diameter sW¼ sM¼ 1, that

was considered as the simulation unit of length. The clay

platelets were modeled by a rigid chain of disks; each disk of

the clay chain had unitary diameter, which was also the

distance between the centers of two adjacent beads. The

rigidity of the chain was fixed, such that the angle formed

by three consecutive bonded beads was 1808. Since the clay

was modeled by a chain of 30 disks, the length/thickness

anisotropy of the clay was naturally taken into account in

the simulation.

The particle pair interaction between like components,

Uii(r), was given by

Macrom

� 2010

rly V

UiiðrÞ ¼1 if r � sii

0 if r > sii

�(1)

ol. React. Eng. 2010, 4, 000–000

WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

iew Publication; these are NOT the fina

where r is the interparticle distance. The cross particle-

particle pair interaction, Uij(r), was defined by

l pag

UijðrÞ ¼1 if r � sij

0 if r > sij

�; j„i (2)

where the subscript i and j stands for any of the

components. The cross interaction diameter, sij, was

calculated from

sij ¼ 0:5 si þ sj

� �1 þ Dij

� �(3)

where Dij> 0 is the nonadditive parameter. This simple

model potential was used due to computer efficiency and

mainly because it is the simplest model that is able to

show phase separation. Moreover, the larger Dij is, the

larger the interfacial tension (or repulsion) between the

component i and j is.[35] Therefore, one can obtain

the equilibrium location of the clay in miniemulsion

monomer droplets as a function of the clay hydrophobicity

and/or hydrophilicity. The Dmonomer/water ¼ 0.9 was main-

tained constant to reflect the insolubility of the monomer

in water.

The Monte-Carlo simulations were performed in the

canonical ensemble. The above-mentioned three-compo-

nent mixture was inserted in a circular simulation cell of

diameter D, with an impenetrable wall, such that the

interaction between a fluid disk and the wall is

Ui�wallðRÞ ¼1 if R � 0:5aD0 if R < 0:5aD

�(4)

where R is the distance of a disk (water, monomer, or clay)

and the center of the simulation cell. In order to mimic the

continuous aqueous phase, a¼ 1 if the disk i belongs to

water and a¼ 0.9 otherwise.

The composition of the cell was constant using 5 clay

platelets composed by 30 disks, and 1 050 monomer and

2 250 water disks. The simulation cell had a diameter

D¼ 100. The size of the clay platelets and that of the

monomer droplets mimic those obtained for an MMT type

clay platelet (100–150 nm) and monomer droplet sizes in

the range 200–250 nm typically found in previous experi-

mental procedure.[16]

The system was left to equilibrate for 106 configurations

with an acceptance ratio of 45%, according to the Metropolis

algorithm. It should be mentioned that the clay platelets

were allowed to undergo translational and rotational

movement. In around 2% of the movements, the disk

(water or monomer) was deleted from its position and it

was tried to be randomly inserted in the simulation cell in

order to speed up the equilibration of the system. Two-

dimensional profiles, ri(x,y) were collected in additional

0.5� 106 configurations using square elements of side

DOI: 10.1002/mren.200900084

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https://www.researchgate.net/publication/200104901_A_Guide_to_Monte_Carlo_Simulation_in_Statistical_Physics?el=1_x_8&enrichId=rgreq-3da92b124e80875b92e896644f8ccea0-XXX&enrichSource=Y292ZXJQYWdlOzIzMDIzNDkwNjtBUzoxMDMxMzk0NjYyODUwNjRAMTQwMTYwMTc3MzIxMg==


Table 2. Summary of d-spacing, organic content, and exchangeamount values for C30B and CMA16 organoclays.

Sample d-Spacing Organic

content

Exchange

amount

A wt.-% mequiv. � (g clay)�1

CMA16 17.8 22.2 0.75

C30B 18.5 24.7 0.92

Figure 1. Equilibrium morphology map of a clay/monomer hybridminiemulsion droplet. In each figure, x and y axis are the hori-zontal and vertical ones, respectively. The density distribution,ri(x,y), is perpendicular to the xy plane. The water is depicted inlight gray, monomer in dark gray, and clay platelets in black. Themonomer/water interface is the darker gray region.

d¼ 1.0 in x and y direction. At least two independent

simulations with the same conditions were run and

analogous results were obtained.

The main idea of Figure 1, is to show how the

compatibility of the clay with the monomer or with the

water may affect the structure of a miniemulsion monomer

droplet. For example, Dclay/monomer¼ 0.3 and Dclay/water¼ 0.6

may be suitable for describing a system with a partially

hydrophobic clay that is more compatible with the organic

phase. We can observe that in this case, the clay is located at

the monomer/water interface, but mostly it is more in

contact with the monomer. If the compatibility with

monomer is reduced,Dclay/monomer ¼ 0.6, the clay tends to be

at monomer/water interface, however, the contact of the

water with clay is now possible. In most of the cases the clay

is located at the monomer/water interface, due to the

entropic contribution, that drives the clay to be at this

interface in order to increase the entropy of the system.

