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Why do polymers have much larger molecular weights than water molecules?

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Diagram illustrating a homopolymer arrangement using polyvinyl chloride as an example, showing a chain of identical repeating vinyl chloride units with the chemical structure highlighted. — polymer Industrial polymers are synthesized from simple compounds joined together to form long chains. For example, polyvinyl chloride is an industrial homopolymer synthesized from repeating units of vinyl chloride.

Polymers have significantly larger molecular weights than water because they are macromolecules—essentially "giant molecules"—formed by the chemical aggregation of many smaller units called monomers.12

While a single water molecule consists of only three atoms (one oxygen and two hydrogen) with a molecular weight of 18 atomic mass units, a polymer is constructed by linking together hundreds or even thousands of monomer units through stable covalent chemical bonds. This process, known as polymerization, results in long, chainlike or network structures that can reach molecular weights ranging from tens of thousands to several million atomic mass units.342

It is this vast size that distinguishes polymers from simpler substances and provides them with their unique physical properties, such as high tensile strength, elasticity, and the ability to be molded into plastics or drawn into fibres.42