Fig. 3. Pentad (image) Moscow Institute of Physics and Technology Share Print E-Mail Caption Pentad. The relative abundance of pentads -- isotactic five-unit segments in a polymer chain -- is a good measure of the polymer's overall isotacticity. Credit MIPT Press Office Usage Restrictions None Share Print E-Mail Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.