In a previous paper [Phys. Rev. E 83, 021801 (2011)] we performed neutron reflectivity (NR) measurements on a five-layer polystyrene (PS) thin film consisting of alternatively stacked deuterated polystyrene (dPS) and hydrogenated polystyrene (hPS) layers (dPS/hPS/dPS/hPS/dPS, ∼100 nm thick) on a Si substrate to reveal the distribution of Tg along the depth direction. Information on the Tg distribution is very useful to understand the interesting but unusual properties of polymer thin films. However, one problem that we have to clarify is if there are effects of deuterium labeling on Tg or not. To tackle the problem we performed low-energy muon spin relaxation (μSR) measurements on the above-mentioned deuterium-labeled five-layer PS thin film as well as dPS and hPS single-layer thin films ∼100 nm thick as a function of muon implantation energy. It was found that the deuterium labeling had no significant effects on the Tg distribution, guaranteeing that we can safely discuss the unusual thin film properties based on the Tg distribution revealed by NR on the deuterium-labeled thin films. In addition, the μSR result suggested that the higher Tg near the Si substrate is due to the strong orientation of phenyl rings.

We investigated changes in the hierarchical structures of polyethylene (PE) during tensile testing by means of time-resolved ultrasmall-angle scattering (USAXS), small-angle scattering, and wide-angle X-ray scattering. We discovered the enhancement of density fluctuation on the submicron scale by USAXS, which led to the generation of voids and necking. The spatial inhomogeneity of the stress fields associated with density or crystallinity fluctuation on the submicron scale induced the inhomogeneous flow during stretching. In other words, the change in the higher order structure than in the lamellar structure dominated the mechanical properties of PE. The enhancement of the fluctuation in linear low-density PE (LLDPE) was smaller than that in high-density PE (HDPE). Mechanical melting in the LLDPE suppressed the inhomogeneous flow and delayed the generation of voids and necking. As a result, the LLDPE exhibited two yield points on a S–S curve, while the HDPE exhibited one yield point.

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