surfactants (lec_2)_ppt [compatibility mode]

8/10/2019 SURFACTANTS (Lec_2)_ppt [Compatibility Mode]

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SURFACTANTSSURFACTANTS


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ReviewReview

Why water droplets are spherical?Why water droplets are spherical?

Whats the reason for the capillary rise??Whats the reason for the capillary rise??

Whats the origin of downward meniscus????Whats the origin of downward meniscus????


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DO YOU KNOW?DO YOU KNOW?


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Description of A SurfactantDescription of A Surfactant


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Surfactants are also known as amphiphils, colloidalSurfactants are also known as amphiphils, colloidalelectrolyte, amphipathic compounds.electrolyte, amphipathic compounds.


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A surfactant moleculeA surfactant molecule


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Examples of polar and non polar groupsExamples of polar and non polar groups

Polar group (head)Polar group (head) NonNon--polar group (tail)polar group (tail)

--Hydroxyl group (OH)Hydroxyl group (OH)

--Aldehydic group (CHO)Aldehydic group (CHO)

--Carboxylic groupCarboxylic group

(COOH)(COOH)--Sulfate esterSulfate ester

--Nitro group (NONitro group (NO22))

--Amine group (NHAmine group (NH22))

--Halogen (CL or Br)Halogen (CL or Br)

--Lower alkyl group CLower alkyl group C33CC88((CHCH33--CHCH22--CHCH22------))

--Branching alkyl chainsBranching alkyl chains--

Aromatic ring such asAromatic ring such asbenzene or naphthalenebenzene or naphthalene


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Types and Chemical Structures ofTypes and Chemical Structures ofSurfactantsSurfactants


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ExamplesExamples

AnionicAnionic; sodium; sodium dodecyldodecyl ((lauryllauryl))sulphatesulphate

Cationic;Cationic;CetrimideCetrimide

NonNon--ionic:ionic:TweensTweens, spans, spans


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HHydrophilicydrophilic--LLipophilicipophilicBBalance (alance (HLBHLB))

It is an arbitrary scale fromIt is an arbitrary scale from 00 toto 2020 depicting thedepicting the

Hydrophilic/Hydrophilic/LipophilicLipophilic balance of a surfactant.balance of a surfactant.

Products with low HLB are more oil soluble. HighProducts with low HLB are more oil soluble. High

HLB represents good water solubility.HLB represents good water solubility.


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HHydrophilicydrophilic--LLipophilicipophilicBBalance (alance (HLBHLB))


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Surfactant classificationSurfactant classificationAccording to charges:According to charges: 33 types:types:A. IonicA. Ionic

AnionicAnionic e.g. sodium stearate, sodium lauryle.g. sodium stearate, sodium laurylsulphatesulphate CHCH33(CH(CH22))1111 OSOOSO33

--NaNa++

CationicCationic e.g.e.g.quaternary ammoniumquaternary ammoniumcompounds, hexadecyl trimethyl ammoniumcompounds, hexadecyl trimethyl ammoniumbromide (cetrimide).bromide (cetrimide).

B. NonionicB. Nonionic e.g. polyethylene oxidee.g. polyethylene oxide--Sorbitan monoSorbitan mono--oleate (Span)oleate (Span)

--Polyoxyethylene (CHPolyoxyethylene (CH33CHCH22O)O) Sorbitan monoSorbitan mono--oleate (Polysorbateoleate (Polysorbate 8080 = Tween= Tween 8080))


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Surfactant classification (cont.)Surfactant classification (cont.)

According to HLB Values:According to HLB Values: Know HLB:Know HLB:

Can determine surfactant suitability as:Can determine surfactant suitability as:

AntiAnti--foaming agent (HLB=foaming agent (HLB=00--33))Emulsifying agent w/ o (HLB=Emulsifying agent w/ o (HLB=44--66))

Wetting/ spreading agent (HLB=Wetting/ spreading agent (HLB=77--99))

Emulsifying agent o/ w (HLB=Emulsifying agent o/ w (HLB=88--1818))

Detergent (HLB=Detergent (HLB=1313--1515))SolubilisingSolubilisingagent (HLB=agent (HLB=1010--1818))


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CCriticalriticalMMicelleicelleCConcentration (oncentration (CMCCMC))

After saturation of the liquid surface withAfter saturation of the liquid surface withsurfactant molecules, any excess willsurfactant molecules, any excess willdistributed in the bulk of the solution.distributed in the bulk of the solution.

The solution looks like any other particles ofThe solution looks like any other particles ofsolute distributed randomly throughout thesolute distributed randomly throughout thewater. When the concentration gets highwater. When the concentration gets highenough, the molecules begin to arrangeenough, the molecules begin to arrangethemselves in hollow spheres, rods and disksthemselves in hollow spheres, rods and diskscalledcalledMicellesMicelles also calledalso called associated colloids.associated colloids.


