Preparation of Perfluorinated Surfactant Activates for Antifouling Paints

doi:10.4236/jsemat.2012.24041

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Journal of Surface Engineered Materials and Advanced Technology, 2012, 2, 271-277

http://dx.doi.org/10.4236/jsemat.2012.24041 Published Online October 2012 (http://www.SciRP.org/journal/jsemat)

271

Preparation of Perfluorinated Surfactant Activates for

Antifouling Paints

A. Bacha1, R. Méghabar2

1Chemistry Laboratory, Faculty of Sciences and Technology, University of Djelfa, Djelfa, Algeria; 2Laboratory of Polymer Chemis-

try, University of Es-Senia, Oran, Algeria.

Email: [email protected]

Received July 8th, 2012; revised August 15th, 2012; accepted August 26th, 2012

ABSTRACT

Antifouling paints are the most reliable way to prevent biofouling of submerged surfaces. The high toxicity of organotin

paints, prompted us to look for ideas to develop paints that do not present environmental risks. In this work, we prepare

a painting by a modification of acrylic acid monomer containing a free carboxyl group. The biocide that is selected is

the perfluorinated chain with eight carbons. Chemical modifications of the resins are made through a radical reaction.

The magnitudes of changes are monitored by proton nuclear magnetic resonance NMR, gel permeation chromatography

(GPC) and the light scattering (LS) at a fixed angle 90°. The glass transition temperature of the surfactant is obtained by

the differential scanning calorimetry (DSC). The antifouling properties of the paint are followed by exposure of panels

to the marine environment by visual observation.

Keywords: Surfactant; Antifouling; Glass Transition Temperature; Aluminum Panels; Differential Scanning

Calorimetry; Critical Micelle Concentration (CMC)

1. Introduction

The paintings with fluorine atoms are used in many

applications and this is due to their unique properties like

low surface tension, non-adhesive nature and antifouling

properties along. Fluorine is difficult to polarize. This is

especially advantageous for their applications in surface

coatings. Hence fluoropolymers can hinder water reach-

ing the metallic surface in tow ways: fluorinated poly-

mers are not wetted by water and secondly the molecular

absorption of water into these polymers is relatively

small [1]. During recent years, the most successful

antifouling marine paints are those consisting of trior-

ganotin-based. They are hydrolysable polymers containing

triorganotin ester groups that are released by a reaction

with seawater. However, the high toxicity of these

compound has been shown [2-4]. These environmental

concerns lead to develop new antifouling paints, environ-

mental friendly and effective over the long term. Our

work concerns the synthesis of products (perfluorinated

surfactants) that can enter into the formulation of anti-

fouling paints by an economic way.

Perfluorinated surfactants are classified as biocides [5].

In particular salts with perfluorinated chain with at least

eight carbons are effective biocides [6]. The most com-

mon way to present these compound is the radical telo-

merization [7]. The synthesis involves a single step

(Figure 1).

The product is a surfactant with a hydrophobic carbon

chain and a hydrophilic portion represented by a function

in the same loaded organic molecule [8-9]. This property

provides a potentially effective antibacterial effect [9].

This article describes the synthesis, characterization and

biocidal potential of this new surfactant molecule.

2. Experimentation

2.1. Materials

The perfluorinated acrylic surfactant (PAS) was synthe-

sized in the physics laboratory materials, Faculty of Sci-

ence and Technology (University of Djelfa (Algeria)),

this synthesis is described in detail in Section 2.3.

The product used is compared with tributyltin (TBT)

nonfluorinated synthesized in the laboratory of polymer

chemistry at the University of Oran Es-Senia (Algeria)

[10]. The product was vacuum distilled before use and

stored at 0˚C to avoid thermal polymerization. Azoiso-

butyronitrile (AIBN) and perfluorinated thiol were used

Figure 1. Telomerization of acrylic acid (R ≡ C8F17C2H4-)

Preparation of Perfluorinated Surfactant Activates for Antifouling Paints

272

as a free radical initiator and a chain transfer agent, res-

pectively. The solvents like tetrahydofuran (THF), ace-

tonitrile, pentane, diethyl ether (Merck) and analytical

products were used directly without further purification.

Water was deionized.

2.2. Measures

Proton NMR measurements were performed on a Brucker

WB 360 spectrometer (ref. Internal CDCl3). Chemical

shifts are expressed in 10–6.

The determination of critical micelle concentrations of

PSA product is given by the light scattering (LS) at a

fixed angle 90°. The optical constant of the device (under

the experimental conditions used here) is K = 0735.102.

