Macromolecules

Polymers are defined as high molecular mass macromolecules, which consist of repeating structural units derived from the corresponding monomers. These polymers may be of natural or synthetic origin.
Polysaccharides are polymeric carbohydrate molecules composed of long chains of monosaccharide units bound together by glycosidic. Examples of natural polymers are- starch, glycogen, cellulose, pectin, wool, silk, rubber, chitin, rayon etc.

Epoxy resins, also known as polyepoxides, are a class of reactive prepolymers and polymers which contain epoxide groups. Epoxy resins may react (cross-linked) either with themselves through catalytic homopolymerisation, or with a wide range of co-reactants including polyfunctional amines, acids (and acid anhydrides), phenols, alcohols, and thiols. Examples are- Bisphenol A (BPA), Bisphenol F (BPF), Epoxy phenol novolac (EPN), etc.
Examples of polyvinyl resins are- PVA (poly vinyl alcohol), PVAc (poly vinyl acetate) etc.

1. PA 6/66 (nylon 6/66) is a copolymer and is made from caprolactam, hexamethylenediamine and adipic acid.
2. PA 6I (nylon 6I) is an amorphous polymer which is made from the polymerisation of hexamethylenediamine and isophthalic acid.
   PA 66/610 (nylon 66/610) is made from hexamethylenediamine, adipic acid and sebacic acid.
3. A model from Solvay Industries and Trogamid from Evonik Industries are semi-aromatic polyamides and are made from the polymerisation of hexamethylenediamine and terephthalic acid.
   Hence, 2 and 3 statements are false.

1. Vectran is an aromatic polyester used for reinforcing fibres for ropes and sailcloth. It is also used in manufacturing badminton strings, bike tires and in electronics applications.
2. HDPE is known for its large strength to density ratio. The density of high-density polyethylene can range from 0.93 to 0.97 g/cm3. Although the density of HDPE is only marginally higher than that of low-density polyethylene, HDPE has little branching, giving it stronger intermolecular forces and tensile strength than LDPE.
3. Polyethylene terephthalate (PET) or polyethylene terephthalic ester (PETE) is a condensation polymer produced from the monomers ethylene glycol, (a dialcohol) and dimethyl terephthalate (a diester). PET fibers are manufactured under the trade names of Dacron. Polytetrafluoroethylene (PTFE) is a synthetic fluoropolymer of tetrafluoroethylene that has numerous applications. The best known brand name of PTFE is Teflon by DuPont Co.
   Hence, statement 2 is false.

1. Vulcanization is a chemical process for converting natural rubber or related polymers into more durable materials via the addition of sulphur or a solution of S₂Cl₂ in CS₂.
2. Buna-N is the copolymer of butadiene and acrylonitrile.
3. Cellulose is treated with sulfuric acid and potassium nitrate to give cellulose mononitrate. This was used commercially as celluloid, a highly flammable plastic used in the first half of the 20th Century for lacquers and photographic film.
   Hence, the statement 1 is incorrect.

1. Nylon 2–nylon 6 (nylon 2,6) is an alternating polyamide copolymer of glycine and amino caproic acid and is biodegradable.
2. Glyptal is the condensation polymer of ethylene glycol and phthalic acid. It is used in the manufacture of paints and lacquers.
   Bakelite is the condensation polymer of phenol and formaldehyde. It is used in the making of combs, electrical switches, hardness of utensils and computer discs.
3. Urea formaldehyde resin (UFR) is the condensation polymer of urea and formaldehyde and is used in the making of unbreakable cups and laminated sheets.
   Hence, statement 2 is not true.

Synthetic polymers are human-made polymers. From the utility point of view, they can be classified into four main categories: thermoplastics, thermosets, elastomers and synthetic fibers.
An elastomer is a polymer with viscoelasticity (having both viscosity and elasticity) and very weak inter-molecular forces. Examples are- polychloroprene, neoprene, baypren, elastolefin urea formaldehyde resin (UFR) etc.

On the basis of molecular forces, polymers are classified in the following four types-

1. Elastomers: These are rubber – like solids with elastic properties. In these elastomeric polymers, the polymer chains are held together by the weakest intermolecular forces. These weak binding forces permit the polymer to be stretched. A few ‘crosslinks’ are introduced in between the chains, which help the polymer to retract to its original position after the force is released as in vulcanised rubber. The examples
   are buna-S, buna-N, neoprene etc.
2. Fibres: Fibres are the thread forming solids which possess high tensile strength and high modulus. These characteristics can be attributed to the strong intermolecular forces like hydrogen bonding. These strong forces also lead to close packing of chains and thus impart crystalline nature. The examples are polyamides (nylon 6, 6), polyesters (terylene), etc.
3. Thermoplastic polymers: These are the linear or slightly branched long chain molecules capable of repeatedly softening on heating and hardening on cooling. These polymers possess intermolecular forces of attraction intermediate between elastomers and fibres. Some common thermoplastics are polythene, polystyrene, polyvinyls, etc.
   4 Thermosetting polymers: These polymers are cross linked or heavily branched molecules, which on heating undergo extensive cross linking in moulds and again become infusible. These cannot be reused. Some common examples are bakelite, urea-formaldelyde resins (UFR), etc.

