Introduction to Polymers

Polymers

• Polymers consist of macromolecules, which are large molecules made of repeating units called monomers.
• Monomers combine to form polymers through a process called polymerization, influenced by temperature, pressure, and catalysts.
• Polymers can be linear, branched, or cross-linked.

Classification of Polymers by Source

• Natural polymers are formed in living organisms like plants and animals.
• Examples include starch and cellulose, which are polymers of glucose, proteins (polymers of α-amino acids), nucleic acids (DNA & RNA), and natural rubber (polyisoprene).
• Synthetic polymers are created in labs or chemical industries.
• Examples include polyethene, PVC, polystyrene, Teflon, nylon-6,6, and bakelite.

Classification of Polymers by Monomer Type

• Homopolymers consist of only one type of monomer.
• Examples include polyethene, PVC, polystyrene, and Teflon.
• Copolymers are formed by combining two or more different types of monomers.
• Examples include nylon 6,6, bakelite, and terylene (Dacron).

Classification of Polymers by Synthesis

• Addition polymers form through the direct combination of monomer units without the elimination of molecules, a process called addition polymerization.
• Monomers are usually unsaturated and the reaction occurs in a single step.
• Examples include polyethene, PVC, polystyrene, Teflon, and benzene.
• Condensation polymers form when monomers combine with the elimination of smaller molecules like water, ammonia, or hydrogen chloride, a process called condensation polymerization.
• Monomer units have two or more functional groups and the reaction occurs in steps.
• Examples include nylon-6,6, bakelite, and terylene or Darcon (Polyester).

Preparation and Uses of Polymers

• Polyethene is a thermoplastic used in housewares, carpet backing, packaging, and cable insulation.
• PVC is used in pipes, fittings, carpets, containers, window frames, CD/DVDs, cable insulation, and blood bags
• Teflon is used as a non-stick coating for cookware and in waterproof clothing, electrical insulation, gaskets, and valves.
• Polystyrene is used in rigid trays, containers, disposable utensils, and foamed cups.
• When combined with additives can be used to make electronics, automobile parts and toys.
• Nylon-6,6 is used to make ropes for climbing and parachutes.
• Bakelite, a thermosetting plastic, is used electrical switches and cookware handles.

Elastomers

• Elastomers have both viscosity and elasticity, like rubber.
• Polymer chains are held together by weak intermolecular bonds, allowing them to stretch and return to their original size under pressure.

Natural and Synthetic Elastomers

• Natural elastomers are extracted from natural resources, mainly from the latex of the Hevea brasiliensis rubber tree.
• Polyisoprene rubber, chemically is cis-1,4-polyisoprene, is also called natural rubber(NR).
• The natural rubber is addition polymer of monomer unit isoprene.
• Trans-1,4-polyisoprene is also called gutta-percha.
• Synthetic elastomers are produced artificially, serving as substitutes for natural rubber, often with improved properties.
• Neoprene (polychloroprene) is a family of synthetic rubbers made by addition polymerization of chloroprene.
• Polybutadiene is a synthetic rubber formed by polymerizing 1,3-butadiene.
• Buna-S (SBR) is a copolymer of 1,3-butadiene and styrene, produced through polymerization in a 3:1 ratio with sodium.

Vulcanization

• Vulcanization is the chemical process of heating rubber with sulfur, accelerators, and activators at 140–160°C.
• It forms cross-links between the long rubber molecules.
• It improves features like elasticity, resilience, tensile strength, viscosity, hardness, and weather resistance.
• The process is named after Vulcan, the Roman god of fire.
• Sulfur vulcanization is applied to polyisoprene (natural rubber) and styrene-butadiene rubber (SBR), which are used for tires.
• The sulfur atoms will sometimes replace the C-H bonds during vulcanization to create different polymer chains.
• The # of Sulfur atoms in the crosslink influences the physical properties of the final rubber product
• Short crosslinks = Better Heat Resistance
• Higher sulfur atoms = Good dynamic properties but less heat resistance

Fibres

• Fibers are thin, long, flexible polymers that form thread-like structures sourced from plants and animals.

