Polymers

Glycogen is the polymer of glucose stored by animals, it is analogous to starch and sometimes referred as animal starch and serves as long term energy storage in animals, therefore, option (iv) is correct answer.

Cellulose is structural polymer of glucose units found in plants, amylose and amylopectin are the polysaccharides found in starch granules. therefore options (i),(ii),(iii) are incorrect answers.

semisynthetic polymer are those which are obtained from nature and used and applied after modification but cis-polyisoprene is completely synthetic polymer, and synthetic polymers are Human made therefore, option (i) is the correct answer.

Cellulose nitrate, cellulose acetate, vulcanised rubber are semisynthetic polymers therefore options (ii),(iii),(iv) are incorrect.

Polyacrylonitrile (C3H3N)n is vinyl polymer and derivative of acrylate family of polymer.The commercial name of polyacrylonitrile is Orlon therefore option (ii) is the correct answer.

Above is the diagram of polyacrylo nitrile.

Above is the diagram of Dacron.

Above is the diagram of Bakelite.

Above is the diagram of PVC.

is the commercial name of polyester.PVC is the thermoplastic polymer and bakelite is thermosetting therefore options (i),(iii),(iv) are incorrect.

PHBV is the biodegradable polyster.

Biodegradable polymer is the polymer which breaks down by bacterial decomposition prepared to result in nature by products. . Therefore option (iii) is the correct answer.

Polymers given in the options (i),(ii),(iv) are not biodegradable polymers therefore these are incorrect answers.

Ethylene glycol is one of the monomer unit for the formation of glyptal polymer.By polymerization reaction between ethylene glycol and phthalic acid gives glyptal. Therefore option (i) is correct.

By using ethylene monomer we get (ii) polymer, therefore this is not thr correct answer.

Options (iii) and (iv) are also incorrect as they do not involve ethylene glycol as there monomer unit.

LDPE(low density polyethylene) is not hard because branching prevents from stacking and thus reduces intermolecular forces of attraction so it is tough but not, therefore option (ii) is the correct answer.

All the properties about LDPE like option (i),(iii),(iv) are correct.LDPE is tough, poor conductor of electricity and has highly branched structure therefore options (i),(iii),(iv) are incorrect answers.

By using iso-Butene as monomer unit we get the given polymer.Therefore option (i) is the correct answer.

Options (ii),(iii),(iv) on polymerization can't give required polymer therefore these options are incorrect.They are not monomer units used for given polymer.

By using the given monomer unit of caprolactam formation of Nylon-6 takes place.

Nylon-6 can be prepared by ring-opening polymerisation of therefore option(iv) is the correct answer.

Nylon 6,6 can be prepared by polymerisation of Hexamethylene diamine and adipic acid,

Nylon2-nylon 6 is the alternating copolymer of glycine and amino caproic acid,

Melamine polymer is made from melamine and formaldehyde by condensation of two monomers. Therefore options (i),(ii),(iii) are incorrect.

Now first let’s take a look to what diene means, ‘DIENE’ is a molecule containing 2 carbon-carbon double bonds. So now when we look into the preparation of each of the above options we need to search for carbon-carbon double bond.

Preparation of Dacron:

Preparation of Buna-S:

Preparation of Neoprene:

Preparation of Novolac: Option ii and iii, with Buna-S and Neoprene is the answer for the above question.

Explanation: Now first let’s take a look to what diene means, ‘DIENE’ is a molecule containing 2 carbon-carbon double bonds. So now when we look into the preparation of each of the above options we need to search for carbon-carbon double bond.

Preparation of Dacron:

Preparation of Buna-S:

Preparation of Neoprene:

Preparation of Novolac:

Now when we observe the above reactions we find carbon carbon double bond only in Buna-S and neoprene, meaning that they have diene monomer for their preparation.

Now when we observe the above reactions we find carbon carbon double bond only in Buna-S and neoprene, meaning that they have diene monomer for their preparation.

