Highly stretchable plastics: Effects of folding polymer chains

The mechanical properties of polymer materials are highly dependent on the interactions and mobility of the molecular chains. A polymer may have similar chemical composition but a different architecture, affecting the molecular arrangement in the bulk material as well as the chain inter- and intramolecular interactions. In this talk, I describe our work on changing the architecture of a synthetic poly(butylmethacrylate) to adopt conformations similar to natural polymers, i.e., chemical folding through the creation of strong intramolecular interactions. Intramolecular collapse is induced through intramolecular cross-linking which leads to an increase in the number of intramolecular segmental interactions, in addition to inhibition of intermolecular entanglements. In both the glassy and rubbery states, this molecular rearrangement increases material stiffness. In the glassy state, it also leads to reduced failure strain, but surprisingly, in the rubbery state, the large strain elasticity is actually increased. An intermediate level of intramolecular cross-linking degree finds an ideal a balance between intra- and intermolecular interactions, leading to optimal mechanical properties. In the rubbery state, the synthetic material presents virtually infinite stretchability in the absence of plasticizer. The combination of increased stiffness and toughness shows that some of the properties typically observed in biological materials can be reproduced in synthetic polymers through implementation of Nature`s choice for polymer architecture.