Polymers

The word polymer has a Greek origin. which means many units (parts). Polymer is defined as a chemical substance of a high molecular mass formed by the combination of a large number of simple molecules, called monomers. e.g.,

Polymerisation
The process by which the monomers get combined and transformed into polymers. is known as polymerisation.

n [Monomer] → Polymer

Difference between Polymers and Macromolecules

Polymers have a molecular structure consisting chiefly or entirely of a large number of similar units bonded together. These units are called repeating units. These repeating units represent the monomers from which the polymer is made. Most of the times a macromolecule is formed due to polymerization. Then they are called polymer molecules. But some macromolecules are formed due to the chemical bonding of more atoms together. The main difference between polymer and macromolecule is that polymers contain repeating units that represent the monomers whereas not all macromolecules have a monomer in their structure.

Classification of Polymers :

1.Based on Source of Origin

1. Natural polymers
2. Synthetic polymers
3. Semisynthetic polymers 

2.Based on Structure

1. Linear polymers
2. Branched chain polymers
3. Cross-linked polymers or network polymers   

3.Mode of Polymerisation

1. Addition polymers
2. Condensation polymers  

4.Molecular Forces

1. Elastomers
2. Fibres
3. Thermoplastics
4. Thermosetting plastics    

1.Based on Source of Origin

1. Natural polymers[Those polymers which occur in nature. i.e., in plants or animals. are called natural polymers.e.g;silk, wool, DNA, cellulose and proteins]
2. Synthetic polymers[The polymers which are prepared in the laboratory are known as synthetic polymers or man-made polymers, e.g., polythene, synthetic rubber, PVC, nylon-66, teflon, orlon etc.]
3. Semisynthetic polymers [Polymers obtained by making some modification in natural polymers by artificial means, are known as semi synthetic polymers, e.g., cellulose acetate (rayon), vulcanised rubber etc.]

2.Based on Structure   

1. Linear polymers:[
   
   

   Linear polymers are the polymers in which monomeric units are linked together to form long straight chains. The polymeric chains are stacked over one another to give well packed structure. As a result of close packing, these polymers have high densities, high tensile strenghts and high melting points.

   
   

   Eg : polythelene, nylons, polyesters, polystyrene etc…]

   
   

   
   

   properties:

   
   

   1)High melting point

   
   

   2)High density

   3)High tensile strength due to close packing of polymer chains.

   Applications:

   food packaging, shampoo bottles,Milk, water, and juice containers, grocery bags, toys, liquid detergent bottles,Soft drink based cups, flower pots, drain pipes, signs, stadium seats, trash cans, re-cycling bins, traffic barrier cones, golf bag liners, toys
2. Branched chain polymers:[In such polymers, the monomer units are linked to form long chains with some branched chains of different lengths with source(irregular packing). As a result of branching, these polymers are not closely packed in space. Thus, they have low densities, low tensile strength as well as low melting and boiling points. Some common examples of such polymers are low density polyethene, starch, glycogen etc.]
   properties:
   1)A low density
   2)Lower melting points and tensile strengths are evident, because the intermolecular bonds are weaker and require less energy to break.
   3)
   Applications:
3. Cross-linked polymers or network polymers:[In such polymers, the monomer units are linked together to form three dimensional network 3D. These are expected to be quite hard, rigid and brittle. Examples of cross linked polymers are bakelite, glyptal, melamine-formaldehyde polymer ,Vulcanised Rubberetc.They are mainly Thermosets Polymers]
   properties:
   1)They get degraded on Excessive Heating, though they can also resist the HIGH TEMPERATURES compared to Thermoplastics Polymers.
   2)High density
   3)Higher melting points and tensile strengths are evident, because the intermolecular bonds are strong and require high energy to break.
   Applications:
   

   cross linking polymer used to boost the thermal, physical properties.

   Synthetic rubber used for tires is made by crosslinking rubber through the process of vulcanization This crosslinking makes them more elastic.

   A crossed link polymer Ethylene-vinyl-acetate is used in solar panel manufacturing.

   Cross-linked polymers are used in making large number of materials because they are mechanically strong and resistant to heat, wear and attack by solvents. .

3.Mode of Polymerisation

1. Addition polymers :A simple representation is -[A-A-A-A-A]-

   The polymers formed by the polymerisation of monomers containing double or triple bonds (unsaturated compounds) are called addition polymers. Addition polymers have the same empirical formula as their monomers. Addition polymers can further be classified on the basis of the types of monomers into the following two classes:
   A. Homopolymers: The polymers which are obtained by the polymerisation of a single type of monomer are called homopolymers.
   