Primarily let us see what does Thermosetting polymers mean, a thermosetting polymer is a polymer which becomes irreversibly hard when it is heated and becomes infusible. Hence it can’t be reused. Polymer initially is a liquid, which under the influence of heat gains energy to undergo the required chemical reactions to increase cross-linking among the polymer chains. Hence we understood why point i and iii stands right as the characteristics. Dealing with point ii we observe that they say ‘linear slightly branched’ which is completely false according to the point which we have proved right in i. Coming to point iv we observe that it is not only completely converse to that of iii, which stands out true, but also a property of thermoplastic hence we conclude that point iv is false.

Now Thermoplastics are polymer plastics which turn soft on heating and become hard on cooling. Natural rubber on undergoing vulcanization is said to be a thermosetting polymer. Vulcanization is basically a chemical process where the physical properties of rubber are improved. Neoprene is a thermoset or thermosetting material not a thermoplastic material. Being in the category of thermoplastic, Teflon is used for non- stick cookware and Polystyrene finds its use in CD cases and domestic appliances.

Fibers usually possess a crystalline nature. Amongst the above given polymers Nylon and Terylene possess a strong intermolecular force of attraction in terms of hydrogen bonding. This provides a close packing in the chain.

Addition polymers are those formed just by mere addition of 2 or more monomers without the byproducts.

Orion and polystyrene are addition polymers made by polymerization of CH2 = CH – CN (acrylonitrile) and, C6H5 – CH = CH2 styrene respectively.

Condensation polymers are polymers formed through a condensation reaction, where molecules join together, losing small molecules as by-products such as water or methanol.

Bakelite is a condensation polymer of phenol and formaldehyde

Melamine formaldehyde resin is a condensation polymer of melamine (2, 4, 6-triamino-1, 3, 5-triazine) and formaldehyde.

The polymers which are easily decomposed and not harmful for the environment are known as a biodegradable polymer.

(i) PHBV, being a biodegradable polymer, is obtained by condensation polymerization of 3 hydroxybutanoic acid and 3 hxydroypentanoic acid.

Synthetic rubber are those which resemble natural rubber more or less closely especially in physical properties and also able to be vulcanized

Nylon and polyester are basically well known thread forming fibers which have already identified themselves in the field of textile. Possession of high tensile strength and high melting point have made them their identity in the textile fields. They have strong intermolecular forces like hydrogen bonding. Force of attraction between the molecules of rubber is Vander Waal force which is the weakest force. Usually nonpolar materials such as polystyrene will have relatively weak attractive interactions in contrast to polar molecules. Hence we conclude the answer.

now let’s understand what Vinylic monomer means. They are basically a monomer containing a carbon-carbon double bond in them.

Vinyl group looks as follows

Acrilan, Polystyrene and Teflon preparation looks as follows:

Nylon preparation looks as follows:

With the above images we can conclude that option I, ii and Iv stand right for the question.

Vulcanization Is basically a chemical process where the rubber is treated with sulphur and heated to a greater extent to improves its properties like elasticity and to harden it. So now when we observe the options we see that option I and iv go very well with the definition. Vulcanized rubber is soluble in organic solvents, one of the reasons of vulcanization is also the betterment of solubility of rubber in organic solvents hence option ii stays false. Vulcanization makes rubber. A crystalline solid neither expands on heating nor contracts on cooling, which is converse to the property shown by the vulcanized rubber. Hence we prove that point iii stays false.

The structure of 2-methyl-1,3-butadiene is the following:

A linear polymer of 2-methyl-1,3-butadiene is known as natural rubber. It is brittle at low temperature below 283K. But when this raw rubber is heated between 373K to 415K with sulphur in presence of a suitable additive, sulphur forms a cross-linking. The double bonds act as reactive sites where this cross-linking occur. During this reaction, the double bonds are broken and new S-S bonds are formed.

This process is known as vulcanization of rubber. Sulphur here acts as a crosslinking agent and the rubber gets stiffened during this process having improved physical properties than natural rubber.

