Polymer

A polymer is a large molecule composed of repeating structural units called monomers, which are covalently bonded together in a chain or network.  Polymers can be naturally occurring, like DNA, proteins, and cellulose, or synthetic, like plastics, rubber, and nylon.  Polymers are widely used due to their versatility, being found in materials with diverse characteristics, such as strength, flexibility, or elasticity.  The properties of a polymer depend on:

Monomer Type  -  The specific building blocks used.
Polymer Structure  -  Linear, branched, or cross-linked configurations.
Degree of Polymerization  -  The number of monomer units in the polymer chain.

Polymers are classified into several categories based on different criteria, such as origin, structure, polymerization process, and thermal behavior.  These categories help in understanding the properties, applications, and manufacturing processes of different polymers.  Here's a breakdown of the main categories:

Based on Origin

Natural Polymer  -  Polymers are chains of repeated molecules linked together.  Natural polymers are those that occur naturally and are found in living things such as plants and animals.  There are three main types of structures found in natural polymers, proteins, sugars, and nucleotides.
Synthetic Polymer  -  There are many synthetic polymers, and every synthetic polymer has specific uses.  These uses can range from applications in clothing, body armor, pipes, and upholstery.  Synthetic polymers can be classified into four main categories: thermoplastics, thermosets, elastomers, and synthetic fibers.  Each of these categories have several polymers within them.
Semi-Synthetic Polymer  -  It is a type of polymer derived by chemically modifying natural polymers.  These modifications are carried out to enhance or alter the properties of the original natural polymer to make it more suitable for specific applications.

Based on Structure

Linear Polymer  -  A type of polymer in which the monomeric units are connected in a straight or single continuous chain, with minimal or no branching.  The repeating units are linked end-to-end, forming a linear molecular structure.
Branched Polymer  -  A type of polymer where the main chain of the molecule has side chains or branches attached to it.  These branches are composed of the same or different monomer units as the main chain.  The branching alters the physical and chemical properties of the polymer compared to a linear polymer.
Cross-Linked Polymer  -  A type of polymer where the long chains of molecules are connected by covalent bonds to form a three-dimensional network structure.  These connections, called cross-links, can occur during the polymerization process or through chemical treatment after the polymer is formed.

Based on Thermal Behavior

Thermoplastic  -  A type of polymer material that becomes pliable or moldable when heated above a certain temperature and solidifies upon cooling.  This process can be repeated multiple times without significantly degrading the material's properties, making thermoplastics highly versatile and recyclable.
Thermosetting Polymer  -  A type of polymer material that irreversibly hardens or sets when heated or chemically cured.  Unlike thermoplastics, thermosetting polymers do not soften upon reheating after they have set.  This is due to the formation of a three-dimensional cross-linked molecular structure during the curing process.

Based on Polymerization Process

Addition Polymer  -  A type of polymer formed by the repeated addition of monomer units without the loss of any small molecules.  The monomers used in addition polymerization typically contain a double bond or other reactive groups, such as alkenes, which allow them to react and link together in a chain reaction.
Condensation Polymer  -  A type of polymer formed through a condensation reaction, in which monomers react together and release small molecules as by-products, such as water, ammonia, or hydrogen chloride. The monomers involved typically have two or more reactive functional groups.

Based on Molecular Forces

Elastomer  -  Have weak intermolecular forces; highly elastic.   A polymer material with elastic properties similar to natural rubber.  The term is derived from "elastic polymer," indicating its ability to undergo significant deformation and return to its original shape when the applied stress is removed.  Elastomers are characterized by their flexibility, stretchability, and resilience, making them valuable for a wide range of applications.
Fiber  -  Strong intermolecular forces; high tensile strength.  The interactions between molecules within a fiber that contribute to its strength, elasticity, and other mechanical properties.  These forces play a critical role in determining the structure and performance characteristics of fibers, whether natural or synthetic.
Plastic  -  Moderate intermolecular forces; can be either thermoplastics or thermosetting.  The intermolecular and intramolecular interactions within plastic materials that determine their mechanical, thermal, and physical properties.  Plastics are polymers composed of long chains of repeating units (monomers), and the molecular forces in these polymers dictate their strength, flexibility, and durability.

Based on Functionality

Homopolymer  -  A polymer made up of only one type of repeating monomer unit. It consists of identical monomers that are chemically bonded to form long chains.  The structure of a homopolymer is uniform and consistent throughout because it is built from just one type of molecule.
Copolymer  -  A polymer made from two or more different types of monomer units that are chemically bonded together.  By combining different monomers, copolymers can be tailored to have properties that are intermediate or even superior to those of homopolymers.