Also, entropy provokes that clay is forming stacks at the

monomer droplet surface, to reduce the unfavorable

interactions.

According to the morphology map in Figure 1, it is

possible to encapsulate organically modified hydrophobic

clays within monomer droplets, when the clay is very

compatible with the monomer system employed and at the

same time does not provide favorable interaction with

water molecules or in water dissolved ions, i.e., the clay is

superhydrophobic (Dclay/monomer¼ 0.3, Dclay/water ¼ 0.9).

Obviously, encapsulating the clay platelets in the monomer

droplets does not necessarily ensure that upon polymer-




ization the morphology will be the same, but it can be

speculated that the morphology will not change signifi-

cantly during the polymerization because the increased

viscosity of the polymer particle due to polymerization will

considerably reduced the diffusion of the platelet within

the polymer particle. This will be especially true if the

organomodifier of the clay is reactive and allows covalent

bonding with polymer matrix. This also implies that the

only nucleation mechanism during the polymerization

should be monomer droplet nucleation. More challenging

seems, in view of the literature in this field, to modify

natural clays to fulfill the required conditions. This aspect

has been ignored on most of the reported works.

Monomer Compatibility and Hydrophobicity of C30Band CMA16 Clays

Table 2 presents the organic contents of organomodifiers in

C30B and CMA16, from which the exchanged mequiv. per

1 g of clay[16] were calculated. The final mequiv. � (g clay)�1

was a little bit lower in the case of CMA16 than in the case of

C30B, where the value 0.92 mequiv. � (g clay)�1 was pretty

close to the cation exchange capacity (CEC) of Cloisite-Na

[0.926 mequiv � (g clay)�1]. However, this calculation from

organic content was only a notional amount of exchanged

organomodifier as some of the surfactant can be present

even with its counterion.[36]

We have tried to measure the exact value of the contact

angles (CAs, interfacial tensions) clay/monomer and clay/

water. To calculate the clay/monomer CA the Washburn

method is the most suited alternative, but in the case of

organoclay powders there are many uncertainties[37] as

reported Fu and Qutubuddin.[38] Therefore, the clay/

monomer CA could not be measured and instead a

qualitative assessment of both clays in the monomer

mixture was carried out as described bellow. The clay/

water CA was measured using the pressed disks of

organoclays by sessile drop of water. Although these

measurements might not be strictly speaking correct,[39]

they can be useful for comparison purposes.[40,41] The

snapshots, from which the CA was calculated, were taken

after 1 min of the deposition of sessile drop of water. The



M. Micusık et al.

Figure 2. The dispersion of 3wbm.-% of C30B and CMA16 after(a) 48min and after (b) 8 d in the BA/MMA¼90:10 monomers.

Figure 3. UV absorption of clay dispersions in BA/MMA¼90:10 atwavelength of 401 nm.

6

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calculated CAs were 698 for C30B and 688 for CMA16. The

value for the C30B clay (698) is between the value of 608recently measured by Malucelli et al.[40] for the static CA and

the value of 738 measured by Pegoretti et al.[41] for the

advancing CA of water on compressed clay disks of C30B.

According to these values there is no difference in the

hydrophilicity of these two clays, because both organomo-

difiers (C30B and CMA16) posses groups that can interact

with water molecules (the hydroxyl groups in 30B and

methacrylic group in MA16) and do not differ much in the

hydrophobic part (alkyl chain of �C18 for C30B and C16 for

MA16).

The compatibility of the clay with the monomer system

(BA/MMA¼ 90:10 wt.-%) used in the miniemulsion poly-

merization was assessed by two techniques. Figure 2 shows

the dispersions of 3 wbm.-% of both clays in the monomer

system after 3 h mixing with magnetic stirrer at 1 000 rpm.

C30B has sedimented relatively fast (�48 min), while in the

CMA16 case the separation of phases did not occur after

�8 d (Figure 2b). This better swelling ability and compat-

ibility of CMA16 was also confirmed by UV-Vis absorption

at 401 nm (at this wavelength the monomer system does

not absorb), where dispersion containing 1 wbm.-% CMA16

was showing slightly slower absorption than 1 wbm.-%

C30B monomer dispersion (Figure 3). It was more clear in

dispersions containing 3 wbm.-% clay, where CMA16

absorption was �3.4, while the absorption of C30B were

out of range of the UV-Vis spectrometer (>5). The lower is

the optical density, the more exfoliated are the MMT

platelets, what means that the lower absorption in the case

of CMA16, indicates higher exfoliation state.