In this structure, the same molecule ‘A' is joined with each other to form the polymer —A—A—A—A—A—A—.So here the monomer is –A-. Since the same or identical monomer is being repeated to form this above polymer, so this is a homopolymer. (‘Homo' means same or identical)

This polymer has been obtained from two different species of monomers ‘A' and ‘B'. Here the monomers A' and ‘B' are being joined in a random manner in the same polymer chain. So this is an example of a copolymer. A Copolymer is formed usually when the mixture of two or more unsaturated monomers react.

This is a chain-growth polymerization.

The basic difference between chain growth and step-growth polymerization is as follows:

In step-growth polymerisation, bifunctional or trifunctional monomers in the growing chains further react with each other to form longer chains. But in the case of chain-growth polymerization, only monomers react with each other to continue the growing chain.

In this diagram, two monomers simply and combine to form the polymer by chain- growth polymerization reaction.

This is a cross-linked or Network polymer.

When monomers having two or more than functional groups combine, they do so by the formation of strong covalent bonds between them. Two linear polymers are joined by cross-linking.

This is a polyisoprene or natural rubber.

The monomeric unit of this polymer is 2-methyl-1,3-butadiene.

2-methyl-1,3-butadiene

. Various chains are joined with each other by weak Vander Waals interaction.

When an elastic material is stretched by applying an external force, it can again come back to its original position after the applied force is removed. Rubbers can be stretched by applying force and come back to its original form after the removal of applied force. So they are called elastomers.

Enzymes are the substances which can act as biocatalysts in living organisms. They are mainly composed of proteins. Proteins are the polymers having monomeric unit known as amino acids. Thus, enzymes are also polymers.

Yes, nucleic acids, proteins and starch can be considered as step-growth polymers.

Step growth polymers are condensation polymers. Monomers which possess bifunctional or trifunctional functional groups can combine by the loss of a simple molecule like water, alcohol etc. leading to the formation of polymers having high molecular mass.

For example, DNA(deoxyribonucleic acid), proteins and starch all are formed by removal of water molecule when their respective monomeric units join together.

Melamine and formaldehyde are the two starting monomers for this Resin intermediate. Their condensed polymerisation gives melamine polymer by the following reaction:

+ HCHO

(Melamine) (Formaldehyde)

Natural rubber which is a polymer of 2-methyl-1, 3-butadiene, their polymeric chains are held together by weak Vander Waals interactions. So it becomes soft at a temperature above 335K and becomes brittle at low temperature below 283K. The natural rubber also tends to get attacked by oxidizing agents. To improve these physical properties, cross-linking is done which helps to bind it's planar polymer sheets thus increasing elastomeric properties, thermal stability.

In cis-polyisoprene, various polymer chains are joined with each other by weak Vander Waals interactions and these polymer chains are coiled. Due to the presence of these weak forces the polymer can be stretched by applying force. The polymer returns to its original state as soon as the external force is removed, thus exhibiting elastic property.

HDP and LDP are high-density polythene and low-density polythene respectively.HDP has a linear structure whereas LDP is highly branched.HDP has high density due to close packing of molecules in it.

HDP and LDP differ in various aspects as given below:

HDP LDP

Chemically inert and tough chemically inert but flexible

Has higher melting point has a lower melting point

Used to make buckets, used to make flexible pipes,

dustbins etc. toys etc.

Benzoyl peroxide helps to generate free radical in chain initiation step which is the first step of the reaction in Addition polymerization reaction. Thus it acts as a free radical generating initiator catalyst.

Addition polymerization reaction occurs in three steps.

i) Chain initiation step ii) Chain propagating step iii) Chain terminating step

i) Chain initiation step:

In this step, a mixture of ethene with small amount of benzoyl peroxide is heated or is exposed to light. In the presence of heat or light, the O-O linkage in benzoyl peroxide breaks to generate two molecules of benzoyl free radical and finally to two molecules of phenyl free radical.

Later, this phenyl free radical is captured by the ∏-bond of Ethene molecule to generate a larger free radical.

ii) Chain propagating step:

This larger free radical generated in chain initiation step further reacts with the second molecule of ethane to form another larger size free radical.