   Some Common Addition HomoPolymers

   Name(s)	Formula	Monomer	Properties	Uses
   Polyethylene low density (LDPE)	–(CH2-CH2)n–	ethylene CH2=CH2	soft, waxy solid	film wrap, plastic bags
   Polyethylene high density (HDPE)	–(CH2-CH2)n–	ethylene CH2=CH2	rigid, translucent solid	electrical insulation bottles, toys
   Polypropylene (PP) different grades	–[CH2-CH(CH3)]n–	propylene CH2=CHCH3	atactic: soft, elastic solid isotactic: hard, strong solid	similar to LDPE carpet, upholstery
   Poly(vinyl chloride) (PVC)	–(CH2-CHCl)n–	vinyl chloride CH2=CHCl	strong rigid solid	pipes, siding, flooring
   Poly(vinylidene chloride) (Saran A)	–(CH2-CCl2)n–	vinylidene chloride CH2=CCl2	dense, high-melting solid	seat covers, films
   Polystyrene (PS)	–[CH2-CH(C6H5)]n–	styrene CH2=CHC6H5	hard, rigid, clear solid soluble in organic solvents	toys, cabinets packaging (foamed)
   Polyacrylonitrile (PAN, Orlon, Acrilan)	–(CH2-CHCN)n–	acrylonitrile CH2=CHCN	high-melting solid soluble in organic solvents	rugs, blankets clothing
   Polytetrafluoroethylene (PTFE, Teflon)	–(CF2-CF2)n–	tetrafluoroethylene CF2=CF2	resistant, smooth solid	non-stick surfaces electrical insulation
   Poly(methyl methacrylate) (PMMA, Lucite, Plexiglas)	–[CH2-C(CH3)CO2CH3]n–	methyl methacrylate CH2=C(CH3)CO2CH3	hard, transparent solid	lighting covers, signs skylights
   Poly(vinyl acetate) (PVAc)	–(CH2-CHOCOCH3)n–	vinyl acetate CH2=CHOCOCH3	soft, sticky solid	latex paints, adhesives
   cis-Polyisoprene natural rubber	–[CH2-CH=C(CH3)-CH2]n–	isoprene CH2=CH-C(CH3)=CH2	soft, sticky solid	requires vulcanization for practical use
   Polychloroprene (cis + trans) (Neoprene)	–[CH2-CH=CCl-CH2]n–	chloroprene CH2=CH-CCl=CH2	tough, rubbery solid	synthetic rubber oil resistant

[Thanking  William Reusch ,Professor Emeritus (Chemistry) at Michigan State University]

B.Copolymers:The polymers which are obtained by the polymerisation of two or more monomers are called copolymers.

Some Useful Addition Copolymers

Monomer A	Monomer B	Copolymer	Uses
H2C=CHCl	H2C=CCl2	Saran	films & fibers
H2C=CHC6H5	H2C=C-CH=CH2	SBR styrene butadiene rubber	tires
H2C=CHCN	H2C=C-CH=CH2	Nitrile Rubber	adhesives hoses
H2C=C(CH3)2	H2C=C-CH=CH2	Butyl Rubber	inner tubes
F2C=CF(CF3)	H2C=CHF	Viton	gaskets

 

Polymerization Methods

Addition polymerization is the successive addition of alkene monomers to one another. The addition reaction may occur by way of 

• radical, (Link)
• cationic, (Link)
• or anionic intermediates.(Link)

2. Condensation polymers: The polymers which are formed by the combination of monomers with the elimination of small molecules such as water, alcohol, hydrogen chloride etc., are known as condensation polymers, e.g., polyester Dacron and nylon 6,6 is formed by the condensation of hexamethylene diamine with adipic acid.

   
   
   
   

Some Condensation Polymers

Formula	Type	Components	Tg ºC	Tm ºC
~[CO(CH2)4CO-OCH2CH2O]n~	polyester	HO2C-(CH2)4-CO2H HO-CH2CH2-OH	< 0	50
	polyester Dacron Mylar	para HO2C-C6H4-CO2H HO-CH2CH2-OH	70	265
	polyester	meta HO2C-C6H4-CO2H HO-CH2CH2-OH	50	240
	polycarbonate Lexan	(HO-C6H4-)2C(CH3)2   (Bisphenol A) X2C=O   (X = OCH3 or Cl)	150	267
~[CO(CH2)4CO-NH(CH2)6NH]n~	polyamide Nylon 66	HO2C-(CH2)4-CO2H H2N-(CH2)6-NH2	45	265
~[CO(CH2)5NH]n~	polyamide Nylon 6 Perlon		53	223

[Thanking  William Reusch ,Professor Emeritus (Chemistry) at Michigan State University]

4.Molecular Forces

1. Elastomers:[Elastomer materials are those materials that are made of polymers that are joined by chemical bonds(by weakest intermolecular forces), acquiring a final slightly crosslinked structure.e.g., natural rubber, buna-S, buna-N etc  . 
   
   

   The main characteristic of elastomer materials is the high elongation and flexibility or elasticity of these materials, against its breaking or cracking.