From the above it can be concluded that CMA16 is more

compatible and better swollen by the monomer mixture

(BA/MMA¼ 90:10) than C30B, i.e., CMA16 has lower Dclay/

monomer, but it has the same ability to interact with water

molecules as C30B, namely similar hydrophilicity (the same

Dclay/water).




Miniemulsion Polymerization

Miniemulsion polymerization can be a promising tech-

nique to encapsulate organomodified MMT clay platelets

provided that the conditions discussed in Figure 1 are met.

However, in addition to these conditions, it must be ensured

that droplet nucleation is the main nucleation mechanism.

In principle this requires to reduce the size of the

miniemulsion droplets in such a way that the available

surfactant will be mostly stabilizing the droplets and no

excess of surfactant would be available to form micelles or

to stabilize particles created by homogeneous nuclea-

tion.[33] However, in order to encapsulate all MMT platelets,

the size of the droplets should not be smaller than 300 nm,

because the distribution in size of MMT platelets is in the

range of 20–300 nm.[42] The average length of MMT

platelets calculated by Fornes and Paul[42] was 118 nm

and most of the clay was shorter than 200 nm, so

theoretically droplets of 200 nm could accommodate most

of the MMT platelets. An additional issue is the stability of

the resulting latexes and the potential interactions of the

surfactant and the organomodifier of the clay and/or

the charge of the clay. The literature reveals that in most of

the cases large amounts of surfactants (above 4 wbm.-%)

were employed to achieve stable latexes even at relatively

low SC.[23,26,27]

In this work two types of surfactant systems were used: a

mixture of anionic (Dowfax 2A1) and nonionic (Disponil

AFX4060) and a pure anionic system. Table 3 presents a

summary of the miniemulsion polymerizations carried out

with the two surfactant systems. Formulations with C30B

are in sample code (see Table 3) labeled with C and those

with CMA16 are labeled with CM, the mixture of

surfactants is in sample code represented by number 1

and pure anionic system by number 2, and the number after

dash represents the wbm.-% of clay. The small letters at the

end of the code denotes the initiator used (‘‘k’’ for KPS, ‘‘a’’ for

DOI: 10.1002/mren.200900084



Table 3. Summary of prepared formulations containing C30B or CMA16 clay, their final conversion (X), droplet size (Dd), particle size (Dp),and the ratio of droplet and particle number (Np/Nd).

Sample Clay Initiator/X Coag. BufferRpept.

agent/pH

Dd Dp Np/Nd

wt.-% nm nm

1 wbm.-% anionic/0.6 wbm.-% nonionic surfactant system

blank 1a 0 AIBN/91 – NaHCO3/8.5 232 210 1.06

C1-1a C30B/1 AIBN/92 4.8 NaHCO3/8.3 400 380 0.88

C1-2a C30B/2 AIBN/94 1 NaHCO3/8.7 498 414 1.40

CM1-1,2 CMA16/1, 2 KPS, AIBN 62–75 NaHCO3 þNa4P2O7 211–261 – –

CM12-2aa) CMA16/2 AIBN/100 4 NaHCO3 þNa4P2O7/8.6 159 169 0.72

2 wbm.-% anionic surfactant system

blank 2 0 KPS/98 – NaHCO3/7.2 84 129 0.23

C2-1k C30B/1 KPS/99 – NaHCO3/8.4 165 156 1.01

C2-2k C30B/2 KPS/- 25 NaHCO3 þNa4P2O7/8.2 180 – –

C2-2a C30B/2 AIBN/94 1.8 NaHCO3 þNa4P2O7/8.6 152 165 0.62

C2-2v C30B/2 V501/100 – NaHCO3/8.7 172 190 0.64

CM2-1k CMA16/1 KPS/98 – NaHCO3 þNa4P2O7/8.3 105 139 0.37

CM2-2k CMA16/2 KPS/96 0.6 NaHCO3 þNa4P2O7/8.8 137 140 0.77

a)This formulation contained 2 wbm.-% anionic/0.6 wbm.-% nonionic surfactant.

AIBN, and ‘‘v’’ for V501). Blanks without clay are denoted as

blank and following the nomenclature as in the case of

composites. Figure 4 presents the backscattering measure-

ments of miniemulsions (30 wt.-% dispersed phase) with

C30B using both surfactant systems at 60 8C. As it can be

seen the stability of the miniemulsions was good for 6 h and

the average droplet sizes measured were 380 and 235 nm

0

10

20

30

40

50

60

70a)

0 10 20 30 40

0min301h001h302h002h403h003h304h004h305H106H00B

acks

catte

ring

Inte

nsity

[%]

h [mm]

Figure 4. Stability study of miniemulsions containing 30wt.-% SC, 3w0.6wbm.-% nonionic surfactant and (b) 2wbm.-% anionic surfactan




for the mixture of surfactants and the anionic surfactant,

respectively.

