بسم الله الرحمن الرحيم

PALESTINE POLYTECHNIC UNIVERSITYCOLLEGE OF APPLIED SCIENCE

DEPARTMENT OF APPLIED CHEMISTRY

PHASE BEHAVIOR OF NONIONIC SURFACTANT

PREPARED BY:BARAA QARAJEH &

NUHA MAHAREEQ

TO MR:YASSIN QAWASMEH

MICROEMULSIONMacroscopically isotropic mixture of at least three component:

1. Water

2. Oil

3. Surfactant

• Are single thermodynamically stable phase

PHASE INVERSION

refers to a phenomenon that occurs when agitated oil in water emulsion, reverts to a water in oil and vice versa.

Emulsification via phase inversion is widely used in fabrication of cosmetic products, pharmaceutical products (e.g., vesicles for drug delivery), foodstuff and detergent.

How we can determine the phase inversion:

1. At low temp=22C, extended central miscibility gap exist.

The inclination of tie-lines result from preferred solubility of C4E1 in water and indicates that the surfactant rich water phase(a).Coexist with oil excise phase (b).

2. at temp= 31.23,Three phase triangle evolves from lower critical tie-line, which connects a critical phase (a) at the critical endpoint cepβ.

3. At temp= 37, critical phase separated into two phases:

1. Increasingly water rich

2. Increasingly surfactant rich

<<result : three phase triangle open with small

phase region water rich, and large phase region oil rich.

4. At temp= 49.2, increasing in temp affects:

a. the ph phase region shrink.

b. the p phase region grows and touch the binary Water

and C4E1 side of Gibbs triangle.

5. At temp= 52,Extension of the three phase triangle

triangle is almost symmetric

the solubilization of equal volumes of water and oil.

<< surfactant at the optimum state.

6. At temp= 72.89,Upper critical tie-line connects a critical surfactant rich oil phase with an excise water phase.

7. At temp= 82, the extended central miscibility gab exist.

the +ve inclination of the tie-line indicates that the surfactant rich oil phase coexist with a water-excess phase.

<<< so clear, that’s the phase inversion occures over an extended temp range, which make the exact location of phase inversion is diffecult.

PHASE INVERSION

THE OPTIMUM STATE:

The optimum state occurs at the tip of three phase triangle i.e the composition of the surfactant rich middle phase.

Therapy: the tip of this symmetric triangle sets the lowest possible amount of surfactant is equal to solubilize equal volumes of water and oil.

When increasing the hydrophobic chain length of the surfactant from C8E5 to C10E5,the mean temp Tm is lowered from Tm=61.5 to Tm= 44.6.C

Comparing between both Gibbs triangles with increasing the amphiphilicity, decreasing the X-point to wc.m =0.14 and the

striking appearance of the lamellar mesophase (Lα) is observed. Then extends deep into the water and oil corners of the Gibbs triangle.

Therapy the Lα phase intrudes into the two phase regions:

the on the water rich side.

the on the oil rich side.

the three phase triangle result.

It appears as if certain ratios of surfactant and oil, or surfactant and water, particularly favor the existence of the lamellar phase.

With increasing the hydrophobic chain length of the surf, the highet of the triangle decreases i.e the x point shifted to lower surf mass fraction

Lamellar phase (Lα) is absent in C8E5 system but extends over a large regions in C10E5 & C12E5 systems.

Increasing both the hydrophobic chain length and the size of the hydrophilic group of the surf, the x point shifts to lower value of wc,m.

<< the efficiency increases.

Therapy the stability range of the bicontinous one-phase microemulsion shrinks, due to the increased extension of the lamellar phase.

<< looking at the phase transition as a function of temp, one realizes that the ability of the surfactant to solubilize water and oil runs through a max at the Tm and decreases below and above this temp.

The +vly defining the efficiency of the of a surfactant by the lowest amount of surf wc,m required equal volumes of water and oil at the mean temp (Tm).

EFFICIENCY

The amount of surfactant needed should be min in technical applications.

We can demonstrate this by:

The hydrophobic chain length n is varied bet 6-12, the

# of oxyethylene groups x bet 2-7.

For n < 14, the phase behavior changes qualitativily and no x point can be found anymore to the vast extension of the lamellar phase.

Increasing n ==< wc,m decreasing.

<< the surfactant become more efficient, since the surfactant be more hydrophobic.

<< the x point shifts to lower temp.

Increasing the x, the points shift to higher temp,

<< due to an increasing hydrophilicity of the surfactant.

<< Wc,m increasing slightly.

Increasing the k(of the n-alkane), the x points shift to higher temp and wc,m increasing.

<< I,e the surfactant becomes less efficient.

Increasing of oil chain length Tα (critical temp of lower miscibility gap) shifts to higher temp.

MONOMERIC SOLUBILITY

Can distinguish bet surfactant molecules by the reside at microscopic w/o interface

<< surfactant molecules dissolves in the excess phase of water or oil.

The significant of this fact not only that part of the surfactant is lost in this way, but that the associated osmotic pressure seems to be an important variable influencing the driving force for microemulsion forming.

The solubility of monomer of the surf/w ,wcmon,a easily determined from surface tension measurmentes

The solubility of monomer of the surf/o ,wcmon,b is difficult, which provided by the macroscopic phase behavior through the determination of the mass fraction of the surf wc,o .

Wc,mon,b = wc,o +wc,mon,a [α(1-wc,o)-1]/wc,o +α(1-wc,o )-wc,mon,a

.

In fig 5.9 :

Show the solubility of wc,mon,b in n-octane at the mean temp(Tm )

Therapy:the solubility of wc,mon,a in water was set as:

• .03= C6E2

• .02= C6E3

• .01= C6E4

• .006= C7E3

• .002=C7Ex .

From the fig:

The monomeric solubility wc,mon,b in n-octane decreases with n

And increases slightly with x

OVER VIEW OF MICROSTRUCTURE

The extensive study of microstructure of the model system H2O-n-octane-C12E5 by TEM, SANS NMR and others.

by seen fig 5.4 & 5.7, represent the possible microstructures into the extended one-phase region

The structure of the microemulsion is bicontinuous with zero mean curvature of the amphiphilic film(J= 0),Negative Gauss curvature(K > o)

When wc increases, length scale of the structure become smaller, because the total area of the internal interface increases.

At high surfactant conc, the lamellar phase is observed with zero curvature.

MICROSTRUCTURE

i.e J=0 & K=0

Moving both wc & temp-wise away from the x point, a transition to O/W & W/O droplets is found at low & high temp with the droplet size decreasing as one movies further away from the x point.

The change of the structure as a function of the oil-water plus oil volume fraction ᶲ ,in fig(5.22) within the one-phase channel on the water-rich side.

the mixture consist of stable dispersions of oil droplets in water, which transform into a branched tubular oil network with rising temp.

Increasing ᶲ, bicontinuous structure is found around the mean temp of the three phase body.

i.e if .2> ᶲ > .8 on the oil-rich side, the dispersed water droplets are found at high temp, which transform into a branched tubular water network with decreasing temp.

<< a gradual change in the mean and Gauss curvature of the amphiphilic film with temp and composition is the over all observation.

THE FISH PHASE DIAGRAM.