Notes on Classification and Charactristics of Polymer

7/31/2019 Notes on Classification and Charactristics of Polymer

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Notes

On

CLASSIFICATION AND CHARACTRISTICS OF POLYMER

Keyur Vasava


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Polymer

The w o rd Po lym er com es f ro m t he Greek " po ly"m ean ing m any, and " m ero s" , par t s o r un it s. Apo lym er is a gro up o f m any u nit s. Yo u co m bine m any" m o n om e rs" (in divid ual u nit s) t o creat e a p o lym e r.

Po lym ers ar e su bst an ces co nt ain in g a lar ge n u m b ero f st ru ct ural u nit s jo in ed b y t he sam e t ype o f lin kage.These su bstances o f ten fo rm in to a chain -likest ruct ure. Po lym ers in t he nat ural w o rld have beenaro u n d sin ce t h e b egin n in g o f t im e . St arch , ce llu lo se ,

and rubber all possess po lymer ic p rope rt i es.

IUPAC def ini t ion: A polymer is a substance

com po sed of m olecules characte rized by t hem ul t ip le repet i t ion of on e o r m ore species ofatom s or groups of atom s l inked t o each ot herin am o u nt s su ff icie nt t o p ro vid e a set o fprop er t ies th at do no t vary m arkedly w i th t headdi t ion o f one or a few of t he con st i tu t iona lrepeat ing u nit s.


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purpose

Po lym e rs are b eco m i ng in creasin gly im p o rt an t in t h ef ield o f d rug de liver y. The phar m aceut icalapp licat io ns o f po lym ers range f ro m t h eir use asb in ders in tab le t s, fo r visco sit y an d f lo w co nt ro ll in gagent s in l iqu ids, suspensio ns and em ulsio ns.Po lym e rs can b e u sed as f ilm co at in gs t o d isgu ise t h e

un pleasant tast e o f a dr ug, to e nh ance dr ug st ab il it y

and t o m od if y d r ug r elease char act e ri st i cs.

Classificat ion of Polym er:

1)Based on or igin o f Polym ers.

2)Based on presence of carb on atom :

3)Based up on t he ph ysical prop ert y related toheat ing:

4)Based on m icrost r ucture of po lym er:

5)Based on react ion m od e of p olym erizat ion:

6)Based on m echanism of po lym erizat ion:

7)Spat ial ly or iented po lym ers:

8)Based on d egradat ion of po lym er:


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Based o n o r igin o f po lym er:

N atura l po lym ers:

Pro te in- si lk, col lagen, and kerat in Carb oh ydrat es -cel lulo se, star ch, glycogen DNA- RNA Oth er Natu ral polym ers: Rubb er (hydrocarbon base)

and sil icon es (alter nat ing si l icon and o xygen),Col lagen ,Album in, Casein.

Sem i synth et ic polym ers : Gelet in , f ib r inogen ch it i n & ch i toson , dext ran, a lginate

Synth et ic polym ers: Polyet hylene, nylo n & PVC.

Based on presen ce of Carbo n Atom :

O rganic po lym ers:M onom ers o f the po lymercontain C and as ot her a tom s m ost ly H and O.eg) polyprope len

Ino rgan ic po lym ers:M onom ers o f the po lym er

general ly no t cont ain C as an at om . eg)si l iconpo lymer


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Based upo n p hysical propert y related to he at ing:

Th e r m o p la st ic Po ly m e r s: m at er ial t hat is p last ic o rdefo rm able m e lt to l iq u id w h en heated and f reezest o b re et l e. Eg) Po lye thylen e, p vc, seal in g w ax .

Th erm ose tt in g Po lym e rs:Therm o set s, w h ich aredensely cro ss-lin ked in t he fo rm o f a net w o r k,d egrad e u po n h eat in g, w h ile t h er m o plast ics, w h ichdo no t co ntain cro ss-lin ks, m elt u po n h eat ing. Eg)Asbestos .

Rubb ers a nd Elasto m ers:Rubbery materials that

can st retch m any t im es their or iginal lengt h; th eydo not mel t upon appl icat ion of heat , they wi l ldegrade if heated to h igh enoughtemperature.Eg)Natural rubber, synthetic rubber,silicone ru bb er.

Fibers:Nylon, ter ylene.

Liquid resins: Epoxy adhesive,polysulphidesealants


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Based on m icrost ructu re o f p olym er:

ho m op olym ers: cont ain a single k ind ofmonomer .eg) -A-A-A-A-A-A-A-A- Ho m o po lym e r

polystyrene. copo lym ers: cont ain m ore t han one k ind o f

m on om er(a) rando m (b) al ternat ing (c) b lock (d)graft

a) -A-B-B-A-B-A-A-B- Ran d om Co p o lym erb ) -A-B-A-B-A-B-A-B- Alt er n at in g Co p olym erc) -A-A-A-A-B-B-B-B- Blo ck co p o lym er

Based on reaction m ode of po lym erisation:

Add it ion Polym ers:

t he m onom er m olecules bond to each ot her

w ithou t th e loss of any other atom s.

Prepared by t he M ono m ers cont ain one or

m ore double or t r ip le bonds or by t he r ing

opening of cyclic st ructu res.

Eg)neoprene.


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Condensation Polymers:

Usually tw o d i ffe rent m onom ers combines w i th t he loss o f a

sm all m olecules ,usually w ater

Form ed by successive reactio ns of f unct ional group s , and

repeat ing un it o f the p o lymer has few er atom s th an the

monomers .

Eg)nylon,silk,polyesters.


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Based on m echan ism of polym er isat ion:

A) Cha in Polym erizat ion Add it io n po lym ers Free radical Anionic Cationic Zegle r na t ta Copolymerzat ionEg) vinyl acet ic acid,acr i l ic acid polym er

(b ) Step Grow th Po lym er iza t ion Condensat io nPolymers

eg) po tassium viny l t r i f lurob urate.

Base d on spat ial ly orient ed po lym er:

Rando m atact ic: rando m ly arranged po lymer do

no t crystall ize. Eg) Polyet hylen e

Isot act ic: i f al l t he Y un its are in t he sam eplane,and isot act ic polym er h aving tendancy to

form a hel ix .

eg)polychloroprene.

Sym m et rical synd iot act ic: i f a Y un it ap pears

alternat ively on top and bot t om .

Eg)polystyrene


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Based o n degradation of polym er:

Biodgradab le polym ers: It can be def ined as po lym ers co m p r ised of

m o no m ers linked t o o ne ano t her t hro ugh f unct io nal

group and have unstab le lin kage in t he backbo ne.

And they delivers t he dr ug in to b ody af terb iodegradat ion o f po lym er.

eg)Col lagen, Album in,Casein,poly lactate etc.

CH ARACTERISTICS O F PO LYM ER:

Solubility Hydrop hobicity/ Hydrop hilicity

Gla ss tra nsit ion t em pera tu re

Rheologic

M olecula r w eight

analyt ical


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Solubility

W ater so luble polym ers:Som e polym ers are f ree ly so luble in w ater even t hou ght hey are of very h igh m olecular w eight .Exam ples of suchpolym ers are: po lyviny l a lcoho l ,Polyethylene oxide et c.

Hydrogels:These are h ighly hydroph i l lic polym ers t hat h ave beencrossl inked by m eans of covalent b ond s. Because t hepo lym er cannot dissolve due t o covalent crossl inks,w aterupt ake is m ore t han in hydrophi l l ic l inear po lym er.

H ydropho bicity/ Hydrop hi licit y

Accord ing to the na tu re o f the po lym er w ater in te ract ions po lym ers can

be bro adly c lassi f ied in to th e fo l low ing categor ies:

Hydrophob ic po lym ers:

These are essent ia l ly w ater im perm eable and w hen p laced in anaqueous environm ent, w i l l absorb very l i t t le w ater.

Str uctu ra l paramet ers th at contr ibut e to t h is prop er t y are chainst i f fn ess,high degree of crystal l in i t y and pr esence of highlyhydro ph obic group s, These absorb less th an 5% of w ater

Hydroph i l l ic po lym ers:

These absorb m ore t han 5% of w ater.

Param etars th at cont r ibut e to th is prop er t y are Chainflexibi l i t y,absence of Crystal l in i t y and presence of grou p asam ino,Carboxyl and hyd roxyl.


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Glass Transition Temperature

A parameter of particular interest in syntheticpolymer manufacturing is the glass transitiontemperature (Tg), which describes the

temperature at which amorphous polymers

undergo a second order phase transition from a

rubbery, viscous amorphous solid to a brittle,glassy amorphous solid. The glass transition

temperature may be engineered by altering the

degree of branching or cross-linking in the

polymer or by the addition of plasticizer.

RHEOLOGY

Rheo = flow

Viscosit y (h, po ise) is an expression of t heresistan ce of a fluid t o flo w .

Fluidit y (f) = 1/h

New ton s t heory


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New t ons t heo ry

F/ A = h dn/ d r ; h = F/ G;G = dn/ d r = velocit y gr ad ient / rat e o f sh ear

F = F/ A = shear st ress

Rate of shear is directly p rop or t ional t oshearing stress.

Rheogram s of d ifferent f lu ids


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Importance

The num ber average m olecular w eight M n and the

w eight average m olecular weight M w impor tant fo r

th e polym er d ist r ibut ion w hich are f rom di f ferent

sou rce and m oleculari ly are sam e .

M n= N iM i/N i

where,N i num ber o f mo lecules of m olecular w t M i,

Polydispe rsit y Ind ex (PD I)

The rat io of Mw/ Mn called Polydispersityindex.

Gives in form at ion abou t d ist r ibu t ion o fpo l ymer

Highly branched po lym ers : PDI > 20

General ly (co m m ercial po lym ers) : 2 < PDI

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Notes on Classification and Charactristics of Polymer