Table 3 shows that coagulum-free latexes (or small

amount of coagulum except for runs CM1-1,2 and C2-2k)

were obtained in the formulations containing 1 and

2 wbm.-% of either clays. When 3 wbm.-% clay was used

the amounts of coagulum were larger and these data were

b)

0

10

20

30

40

50

60

0 10 20 30 40 50

t0301h101h252h052h303h3h254h104h355h5h306hB

acks

catte

ring

Inte

nsity

[%]

h [mm]

bm.-% C30B, 3wbm.-% SA, 1wbm.-% NaHCO3, (a) 1wbm.-% anionic/t.



M. Micusık et al.

100 1000 100000

5

10

15

20

25Vo

lum

e [%

]

Size [nm]

C1-2a miniemulsionC1-2a final latexC2-2a miniemulsionC2-2a final latex

Figure 5. Droplet and particle size distributions measured by DLSfor miniemulsions and final latexes of experiments C1-2a andC2-2a carried out with C30B clay.

100 1000 10000

0

2

4

6

8

10

12

14

16

Volu

me

[%]

Size [nm]

CM12-2a miniemulsionCM12-2a final latexCM2-2 miniemulsionCM2-2 final latex

Figure 6. Droplet and particle size distributions measured by DLSfor miniemulsions and final latexes of experiments CM12-2a andCM2-2k carried out with CMA16 clay.

8

REa

not included in the table. Interestingly, in most of the cases

the ratios Np/Nd calculated from the initial droplet size and

final particle size were close to one, which was an indication

of the predominant droplet nucleation. Also noticeable was

the larger droplet sizes for the polymerizations with the

mixture of anionic/nonionic surfactants for the two types

of clay (runs C1-1a, C1-2a vs. C2-1k, C2-2a and C2-2v, and

Figure 7. TEM picture of latex C1-2a synthesized with C30B and a mixture of surfactantsby miniemulsion polymerization: (a) whole latex, (b), (c) large particles obtained aftercentrifugation of a diluted latex sample at 5 500 rpm, (d) small particles obtained fromthe supernatant. The scale bar of the inclusion is 100nm.

runs CM12-2a vs. CM2-2k). This was

expected because nonionic surfactants

partially dissolved in the monomer phase

and hence their stabilization capabilities

are lower than those of anionic surfac-

tants, resulting in larger miniemulsion

droplets being stabilized. Figure 5 displays

the droplet/particle size distribution for

runs C1-2a and C2-2a. In addition to the

difference in the average value discussed

above, the final particle size distribution

was bimodal for the case of the mixture of

anionic/nonionic surfactants and uni-

modal for the latexes synthesized only

with the anionic surfactant. The droplet

size distributions were also significantly

different even if both cases showed

bimodal distributions. For the mixture

of surfactants a mm size mode was

observed, whereas for the anionic case

although large droplets were also pro-

duced, they were mostly sub-mm size.

Interestingly, the mm size droplets of

experiment C1-2a did polymerize (a frac-

tion of them) and the initial bimodal

droplet size distribution was maintained

in the final latex.

Figure 6 presents the droplet/particle

size distributions for runs CM12-2a and




CM2-2k with reactive CMA16. The miniemulsion prepared

with the mixture of surfactants produced slightly larger

particle sizes, but in this case no mm sizes droplets were

observed. Here it is worth to mention that in the case of

CMA16 and 1 wbm.-% anionic/0.6 wbm.-% nonionic sur-

factant system the latexes were not stable (CM1-1,2 in

Table 3). This was attributed to the better compatibility of

DOI: 10.1002/mren.200900084



CMA16 with the monomer mixture that facilitated break-

age and production of smaller droplets, which needed more

charge to stabilize the latex (note that stable latex was

achieved when the amount of anionic surfactant portion

was increased in CM12-2a).

Morphology of the Hybrid Latex Particles

Figure 7 presents a series of TEM images for latex C1-2a.

Figure 7a clearly confirms the bimodal nature of the latex

with particles above and below the mm size. Figure 7b–d

present TEM images of each population after ultracentri-

fugation of the latex to analyze both populations separately

(5 500 rpm for 30 min).

