Composition, Properties and Uses of Polymer Questions in English

(B) Orlon is a polymer of acrylonitrile.
The chemical name of acrylonitrile is vinyl cyanide.
Its structure is $CH_2 = CH - CN$.
Therefore,the monomeric unit of Orlon is $CH_2 = CH - CN$.

(D) $PVC$ is Polyvinyl chloride.
$PTFE$ is Polytetrafluoroethylene,commonly known as Teflon.
$PMMA$ is Polymethyl methacrylate.
$Buna-S$ is a synthetic copolymer of butadiene and styrene,not natural rubber. Natural rubber is a polymer of isoprene ($2$-methyl-$1,3$-butadiene).
Therefore,the statement '$Buna-S$ stands for natural rubber' is incorrect.

(A) Novolac is a linear condensation polymer formed by the reaction of phenol and formaldehyde in the presence of an acid catalyst.
It is used in paints and as a binder in laminated wooden planks.
In contrast,Bakelite is the cross-linked condensation product of phenol and formaldehyde.

(D) Neoprene is a synthetic rubber formed by the free radical polymerization of chloroprene ($2$-chloro-$1,3$-butadiene).
Since chloroprene contains a chlorine atom and two double bonds,the resulting polymer is classified as a polyhalodiene.

(C) Natural rubber is a polymer of isoprene ($2$-methyl-$1,3$-butadiene).
Neoprene is a synthetic rubber formed by the polymerization of chloroprene ($2$-chloro-$1,3$-butadiene).
Neoprene is structurally similar to natural rubber and is often used as a synthetic substitute for it due to its superior resistance to oils and chemicals.

(B) $Buna-S$ is a synthetic rubber formed by the copolymerization of $1,3-butadiene$ and $styrene$ in the presence of a peroxide catalyst. The name $Buna-S$ is derived from $Bu$ (butadiene),$na$ (sodium,which acts as a catalyst),and $S$ (styrene).

(C) $1$. Butyl rubber is a copolymer of isobutylene and a small amount of isoprene,and it is generally considered a linear or slightly branched elastomer.
$2$. Dacron (also known as Terylene) is a copolymer formed by the condensation of ethylene glycol and terephthalic acid.
$3$. Dextron (or Dextran) is a polysaccharide,not a polyamide. Polyamides are polymers containing amide linkages (e.g.,Nylon-$6$,$6$).
$4$. Orlon is polyacrylonitrile,which is used as a substitute for wool in synthetic textiles.
Therefore,the statement that Dextron is a biodegradable polyamide is incorrect.

(B) Teflon (Polytetrafluoroethylene) is a polymer that exhibits high chemical resistance,low friction,and excellent electrical insulating properties. Due to its low coefficient of friction,it is used as a lubricant,and due to its high dielectric strength,it is used as an electrical insulator.

(D) Polystyrene is a synthetic aromatic hydrocarbon polymer made from the monomer styrene. It is widely used in the production of chewing gum base due to its rubbery and elastic properties.

(D) Non-stick cookware is coated with $Polytetrafluoroethylene$ $(PTFE)$,commonly known as $Teflon$.
$PTFE$ is a polymer of tetrafluoroethylene $(CF_2=CF_2)$.
It is chemically inert and resistant to attack by corrosive reagents,making it ideal for non-stick coatings.

(A) Soft drink bottles and baby feeding bottles are typically manufactured using $Polyethylene \ terephthalate$ $(PET)$,which is a type of polyester. Therefore,the correct option is $A$.

(C) Glyptal is a polyester formed by the condensation polymerization of ethylene glycol and phthalic acid. It is widely used in the manufacture of paints and lacquers.

(D) Nylon-$6$,$6$ is a polyamide polymer known for its high tensile strength and elasticity. Due to these properties,it is widely used in the manufacturing of tyre cords,ropes,and fabrics.

(B) Natural rubber is a linear polymer of $2$-methyl-$1,3$-butadiene,which is commonly known as isoprene.
It is a $cis$-$-1,4$-polyisoprene,where the double bonds are in the $cis$-configuration,which gives it elastic properties.

(A) Natural rubber is a polymer of $isoprene$ ($2$-methyl-$1,3$-butadiene).
In natural rubber,the double bonds are in the $cis$-configuration,making it $cis$-polyisoprene.
Gutta-percha is a naturally occurring isomer of natural rubber where the double bonds are in the $trans$-configuration,making it $trans$-polyisoprene.
Therefore,natural rubber and gutta-percha are $cis$-polyisoprene and $trans$-polyisoprene respectively.

