Chemistry Test - 22

Explanation:

⇒ Thermoplastic polymer is either linear or branched chain polymer.
⇒ It becomes soft on heating under pressure and on cooling, it becomes hard.
⇒ It can be remoulded and recycled.

Examples of thermoplastic polymer include polythene, polystyrene, PVC.

Explanation:

⇒ - [NH(CH)₂NHCO(CH₂)₄CO]_n^- is copolymer because polymers whose repeating structural units are derived from two or more types of monomer units are called copolymer.

⇒ nH₂ N(CH₂)NH₂ + nHOOC(CH₂)₄ COOH \(\xrightarrow[nH_2O]{Polymerisatiaon}\) - [NH(CH₂)NHCO(CH₂)₄CO]_n^-

⇒ - [NH(CH)₂NHCO(CH2)4CO]n- is copolymer because polymers whose repeating structural units are derived from two or more types of monomer units are called copolymer.

⇒  nH2 N(CH2)NH2 + nHOOC(CH2)4 COOH \(\xrightarrow[nH_2O]{Polymerisatiaon}\) - [NH(CH2)NHCO(CH2)4CO]n-

Explanation:

Natural rubber may be considered as a linear polymer of isoprene (2-methyl-1,3-butadiene) and also called as cis-1,4-polyisoprene.

Polyisoprene

Explanation:

Condensation polymer:

• it is a form of a step-growth polymerization where smaller molecules or monomers react with each other to form larger structural units (usually polymers) while releasing by-products such as water or methanol molecule.
• The by-products are normally referred to as condensate.
• The molecules should have one or two functional groups (like alcohol, amine, or carboxylic acid groups).
• The reaction occurs between two similar or different functional groups or monomers. It can take place between a dimer and oligomer, one monomer and one dimer or between a chain and another chain of polymers.
• Smaller molecules usually combine to form larger molecules.
• Examples-
  • Acetone → mesityl oxide
  • Nylon and Polyester

Explanation-

When the polymer is classified based on the structure of the monomer chain it can be classified as 

• Linear polymers
• Branched-chain Polymers
• Cross-linked polymers

Cross-linked Polymers-

• They have a stronger covalent bond between various linear polymer chains.
• Bakelite and melamine are examples in this category.
• Cross-linked or network polymers are formed from either mono or bi- or tri-functional monomers.

Two mono-functional monomers can form a bifunctional adduct

So option 4 is not related to cross-linked polymers, so it is incorrect.

Other Important points-

Linear Polymers

• The structure of polymers containing long and straight chains falls into this category. PVC, i.e. poly-vinyl chloride is largely used for making pipes and electric cables is an example of a linear polymer.

Branched-chain Polymers

• When linear chains of a polymer form branches, then, such polymers are categorized as branched-chain polymers.
• For example, Low-density polythene.

Explanation-

Cationic addition polymerization reaction-

• cationic polymerization is a type of chain-growth polymerization in which a cationic initiator transfers charge to a monomer which then becomes reactive.
• This reactive monomer goes on to react similarly with other monomers to form a polymer.
• The types of monomers necessary for cationic polymerization are limited to alkenes with electron-donating substituents and heterocycles.
• Similar to anionic polymerization reactions, cationic polymerization reactions are very sensitive to the type of solvent used.
• Specifically, the ability of a solvent to form free ions will dictate the reactivity of the propagating cationic chain.
• Cationic polymerization is used in the production of polyisobutylene (used in inner tubes) and poly(N-vinylcarbazole) 
• Butyl rubber is prepared by copolymerizing isobutylene with 1.5 to 4.5% of isoprene. Both monomers are obtained by petroleum refinery cracking. It is formed by a cationic addition polymerization reaction.

Additional Information Polymerization - The process of formation of polymers from the reaction of monomer subunits. It is of two types i.e. Addition condensation and condensation polymerization. 