Figure 7b and c show plenty of C30B platelets in the large

particles. Whether the platelets are fully encapsulated,

protruding from the particle or at the surface is hard to say

from the images. Figure 7d shows that the population of

small particles was broad and the larger particles in this

population contained individualized platelets as it can be

seen in the inclusion in Figure 7d.

This latex was further analyzed by Wet-STEM to have

additional information about the location of the clay

Figure 8. Wet-STEM pictures of latex C1-2a.




platelets in the wet state before film forming. Figure 8

displays two micrographs, which only captured large

particles. The micrographs show white areas at the junction

of the polymer particles and also within the particles as

veins that corresponded well with the shapes of platelets in

Figure 7b,c. One can speculate that these veins corre-

sponded to clay platelets encapsulated in the polymer

particles, but admittedly it is uncertain.

Figure 9 shows the TEM pictures for latex CM12-2a and

the presence of clay platelets at the surface of the particles

can be distinguished (Figure 9b). Also noticeable is the

presence of considerable number of snowman/dumbbell-

like particles (indicated by arrows). Voorn et al.[43] have

observed similar particles in a completely different process

using MMT clay modified with a reactive silane by the

edges. They explained that the dumbbell-like morphology

was a consequence of the polymerization starting in the

platelets and hence they claimed that in these particles

platelets were encapsulated. In our case it likely indicated

the reactivity of CMA16, but the presence of clay was not

clear at the particle-particle interphase. The structures

denoted by arrows in Figure 9b looks to be formed on the

platelet surface, what would confirm the CMA16 reactivity,

but no clear encapsulation was observed.

Figure 10a,b present the TEM micrographs for latex C2-2a

synthesized with only anionic surfactant and C30B. The

micrograph confirms the DLS information regarding the

size of the particles which was smaller and in the sub-mm

range. Unfortunately, not much can be said about the

location of the clay platelets in the polymer particles.

Morphology of the Films

Films were cast from the latex and cryo-sectioned speci-

mens observed by cryo-TEM. Films were also analyzed by

WAXD to explore the degree of exfoliation of the clay

platelets in the film. Figure 11 presents the TEM micro-

graphs of the thin films of latex C1-2a, C2-2v, and CM2-2k.

Film C1-2a (Figure 11a and b) shows a clear honeycomb

structure where the size of the original bimodal particles

was preserved. Clay stacks and individual platelets can be

recognized from the micrograph. This micrograph may shed

light about the uncertain location of the platelets (see TEM

and Wet-STEM micrographs in Figure 7 and 8). Although

clay platelets can migrate during film formation it is very

unlikely that they will migrate from the inner part of large

particles to the surface. Therefore, it can be concluded that

platelets were preferentially located close to the surface of

the particles. The micrograph for film C2-2v (Figure 11c

and d) did not show a clear honeycomb structure although

some sections looked like that. The clay platelets were

better dispersed because the size of the particles was

smaller and intercalated and exfoliated structures can be

observed (see larger magnification in Figure 11d). The



M. Micusık et al.

Figure 9. TEM micrographs of latex CM12-2a.

Figure 10. TEM micrographs of latex (a), (b) C2-2a.

10

REa

micrograph for film CM2-2k (Figure 11e and f) made with

CMA16 clay did not show any defined structure and clay

platelets were well distributed in the polymer matrix.

Figure 12 displays the WAXD spectra for the nanocom-

posite films and the results are in good agreement with TEM

pictures. Thus, the films made of the latex with C30B, either

using the mixture of surfactants (C1-2a) or with only

anionic (C2-2v) both show intercalated structures (�28–

31 A). However, film C1-2a shows an additional peak at the

same distance as the original peak in the C30B clay

indicating that some stacks of the clay were still present.

This agrees well with the data of TEM for this latex (see

Figure 7a and b) and the film (Figure 11a and b), and the fact

that C30B is not very compatible with monomer system and

hence it was preferentially located at the surface of the

particles. When only anionic surfactant was employed

(C2-2v) stacking was reduced and no peak at 18.5 A was

observed in the WAXD spectra.

For the latexes synthesized with CMA16, the WAXD

shows no peak at all, which indicated an exfoliated



rly View Publication; these are NOT the final page numbers, u

structure. TEM of the latex and of

the film also confirmed that the

clay platelets were better dis-

persed in the matrix (no honey-

comb-like structure could be dis-

tinguished).

Overall the results for the two

types of clay are in reasonable

agreement with the morphology

predictions of Figure 1. According

to the properties of the organomo-

dified clays described above the

interfacial tension of the clays with

water were very close and the main

difference between them was the

compatibility with the monomer

mixture, namely, the interfacial

tension clay/monomer was smal-

ler for CMA16 clay. Additionally,

the reactivity of the CMA16 influ-

ences the entropic contribution to

the location of the clay in the final

latex. Although CMA16 seems to be

mostly located on the surface, it is

in contrast to C30B not forming

stacks, which is not only due to its

better compatibility, but also due

to its reactivity. This meant that

the morphology of the miniemul-

sion droplets for CMA16 clay can be

considered to be located in the

lower row and between the values

0.6 and 0.9 in the Dclay/water axis.

