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1. POLYMERS Chemistry Project BY- NILAKSHI PRIYA Roll no. 11 Class 11Sc.

2. CONTENTS: Introduction Natural and Synthetic Polymers Types of Natural Polymers Types of synthetic polymers Applications Conclusion Bibliography

3. INTRODUCTION Prior to the early 1920's, chemists doubted the existence of molecules having molecular weights greater than a few thousand. This limiting view was challenged by  Hermann Staudinger , a German chemist with experience in studying natural compounds such as rubber and cellulose. In contrast to the prevailing rationalization of these substances as aggregates of small molecules, Staudinger proposed they were made up of  macromolecules  composed of 10,000 or more atoms. He formulated a  polymeric  structure for  rubber , based on a repeating isoprene unit (referred to as a monomer). For his contributions to chemistry, Staudinger received the 1953 Nobel Prize. The terms  polymer  and  monomer  were derived from the Greek roots  poly  (many),  mono  (one) and  meros  (part). Recognition that polymeric macromolecules make up many important natural materials was followed by the creation of synthetic analogs having a variety of properties. Indeed, applications of these materials as fibers, flexible films, adhesives, resistant paints and tough but light solids have transformed modern society. Some important examples of these substances are discussed in the following sections.

4. NATURAL AND SYNTHETIC POLYMERS There are two types of polymers: Natural and Synthetic. Natural polymers are substances that are obtained naturally. They are formed either by the process of addition polymerization or condensation polymerization. Polymers are extensively found in nature. Our body too is made up of many natural polymers like nucleic acids, proteins, etc. Cellulose is another natural polymer which is a main structural component of plants.  Some other examples of natural polymers include DNA and RNA . Synthetic polymers are man-made polymers that consist of duplicate structural units known as monomers.  They are manufactured using chemical reactions that join lots of small molecules together to make long molecules . Synthetic polymers include most of today’s plastic materials that one can encounter in their day-to-day life such as plastics used in cars, mobile phones, electrical appliances, packaging material, etc.  These include polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), etc.

5. TYPES OF NATURAL POLYMERS CELLULOSE Cellulose is an organic polysaccharide consisting of a linear chain of several hundred to over ten thousand linked D-glucose units having the formula ( C 6 ​ H 10​ O 5 ​ ) n ​ ). Cellulose is the major component of plant cell walls, which helps plants stay stiff and upright. Even though humans cannot digest cellulose, it is an important source of fiber in the diet. Cellulose aids digestion by allowing food to pass more readily through the intestines and pushing waste out of the body. The primary components of the plant cell wall are cellulose, hemicelluloses, and pectin. In the pharmaceutical sector, cellulose is primarily utilized as a diluent/binder in tablets for both the granulation and direct compression processes. Carboxylated methylcellulose is utilized in medication formulations as a binder, film-coating agent, and an ointment base.

6. cellulose

7. NATURAL RUBBER Rubber, also known as latex, is an elastomer, a polymer that is prominently known for its elastic properties. Natural rubber is primarily harvested in the form of the latex from the rubber tree (Hevea brasiliensis ). Latex is a stable dispersion (emulsion) of polymer microparticles in water that is extracted from the bark by cutting incisions and collecting the fluid in vessels, a technique known as “tapping.” After that, the latex is refined into rubber, which is ready for commercial use. Latex is allowed to agglomerate in the collection cup in large places. The coagulated lumps are collected and dried before being sold. Although 20,000 species of plants produce latex, only 2,500 species have been found to contain rubber in their latex. Natural rubber is widely employed in a variety of applications and products, both individually and in conjunction with other materials. Around 25 million tonnes of rubber are produced each year, of which 30 percent is natural. It is an essential raw material used in the creation of more than 40,000 products including medical equipment, surgical gloves, aircraft/car tires, pacifiers, clothes, toys, etc.

8. NATURAL RUBBER

9. WOOL Wool is another type of naturally occurring polymer that we use in our daily life. Most of us are familiar with the warm clothes made of wool that we use in winters to comfort ourselves from cold weather.  Wool is one of the most reusable textile fibers present on our planet. It is obtained from sheep and other animals, including cashmere and mohair from goats, qiviut from muskoxen, hide and fur clothing from bison, angora from rabbits, and other types of wool from camelids. The polymeric structure of wool contains a group of proteins known as keratins linked together via covalent bonding.  In addition to its chemical complexity, wool also has a complex physical structure. The surface is made up of overlapping cuticles. Place it under a microscope and you see a scaly surface, which is very different from the smooth surface of synthetic fibers. These properties provide wool’s flexibility, elasticity, resilience, and good wrinkle recovery properties. It’s also what allows it to absorb both moisture and dyes so well. In addition to clothing, wool has been used for blankets, horse rugs, saddle cloths, carpeting, insulation, and upholstery. It is also used to cover piano hammers to absorb odors and noise. Wool can also be used for soundproofing in heavy machinery and speakers.