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Micelles ShapesMicelles Shapes


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Factors Governing Micelle ShapeFactors Governing Micelle Shape


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Example of the effect of molecular structureExample of the effect of molecular structureon the micelle shapeon the micelle shape


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Factors affecting critical micelleFactors affecting critical micelleconcentrationconcentration

11-- In case of polar solvents(In case of polar solvents(e.ge.gwater)water)

A)increasing the length of hydrocarbonA)increasing the length of hydrocarbonchain (minor interaction with waterchain (minor interaction with water i.ei.e

facilitate the transfer from an aqueous phasefacilitate the transfer from an aqueous phaseto micelles)produces a decrease in the CMCto micelles)produces a decrease in the CMC

B)increased polarity of the polarB)increased polarity of the polarportion(greater interaction with waterportion(greater interaction with water i.ei.e

retard the transfer from an aqueous phase toretard the transfer from an aqueous phase tomicelles)produces an increase in CMCmicelles)produces an increase in CMC


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AdditivesAdditives

--With ionic micelles, electrolyte addition reducesWith ionic micelles, electrolyte addition reduces

the repulsion between charged groups at thethe repulsion between charged groups at thesurface of the micelle CMC decreases as electrolytesurface of the micelle CMC decreases as electrolyteincreases.increases.

--Addition of organic molecules affect CMC.Addition of organic molecules affect CMC.Influence water structure. Sugars structure makersInfluence water structure. Sugars structure makers

lower CMC; urea andlower CMC; urea and formamideformamidestructurestructurebreakersbreakers increase CMC.increase CMC.


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22--In case of nonIn case of non--polar solvents(polar solvents(e.ge.gchloroform)chloroform)

The increased polarity of the hydrophilic part willThe increased polarity of the hydrophilic part will

lower CMC whereas, the longer the hydrocarbonlower CMC whereas, the longer the hydrocarbonchain , the higher the CMCchain , the higher the CMC

33--Nature of hydrocarbon chainNature of hydrocarbon chain

The branched chain ring systems and doubleThe branched chain ring systems and doublebonds tend to raise CMC.bonds tend to raise CMC.

44--TemperatureTemperature the increased temperature increases CMC.the increased temperature increases CMC.


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Mechanism of Surfactants ApplicationsMechanism of Surfactants Applications

Adsorption andAdsorption and micellisationmicellisation..

AdsorptionAdsorption basic function of wetting,basic function of wetting,

spreading, suspending and emulsifying ,spreading, suspending and emulsifying ,detergents , foaming , antifoaming agentsdetergents , foaming , antifoaming agents

MicellisationMicellisation basic function ofbasic function of solubilizingsolubilizingagent.agent.


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A. ADSORPTION AT INTERFACESA. ADSORPTION AT INTERFACES

Spreading agentSpreading agent

Wetting agentWetting agent

DetergentDetergent

Foam and Antifoaming agentFoam and Antifoaming agent


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Mechanism of action by adsorptionMechanism of action by adsorptionA. Spreading AgentA. Spreading Agent

Spreading depends onSpreading depends on

Strength of interactionsStrength of interactions

Spreading coefficient (S)Spreading coefficient (S)

spreading occur if S=+ve.spreading occur if S=+ve.S=S=WaWa --WcWc


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How does surfactant help spreading of oil onHow does surfactant help spreading of oil onwater?water?

Surfactant adsorp at water surfaceSurfactant adsorp at water surface

Surfactant adsorp at oil surfaceSurfactant adsorp at oil surface

Surfactant adsorp at w/o interface.Surfactant adsorp at w/o interface.

Applications of spreading agents:Applications of spreading agents: To produce thin and uniform film.To produce thin and uniform film.

Facilitate spreading of eye ointment.Facilitate spreading of eye ointment.

Spreading of medicinal lotions and sprays to theSpreading of medicinal lotions and sprays to the

surface of the skin and mucous membranes.surface of the skin and mucous membranes. Displacement of air from cotton pads so thatDisplacement of air from cotton pads so that

medicinal solution can be absorbed.medicinal solution can be absorbed.


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Mechanism of action by adsorptionMechanism of action by adsorptionB. Wetting AgentB. Wetting Agent


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B. Wetting Agent (cont.)B. Wetting Agent (cont.)

Wetting occur ifWetting occur if


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Mechanism of action by adsorptionMechanism of action by adsorptionC. DetergentC. Detergent


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How can we eliminate a fat soil?How can we eliminate a fat soil?


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h i f i b d ih i f i b d i


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Mechanism of action by adsorptionMechanism of action by adsorptionD. Foam and AntiD. Foam and Anti--foaming Agentfoaming Agent

A foam is a relatively stable structureA foam is a relatively stable structureconsisting of air pockets enclosed withinconsisting of air pockets enclosed withinthin film of liquid; the gasthin film of liquid; the gas--inin--liquidliquid

dispersion is stabilized by a foaming agent.dispersion is stabilized by a foaming agent.


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The foam dissipate as the liquid drains awayThe foam dissipate as the liquid drains awayfrom the area surrounding the air globulesfrom the area surrounding the air globulesand the film finally collapses.and the film finally collapses.

Foams are sometimes useful in pharmacyFoams are sometimes useful in pharmacye.g. tooth paste, burn dressing, shampooe.g. tooth paste, burn dressing, shampooand nonand non--aqueous spray for topical, rectalaqueous spray for topical, rectaland vaginal administration.and vaginal administration.


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Mechanism of Action ByMechanism of Action By MicellizationMicellization

SolubilizationSolubilization: the process of: the process of solubilizationsolubilizationdepends on the concentration ofdepends on the concentration of solubilizingsolubilizing

agent(surfactant).agent(surfactant).

surfactants (lec_2)_ppt [compatibility mode]

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