A large number of simple molecules called monomers combine together to form a macromolecule called a polymer. Each polymer has a repeating structural unit. If the repeating structural unit is derived from one type of monomer molecules, the polymer is said to be a homopolymer and if it is derived from two or more different types of monomer molecules, the polymer is said to be  a copolymer. Both homopolymers and copolymer may be formed either by addition or condensation reactions. Alkenes and dienes polymerize by addition (chain growth)mechanism involving carbocations, carbanions or free radical intermediates. Dienes (chloroprene, isoprene, etc.) polymerize by 1,4-addition mechanism to give cis- or trans- polymers. Natural rubber is however, cis-polyisoprene. Natural rubber is quite soft and tacky but these properties can be improved by a process called vulcanization. In contrast, bifunctional monomer molecules undergo, condensation or step-growth polymerization. Polymers which can be heated and reshaped as many times as desired are called thermoplastics while those which can be heated only once to give a particular shape are called thermosetting polymers.

Which of the following sets contains only thermoplastics?

PVC, PMMA, Polystyrene

The correct answer is option 3. PVC, PMMA, Polystyrene.

Let us break down each polymer in the set:

PVC (Polyvinyl chloride): PVC is a thermoplastic polymer widely used in construction, healthcare, and consumer products. It is formed through the polymerization of vinyl chloride monomers. PVC is known for its versatility, durability, and chemical resistance. It can be easily softened by heating and reshaped into various forms, making it suitable for applications such as pipes, window frames, flooring, and medical tubing.

PMMA (Polymethyl methacrylate): PMMA, also known as acrylic or acrylic glass, is a transparent thermoplastic material with excellent optical properties. It is synthesized from methyl methacrylate monomers through polymerization. PMMA is commonly used as a lightweight and shatter-resistant alternative to glass in applications such as windows, signage, lighting fixtures, and automotive parts.

Polystyrene: Polystyrene is a versatile thermoplastic polymer synthesized from styrene monomers. It is known for its low cost, rigidity, and ease of processing. Polystyrene can be found in various forms, including solid (used in packaging and disposable utensils), foam (used in insulation, packaging, and food containers), and expanded (used in protective packaging and thermal insulation).

All three of these polymers—PVC, PMMA, and Polystyrene—are thermoplastics. Thermoplastics are polymers that can be repeatedly softened by heating and hardened by cooling without undergoing significant chemical change. They can be molded and reshaped multiple times, which makes them versatile and suitable for a wide range of applications.

Therefore, the set PVC, PMMA, Polystyrene contains only thermoplastic polymers, as requested.