The morphology of the hybrid

particles for the experiments CM12-2a indicated morphol-

ogy closer to the position 0.6 in the x axis, which would

mean that the CMA16 clay was still relatively hydrophilic.

For the C30B clay the expected morphology would be

located in the same position in the x axis, but in a higher

level in the y axis (higher clay/monomer interfacial

tension). Figure 7, 8, and 11 suggested a preferential

location of the platelets at the polymer/water interphase,

which will be coherent with the position at x and y axis 0.6.

It is worth to note that in this comparison we are assuming

that the morphology of the droplets was preserved after

polymerization and that particles in the latex were

produced by droplet nucleation.

Another important point that needs to be mentioned

is that the stability of the latexes was extremely dependent

on the nature of initiator employed. Thus, in Table 3 we

present three experiments carried out with C30B and

2 wbm.-% anionic surfactant with the only difference of the

initiator used: KPS, AIBN, and V501. All these initiators were

thermal initiators, but only KPS provided charged radicals

DOI: 10.1002/mren.200900084

se DOI for citation !!


Figure 11. TEM micrographs of cryo-sectioned thin films for latexes: (a), (b) C1-2a, (c), (d) C2-2v,and (e), (f) CM2-2k.

(sulfate radicals). AIBN and V501 differ in the water

solubility. As it can be seen in Table 3, with KPS the latex

was unstable and significant amount of coagulum was

formed. However, very low amount of coagulum was

produced with the oil soluble azo-initiator AIBN and none

with the water soluble azo-initiator V501. This behavior

was related with the location of the platelets in the

monomer droplets. If the clay platelets were fully

encapsulated, we would not have expected any dependence

on the initiator used. In fact the formulation with 2 wbm.-%

CMA16 was less sensitive to KPS than with C30B (only little

coagulum), which was in agreement with the morphologies

achieved for C30B clay that were preferentially located at



Early View Publication; these are NOT the final page numb

the interphase between polymer

and aqueous phase and hence

more exposed to interaction

between charged oligomers (nega-

tive) and the organomodifier of the

clay and/or the edges of the clay.

Adhesive Properties of theNanocomposite Films

The adhesive properties, tack and

shear resistance, and the gel con-

tent of the latexes were measured

for some of the nanocomposite

latex synthesized with the C30B

and CMA16 organomodified clays.

The data in the Table 4 indicate

that the gel content was lower for

the series of latexes synthesized

with the mixture of surfactants

than for the series with only

anionic surfactant. Interestingly,

the nanocomposites synthesized

with reactive CMA16 clay con-

tained a higher amount of gel than

those synthesized with C30B, espe-

cially when only anionic surfac-

tant was used in the formulation

(CM2-1k and CM2-2k). This was

also observed by Diaconu et al.[16]

in the polymerization with C30B

and CMA16 by miniemulsion poly-

merization using higher amount of

sodium dodecylsulfate (4 wbm.-%).

The higher gel content was likely

due to the fact that the MA16

modifier cationically attached to

the platelet in the CMA16 clay has a

pendant double bond that reacted

during polymerization and created

crosslink points and hence gel polymer. It is worth noting

that it has been reported that small amounts of crosslinker

were enough to produce such amounts of gel polymer in

acrylic formulations.[44,45]

The tack and shear resistances for the blank and

nanocomposites C1-2a, CM12-2a, C2-2a, and CM2-2k

revealed that latexes containing clay were just slightly

less tacky, but they provided improved shear resistance,

which was very remarkable for latexes CM2-1k and CM2-2k

that were synthesized with CMA16. This extraordinary

improvement in the shear resistance was likely due to

the gel content produced thanks to the reactivity of CMA16

clay.


ers, use DOI for citation !! R

M. Micusık et al.

2 4 6 8 10 12

0

100

200

300

400

500

CM2-2k

CM12-2a

C2-2v

31.1 Å

Cou

nts

[a.u

.]

[°]

18.5 Å - C30B

C1-2a

Figure 12. WAXD spectra of the nanocomposite latex films ofC1-2a, C2-2a, CM12-2a, and CM2-2k.

Table 4. Adhesive properties (tack and shear resistances) and gelcontent of the prepared latexes.