The relative molecular weight and molecular weight

distributions were determined by the gel permeation

chromatography (GPC), the device with THF as eluent,

flow rate: 0.8 ml/min, volume of injection loop: 0.2 ml,

with two columns as support a mixed gel porosity and

particle size of 10 μ and differential refractometer (Brice-

Phoenix) as concentration detector (λ = 632 nm).

Thermogram of Differential Scanning Calorimetry

(DSC) was taken on an appliance model Mettler TA

4000 at a heating rate of 10˚C/min. Temperature (Tg)

was taken at the beginning of the jump corresponding to

the heat capacity

2.3. Telomerization of Acrylic Acid

A mixture of 7.2 g (0.1 mol) of acrylic acid, 36 g (0.075

mol) of perfluorinated thiol is added dropwise to 0.164 g

(10–3 mol) of AIBN in 100 ml of THF. The mixture was

left stirring under nitrogen bubbling at THF reflux for

four hours at 80˚C. After concentration, the reaction

mixture was precipitated in acetonitrile to remove the

thiol and the remaining monomer. The product obtained

was dried under vacuum. 1H NMR (D2O): δ (ppm): 2.6;

2.75 (m, 4H, CH2SCH2); 2.8; 2.9 (t, 2H, CH2COO); 3.3;

3.4 (s, C8F17CH2).

2.4 Determination of Critical Micelle

Concentration

Fundamental solutions are obtained by dissolving the

product in 50 ml of distilled THF solvant. The solutions

were then diluted volumetrically generally reports 3/4,

1/2 and 1/4, different solutions were clarified by cen-

trifugation at 18000 rev/min for 4 hours.

The concentration range studied, respectively: 0.36 ×

10–4 and 2.04 × 10–4 g/ml.

2.5 Preparation of Painting and the Panels

The panels used are of rectangular shapes (7.5 cm × 6.5

cm) aluminum, 3 mm thick; test paints were applied di-

rectly using a flat brush on the surface of the panel with

the previously scraped sandpaper, cleaned and washed

with methanol. Each panel is painted on both sides by

double layers, leaving at least 24 hours between the two

applications.

After a drying time (up to one week), the panels are

arranged and fixed on a metal support. The painted pan-

els are called as a witness P1, P2 perfluorinated acrylic

surfactant (PAS), and P3 (TBT).

The painting of the PSA is prepared by dissolving the

resin (35 parts) in methoxy-propanol-2 (65 parts). The

formulations are prepared in a laboratory dissolver.

2.6. Exposure to the Marine Environment

All panels are put to tests to evaluate its biocidal proper-

ties. For this, the panels were painted immersed to a

depth of 4 m in the port of Oran, near the wharf customs

dock in the sports complex (Rowing), during twenty-four

months corresponding to four cold and warm seasons.

Oran is the second economic city located west of Al-

geria. The salinity and temperature of the location are in

Table 1.

Panels are photographed and study of the behavior of

marine fouling deposit is made (the date of immersion is

March 2009).

Photos were taken by a camera Samsung Lens 3X

zoom 6.2 - 18.6 mm 2.8 - 5.2. 10.2 Mega Pixels Intelli-

gent LCD.

3. Results and Discuss

3.1. Synthesis of Perfluorinated Acrylic

Surfactant (PAS)

The preparation of acrylic polymers of low molecular

mass [11] is of major importance. The products obtained

are soluble in water and found many applications.

The presence of fluorescent atoms along the chain de-

termines the degree of polymerization of the surfactant.

3.2. Gel Permeation Chromatography of PAS

The curve of Figure 2 shows the evolution of the signal

intensity as a function of elution volume of surfactant

(PAS).

It is observed that the maximum intensity of the peak

in the chromatogram appears to 36.06 ml, the peak is

narrow and symmetric product of typical well-defined

Table 1. Changes in physicochemical parameters of the

natural sea water at the port of Oran in 2010.

Temperature pH Salinity

(‰)

Conductivity

(mS/cm)

10 - 23 8.4 - 8.8 34 - 36 39 - 45

Preparation of Perfluorinated Surfactant Activates for Antifouling Paints 273

Figure 2. Gel permeation chromatography of perfluorina-

ted acrylic surfactant (PAS).

and iso-molecular. The polydispersity Mw/Mn was 1.24,

see the Table 2, this chromatogram confirms the hom-

ogeneity of the product (Figure 2).

3.3. Critical Micelle Concentrations (CMC)

The value of the critical micelle concentration (CMC) of

perfluorinated acrylic surfactant (PAS) in the solutions

was examined by the technique of light scattering (LS).