Addition polymerization - 

• the polymers are formed by the simple addition of monomer units.
• The monomer has at least one double in its structure so that it can undergo additional polymerization.
• The polymer molecular weight is a multiple of monomer molecular wt.
• No side product is obtained in addition to polymerization. 
• The polymer obtained by the addition mechanism is called the addition polymer.
• Ex - polyethylene, Teflon, PVC etc.

polystyrene:

• The chemical component of thermocol is polystyrene.
• It is a compound containing polymers of styrene.
• The monomer of thermocol is styrene.
• It is a plastic material that is thermally slender.

Explanation-

Nylon-66-

• Nylon 66 is synthesized by polycondensation of hexamethylenediamine and adipic acid. 
• Equivalent amounts of hexamethylenediamine and adipic acid are combined with water in a reactor.
• This is crystallized to make nylon salt, an ammonium/carboxylate mixture.
• The nylon salt goes into a reaction vessel where the polymerization process takes place either in batches or continuously.
• Nylon 6,6 has strong intermolecular forces like hydrogen bonding.The substantial strength of polyamides such as nylon 6,6 and Kevlar results from hydrogen bond.

Other Important Points-

Hydrogen Bonding-

• Hydrogen bonding refers to the formation of Hydrogen bonds, which are a special class of attractive intermolecular forces that arise due to the dipole-dipole interaction between a hydrogen atom that is bonded to a highly electronegative atom and another highly electronegative atom that lies in the vicinity of the hydrogen atom.

Explanation-

Nylon 2 -Nylon 6

• The biodegradable polymer which can be produced from glycine and aminocaproic acid is Nylon 2 - nylon - 6.
• It is a polyamide copolymerization of glycine (H₂N−CH₂−COOH) and aminocaproic acid (H₂N−(CH₂)₅−COOH).

PHBV

• Poly (3-hydroxybutyrate-co-3-hydroxy valerate) (PHBV) is a biodegradable polyhydroxyalkanoate-type polymer. It is a copolymer of 3 - hydroxybutanoic acid and 3 - hydroxypentanoic acid.

Buna-N​

• Buna - N is a copolymer of acrylonitrile and 1,3 - butadiene.

Nylon 6, 6

• Nylon - 6,6 is a condensation copolymer made from monomers adipic acid and hexamethylenediamine.
   

Explanation-

Biodegradable polymer-

• These are those polymers that get decomposed under aerobic or anaerobic conditions, as a result of the action of microorganisms/enzymes.
• The materials develop it like starch, cellulose, and polyesters. Aliphatic polyesters are the most commonly used polymers of this type.
• Examples-
  • Nylon 2–Nylon 6: It is a polyamide copolymerization of glycine (H₂N−CH₂−COOH) and aminocaproic acid (H₂N−(CH₂)₅−COOH).
  • Polyhydroxybutyrate (PHB): It is formed by the condensation of hydroxybutyric acid (3-hydroxy butanoic acid) molecules.
  • Poly β-hydroxybutyrate – co-β-hydroxy valerate (PHBV): It is derived by combining 3-hydroxy butanoic acid and 3-hydroxy pentanoic acid, in which monomers are cross-linked by an ester linkage.

 Important Points

Non-biodegradable polymer-

• They consist of long chains of carbon and hydrogen atoms.
• These molecules form an interatomic type of bonding and is adamant meaning it is tough for microbes to break the bonds and digest them. Thus a long period is required to decompose them.
• Examples-

  • Linear high-density polyethene (HDPE)

  • Branched low-density polyethene (LDPE)

  • Ultra-high molecular weight polyethylene(UHMWPE)

Explanation-

• Polymerization is a process of reacting monomer molecules together in a chemical reaction to form long polymer chains.
• In chemical compounds, polymerization can occur by various types of reaction mechanisms that vary in complexity due to the functional groups present in the reactants and the steric effects that are present.
• Copolymerisation is the type of polymerization reaction involving more than one type of monomer.
• The number of monomers involved in the reaction is usually 2. Buna-N is one such polymer that is formed by copolymerization. 
• Buna−N is a synthetic rubber copolymer made up of 1,3−Butadiene (H₂​C=CH – CH=CH₂​) and acrylonitrile (H_2​C=CH– CN).
• The synthesis is as follows: