Skip to main content


This simulation models two fundamental polymerization reaction types: stepwise growth and chain addition. For decades, polymers have become and increasingly important and widely used in most industries, including automotive, aerospace, and medical fields, and in a variety of applications. The synthesis of polymers is dissimilar to the synthesis of other materials. This molecular simulation will allow the user to easily visualize the difference in the reaction mechanisms, to see the difference in the resulting products, and to practice calculations for the prediction of molecular weights, molecular weight distributions, and kinetics. The stepwise growth module is also capable of modeling gelation.

The details of the chemistry are neglected in this simulation. The reactions proceed using a simplified logic. For instance, in the stepwise growth polymerization, “alcohol” type monomers react only with “acid” type monomers. In the free radical chain addition model, activated “radical” species react with monomers and with other radicals. No true chemistry is implied except for reaction rules where “type A” dots are (or are not) allowed to bond with “type B” dots.

Since stepwise growth and chain addition operate via different reactive mechanisms, this module consists of two sub-modules to account for the different chemistries involved. Both of these sub-modules are built into the same web resource in order to help students visualize how the different polymerization reactions function and how they result in significantly different polymers. This module will help the student develop an understanding of molecular weight distributions and polymer structures, which is a critical prerequisite to understanding how these factors influence polymer properties and behaviors.