10. STARCH Like cellulose, starch is another plant-derived natural polymer. It is a polysaccharide carbohydrate consisting of a large number of glucose molecules joined together by glycosidic bonds and found especially in seeds, bulbs, and tubers. Starch is the principal source of dietary calories to the world’s human population. Pure starch is a white, tasteless, and odorless powder that is insoluble in cold water or alcohol. Starch is an appealing bio-based polymer because of its inexpensive cost, biodegradability, abundance, and renewable supply. The cyclic structure of the starch molecules together with strong hydrogen bonding gives starch a rigid structure and leads to highly ordered crystalline regions. Starch and its derivatives are frequently used as additives in food, cosmetics, and pharmaceuticals, for example as thickeners, gelling agents, and encapsulating agents. In papermaking, chemically modified starch is used as an additive to increase dry strength and to bind pigments, and in textile making, it is used as a sizing agent to reduce wear and warp during weaving.

11. PROTEIN Protein is a linear polymer chain of amino acid residues called a polypeptide. A protein contains at least one long polypeptide in which at least 20 natural amino acids are linked by amide bonds. The individual amino acid residues are bonded together by peptide bonds and adjacent amino acid residues. The sequence of amino acid residues in a protein is defined by the sequence of a gene, which is encoded in the genetic code. In addition to the 20 natural amino acids, there are amino acids that are not directly synthesized from ribosomes, such as L-3,4-dihydroxyphenylalanine (DOPA), hydroxyproline ( Hyp ), tyrosine, and selenomethionine , and these compounds are synthesized via posttranslational modifications. Short polypeptides, containing less than 20–30 residues, are rarely considered to be proteins and are commonly called peptides, or sometimes oligopeptide. Every cell in the human body contains proteins that have distinct cellular functions. Humans need protein in their diet to help their bodies repair cells and make new ones. Protein is also important for growth and development in children, teens, and pregnant women. Proteins allow cells to detect and react to hormones and toxins in their surroundings, and as the chief ingredient in antibodies, which help us resist infection, they play a part in protecting our bodies against foreign invaders. The lack of specific proteins in the brain may be linked to such mysterious, terrifying conditions as Alzheimer’s and Creutzfeldt-Jakob diseases.

12. TYPES OF SYNTHETIC POLYMERS Low-Density Polyethylene (LDPE) Low-Density Polyethylene (LDPE) polymers are one of the most popular types of synthetic organic polymers found in everyday life. It is a thermoplastic polymer manufactured from the monomer ethylene. LDPE was one of the first polymers to be synthesized, and Imperial Chemical Industries synthesized it in 1933 using a high-pressure free radical polymerization technique. The most prominent feature of LDPE is its side branching that prevents the polymers from getting near enough to each other to experience the highest dispersion forces. As a result, the attraction is very faint and results in the polymer density range of 917–930 kilograms per cubic meter. The plastic formed from low-density polyethylene has a low melting point, is easily molded and its low density makes it buoyant in water. The most common use of LDPE is in the manufacturing of plastic bags that we use to carry items; however, certain governments around the globe have banned the use of plastic bags due to rising environmental concerns. LDPE is also used for manufacturing various containers, dispensing bottles, wash bottles, tubing, plastic parts for computer components, and various molded laboratory equipment.