This propagation step continues to form larger and larger free radical which is comprised of ‘n' number of Ethene molecules, where n is a very large number.

iii) Chain terminating step:

Since the various free radicals are formed in chain propagation step, eventually, they collide with each other producing a final molecule. Chain termination is a random process, polythene will be made up of chains of different lengths.

To terminate the chain propagation step, chain-terminating step can be done in different ways,otherwise, we cannot get the desired polymerized product polythene.

One of the modes for the termination of the chain is given below:

Thus we get our desired polymer polythene.

Nylon is a copolymer of the amino acid Glycine (H2N-CH2-COOH) and aminocaproic acid [H2N(CH2)5COOH]. Glycine and aminocaproic acid combine in the following way.

In this structure, one molecule of Nylon can join another by intermolecular H –bonding which is present between two terminal groups –C=O and –NH. Since intermolecular H –bonding is relatively strong, it can lead to close packing of chains that impacts the crystalline character of Nylon.

Urea-formaldehyde resin is used in laminated sheets.

Formation of this resin is given below:

(Urea-formaldehyde resin)

Thus, for the formation of laminated sheets, urea and formaldehyde are the monomeric units.

Proteins have some structural similarity with synthetic polyamides.

Polyamides like Nylon is formed by the combination of Glycine and aminocaproic acid molecule through an amide linkage.

amide linkage

Similar amide linkage is present in protein also when two amino acids join with each other.

Peptide bond present in protein is an amide linkage.

Thus, in both proteins and synthetic polyamides amide linkage is present.

In addition polymerization, peroxy free radicals are generated in chain initiation step. This free radical combines with an unsaturated monomer(containing double/triple bond) to form larger free radical.

If the monomer is mixed with even traces of impurities, these impurities may act as inhibitors. This leads to the sudden termination of chain reaction or the formation of polymers with shorter chain length. Thus, we cannot get the desired polymer.

(i) High-density polythene(HDP) – (e) Ethene.

Explanation- Polythene is the polymer formed by the addition polymerization of ethene. There are two types of polythenes namely- High-density polythene(HDP) and Low-density polythene(LDP).

(ii) Neoprene – (c) Chloroprene.

Explanation- Neoprene (also known as polychloropropene) is a polymer formed from chloroprene which is 2-chloro-1,3-butadiene through polymerization by the production of free radicals in the intermediate stages of the reaction. It is thus called free radical polymerization.

Note:-We know hν stands for sunlight and as there is sunlight it is obvious that the reaction will proceed via formation of free radicals.

(iii) Natural Rubber – (a) Isoprene

Rubber is a natural polymer and possess elastic properties. Natural rubber consists of a linear polymer of 2-methyl-1,3-butadiene which is commonly known as isoprene. It is also called cis-1,4-polyisoprene.

This is isoprene.

(iv) Teflon – (b) Tetrafluoroethene

Teflon is prepared by the polymerization of Tetrafluoroethene(PTFE) molecules. It is done so by heating PTFE molecules under high pressure and in presence of ammonium peroxo sulphate [(

Tetrafluoroethene Teflon

(v) Acrilan – (d) Acrylonitrile

Acrilan is formed by the addition polymerization of acrylonitrile in presence of a peroxide catalyst. Acrilan is better known as Polyacrylonitrile(PAN) or orlon.

Acrylonitrile Polyacrylonitrile

Note:- Some polymers have their name starting with ‘Poly’ are examples of addition polymers. Example- Polythene, Poly tetrafluoro ethylene(Teflon), Polyacrylonitrile(Orlon), Polyisoprene ,Polyvinyl chloride(PVC) ,etc.

(i) Nylon-6 – (c) Polycaprolactum

For the preparation of Nylon-6(or Perlon), the first caprolactum is prepared from cyclohexane

Then caprolactum is heated with traces of water and on continued heating polymerization occurs and Nylon-6 is produced.

(ii) PVC – (a) Polyvinyl Chloride

When multiple molecules of vinyl chloride ( is heated in an inert solvent in the presence of dibenzoyl peroxide then PVC is obtained.

