Composition, Properties and Uses of Polymer Questions in English

(A) . Chloroprene $(CH_2=C(Cl)-CH=CH_2)$ undergoes polymerization to form Neoprene,which is a type of synthetic rubber.
$n(CH_2=C(Cl)-CH=CH_2) \xrightarrow{\text{Polymerization}} (-CH_2-C(Cl)=CH-CH_2-)_n$

(A) Teflon is a polymer of tetrafluoroethene $(CF_2 = CF_2)$.
Its chemical structure is represented as $[ - CF_2 - CF_2 - ]_n$.

(A) Bakelite is a thermosetting polymer formed by the condensation polymerization of phenol and formaldehyde in the presence of an acid or base catalyst.
Polystyrene is prepared by the polymerization of styrene monomers.
Nylon is a polyamide formed by the condensation polymerization of diamines and dicarboxylic acids.
$PVC$ (polyvinyl chloride) is formed by the addition polymerization of vinyl chloride monomers.
Therefore,phenol is a key constituent in the manufacture of Bakelite.

(C) Bakelite is a thermosetting polymer.
It becomes infusible on heating and cannot be remoulded.

(C) . Natural rubber is the only addition polymer of nature and is known as $Cis-1,4-polyisoprene$. It exhibits elastic properties due to its coiled structure.

(D) Condensation polymers are polymers formed through a condensation reaction,where molecules join together with the loss of small molecules as by-products,such as $H_2O$ or methanol.
$1$. Nylon is a type of condensation polymer called a polyamide,formed by the reaction of a dicarboxylic acid with a diamine,releasing $H_2O$.
$2$. Bakelite is formed from a condensation reaction of phenol with formaldehyde,with the removal of $H_2O$.
$3$. Urea-formaldehyde resin is an amino plastic resin formed by the reaction between urea and formaldehyde,with the removal of $H_2O$ molecules.
Since all the given options are examples of condensation polymers,the correct answer is $D$.

(A) Polythene is a thermoplastic polymer.
Thermoplastics are polymers that become soft on heating and can be remoulded into different shapes repeatedly.

(C) $Bakelite$ is a thermosetting phenol-formaldehyde resin.
$Resins$ are amorphous organic solids or semisolids which usually have a typical lustre and are often transparent or translucent.

(C) Both Buna-$S$ and Neoprene are examples of synthetic rubber.
Buna-$S$ is a copolymer of $1,3$-butadiene and styrene.
Neoprene is a polymer of chloroprene ($2$-chloro-$1,3$-butadiene).

(C) The correct answer is $C$. Syndiotactic polyvinyl chloride.
In $syndiotactic$ polymers,the substituent groups (chlorine atoms in $PVC$) are arranged in an alternating pattern on opposite sides of the polymer chain.
This regular stereochemical arrangement allows for efficient packing of the polymer chains,resulting in a higher degree of crystallinity compared to $atactic$ (random) or $isotactic$ (same side) configurations for $PVC$.

(D) Mercerisation is a treatment of cotton yarn or fabric with a concentrated solution of $NaOH$ (sodium hydroxide).
This process causes the cellulose fibers to swell,which increases the luster,strength,and affinity for dyes.
None of the options $A$,$B$,or $C$ describe this process.
Therefore,the correct process is treatment with concentrated $NaOH$ solution.

(C) Hard plastics can be made soft and flexible by adding substances known as plasticisers. For example,$PVC$ (polyvinyl chloride) is naturally stiff and hard,but the addition of di-$n$-butyl phthalate acts as a plasticiser,making it soft and rubber-like.

(B) Alkyd resins are a type of polyester formed by the condensation polymerization of polybasic acids (such as phthalic acid) and polyhydric alcohols (such as glycerol or glycol). $Glyptal$ is a common example of an alkyd resin formed from ethylene glycol and phthalic acid,while other alkyd resins use glycerol. Given the options,$Glycerol$ is a classic polyhydric alcohol used in the synthesis of these resins.

(B) Celluloids are a class of compounds created from cellulose nitrate and camphor,with added dyes and other agents.
It is generally considered the first thermoplastic material.

(B) Cellulose acetate is a non-inflammable material compared to cellulose nitrate.
Therefore,it is widely used in the manufacture of non-inflammable photographic films.

(B) $Terylene$ is a condensation polymer.
It is formed by the condensation of ethylene glycol $(HOCH_2-CH_2OH)$ and terephthalic acid $(HOOC-C_6H_4-COOH)$.
The reaction involves the elimination of water molecules,which is characteristic of condensation polymerization.
The structure of $Terylene$ contains a benzene ring in every repeating unit.