(C) Natural rubber is an elastomer that exhibits elastic properties at room temperature. However,it becomes brittle at low temperatures,specifically below $283 \ K$ $(10\,^oC)$. At this temperature,the polymer chains lose their flexibility,causing the material to lose its elasticity and become brittle.

(B) The process of heating natural rubber with sulfur or sulfur compounds is known as $Vulcanization$.
This process improves the physical properties of rubber,such as its elasticity,strength,and resistance to heat and cold,by creating cross-links between polymer chains.

(B) Vulcanization is a chemical process for converting natural rubber or related polymers into more durable materials by the addition of sulfur or other equivalent curatives.
In this process,sulfur forms cross-links between the polymer chains of polyisoprene.
These cross-links make the rubber harder,more durable,and resistant to heat and chemical degradation.
Therefore,the correct statement is that sulfur cross-links are added.

(C) Ebonite is a hard,non-conductive material produced by the vulcanization of natural rubber with a high percentage of sulfur (typically $25\% - 40\%$).
Due to the high sulfur content,it becomes extremely hard and rigid,making it a form of highly vulcanized rubber.

(B) The polydispersity index $(PDI)$ is defined as the ratio of weight average molecular mass $(M_w)$ to number average molecular mass $(M_n)$.
$PDI = \frac{M_w}{M_n}$
Given:
$M_n = 30000$
$M_w = 40000$
$PDI = \frac{40000}{30000} = \frac{4}{3} \approx 1.33$
Since $1.33 > 1$,the correct option is $B$.

(C) Turbidity is defined as the cloudiness or haziness of a fluid caused by large numbers of individual particles that are generally invisible to the naked eye. In the context of polymer solutions,the turbidity is a measure of the light scattered by the polymer molecules present in the solution. This scattering is used to determine the molecular weight of the polymer.

(D) Polymers are macromolecules formed by the polymerization of monomers. They are characterized by very high molecular masses,typically ranging from $10^3$ to $10^7 \ u$. Therefore,the statement that polymers have low molecular masses is incorrect.

(D) Size Exclusion Chromatography $(SEC)$,also known as Gel Permeation Chromatography $(GPC)$,is the standard technique used to determine the molecular weight distribution and average molecular mass of polymers. In this method,polymer molecules are separated based on their hydrodynamic volume as they pass through a porous stationary phase.

(C) Biodegradable polymers are polymers that degrade by microbial action.
Nylon-$2$-Nylon-$6$ is a polyamide copolymer of glycine $(H_2N-CH_2-COOH)$ and amino caproic acid $(H_2N-(CH_2)_5-COOH)$.
It is a well-known biodegradable polymer used in surgical sutures.

(B) The biodegradable polymer used for post-operative stitches is $PGA$ (Polyglycolic acid).
It is a synthetic polymer that undergoes hydrolysis in the body,making it suitable for surgical sutures.

(B) Statement $(1)$ is correct: Biodegradable polymers are designed to break down into harmless,often essential,substances in the environment.
Statement $(2)$ is incorrect: Non-biodegradable polymers are inert and resistant to environmental degradation processes.
Statement $(3)$ is incorrect: Non-biodegradable polymers do not easily break down into essential life substances.
Statement $(4)$ is correct: $PHBV$ (Poly-$\beta$-hydroxybutyrate-co-$\beta$-hydroxyvalerate) is a well-known biodegradable polymer that undergoes bacterial degradation in the environment.
Therefore,statements $(1)$ and $(4)$ are correct.

(A) $PHBV$ stands for Poly($\beta$-hydroxybutyrate-co-$\beta$-hydroxyvalerate).
It is a copolymer formed by the condensation polymerization of $3$-hydroxybutanoic acid and $3$-hydroxypentanoic acid.
The structure consists of repeating units of these two monomers linked by ester bonds.
The correct repeating unit structure is $[-O-CH(CH_3)-CH_2-CO-O-CH(CH_2CH_3)-CH_2-CO-]_n$.

(C) $Nylon$ is a polyamide polymer formed from adipic acid and hexamethylenediamine,thus it contains nitrogen atoms in its backbone.
$Polyvinyl \ chloride$ is a polymer of vinyl chloride $(CH_2=CHCl)$,which does not contain nitrogen.
$Bakelite$ is a thermosetting phenol-formaldehyde resin,which does not contain nitrogen.
$Terylene$ (also known as $Dacron$) is a polyester formed from ethylene glycol and terephthalic acid,which does not contain nitrogen.

(B) Nylon $6$ is synthesized from caprolactam.
When caprolactam is heated with water at high temperatures,it undergoes ring-opening polymerization to form Nylon $6$.
The repeating unit is $[CO-(CH_2)_5-NH]$.

