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MANOJ KUMAR 

III Semester 

ME

Seminar on

HYDROPHOBIC AND HYDROPHILIC

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• Some of the common natural

Hydrophobic materials are

a!es" oil and fats#

Hydrophobicity comes also from the $ree% ord Hydro&ater'

and (hobicity &fear' it refers to the physical property of amaterial that repels a mass of ater#

)HA* IS MEAN* H+,RO(HO-I.I*+ /

*he e0aluation of hydrophobicity

is made throu$h ater contact

an$le measurements#

A ater droplet ould be

spherical so the ater contact

an$le ill be si$nificantly hi$h#

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• At the molecular le0el" the hydrophobic effect is important in

dri0in$ protein foldin$ formation of lipid bilayers and micelles"

insertion of membrane proteins into the nonpolar lipiden0ironment and protein1small molecule interactions# Substances

for hich this effect is obser0ed are %non as hydrophobes#

H+,RO(HO-I. E22E.*

*he hydrophobic effect represents the

tendency of ater to e!clude non1polar

molecules# *he effect ori$inates from

the disruption of hi$hly dynamic

hydro$en bonds beteen molecules of

li3uid ater#

.ontinued4#

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SU(ER H+,RO(HO-I. .OA*IN5

Super hydrophobic technolo$y

ma%es ater bounce" it stops it"

rolls it off the surface#

*he process of coatin$ the surface of a material ith hydrophobic

 property material in order to a0oid stic%in$ of li3uids on thatsurface#

*his is absolutely uni3ue ay of coatin$ unli%e con0entional hich

shrin% continuously durin$ dryin$ to produce lo porosity films#

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+oun$6s e3uation is used to describe the interactions beteen

the forces of cohesion and adhesion and measure hat is

referred to as surface ener$y#

www.ramehart.com/contactangle.ht

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• A drop ith a contact an$le o0er 789 is hydrophobic#

• *his condition is e!emplified by poor ettin$" pooradhesi0eness and the solid surface free ener$y is lo#

Continued..

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Hydrophobic interactions

• Hydrophobic interactions describe the relations beteen ater and

hydrophobes &lo ater1soluble molecules'#

• Hydrophobes are nonpolar molecules and usually ha0e a lon$ chain

of carbons that do not interact ith ater molecules#

• *he mi!in$ of fat and ater is a $ood e!ample of this particularinteraction#

• *he common misconception is that ater and fat doesn:t mi! because

the ;an der )aals

•

forces that are actin$ upon both ater and fat molecules are too ea%#

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.auses of Hydrophobic Interactions

• American chemist )alter Kau<mann disco0ered that nonpolarsubstances li%e fat molecules tend to clump up to$ether rather

that distributin$ itself in a ater medium" because this allo the

fat molecules to ha0e minimal contact ith ater#

Hdro!ho"ic

interaction# $Chem%i&i

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2ormation of Hydrophobic Interactions

• *he mi!in$ hydrophobes and ater molecules is not spontaneous=

hoe0er" hydrophobic interactions beteen hydrophobes are spontaneous#

• )hen hydropobes come to$ether and interact ith each other" enthalpy

increases & is positi0e' because some of hydro$en bonds that form the

clathrate ca$e ill be bro%en#

• *earin$ don a portion of the clathrate ca$e ill cause the entropy to

increase & is positi0e'" since formin$ it decreases the entropy#

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Accordin$ to the formula> ?5@ ?H1*?S

  ?H@Small positi0e 0alue

  ?S@ar$e positi0e 0alue

Result >?5@ Ne$ati0e

A ne$ati0e ?5 indicates that hydrophobic interactions are spontaneous 

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A((I.A*IONS

• A primary purpose of hydrophobic coatin$s such as polytetrafluoroethylene&(*2E' 

or poly!ylylene is to act as a barrier a$ainst ater commonly seen in automobiles

• '#ed in (a"rication on metallic nano rod to !re)ent icing.

• It# i# widel u#ed in aero#!ace indu#tr (or !ro)iding anti$icing

coating on the #ur(ace o( the aero!lane .

• Hdro!ho"ic #el( cleaning gla##e# are in#talled in tra*c #en#orcontrol unit.

• %e induce hdro!ho"ic reco)er a(ter !la#ma treatment+ a!h#ical contact treatment ,PC- .

