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Linear Polymers: Appearance of real linear polymer chains as recorded using an atomic force microscope on surface under liquid medium. Chain contour length for this polymer is ~204 nm; thickness is ~0.4 nm. (The contour length of a polymer chain is its length at maximum physically possible extension). Linear Polymer: Branched Polymer: Linear Polymer: Cross-linked Polymer: Star Polymer: Dendrimers: Natural Polymers: Polymers in Plants Cellulose Cellulose, a linear polymer of D-glucose units (two are shown) linked by β(1→4)-glycosidic bonds. Starch Natural Rubber Natural rubber is a polymer of isoprene Charles GOODYEAR discovered vulcanization in 1839 Natural Polymers: Polymers in Animals Protein Functions of Proteins • All enzymes are proteins. • Structural: e.g. collagen in teehth and bone; keratin in skin, hair and nails. • Contractile proteins: actin and myosin in muscles allow contraction and therefore movement. • Hormones: many hormones have a protein structure (e.g. insulin, glucagon, growth hormone). • Transport: for example, haemoglobin facilitates the transport of oxygen around the body • Defence: immunoglobulins (antibodies) protect the body against foreign invaders; fibrinogen in the blood is vital for the clotting process. Chitin the exoskeletons of crabs, lobsters and shrimps (polymer of the N-Acetylglucosamine units) Semi-synthetic Polymers: Cellulose nitrate and cellulose acetate obtained from natural polymers by subjecting them to some chemical processes Cellulose nitrate Cellulose triacetate Synthetic Polymers 1950s Black Bakelite Telephone Bakelite Sockets & Switches Bakelite (1909) Blue Bakelite Handle Poly(methyl methacrylate) (PMMA) (1935) PMMA sheet (organic glass) Plexiglass aquarium Polystyrene (1937) Styrofoam - a brand of polystyrene foam rigid polystyrene case, weight 2.6 Kg Nylon 6,6 (1938) A 1949 advertisement in Life Magazine sings the praises of nylon products. Natural animal bristles were replaced by synthetic fibers, usually nylon, by DuPont in 1938. Polyesters (1950) Recycled PET Fabric Poly(ethylene terephthalate)-PET bottles Polycarbonates (1957) GE Lexan® face shield Lexan MR-10 windshields