Natural Fibres

• Natural fibers are obtained directly from plants and animals.
• Plant fibers include cotton and jute from sources like bamboo, coconut, flax, hemp, and cereals.
• Animal fibers include wool and silk, made of animal proteins such as protective epidermal coating.
• Mineral fibers are inorganic materials like asbestos, used for fire and acid resistance.

Synthetic Fibres

• Synthetic fibers are artificially created macromolecules linked together.
• Examples include Rayon, Nylon, Acrylic, polyester, and acetate.

Natural and Artificial Fibres

• silk can be woven into textiles.
• It mainly consists of fibroin, a protein generated by insect larvae to build cocoons.
• Silk's glossy appearance is caused by it's triangular prism structure, and allows material to refract incoming light at various angles.
• Rayon is human-made from regenerated cellulose from wood and agricultural products.
• Rayon's molecular structure is that same as cellulose, it is also known as Viscose

Uses for Fibres

• Fibres are used to create ropes, specifically nylon ropes used in rock climbing and parachutes.
• Artificial textile fibres that are made from polyester, are used to create light, crease-resistant clothing, bed linen, and sails.

Drugs

• Drugs are chemical substances used to prevent, diagnose, and treat diseases.
• WHO defines a drug as any product used to modify or explore physiological systems.
• Treating diseases with chemicals is called chemotherapy.
• Paul Ehrlich is the father of chemotherapy.A good drug should be non-toxic, have minimal side effects, be effective, act locally, and not cause drug resistance.

Classification of Drugs by Source

• Natural drugs are obtained from plants, animals, and microorganisms.
• Examples include penicillin, atropine, and morphine.
• Synthetic drugs are synthesized in the laboratory.
• Examples include paracetamol and chloramphenicol.

Classification of Drugs by Mode of Action

• Chemotherapeutic drugs treat infectious diseases caused by microorganisms, like bacterial, viral, and malarial infections.
• Pharmacodynamic drugs treat diseases caused by functional disorders, such as anemia, cancer, and diabetes.

Chemotherapeutic Drugs

• Antiseptics inhibit microorganism growth without harming the host cell.
• Examples include Tincture of Iodine (I2 +KI dissolved in C2H5OH), Iodoform CHI3, and Dettol – alcoholic solution of chloro-m-xylenol and terpene.
• Disinfectants are harmful to host cells sterilizing floors and instruments. They remove organisms in swimming pools.
• Chlorine gas is a disinfectant to kill bacteria, viruses, and Protozoa.
• Sulphur Dioxide is used as a preservative to prevent the spread of bacteria in dried fruits.
• Ozone is used in HVAC systems for removing air borne pathogens.
• Antibiotics are substances naturally made by micro-organisms, and can be synthesized in a labsetting.
• Antibiotics eradicate or inhibit growth of bacteria.
• Penicillin was 1st antibiotic, discovered by Alexander Fleming in 1928
• Broad-spectrum antibiotics are effective against a wide range of microorganisms, i.e. chloramphenicol
• Narrow-spectrum antibiotics for a few microorganisms, i.e. Penicillin, streptomycin
• Sulpha-drugs are synthetic antibacterial agents like sulphanilamide and sulphadiazine, which treat urinary tract infections.
• Anti malarials are used against malarial agents like Plasmodium.
• Results in shivering, fever fatigue and anemia.
• Examples include: Chloroquine, Primaquine, Guinine, etc.