(D) Teflon is a polymer of $Tetrafluoroethene$.
It is obtained by the polymerisation of $Tetrafluoroethene$ $(CF_2 = CF_2)$ under high pressure in the presence of a peroxide or persulphate catalyst.
Therefore,the correct option is $(D)$.

(D) Acetate rayon is a semi-synthetic fibre prepared by the acetylation of cellulose using acetic anhydride in the presence of sulfuric acid.
Cellulose is a natural polymer,and its chemical modification results in the formation of cellulose acetate,which is then spun into fibres.

(D) The reaction of $Phenol$ with $Formaldehyde$ $(HCHO)$ leads to the formation of $Bakelite$,which is a well-known thermosetting polymer.
Therefore,the compound required is $Phenol$.

(C) Rayon is a semi-synthetic fiber produced from natural sources like wood pulp or cotton linters.
In the manufacturing process,natural cellulose is chemically treated and then regenerated into fiber form.
Therefore,rayon yarns are obtained from $Cellulose$.

(C) $Terylene$ (also known as $Dacron$) is a condensation polymer formed by the polymerization of $Ethylene \ glycol$ $(HO-CH_2-CH_2-OH)$ and $Terephthalic \ acid$ $(C_6H_4(COOH)_2)$.

(A) Caprolactam,when heated with water at high temperature $(533-543 \ K)$,undergoes ring-opening polymerization to form Nylon-$6$.
The reaction is: $n \ (C_6H_{11}NO) + n \ H_2O \rightarrow [-NH-(CH_2)_5-CO-]_n$.

(A) The name 'nylon' is derived from the two cities where it was simultaneously discovered: $NY$ (New York) and $LON$ (London).

(C) Teflon is flexible,chemically inert to solvents and boiling acids,including aqua-regia,and remains stable up to $598 \ K$.

(D) Nylon polymers,such as $Nylon-6,6$,are formed by the condensation polymerization of diamines and dicarboxylic acids.
They contain amide linkages $(-CONH-)$ in their backbone.
These amide groups are polar and can participate in hydrogen bonding,but they do not exhibit significant acidic or basic character in aqueous solutions.
Therefore,nylon polymers are considered to be neutral.

(C) Nylon is a synthetic polyamide. Depending on the specific chemical structure,additives,and the manufacturing process (such as the addition of flame retardants),nylon yarns can be engineered to be either highly inflammable or non-inflammable. Therefore,both types are known in the industry. The correct option is $(c)$.

(B) The polydispersity index $(PDI)$ is defined as the ratio of the weight average molecular mass $(\overline{M_w})$ to the number average molecular mass $(\overline{M_n})$.
Given: $\overline{M_w} = 40,000$ and $\overline{M_n} = 30,000$.
$PDI = \frac{\overline{M_w}}{\overline{M_n}} = \frac{40,000}{30,000} = 1.33$.
Since $1.33 > 1$,the correct option is $B$.

(B) 'Rayon' is a man-made fibre which consists of purified cellulose in the form of long threads.
Rayon resembles silk in appearance,hence it is called artificial silk.
$\mathop {{\text{Cellulose}}}\limits_{(\text{from wood pulp})}$ $\xrightarrow{\text{NaOH, } CS_2} \mathop {{\text{Viscose}}}\limits_{(\text{Syrup like liquid})}$ $\xrightarrow{\text{Spinneret, dil. } H_2SO_4} \mathop {{\text{Rayon}}}\limits_{(\text{Fine silken thread})}$

(A) Tensile strength is a measurement of the force required to pull a material to the point where it breaks. $In$ general,as the molecular weight increases,the strength,toughness,and chemical stress crack resistance of the polymer increase. Therefore,the tensile strength also increases with an increase in the polymer chain length and the degree of cross-linking.

(B) Glyptals are polyester resins formed by the condensation polymerization of ethylene glycol and phthalic acid. They are primarily used in the manufacture of paints and lacquers,which are used for surface coating.

(B) $EPR$ is a copolymer of ethylene and propylene. Since both monomers are saturated hydrocarbons,the resulting polymer chain is saturated. Because the methyl groups are distributed randomly along the polymer backbone,it is classified as atactic. However,in the context of standard chemistry curriculum classifications regarding the saturation of the backbone,$EPR$ is considered a saturated elastomer.

(C) Neoprene is a polymer of chloroprene ($2$-chloro-$1,3$-butadiene).
Its chemical formula is $n(CH_2=C(Cl)-CH=CH_2) \to [-CH_2-C(Cl)=CH-CH_2-]_n$.
Thus,besides $C$ and $H$,it contains the element $Cl$ (chlorine).

(A) Acrylic resins,such as poly(methyl methacrylate) $(PMMA)$,are synthetic polymers derived from acrylic acid or its derivatives. They are known for their excellent optical clarity,high light transmission,and are typically colourless and transparent in their pure form.