(iii) Acrilan – (b) Polyacrylonitrile

Polyacrylonitrile(PAN) or Acrilan is a thermoplastic (which becomes soft when heated and hard when cooled and can be moulded into shapes) hard material having high melting point. It is prepared by polymerization of acrylonitrile. Its another commercial name is Orlon.

(iv) Natural rubber – (e) cis-polyisoprene

As we have discussed earlier that natural rubber consists of a linear polymer of 2-methyl-1,3-butadiene which is commonly known as isoprene. It is also called cis-1,4-polyisoprene or simply cis-polyisoprene.

Thus, Above is the structure of isoprene

(v)LDP - (d) Low-density polythene

We know as discussed earlier that, there are two types of polythenes namely- High-density polythene(HDP) and Low-density polythene(LDP).

(i)Polyester of glycol and pthalic acid – (b) Glyptal

Polyester means polymers having the ester linkage . So we get to know that glyptal has ester linkage in it.

Now glyptal is a polyester obtained by the condensation of ethylene glycol and pthalic acid. It involves the removal of two simple H₂O molecules.

This is done so to show diagrammatically how the two water molecules are eliminated thereby forming glyptal.

(ii) The Copolymer of 1,3-butadiene and styrene – (c) Buna-S

Buna-S is prepared from two monomers, 1,3-butadiene() and Styrene().

Note:

In the name Buna-S, Bu stands for butadiene, na for sodium which acts as polymerizing agent and S stands for styrene.

(iii) Phenol and formaldehyde resin – (a) Novolac

Novolac is prepared from phenol and formaldehyde. It is thus known as phenol-formaldehyde resin commonly as Bakelite.

Note:

Novolac on heating with formaldehyde(HCHO) undergoes cross-linking to form an infusible mass called bakelite.

(iv) The Polyester of glycol and terepthalic acid – (e) Dacron

Teylene also known as Dacron is prepared by the condensation polymerization reaction of two monomers – Ethylene glycol and Terepthalic acid. Condensation reaction involves the loss of a simple molecule like NH₃, H₂O, HCl, etc(here, H₂O is removed).

(v) Copolymer of 1,3-butadiene and acrylonitrile – (d) Buna-N

Buna-N is obtained by the copolymerization of 1,3-butadiene and acrylonitrile in the presence of a peroxide catalyst.

(i)Bakelite – (d) Electrical switches

Bakelite is a thermoplastic. As a result, they are poor conductors of electricity and subsequently they are highly heat resistant. So they are used in switches to prevent us from getting electrical shocks.

(ii) Low-density polythene – (e)Squeeze bottles

LDP in comparison to HDP has lesser tensile strength, less rigid but chemically more resistant. Therefore, by being a softer material, they are used in squeeze bottles as they are flexible.

(iii) Melamine formaldehyde resin – (a) Unbreakable crockery

The melamine polymers are quite hard. So they are used in making plastic crockery and these articles do not break even if they are dropped.

(iv) Nylon-6 – (f) Tyre cords

Due to the ability to carry heavy weights, along with that Nylon ropes can return to its original shape even after stretching due to its high elasticity. It is also capable of withstanding sudden shocks. Due to these features, they are used.

(v) Polytetrafluoroethylene – (b) Non-stick cookware

In PTFE, due to the nature of C-F bonds, it is highly unreactive.

It has high melting point as well.

Due to these features, PTFE is used in non-stick cookware.

(vi) Polystyrene – (c) Packaging material for shock absorbance.

Polystyrene is used as shock absorbers as they have air bubbles trapped inside them as a result of which energy cannot flow through it.

(i) Nylon-6,6 – (d) Condensation polymerisation

Nylon-6,6 is a copolymer of hexamethylenediamine and adipic acid through condensation polymerisation. The polymerisation type is named such because after the end of the reaction a simple molecule(here, H₂O) is released.

(ii)PVC – (a) Free radical polymerisation

PVC is formed from vinyl chloride monomer through free radical mechanism. Vinyl polymerisation proceeds in three steps:

(1) Chain initiation- The radical initiator is broken into the intermediate free radicals by various means(eg. Sunlight or heat).

