Polymer network (IMAGE) Massachusetts Institute of Technology Caption As this polymer network is stretched, weaker crosslinking bonds (blue) break more easily than any of the strong polymer strands, making it more difficult for a crack to propagate through the material. Credit Courtesy of the researchers, edited by MIT News Usage Restrictions Credit must be given to the creator. No derivatives or adaptations of the work are permitted. License CC BY-ND 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.