(D) The glass-transition temperature $(T_g)$ depends on the chain stiffness and the size of the side groups attached to the polymer backbone.
$1$. Polyethylene $(T_g \approx -120 \ ^{\circ}C)$: Has a flexible backbone with no bulky side groups.
$2$. Polypropylene $(T_g \approx -10 \ ^{\circ}C)$: Has a methyl group as a side chain,increasing stiffness compared to polyethylene.
$3$. Polyvinyl chloride $(T_g \approx 80 \ ^{\circ}C)$: The polar chlorine atom increases intermolecular forces and chain stiffness.
$4$. Polystyrene $(T_g \approx 100 \ ^{\circ}C)$: The bulky phenyl group significantly restricts the rotation of the polymer chain,leading to the highest $T_g$ among the given options.

(B) The polymer described is Polytetrafluoroethylene,commonly known as Teflon ($CF_2=CF_2$ polymer).
It is known for its high chemical inertness and thermal stability.
Its melting point is approximately $327\ ^\circ C$ and it has a high density due to the presence of heavy fluorine atoms in its structure.

(C) Vulcanisation is a process in which natural rubber is heated with sulfur $(S)$.
This process creates cross-links between the polymer chains,which makes the rubber harder,more durable,and less sticky.
Therefore,the process of vulcanisation makes rubber hard.
The correct option is $(C)$.

(B) Terylene,also known as $Dacron$,is a condensation polymer formed by the polymerization of ethylene glycol $(HO-CH_2-CH_2-OH)$ and terephthalic acid $(C_6H_4(COOH)_2)$.
Since the linkage formed between the monomers is an ester linkage $(-COO-)$,$Terylene$ is classified as a polyester.

(B) $Nylon-66$ is a polyamide formed by the condensation polymerization of hexamethylenediamine and adipic acid.
The presence of amide groups $(-CONH-)$ in the polymer chain allows for strong intermolecular hydrogen bonding between the chains.
This hydrogen bonding is responsible for the high crystalline nature and high melting point of $nylon-66$.

(B) To improve physical properties such as water repellency,reduced water absorption,and resistance to oxidising agents,a process called vulcanisation is carried out.
This process consists of heating a mixture of raw rubber with sulphur and an appropriate additive at a temperature range between $373 \ K$ to $415 \ K$.
On vulcanisation,sulphur forms cross-links at the reactive sites of double bonds,which causes the rubber to become stiffened.

(C) Nylon fibres are made of polyamides. They contain amide linkages.
For example:
$(i)$ Nylon-$6$ is obtained by polymerization of $6$-aminohexanoic acid.
$(ii)$ Nylon-$6,6$ is obtained by condensation polymerization of hexamethylenediamine with adipic acid.

(D) . Nylon-$66$ is a polyamide fibre.
Its strength is primarily due to the presence of strong intermolecular forces,specifically hydrogen bonding,between the linear polymer chains.
These hydrogen bonds hold the chains together tightly,providing high tensile strength and crystalline structure.

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

(A) Neoprene is a synthetic polymer that resembles natural rubber in its properties.
Its monomer unit is $2$-chloro-$1,3$-butadiene,commonly known as chloroprene $(CH_2=C(Cl)-CH=CH_2)$.
In contrast,natural rubber is a polymer of isoprene ($2$-methyl-$1,3$-butadiene,$CH_2=C(CH_3)-CH=CH_2$).

(D) Teflon (Polytetrafluoroethylene) has great chemical inertness and high thermal stability,hence it is used for making non-stick utensils.
For this purpose,a thin layer of Teflon is coated on the inner side of the vessel.

(A) The correct answer is $(A)$. This polymer is also known as $PMMA$ (Polymethylmethacrylate).
It is a transparent,excellent light transmitter,and its optical clarity is superior to glass.
Due to these properties,it is widely used in the preparation of contact lenses for eyes.

(A) Magnetic recording tapes are typically made from $Mylar$,which is a trade name for $Polyethylene \ terephthalate$ $(PET)$.
$Dacron$ is another common name for $Polyethylene \ terephthalate$ $(PET)$.
Therefore,$Dacron$ is the polymer used for making magnetic recording tapes.

(C) $Teflon$ (polytetrafluoroethylene) is a synthetic fluoropolymer of tetrafluoroethylene.
It is chemically inert,non-inflammable,and highly resistant to heat.
Due to these properties,it is widely used for non-stick coatings on cookware.

(A) Nylon $66$ is a condensation polymer formed by the polymerization of hexamethylenediamine and adipic acid.
Since it contains amide linkages $(-CONH-)$ in its backbone,it is classified as a polyamide.

(C) . Natural rubber is a polymer of isoprene ($2$-methyl-$1,3$-butadiene). It is used in the production of synthetic rubber and related elastomers.