   Depending on the distribution and degree of the chemical bonds of the polymers, elastomeric materials can have properties or characteristics similar to thermosets or thermoplastics, so elastomeric materials can be classified into:

   • Thermoset Elastomers - are those elastomer materials which do not melt when heated.
   • Thermoplastic Elastomers - are those elastomers which melt when heated.

   properties:
   

   • flexible and elastic
   •  
   Applications:
   

   • Natural rubber - material used in catheters, balloons, medical tubes, elastic thread, and also in some adhesives
   • manufacture of elastic clothing  
2. Fibres:[ Fibres belong to a class of polymers which are thread-like and can be woven into fabrics.A few examples of this class are nylon-66, terylene and polyacrylonitrile]
   properties:
   

   • high tensile strength because the chains possess strong intermolecular forces such as hydrogen bonding
   •  The fibres are crystalline in nature and have sharp melting points
   Applications:
   

   • These are widely used for making clothes, nets, ropes, gauzes, etc
   • manufacture of fibre clothing
3. Thermoplastics: [A thermoplastic, or thermosoftening plastic, is a plastic material, a polymer, that becomes pliable or moldable above a specific temperature and solidifies upon cooling. Most thermoplastics have a high molecular weight. (Wikipedia ) . Thus, they can be cast into different shapes by using suitable moulds, e.g.,
   • 1 Acrylic
   • 2 ABS
   • 3 Chlorinated Polyvinyl Chloride
   • 4 Nylon
   • 5 PLA
   • 6 Polybenzimidazole
   • 7 Polycarbonate
   • 8 Polyether sulfone
   • 9 Polyoxymethylene
   • 10 Polyetherether ketone
   • 11 Polyetherimide
   • 12 Polyethylene
   • 13 Polyphenylene oxide
   • 14 Polyphenylene sulfide
   • 15 Polypropylene
   • 16 Polystyrene
   • 17 Polyvinyl chloride
   • 18 Teflon
   ]

1. Thermosetting plastics: [  A thermosetting polymer (also called a thermosetting plastic or thermosetting resin) is a polymer which becomes irreversibly hardened upon being cured. Curing is caused by the action of heat or suitable radiation and may be promoted by high pressure or the use of a catalyst. It results in extensive cross-linking between polymer chains to give an infusible and insoluble polymer network. A cured thermosetting polymer is called a thermoset.e.g; 

• Polyester resin .
• Polyurethanes
• Polyurea/polyurethane
• Vulcanized rubber.
• Bakelite, a phenol-formaldehyde resin used in electrical insulators and plasticware.
• Duroplast
• Urea-formaldehyde foam used in plywood, particleboard and medium-density fibreboard.
• Melamine resin used on worktop surfaces.^[2]
• Diallyl-phthalate (DAP)
• Epoxy resin 
• Epoxy novolac resins
• Benzoxazines
• Polyimides and Bismaleimides
• Cyanate esters
• Mold or mold runners (the black plastic part in integrated circuits or semiconductors).
• Furan resins
• Silicone
• Thiolyte
• Vinyl ester resins used for wet lay-up laminating, molding and fast setting industrial protection and repair materials.

Some important polymers and their monomer:(monomer,polymerization process,properties and use ) 

 

A.Polyolefins[A polyolefin is a type of polymers produced from a simple olefin as a monomer.C=C]

1. Polythene
2. Polystyrene (Styrone)
3. Polyvinylchloride (PVC)
4. Polypropylene (PP)
5. Teflon
6. Polyacrylonitrile

B.Polyamides[ A polyamide is a macromolecule with repeating units linked by amide bonds -NH-CO- ] 

1. Nylon-66
2. Nylon-6

C.Resins [ a high cross linked 3D sticky flammable organic substance, insoluble in water, exuded by some trees and other plants]

1. Phenol-Formaldehyde Polymer
2. Melamine-formaldehyde Resin
3. Urea-formaldehyde Resin
4. Natural Rubber
5. 5. Neoprene
6. Buna-N    

D.Polyesters [ The polymers which contain an ester linkage are known as polyester]

1. Polymethylmethacrylate (PMMA)
2. Glyptal
3. Terylene (Dacron)    

Molecular masses of Polymers

.....................................

Biopolymers

.........................................

Biodegradable Polymers

..........................................

Some Commercially important Polymers 

.................................................... 

See also

References

External links

1. https://en.wikipedia.org/wiki/Polymer
2. http://pediaa.com/difference-between-polymer-and-macromolecule/
3. https://chem.libretexts.org/Bookshelves/Organic_Chemistry/Supplemental_Modules_(Organic_Chemistry)/Polymers/Addition_Polymers
4. https://www2.chemistry.msu.edu/faculty/reusch/VirtTxtJml/polymers.htm
5. https://www.adhesiveandglue.com/elastomer.html
6.