(2) Chain propagation – The free radicals combine with monomers to form bigger intermediate species.

(3) Chain terminating – The radical intermediates join with one another with the help of chemical bonds.

(iii) HDP – (b) Ziegler-Natta polymerisation or

coordination polymerization

HDP is formed when addition polymerisation of ethene takes place in a solvent in presence of catalyst like (C₂H₅)₃Al and TiCl₄ (Zeigler-Natta catalyst) at a temperature range of 333K to 343K under 6-7atm pressure.

So this process is also termed as Ziegler-Natta polymerization.

The reaction is as follows:

(i) Terylene – (b) Ester linkage

We know, terylene is a polyester, and a polyester is a polymer having the ester linkage.

(ii) Nylon – (d) Amide linkage

Nylons are polyamides which means they have an amide linkage.

(iii) Cellulose – (a) Glycosidic linkage

Explanantion:

Cellulose is derived from D glucose units which have the β ( glycosidic bonds. The linkage here observed is termed as glycosidic linkage.

(iv) Protein – (d) Amide linkage.

If we look at the structure of protein we will find the presence of amide linkage along with amino acids and polypeptide chain.

(v) RNA – (c) Phosphodiester linkage

A phospodiester bond is a covalent bond in which a phosphate group joins adjacent carbons through ester linkages.

The phosphodiester bond links a 3' carbon to a 5' carbon in DNA and RNA.

(i) Natural rubber latex – (f) cis-polyisoprene

As we have discussed earlier that natural rubber consists of a linear polymer of 2-methyl-1,3-butadiene which is commonly known as isoprene. It is also called cis-1,4-polyisoprene or simply cis-polyisoprene.

Isoprene

(ii) Wood laminates – (e) Urea-formaldehyde resin

When we look at the properties of the urea formaldehyde resin, we get to know that they have high tensile strength, high reactivity, low water absorption. Due to these features they are used as adhesive resins for wood laminates.

Urea-Formaldehyde resin

(iii) Ropes and fibres – (a) Nylon

We know that Due to the ability to carry heavy weights along with that Nylon ropes can return to its original shape even after stretching due to its high elasticity. It is also capable of withstanding sudden shocks. Due to these features they are used as ropes and fibres.

(iv) Polyester fabric – (c) Dacron

We know that Dacron is polyester. It is used in making wash and wear fabrics due to its resistance to chemical and biological substances and also to abrasion. Terylene or Dacron is the trade name given.

(v) Synthetic rubber – (b) Neoprene

Neoprene or polychloroprene is an example of synthetic rubber. It provides high resistance to vegetable and mineral oils.

(vi) Unbreakable crockery – (d) Melamine formaldehyde resins

We know that melamine polymers are quite hard. So they are used in making plastic crockery and these articles do not break even if they are dropped.

(i) Acrilan – (d)

Acrilan is commonly known as Polyacrylonitrile(PAN) and the structure given in (d) is PAN. It is an addition polymer.

(ii) Polystyrene – (a)

As we know the structure of styrene

We can resemble to the compound provided in (a) that it is polystyrene as it is a product of addition polymerisation.

(iii) Neoprene – (b)

Neoprene is formed by the free radical polymerisation of chloroprene(2-chloro-1,3-butadiene)

The Polymer thus produced is neoprene which is (b).

(iv) Novolac – (e)

Novolac is prepared from phenol(C₆H₅OH) and formaldehyde(HCHO). It is thus known as phenol-formaldehyde resin commonly as Bakelite.

(v) Buna-S – (c)

Buna-S is prepared from two monomers, 1,3-butadiene() and Styrene().

Rayon is a semi-synthetic polymer and is taken as a better choice than cotton fabric because properties of cellulose get enhanced by acetylation during processing.

Thus, both the assertion and the reason are correct and the reason is the correct explanation of the assertion.

Most of the polymers remain unaffected from the attack of environmental oxidation and enzymes. Thus, they are non-biodegradable.

Polymerization does not induce toxic character in the organic molecules.