The light scattering is sensitive to dust, for this reason

we work in harsh conditions.

The general equation for the scattering of light in the

case of small molecules (or micelles of small size: less

than 12 nm) can be written [12,13]:







 



Or is the optical constant of the device (in the

experimental conditions used here, we have

K



= 0.735

× 102).

The intensity difference ΔI between the solution con-

centration (c) and the solvent.

The

of the surfactant is –0.0519. The negative value which is

obtained for this product is due to the presence of fluo-

rine atoms.

Fluorine significantly lowers the refractive index of

molecules, A2 the second virial coefficient related to

thermodynamic properties (A2 actually represents the

effect of concentration on the scattered intensity) [13].

Table 2. Characterization of perfluorinated acrylic surface-

tant (PAS)

Surfactant Vel (ml) Mn M

w/Mn

Surfactant PAS 36.60 3800 1.24

The results obtained (in a concentration range between

0.36 × 10–4 and 2.04 × 10–4 g/ml) are shown in Tables

3(a) and (b) and illustrated in Figure 3 which shows the

variations of the scattered intensity as a function of

concentration .

These results allow us to located the critical micelle

concentration (CMC) around to 1.545 × 10–4 g/ml. Below

this concentration, the slope of curve is relatively large,

is explained by the fact that there is not yet micelle

formation and because of the translational mobility, the

charges from molecules completely dissociated, are free

to move. Above the CMC, the slope is smaller than the

first and indicates the formation of micelles. Indeed, they

have distributed loads (ionized heads) on the micellar

surface, and are neutralized by counterions found in the

solution. All these factors contribute to the stability of

the micelle, which results in a decrease in the mobility of

monomers charged.

3.4. Glass Transition Temperature

The glass transition temperature was determined by DSC.

This method was used in the research laboratory of the

Thermophysics in Dunkerque (France). And once vali-

dated, this type of analysis could be used for substrates

already applied paint finishes. The results obtained by

this method are presented in Figure 4.

As a result, one must conclude that there is a critical

number of carbon atoms (carbon atoms bond to fluores-

cence atoms) where the growing reach does not affect the

value of the temperature. This could be parsed by the fact

that there is no steric effect or significant obstacle in the

acrylic matrix between carbons, while that given by the

well-TBT alters the thermal properties of the resin [14].

Many studies have been made by DSC to determine the

phase diagrams of mixtures and polymer systems [15,16],

the thermal properties were carried out in a temperature

range from 0˚C to 200˚C (Figure 4).

In this curve, three characteristic temperatures were

detected.

The emulsion of perfluorinated acrylic surfactant (PAS)

showed some weight loss of 2%, which are due to the

solvent. The box in Figure 5 shows a change endother-

mic around 50˚C, which corresponds to the glass transi-

tion temperature Tg, then the product is stable up to 60˚C.

Chemical decomposition will start after this temperature

Preparation of Perfluorinated Surfactant Activates for Antifouling Paints

274

Table 3. (a) Critical micelle concentration (CMC) of per-

fluorinated acrylic surfactant (PAS); (b) Measurements of

light scattering of perfluorinated acrylic surfactant (PAS),

after the CMC.

(a)

c.10–4 g/ml I (u,a) △ I (u,a) (c/I) 10–4

0 Io = 28.85 - -

0.495 32.69 3.0 1.20

0.863 35.58 5.5 1.20

1.182 37.50 8.0 1.18

1.41 39.42 8.0 1.22

C. M. C. = 1.545 40.38 - -

(b)

c.10–4g/ml I(u,a)

1.772 46.16

2.04 52.88

Figure 3. Light scattering of perfluorinated acrylic surfac-

tant (PAS).

Figure 4. The DSC curve and the value of the glass transi-

tion temperature of perfluorinated acrylic surfactant (PAS).

Figure 5. After seven months of immersion, p1 control

panel, p2 PAS and p3 TBT.

Preparation of Perfluorinated Surfactant Activates for Antifouling Paints 275

and maximum decomposition is around 84˚C represented

in the Figure 4 by a strong endothermic peak (Tm).

From these data, it is interesting to note that the sur-

factant is thermoplastic and its temperature Tm remains

unchanged even after a second heating.

Experiments are limited to a temperature of 200˚C to

avoid the evaporation of the product.

3.5. Application to the Marine Environment

Perfluorinated surfactants are very effective agents, anti-

fouling properties are monitored for exposure to the ma-

rine environment, the images corresponding to the sev-

enth month (September 2009) of immersion are pre-

sented in Figure 5.

