Which of the following is a synthetic polymer?

Nylon 6, 6

The correct answer is option 1. Nylon 6, 6.

Let us look at the given options: 

1. Nylon 6,6: This is a synthetic polymer, meaning it is man-made. Nylon 6,6 is a type of polyamide made from the condensation polymerization of hexamethylenediamine and adipic acid. It is widely used in textiles, automotive components, and various industrial applications due to its strength, elasticity, and resistance to abrasion and chemicals.

2. Cellulose: This is a natural polymer. It is a polysaccharide consisting of a linear chain of several hundred to many thousands of β(1→4) linked D-glucose units. Cellulose is the primary structural component of plant cell walls.

3. Cotton: This is a natural polymer, primarily composed of cellulose. Cotton fibers are derived from the seeds of the cotton plant and are used extensively in the textile industry.

4. Proteins: These are natural polymers made up of amino acids linked by peptide bonds. Proteins perform a vast array of functions within living organisms, including catalyzing metabolic reactions, DNA replication, responding to stimuli, and transporting molecules.

Hence, Nylon 6,6 is the only synthetic polymer among the given options.