13. LDPE Water Bottle Shrink Film, Packaging Type: Roll

14. High-Density Polyethylene (HDPE) High-density polyethylene (HDPE), sometimes called “ alkathene ” or “polythene,” is also a thermoplastic polymer produced from the monomer ethylene. In comparison to LDPE, it is a cost-effective thermoplastic with a linear structure and no or low degree of branching. It takes 1.75 kilograms of petroleum (in terms of energy and raw materials) to make one kilogram of HDPE. The density of HDPE can range from 930 to 970 kilograms per cubic meter. Although HDPE is only marginally more in density than LDPE, it is the intermolecular forces and less branching that give HDPE its tensile strength. It is manufactured at low temperature (70-300°C) and low pressure (10-80 bar).  While its higher density versions yield a more rigid result, HDPE can vary in flexibility. Because HDPE shows low reactivity to its environment, it is used to produce containers that are suitable for storing a wide range of compounds.HDPE pipes benefit from the same qualities that make them remarkably effective in containers. HDPE pipes are chemically resistant, allowing them to convey a wide range of liquids and serve as an outer cover for cables and wires. HDPE can resist temperatures ranging from -220°F to 180°F when adequately strengthened for this use. Sewer, water, gas pipes, and coatings over automotive wires, are some of the few applications of HDPE pipes. The cost-effective nature of HDPE makes it a preferable replacement in several areas where plastic is required, e.g., in 3D printers, banners, hovercrafts, and even in plastic surgery.

15. HDPE products

16. Polypropylene (PP) Polypropylene  ( C 3 ​ H 6 ​ ) n ​  is one of the most versatile and cost-effective thermoplastic polymers in all plastics. It is a rigid and partially-crystalline polymer produced via chain-growth polymerization of propene (or propylene) monomer. It has several properties that make it a better choice of plastic than polyethylene, e.g., higher melting point makes it employable in the manufacture of microwave-safe containers, and higher resistance to cracking and stress, even when flexed, makes it less vulnerable to daily wear and tear. It’s one of the most affordable plastics on the market today, and it’s used in industries including automotive manufacture, furniture assembly, and aerospace as both a plastic and fiber. It is used in a variety of applications such as packaging and labeling, textiles, stationery, plastic parts and reusable containers of various types, laboratory equipment, loudspeakers, automotive components, and polymer banknotes. It’s a tough polymer created from the monomer propylene that’s resistant to a wide range of chemical solvents, bases, and acids.

17. Pp plastic granules

18. Polyvinyl chloride (PVC) After polyethylene and polypropylene, polyvinyl chloride (PVC) is the third most extensively used material. It is a high-strength thermoplastic material that comes in two basic forms, rigid and flexible. It is produced by the polymerization of vinyl chloride monomer. It’s a white, brittle solid that comes in powder or granule form. PVC is now replacing conventional building materials such as wood, metal, concrete, rubber, ceramics, and others in a variety of applications due to its versatile properties such as lightweight, durability, low cost, and ease of processing. PVC is utilized in construction because it is less expensive and more durable than traditional materials like copper or ductile iron. Plasticizers, the most common of which are phthalates, can be used to make them softer and more flexible. PVC is utilized in clothes and upholstery, electrical wire insulation, inflatable items, and a variety of other applications where the rubber is replaced.

19. Polystyrene (PS) Polystyrene (PS) is an aromatic polymer manufactured from the liquid petrochemical styrene as its monomer. Polyester can be both an amorphous and a semi-crystalline polymer, depending on its manufacturing and thermal history. To generate a fabric with aggregate qualities, polyester fibers are frequently combined with natural fibers. Polyester synthetic fibers outperform plant-derived fibers in terms of water, wind, and environmental resistance. Its hydrophobic nature makes it perfect for clothes and jackets that will be used in damp conditions. Adding a water-resistant treatment to the fabric enhances this impact. PS is a colorless solid that is used in disposable flatware, plastic models, CD and DVD cases, and smoke detector housings, among other applications. Packing materials, insulation, and foam drink cups are all created from foamed polystyrene. Its sluggish biodegradation is a source of debate, and it is frequently seen scattered outdoors, especially near shorelines and rivers.

20. Synthetic Polymer: Applications Plastic  containers of all shapes and sizes are one of the most prevalent uses of Synthetic Polymers. They are more lightweight and cost less than regular containers. We employ synthetic polymers in our daily lives, in everything from clothing to storage to construction materials and children's toys. Polymers are also important components of materials used in and on the soil to improve aeration, which is the process of creating air spaces between the soil to increase water and mineral permeability. They also help plants grow and thrive.

21. CONCLUSION There are two types of polymers: synthetic and natural. Synthetic polymers are derived from petroleum oil, and made by scientists and engineers. Examples of synthetic polymers include nylon, polyethylene, polyester, Teflon, and epoxy. Natural polymers occur in nature and can be extracted. They are often water-based. Examples of naturally occurring polymers are silk, wool, DNA, cellulose and proteins.

22. BIBLIOGRAPHY Websites: www.chem.libretexts.org www.studiousguy.com