Design of Interfacial Crowding for Elastomeric Reinforcement with Nanocrystals.

Design of the crowding of chains tethered at the faces of β-sheet nanocrystals self-assembled from β-alanine trimers grafted on polyisobutylene (PIB) rubber tailors nanocrystal size and thus the elastic matrix morphology, thereby altering the material's macroscopic elastic properties. Results from transmission electron microscopy, small-angle X-ray scattering, and small-angle neutron scattering characterizations of the morphology demonstrate that increasing the density of chain tethering at the crystalline nanodomain/matrix interface can sharply limit the nanodomain growth in the direction of hydrogen bonding in the crystals. The nanocrystal size, in turn, impacts the gradient in chain stretching away from the crystal surface and the macroscopic volume fraction of unperturbed chains. Nanocomposite mechanical and dynamic mechanical properties at low degrees of deformation are related to the structural hierarchy resulting from the control of interfacial tethering density.