Sample Gel

content

Tack

resistance

Shear

resistance

% cm h

blank 1a 0 1.9� 0.2 0.6� 0.5

C1-1a 1 – –

C1-2a 4 8.3� 1.8 2.7� 3.2

CM12-2a 19 9.8� 1.1 15.0� 11.0

blank 2k 39 – –

C2-1k 17 – –

C2-2a 4 3.0� 0.4 16.8� 19.6

C2-2v 12 – –

CM2-1k 51 7.5� 1.7 > 40.0a)

CM2-2k 52 9.6� 0.7 >56.0a)

a)The experiments were stopped at this time without failure.

12

REa

Conclusion

The equilibrium morphologies of hybrid monomer/clay

miniemulsion droplets were addressed. The morphology

map of this hybrid system determined by a simple Monte-

Carlo simulation helped to understand the preferential

location of MMT clay platelets in BA/MMA (90:10 wt.-%)

miniemulsions and final latexes. The morphology map

showed that the encapsulation of the clay platelets would

only be possible if the clay, besides the compatibility with

monomer system (low Dclay/monomer), would not provide

favorable interactions with water (high Dclay/water).




The predicted morphologies were assessed in nanocom-

posite latexes synthesized with C30B and CMA16 organo-

clays. Both clays have similar clay/water interfacial

tension, but CMA16 is more compatible with the monomer

mixture; namely it has lower clay/monomer interfacial

tension. The morphologies of the latex particles and the

films agreed in a large extent with the predicted

morphologies for both clays. Thus, clay platelets were in

the particle/water interphase for C30B and stacks of clay

could be detected, whereas for CMA16 platelets, although

located also at the polymer/water interphase, were not

stacked. Furthermore, dumbbell-like particles were pro-

duced in this process likely because of the reactivity of the

MA16 modifier. This was proofed by the higher gel content

of the latexes produced with CMA16 clay. In the same

vane the shear resistance of the film, made with latexes

containing CMA16 were significantly better.

Acknowledgements: Financial support from the European Union(Napoleon project IP 011844-2), Basque Government (GV 07/16-IT-303-07), and Ministerio de Ciencia y Tecnologia (CTQ 2006-03412and Programa Consolider-Ingenio 2010 ‘‘CIC nanoGUNE Consoli-der’’ contract CSD2006-00053) is gratefully acknowledged.The SGIker UPV/EHU for the electron microscopy facilities ofthe Gipuzkoa unit and SGI/IZO-SGIker UPV/EHU (supported by the‘‘National Program for the Promotion of Human Resources withinthe National Plan of Scientific Research, Development andInnovation – Fondo Social Europeo, Gobierno Vasco and MCyT’’)is also gratefully acknowledged. B. Lohmeijer (BASF, Germany) iskindly acknowledged for the TEM images of cryosectioned films.

Received: November 18, 2009; Revised: January 7, 2010;Published online: XXX; DOI: 10.1002/mren.200900084

Keywords: acrylic miniemulsions; encapsulation; equilibriummorphologies; films; montmorillonites

[1] M. Biswas, S. S. Ray, Adv. Polym. Sci. 2001, 155, 167.[2] K. R. Ratinac, R. G. Gilbert, L. Ye, A. S. Jones, S. P. Ringer,

Polymer 2006, 47, 6337.[3] B. Chen, J. R. G. Evans, H. Ch Greenwell, P. Boulet, P. V.

Coveney, A. A Bowden, A. Whiting, Chem. Soc. Rev. 2008,37, 568.

[4] A. P. Kumara, D. Depana, N. S. Tomerb, R. P. Singh, Prog. Polym.Sci. 2009, 34, 479.

[5] D. C. Lee, L. W. Jang, J. Appl. Polym. Sci. 1996, 61, 1117.[6] Y. S. Choi, M. H. Choi, K. H. Wang, S. O. Kim, Y. K. Kim, I. J.

Chung, Macromolecules 2001, 34, 8978.[7] G. Diaconu, M. Paulis, J. R. Leiza, Polymer 2008, 49, 2444.[8] H. Li, Y. Yang, Y. Z. Yu, J. Adhes. Sci. Technol. 2004, 18, 1759.[9] H. Li, Y. Z. Yu, Y. K. Yang, Eur. Polym. J. 2005, 41, 2016.

[10] H. L. Min, J. H. Wang, H. Hui, W. Jie, J. Macromol. Sci., Part B:Phys. 2006, 45, 623.

[11] B. J. Park, H. J. Choi, Sci. Technol. Hybrid Mater. 2006, 111, 187.[12] G. Diaconu, M. Paulis, J. R. Leiza, Macromol. React. Eng. 2008,

2, 80.

DOI: 10.1002/mren.200900084



[13] R. P. Moraes, A. M. Santos, P. C. Oliveira, F. C. T. Souza,M. do Amaral, T. S. Valera, N. R. Demarquette, Macromol.Symp. 2006, 245, 106.