There no attack and no fixing of fouling. All panels

have excellent protection against the development of

organisms, except a slight difference in the panel P2,

which corresponds to the acrylic resin there was spots on

its surface.

On the other hand, there are several inhomogeneous

spots on the panel P3 (TBT). The witness panel P1 is just

slightly swollen, no real attack.

After twelve months (Figure 6), the panel P1 is

attacked by marine organisms, a green layer appeared all

along the surface; there is a higher swelling of the left

side of the panel P3 (TBT). This phenomenon seems to

be the first part of the erosion, which propagates the

inside of the panel.

These results were confirmed after twenty months of

immersion (see Figure 7). For the panel P2, the paint is

still present. However this behavior seems to be mainly

controlled by hydrophobic-hydrophilic balance of the

surfactant.

In this period, first we announce that the witness panel

P1, is completely covered by fouling, as green algae and

barnacles. These organizations are well attached marine.

On the contrary, the panels P2 and P3 have a swelling in

the surrounding, which propagates progressively towards

the inner panel. These paintings show an effective

biocide. Note that the rate of swelling of P2 is less than

P3 (TBT).

Regarding the development of green algae, and com-

paring the images c and b of Figure 7, we see that the

second (P2), has a potential biocidal important. This re-

sult is in good agreement with literature [9].

The panel P2 has a biocidal effect of long-term than

the P3 and more the perfluorinated surfactant has not

effect as TBT toxicity [14].

In other words, the nature of the atoms that are exter-

nal (–CF3) is independent of the nature and the arrange-

ment of atoms which are located inside the chain (back-

bone chain), this gives mechanical stability and surface

properties specific to the surfactant (wettability of the

surfaces) [17-19].

Figure 6. After 12 months P1) control panel, P2) PAS and

P3) TBT.

Preparation of Perfluorinated Surfactant Activates for Antifouling Paints

276

Figure 7. After 20 months P1) control panel, P2) PAS and

P3) TBT.

Therefore, the perfluorinated compound (PAS) has a

strength that allows him to stay on the surface, it is per-

pendicular to the matrix [20,21].

4. Conclusions

The need to file biocide performance is always larger in

the field of paint, this paved the way in recent years, a

fruitful research both fundamental and applied. The de-

sired properties are primarily to improve the effective-

ness, duration of action, and decreased toxicity and re-

duced usage price. The solution adopted is to temporarily

fix a biocidal agent, chosen for its extensive range of

activity based on the protection needed.

Our research efforts have focused primarily on the

preparation of biocide molecule (surfactant PAS) and see

its behavior as antifouling paint.

The results obtained are:

1) From the study by the gel permeation chromatog-

raphy (GPC), we can say that the chromatogram led to

noticeable results that are qualitatively consistent. In ad-

dition, for this surfactant, the mass ratio gave 1.24. Fur-

thermore, the results of the Tables 3(a) and (b), allow us

to see that the perfluorinated surfactant PAS present in

dilute media (before the CMC), a significant degree of

association (Mn = 3800), then a critical micelle concen-

tration (CMC) of 1.545 × 10–4g/ml, and beyond the CMC,

the surfactant PAS has a large mass, we are in the pres-

ence of large micelles repellency.

2) The plot of differential scanning calorimetry (DSC)

gives excellent results, which makes this method a reli-

able tool in the study of glass transition temperature of

organic coating systems. From these data, it is interesting

to note that the acrylic surfactant resulting is thermoplas-

tic and temperatures Tg and Tm remains unchanged even

after a second heating.

3) The processing of panels, gives us the most obvious

difference when their protective capacity of corrosion.

The perfluorinated product showed better protection than

non-fluorinated (TBT). The presence on a fluorine of

quantity of 2% - 10% showed significantly improved the

protective properties.

4) In this study, the amount of agent used PAS (5% -

10%) was much less than that used in conventional paints,

which is 20% - 30% of the total. Thus the mechanical

properties of surfactant PAS can be further improved.

These fluorinated products can be used as coat, which

may limit moisture from reaching the outside and inside

the metal and generally give a longer life to the paintings.

In this study, we used a simple product non-hazardous

with fluorine atoms as a main chain. The panels are in

the water until now.

5. Acknowledgements

The author thanks, Professor Hadj Abdelhafid Sahraoui

Preparation of Perfluorinated Surfactant Activates for Antifouling Paints

277

and his team of Thermophysical of the condensed mat-

ter-Maison de la Recherche Environnement Industriel-

Dunkerque (University, Lille III).

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