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Hydrophilicity" also comes from the 5ree% ord Hydro &ater'

and (hilicity &friendship' it refers to a physical property of a

material that can transiently bond ith ater &HBO' throu$h

hydro$en bondin$# 2urthermore it allos the li3uid to enter the

 pores of a material and totally et it#

)HA* IS MEAN* H+,RO(HII.I*+ /

• Almost all natural materials are

hydrophilic in nature#

*he e0aluation of hydrophilicity is

made throu$h ater contact an$le

measurements# A ater droplet

ould occupy as lon$ surface of the

hydrophilic material as possible# So

the ater contact an$le ill be

si$nificantly lo#

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• *his is thermodynamically fa0orable" and ma%es these

molecules soluble not only in ater but also in other polar

sol0ents# *here are hydrophilic and hydrophobic parts of the

cell membrane#

• A hydrophilic molecule or portion of a molecule is one that is

typically char$e1polari<ed and capable of hydro$en bondin$"

enablin$ it to dissol0e more readily in ater than in oil orother hydrophobic sol0ents#

Hydrophilic coatin$s et the surface0ery easily" and maintain the etness for

lon$er time# *hus" usin$ hydrophilic

coatin$s eliminates the need for

additional lubricants#

H+,RO(HII. .OA*IN5

.ontinued4

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Here +al#o we u#e #ame 0gure o( oung1#e2uation to e3!lain hdro!hilicit

A drop ith a small contact an$le

is hydrophilic#

*his condition reflects better

ettin$" better adhesi0eness" and

hi$her surface ener$y#

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Hydrophilic Interactions

Interactions beteen ater and other molecules such that the

other molecules are attracted to ater are called hydrophilic

interactions#

Molecules that ha0e char$ed parts to them are attracted to the

char$es ithin the ater molecule#

*his is an important reason hy ater is such a $ood sol0ent

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.ontinued4#

5lucose molecules ha0e polar hydro!yl&OH' $roups in them and

these attract the ater to them# )hen su$ar is in a crystal the

molecules are attracted to the ater and $o into solution#

Once in solution the molecules stay in solution at least in part

 because they become surrounded by ater molecules# *his layer of

ater molecules surroundin$ another molecule is called a hydrationshell#

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)hat does the stren$th of Hydrophilic Interactions depend on/

• Inhibitory effect mainly depended on their concentration and to a

lesser e!tent on the ion char$e and hydrated ion radii#

•

Ste!wi#e regre##ion anal#i# !ro)ed that the#trength o( interaction de!end# on the !olarit!arameter# o( amino acid# and i# inde!endent o(their chemical #tructure.

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)en<el and .assie States of )ettin$

Here are to natural parameter>

A first natural and simple effect arisin$ from the presence of

microstructures is an increase of the surface area of the material#

r @CDBbhFpB

e can define to le0els= namely" the top of the posts and the $round

on hich they sit# 

A second natural parameter is the ratio 6S beteen the top and

 bottom surface areas" hich is also the post density#

ϕS @ bBFpB

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)hen depositin$ a ater drop on a such solid #It can adopt atleast to type of confi$uration1

Quéré D , Reyssat M

Phil. Trans. R. Soc.

 A 200!"##$%&"'(%&&#

conformin$ to the solid surface &%en7el #ituation'

Sittin$ on the top of the posts&,Ca##ie or (a&ir #tate'

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www.me.umn.edu/8li3339::/;4RI<CA;S/Re#earch/te3turing.htm

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*he Second and simplest picture is the so1called )en<el state

&fi$ure the drop Gust follos the structures on the material&)en<el C7'#

*his ill affect both the ettin$ &the 0alue of the e3uilibrium

an$le" that is the one hich minimi<es the surface ener$y of the

drop' and the adhesion &characteri<ed here by the 0alue of thecontact an$le hysteresis'#

cos@r cos

)en<el state

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.assie state12a%ir state

*hird fi$# implies the creation of a li3uidL0apour interface belo the

drop" on a fraction of surface of the order of CϕS" considerin$ these

interfaces as flat &the drop is lar$e compared ith the pillars"

implyin$ a ne$li$ible cur0ature of the li3uidL0apour interface at the

scale of pillars'#

*he cosine of the apparent contact an$le is then an a0era$e beteenthe cosine of the +oun$ an$le and the cosine of C89" the an$le of a

ater drop on air" here the ei$hts for the a0era$e are" respecti0ely"

ϕS and CϕS#

cos@ 1C D s&CDcos'

&.assie P -a!ter C7QQ'

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 -HAN=S