[14] Q. Sun, Y. Deng, Z. L. Wang, Macromol. Mater. Eng. 2004, 289,288.

[15] A. Samakande, R. D. Sanderson, P. C. Hartmann, Polymer 2009,50, 42.

[16] G. Diaconu, M. Micusık, A. Bonnefond, M. Paulis, J. R. Leiza,Macromolecules 2009, 42, 3316.

[17] Y. Yang, L. Liu, J. Zhang, C. Li, H. Zhao, Langmuir 2007, 23, 2867.[18] D. Donescu, C. Radovici, C. Petcu, S. Serbam, M. C. Corobea,

M. Ghiurea, J. Dispersion Sci. Technol. 2008, 29, 340.[19] L. Fialova, I. Capek, R. Ianchis, M. C. Corobea, D. Donescu,

D. Berek, Polym. J. 2008, 40, 163.[20] E. Bourgeat-Lami, N. Negrete Herrera, J.-L. Putaux, A. Perro, S.

Reculusa, S. Ravaine, E. Duguet, Macromol. Symp. 2007, 248,213.

[21] S. I. Ali, J. P. A. Heuts, B. S. Hawkett, A. M. van Herk, Langmuir2009, 25, 10523.

[22] V. Mellon, ‘‘Synthesis and Characterization of WaterbornePolymer/Laponite Nanocomposite Latexes Through Minie-mulsion Polymerization’’, PhD thesis Universite ClaudeBernard Lyon I 2009, p. 169.

[23] Z. Tong, Y. Deng, Polymer 2007, 48, 4337.[24] N. Negrete-Herrera, J. L. Putaux, L. David, F. De Haas,

E. Bourgeat-Lami, Macromol. Rapid Commun. 2007, 28,1567.

[25] D. J. Voorn, W. Ming, A. M. van Herk, Macromolecules 2006,39, 2137.

[26] M. Mirzataheri, A. R. Mahdavian, M. Atai, Colloid Polym. Sci.2009, 287, 725.

[27] F. Bouanani, D. Bendedouch, P. Hemery, B. Bounaceur,Colloids Surf., A 2008, 317, 751.




[28] D. J. Voorn, W. Ming, A. M. van Herk, Macromol. Symp. 2006,245-246, 584.

[29] A. Bogner, G. Thollet, D. Basset, P. H. Jouneau, C. Gauthier,Ultramicroscopy 2005, 104, 290.

[30] F. Alarcia, J. C. de la Cal, J. M. Asua, Macromol. Mater. Eng.2006, 291, 428.

[31] O. Elizalde, G. Arzamendi, J. R. Leiza, J. M. Asua, Ind. Eng. Chem.Res. 2004, 43, 7401. 7409.

[32] Y. Lyatskaya, A. Balazs, Macromolecules 1998, 31, 6676.[33] J. M. Asua, Prog. Polym. Sci. 2002, 27, 1283.[34] D. P. Landau, K. Binder, ‘‘AGuide toMonte-Carlo Simulation in

Statistical Physics’’, 2nd edition, Cambridge University Press,Cambridge 2005.

[35] Y. Duda, E. Vakarin, J. Alejandre, J. Colloid Interface Sci. 2003,258, 10.

[36] J. M. Cervantes-Uc, J. V. Cauich-Rodrıguez, H. Vazquez-Torres,L. F. Garfias-Mesıas, D. R. Paul, Thermochim. Acta 2007,457, 92.

[37] H. Czachor, Hydrol. Process. 2007, 21, 2239.[38] X. A. Fu, S. Qutubuddin, J. Colloid Interface Sci. 2005, 283,

373.[39] A. Rudawska, E. Jacniacka, Int. J. Adhes. Adhes. 2009, 29, 451.[40] G. Malucelli, S. Ronchetti, N. Lak, A. Priola, N. Tzankova

Dintcheva, F. P. La Mantia, Eur. Polym. J. 2007, 43, 328.[41] A. Pegoretti, A. Dorigato, M. Brugnara, A. Penati, Eur. Polym. J.

2008, 44, 1662.[42] T. D. Fornes, D. R. Paul, Polymer 2003, 44, 4993.[43] D. J. Voorn, W. Ming, A. M. van Herk, Macromolecules 2006,

39, 4654.[44] L. Bouvier-Fontes, R. Pirri, J. M. Asua, J. R. Leiza, Macromol-

ecules 2005, 38, 2722.[45] L. Bouvier-Fontes, R. Pirri, J. M. Asua, J. R. Leiza, Macromol-

ecules 2005, 38, 1164.








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