The classification based on source is sub categorized in-

1. Natural polymers: These polymers are found in plants and animals. Examples are proteins, cellulose, starch, resins and rubber.
2. Semi-synthetic polymers: Cellulose derivatives as cellulose acetate (rayon) and cellulose nitrate, etc. are the usual examples of this sub category.
3. Synthetic polymers: A variety of synthetic polymers as plastic (polythene), synthetic fibres (nylon 6,6) and synthetic rubbers (Buna - S) are examples of manmade polymers extensively used in daily life as well as in industry.

Polytetrafluoroethylene (PTFE) is a synthetic fluoropolymer of tetrafluoroethylene that has numerous applications. The best known brand name of PTFE is Teflon. Polyvinylidene fluoride, or polyvinylidene difluoride (PVDF) is a highly non-reactive and pure thermoplastic fluoropolymer produced by the polymerization of vinylidene difluoride. PVDF is sold under a variety of brand names including Hylar (Solvay), Kynar (Arkema) and Solef (Solvay). Poly ethylene oxide (PEO) is formed from the polymerisation of ethylene oxide. The preparation of PEO is sold under the brand names GoLYTELY, GaviLyte C, NuLytely, GlycoLax, Fortrans etc.
Mylar is the brand name of polyethylene terephthalate (PETP).
Hence, the representation of codes A - 2, B - 1, C - 4, D - 3 is correct.

1. Cellulose is the homopolymer of glucose as monomer unit. Inulin is the homopolymer of fructose as monomer unit.
2. Nylon 6 is obtained by heating caprolactum with water at a high temperature.
3. Plexiglass or polymethyl methacrylate is the addition polymer of methyl methacrylate.
4. Glyptal is the copolymer of ethylene glycol and phthalic acid. Bakelite is the condensation polymer (copolymer) of phenol and formaldehyde.

Polyetherimide (PEI) is an amorphous, amber-to-transparent thermoplastic which is made from the polymerisation of etherimide.

Terylene (polyester) is the condensation polymer of ethylene glycol and dimethyl terephthalate. Nylon 6,6 is the condensation polymer of hexamethylenediamine and adipic acid. Perspex (Polymethyl methacrylate) is prepared by the polymerisation of methyl methacrylate. Polyvinyl chloride (PVC) is formed by the polymerisation of vinyl chloride.
Hence, the correct answer using the codes is a - 3, b - 4, c - 1, d - 2.

A large number of polymer applications in different fields depend on their unique mechanical properties like tensile strength, elasticity, toughness, etc. These mechanical properties are governed by intermolecular forces, e.g., van der Waals forces and hydrogen bonds, present in the polymer. These forces also bind the polymer chains. Under this category, the polymers are classified into the following four sub groups on the basis of magnitude of intermolecular forces present in them- elastomers, fibers, thermoplastic and thermosetting. Elastomers are rubber – like solids with elastic properties. In these elastomeric polymers, the polymer chains are held together by the weakest intermolecular forces. These weak binding forces permit the polymer to be stretched. A few ‘crosslinks’ are introduced in between
the chains, which help the polymer to retract to its original position after the force is released, as in vulcanised rubber. Examples are buna-S, buna-N, neoprene, Bromo Isobutylene Isoprene (bromobutyl), Viton (a brand of synthetic rubber and fluoropolymer elastomer commonly used in O-rings and other molded or extruded goods) etc.

Polyvinyl butyral (PVB) is a resin usually used for applications that require strong binding, optical clarity, adhesion to many surfaces, toughness and flexibility. It is prepared from polyvinyl alcohol by reaction with butyraldehyde. The major application is in the making of laminated safety glass for automobile windshields.
Orlon is a addition polymer of acrylonitrile which is used for making clothes and fabrics like sweaters, hats, yarns, rugs, etc.
Bakelite is the condensation polymer (copolymer) of phenol and formaldehyde. Bakelite is a high electric, heat and chemical resistance polymer and used in the manufacturing of insulation of wires, manufacturing sockets, electrical devices, brake pads, etc.
Twaron is the brandname of Teijin Aramid for a para-aramid. It is a heat-resistant and strong synthetic fibre developed in the early 1970s by the Dutch company AKZO. Twaron is a p-phenylene terephthalamide, the simplest form of the AABB para polyaramide. It is used in the making of bullet-proof body armour, helmets, brake pads, ropes etc.
Hence, the correct answer using the codes is P - 2 - i, Q - 3 - iv, R - 4 - iii, S - 1 - ii.