(C) Bakelite is a cross-linked polymer formed by the condensation reaction of phenol and formaldehyde.
It is a thermosetting polymer,which means it becomes hard and infusible on heating and cannot be remelted or reshaped.
Therefore,the Assertion is correct,but the Reason is incorrect.

(C) Vulcanisation is a process of treating natural rubber with sulphur or some compounds of sulphur under heat to modify its properties.
In this process,sulphur forms cross-links at the reactive sites of double bonds in the rubber chain,which provides mechanical strength and elasticity to the rubber.
Therefore,the Assertion is correct.
However,vulcanisation is not a free radical initiated chain reaction; it is a chemical cross-linking process.
Thus,the Reason is incorrect.

(B) Nylon $2$-nylon $6$ is the correct answer.
It is an alternating polyamide copolymer of glycine $(H_{2}N-CH_{2}-COOH)$ and aminocaproic acid $[H_{2}N(CH_{2})_{5}COOH]$.
This polymer is biodegradable.

(C) Polyacrylonitrile is used as a substitute for wool in making commercial fibres,such as Orlon or Acrilan.

(D) $PHBV$ stands for Poly $\beta$-hydroxybutyrate-co-$\beta$-hydroxyvalerate.
The monomers involved are $3$-hydroxybutanoic acid and $3$-hydroxypentanoic acid.
Both of these monomers contain a chiral carbon atom (the carbon atom attached to the $-OH$ group),making them chiral.

(B) Buna $-N$ is a synthetic copolymer formed by the polymerization of $1,3-$butadiene and acrylonitrile.
Buna $-S$ is a synthetic copolymer formed by the polymerization of $1,3-$butadiene and styrene.

(N/A) The intermolecular forces of attraction in polymers depend on their classification as elastomers,plastics,or fibres.
$1$. Elastomers (e.g.,Buna$-S$,Neoprene) have the weakest intermolecular forces.
$2$. Plastics (e.g.,Polythene,Polyvinyl chloride) have intermediate intermolecular forces.
$3$. Fibres (e.g.,Nylon $6,6$,Nylon $6$) have the strongest intermolecular forces due to strong hydrogen bonding.
Therefore,the increasing order is:
$(i)$ $\text{Buna-}S < \text{Polythene} < \text{Nylon } 6,6$
$(ii)$ $\text{Neoprene} < \text{Polyvinyl chloride} < \text{Nylon } 6$

(N/A) Natural rubber is a linear $cis$-polyisoprene in which the double bonds are present between $C_{2}$ and $C_{3}$ of the isoprene units as shown below:
$CH_2-C(CH_3)=CH-CH_2-CH_2-C(CH_3)=CH-CH_2$
Because of this $cis$-configuration,the chains do not fit together well,leading to weak intermolecular interactions between the various strands of isoprene. As a result,the strands in natural rubber are arranged randomly in a coiled structure. This allows the polymer to stretch,which gives it its characteristic elasticity.

(N/A) Natural rubber,while useful,has several limitations:
$1.$ It is soft and sticky at room temperature,becomes softer at high temperatures $( > 335 \ K)$,and brittle at low temperatures $( < 283 \ K)$.
$2.$ It has a high capacity to absorb water.
$3.$ It possesses low tensile strength and low resistance to abrasion.
$4.$ It is soluble in non-polar solvents.
$5.$ It is easily attacked by oxidizing agents.
Vulcanization is performed to overcome these limitations. In this process,raw rubber is heated with sulfur and appropriate additives at a temperature range of $373 \ K$ to $415 \ K$. This creates cross-links between polymer chains,significantly improving the rubber's mechanical properties,elasticity,and durability.

(N/A) The monomeric repeating unit of Nylon-$6$ is $[NH-(CH_2)_5-CO]_n$,which is derived from the ring-opening polymerization of Caprolactam.
The monomeric repeating unit of Nylon-$6, 6$ is $[NH-(CH_2)_6-NH-CO-(CH_2)_4-CO]_n$,which is derived from the condensation polymerization of Hexamethylenediamine and Adipic acid.

(N/A) The names and structures of the monomers are as follows:

Polymer	Monomer Name and Structure
$(i)$ Buna-$S$	$1,3$-Butadiene $(CH_2=CH-CH=CH_2)$ and Styrene $(C_6H_5-CH=CH_2)$
$(ii)$ Buna-$N$	$1,3$-Butadiene $(CH_2=CH-CH=CH_2)$ and Acrylonitrile $(CH_2=CH-CN)$
$(iii)$ Dacron	Ethylene glycol $(HO-CH_2-CH_2-OH)$ and Terephthalic acid $(HOOC-C_6H_4-COOH)$
$(iv)$ Neoprene	Chloroprene ($2$-chloro-$1,3$-butadiene) $(CH_2=C(Cl)-CH=CH_2)$

(N/A) $(i)$ The monomers of the given polymeric structure (Nylon-$6,6$) are decanedioic acid $[HOOC-(CH_2)_8-COOH]$ and hexamethylene diamine $[H_2N-(CH_2)_6-NH_2]$.
$(ii)$ The monomers of the melamine-formaldehyde polymer are melamine $(C_3H_6N_6)$ and formaldehyde $(HCHO)$.

(N/A) polymer that can be decomposed by microorganisms (bacteria) is called a biodegradable polymer.
An example of a biodegradable aliphatic polyester is Poly$-\beta-$hydroxybutyrate$-co-\beta-$hydroxyvalerate $(PHBV)$.

(N/A) The word 'polymer' is derived from two Greek words: 'poly' meaning many and 'mer' meaning unit or part.
$A$ polymer is defined as a very large molecule (macromolecule) formed by the joining of repeating structural units on a large scale.
Polymers possess a very high molecular mass,typically in the range of $10^{3} - 10^{7} \ u$.
Polymers are the backbone of four major industries: $1.$ Plastics,$2.$ Elastomers,$3.$ Fibres,and $4.$ Paints and varnishes.

(N/A) Preparation: Bakelite is a thermosetting polymer formed by the condensation polymerization of phenol and formaldehyde in the presence of an acid or base catalyst. The reaction involves the formation of ortho- and para-hydroxymethylphenol derivatives,which further undergo cross-linking to form a rigid,infusible solid structure.
Properties: It is a hard,rigid,and infusible thermosetting plastic. It has high thermal stability,excellent electrical insulation properties,and is resistant to most chemicals and solvents.
Uses: It is widely used in making electrical switches,plugs,handles of utensils,computer discs,and various molded components.

(N/A) Polythene is a polymer formed by the polymerization of ethene. It consists of linear or slightly branched long-chain molecules.
These are thermoplastic polymers,meaning they soften on heating and harden on cooling.
There are two main types of polythene:
$(a)$ Low Density Polythene $(LDP)$:
Preparation: It is obtained by the polymerization of ethene under high pressure of $1000$ to $2000 \ atm$ at a temperature of $350 \ K$ to $570 \ K$ in the presence of traces of dioxygen or a peroxide initiator.
Properties: $LDP$ has a branched-chain structure. It is chemically inert,tough,flexible,and a poor conductor of electricity.
Uses: Used in the insulation of electricity-carrying wires,squeeze bottles,toys,and flexible pipes.
$(b)$ High Density Polythene $(HDP)$:
Preparation: It is formed by the addition polymerization of ethene in a hydrocarbon solvent in the presence of a Ziegler-Natta catalyst (triethylaluminium and titanium tetrachloride) at $333 \ K$ to $343 \ K$ and a pressure of $6-7 \ atm$.
Properties: $HDP$ consists of linear molecules,leading to close packing and high density. It is chemically inert,tougher,and harder than $LDP$.
Uses: Used for manufacturing buckets,dustbins,bottles,and pipes.

(N/A) Preparation: Polytetrafluoroethene (Teflon) is manufactured by heating tetrafluoroethene with a free radical or persulphate catalyst at high pressures.
The chemical reaction is: $n CF_2=CF_2 \xrightarrow[\text{High Pressure}]{\text{Catalyst}} -(CF_2-CF_2)-_n$
Properties:
$1$. It is chemically inert and resistant to attack by corrosive reagents.
$2$. It has a high melting point and is tough.
$3$. It is non-stick and has low coefficient of friction.
Uses:
$1$. It is used in making oil seals and gaskets.
$2$. It is used for non-stick surface coating of cooking utensils.

(N/A) Preparation: The addition polymerization of acrylonitrile $(CH_2=CHCN)$ in the presence of a peroxide catalyst leads to the formation of polyacrylonitrile. The reaction is as follows:
$nCH_2=CHCN \xrightarrow{\text{Polymerization, Peroxide catalyst}} [CH_2-CH(CN)]_n$
Uses: Polyacrylonitrile is used as a substitute for wool in making commercial fibres such as orlon or acrilan.

(B) Polyamides are polymers that possess amide linkages $(-CONH-)$ in their backbone.
They are important examples of synthetic fibres and are commonly termed as nylons.
The general method of preparation involves the condensation polymerization of diamines with dicarboxylic acids or the condensation of amino acids or their lactams.
Examples include: $(i)$ $Nylon-6,6$ and $(ii)$ $Nylon-6$.