Pharmacodynamic Drugs

• Antipyretics lower body temperature, such as paracetamol and aspirin.
• Analgesics relieve pain without causing unconsciousness and are drugs like aspirin and morphine.
• Narcotics drugs (Morphine, Heroin, Cocaine, codeine) and non-narcotics (Aspirin, Novalgin) also relieve pain.
• Anesthetics reduce sensation; surgery is more manageable/comfortable like Procaine (Novocaine) - dentistry.
• General anesthetics causes unconsciousness using 2,6-diisopropylphenol (Propofol).
• Locally, it causes the loss of feeling by using Chloropropane to assist with short term surgery (epidural).
• Chloroform used to be an inhalational anethestic, until it liver damage.
• Diethyl Ether used to be historically used from 1846 until it was replaced by the more safer Sevoflurane, CH3-CH2-O-CH2-CH3, for surgeries.
• Nitrous Oxide, N20 (laughing gas) for minor dental procedures.
• Antacids neutralize excess stomach acid with compounds like NaHCO3, Al(OH)3, and Mg(OH)2.
• “ENO” = Mixture of NaHCO3, anhydrous Na2CO3 citric acid and flavoring agents
• Tranquilizers reduce anxiety, agitation, and stress without inducing sleep examples include : Equanil
• Sedatives induce calmness or sleep, ie: Diazepam
• Antidepressents can treat anxiety or depression, example: Fluoxetine (Prozac)
• Hypnotics are usually known as sleeping pills for the purpose of aiding in sleep
• Psychedelic drugs affect conscienceness. Examples: Lysergic acid diethylamide (LSD), N, N-Dimethyltryptamine (DMT or N, N-
• Methamphetamine (contracted from N-methylamphetamine) stimulant for treating ADHD and obesity.
• Drug addiction - physical, societal, psychological effects
• Can be treated by rehabilitation

Dyes

• Dyes: Chemicals that enhance distinguish in different items from water, chemicals, acids, alkali.
• Characteristics: Color, capable of being fixed to fabrics resistant to outside elements.
• Saturated groups -N=N-, -O-N=No, >C=O cause chromophores
• Some groups increase color. called auxochrome.

Natural Dyes

• Are obtained from animal (like colored plants), roots, bark, leaves, fungi such as indigo.
• Alizarin is a also dye extract
• Heena Plant, etc. also produce natural dyes.
• Synthetic dyes are created using aromatic compounds, i.e. benzene.
• The first synthetic dye (Picric acid) was created in 1771 by Woulfe
• Examples of synthetic dyes include: Phenolphthalein, p-hydroxyazobenzene, p-aminoazobenzene, picric acid, methyl orange, etc.

Classifications by Structure

• Azo dyes contain –N=N- as the major chromophore.
• The common auxochromes increase with -NH2, -NR2, -OH, -SO3H.
• Acidic dyes, such as nitro dyes, carry –NO2 and –NO-
• The formula includes Phthalein with an acid in the baseline indicator
• Phenolphthalein is used as an acid base indicator.

Classifications By Way of Usage

• Azo dyes characterize the salts of sulphonic or carboxylic acids. and is applied to nylon. and silk but doesn't work with cotton. with methyl ranges with a (azo dye).
• Basic dyes is formed by amino group.
• Direct dyes are azo and dye threads by placing it in a aqueous solution.
• It is sutible with (H-bonds), to dye wool, etc.. for example : Martius Yellow & Congo Red.
• Dissolve dyes are water-soluble which spread through agents, i.e. phenol to synthetic threads

Types and Uses of Dyes

• Disperse dyes are water-insoluble for nylon, polyesters and polyacrylonitrile
• Vat dyes - which are minimized to colorless combinations, by using alkaline agents. such as sodium
• Then the threads will be applied which oxidizes and dyed, in that way
• Then it is used to dye cottons
• Mordant dyes cannot directly dye a thread but need fabric
• Acids can act as a mediator, metal, etc.. to act as one agent. It can range from aluminim, tin, cobalt, etc.

Pesticides

• Chemicals used to control or kill pests are harmful to animals and agriculture
• In Nepal the order of usage has occurred as follows:

1. organochlorine in 1950's