Polymerization is the chemical process of monomers joining together to form polymers, often it takes many thousands of monomers to make a single polymer.

Thus, only the assertion is correct.

Olefin also called alkene, compound made up of hydrogen and carbon that contains one or more pairs of carbon atoms linked by a double bond. Olefins are examples of unsaturated hydrocarbon (compounds that contain only hydrogen and carbon and at least one double or triple bond).

The olefins monomers undergo the addition polymerization, for example, ethene undergoes addition polymerization to give polyethylene.

Polymerization of vinyl chloride is initiated in the presence of peroxides.

Thus, both the assertion and the reason are correct but the reason is not the correct explanation of the assertion.

Polyamides like nylon are best-used fibers because of high tensile strength due to the presence of the strong intermolecular forces like hydrogen bonding.

These forces strongly hold the chain of polyamides, hence, provides high tensile strength.

Thus, both the assertion and the reason are correct and the reason is the correct explanation of the assertion.

Isoprene molecule is the monomer of the natural rubber.

Thus, the assertion is wrong.

Neoprene is the synthetic rubber which is formed by the polymerization of the polymer chloroprene.

Thus, only the reason statement is correct.

Extensive linkage causes the formation of the three-dimensional network linkage in the polymer.

The polymer with an extensive linkage has many molecules linked to each other thus the molecular mass increases.

These types of polymers are infusible, hard and insoluble.

Thus, both the assertion and the reason are correct but the reason is not the correct explanation of the assertion.

Teflon (Polytetrafluoroethylene) is used to make non-stick cookware as it is chemically inert and thermally stable.

Fluorine has the highest electronegativity due to the small size and high nuclear charge.

Thus, both the assertion and the reason are correct but the reason is not the correct explanation of the assertion.

Synthetic polymers are quite resistant to environmental oxidation and enzyme actions. They do not easily degrade and cause the accumulation of solid waste.

New polymers are being designed and developed. These polymers are biodegradable as they contain the similar functional group as biopolymers.

Biopolymers are polymers of amino acid and carbohydrates linked together with peptide or glycosidic linkage.

Polymers of amino acid can be or cannot be biodegradable for example proteins are biodegradable but keratin is non-biodegradable.

Some examples of biodegradable polymers are nylon 6 and PBHV.

Rubber is a natural polymer that is capable of returning to its original length, shape, and size after the removal of forces (stretching or deformation). Rubber is a common example of an elastomer.

Rubber is the product when the molecules of isoprene undergo polymerization. The chains of polyisoprene are held together by weak van der Waals forces. Rubber has a coiled structure.

Plastics are synthetic or semi-synthetic polymers of organic compounds which possess intermediate intermolecular forces of attraction. The forces are intermediate in between those of elastomers and fibers.

It has a linear, structure that can be molded but cannot regain its original shape after stretching is over.

They are neither too weak or too strong and have no cross-linkage between the chain.

Few examples of plastics are given below with the structure:

Polymer ‘A’ is Novolac and ‘B’ is Bakelite.

Novolac on heating with HCHO undergoes the cross-linkage to give an infusible solid called Bakelite. Novalac has a linear polymer chain whereas Bakelite is a cross-linked polymer.

Low density and high-density polythenes are obtained under different conditions. These differ in their structural features.

Low-density polythene is highly branched structures.

LDP is obtained by free radicle addition reaction at high pressure and high temperature. It is chemically inert and tough but slightly flexible.

High-density polythene consists of closely packed linear molecules. Close packing increases the density.

HDP is obtained by the addition polymerization of the ethene in the presence of the hydrocarbon solvent at low pressure and temperature up to 350 K in the presence of a catalyst called Ziegler-Natta catalyst. Under these conditions, the polymer obtained is highly tough and has a high density due to close packing.

HDP is harder and tougher than LDP.

Polythene, polyvinyl and polystyrene soften on heating and harden on cooling. Such polymers are called thermoplastic polymers.

These possess intermolecular forces of attraction whose strength lies between the strength of intermolecular forces of elastomers and fibers.

These polymers are linear or slightly branched long-chain molecules.