Measuring Tie Chains and Trapped Entanglements in Semicrystalline Polymers.

A label-free method for quantifying stress-transmitter (or elastically effective molecule) content (p) in semicrystalline polymers, including both tie molecules and bridging entanglements, is developed and demonstrated based on swelling with deuterated vapor and characterization with small angle neutron scattering. The p results are compared with the predictions of recent semi empirical, statistical values for tie molecule content and structural characterization parameters, including strain hardening modulus and an infrared spectroscopy derived parameter ( ) that describes the degree of difficulty for the amorphous content to align and reshape over a distance with applied load. A strong correspondence is observed, suggesting that the initial network of elastically active molecules, dictated by the molecular architecture and crystallization conditions, can be directly correlated to the post yield tensile values irrespective of the subsequent morphological changes that result during the tensile deformation.

Characterizing the structure of organic molecules of intrinsic microporosity by molecular simulations and X-ray scattering.

The design of a new class of materials, called organic molecules of intrinsic microporosity (OMIMs), incorporates awkward, concave shapes to prevent efficient packing of molecules, resulting in microporosity. This work presents predictive molecular simulations and experimental wide-angle X-ray scattering (WAXS) for a series of biphenyl-core OMIMs with varying end-group geometries. Development of the utilized simulation protocol was based on comparison of several simulation methods to WAXS patterns.