NSRRC Activity Report 2022

Neutron Science 085 layer were 2.05 × 10 −6 and 1.18 × 10 −6 Å −2 for B 75 D 25 4 and B 75 D 25 17 , respectively. The bottom layer of B 75 D 25 17 , which contained neat PMMA, was formed because of the strong affinity toward the Si substrate. The second discrepancy existed in the middle region. For the B 75 D 25 x (x = 4 and 17) films, each middle region consisted of a periodic structure of alternating PS and PMMA layers. For the B 75 D 25 17 film, the overall interlayer spacing of the hexagonal PLs (HPLs) was 27.2 nm, as shown in Fig. 2(d) . The PS-dominated layers had a high SLD value ( > 3.44 × 10 −6 Å −2 ), whereas the PMMA-dominated layers had a low SLD value (1.38 × 10 −6 Å −2 ). These results are consistent with the dPS 17 chains segregating within the PS layers and a few chains localizing within the PS perforations of the B 75 D 25 17 film. By contrast, the B 75 D 25 4 film ( Fig. 2(c) ) had an interlayer spacing of 23.9 nm in the middle region, in which the PS-rich layers had an SLD of 3.08 × 10 −6 Å −2 and the PMMA-rich layers had an SLD of 1.72 × 10 −6 Å −2 . The reduced contrast in SLD between the PS-rich and PMMA-rich layers for B 75 D 25 4 indicated that the dPS 4 chains were uniformly distributed within the PS layers and perforations. The uniform distribution of dPS 4 resulted in a repeat distance of 23.9 nm within the B 75 D 25 4 film (smaller than that for B 75 D 25 17 ), with the thickness of the PS layers being comparable to that of the perforated PMMA layers. The NR results were consistent with the hypothesis proposed in the scheme displayed in Fig. 1 . In summary, the team of Sun demonstrated morphological diversity by varying the molecular weight ratios of PS-b-PMMA and hPS. When PS-b-PMMA was the major component and hPS x was the minor component, the surface morphologies on the Si substrate were dominated by HPLs or double gyroids. In the PS-b-PMMA-rich region, the PLs were the only discernible phase, regardless of film thickness, if the PS-b-PMMA film contained short (PS 2.8 ) chains. By contrast, if the PS-b-PMMA film contained medium-length (PS 6 ) chains, thin films prefer the HPL phase, and thick films prefer the double-gyroid phase. When the PS-b-PMMA film contained hPS 17 chains whose length was comparable to that of the PS block, the HPL phase became the only discernible structure. (Reported by Tzu-Yen Huang) This report features the work of Ya-Sen Sun and his collaborators published in Macromolecules 55 , 2130 (2022). TLS 23A1 Small/Wide Angle X-ray Scattering ANSTO PLATYPUS – Neutron Reflectometer • GISAXS, NR • Polymers, Morphology, Interfaces, Layers and Blend Films Reference 1. J. W. Hong, J. H. Chang, H. H. Hung, Y. P. Liao, Y. Q. Jian, I. C. Y. Chang, T. Y. Huang, A. Nelson, I. M. Lin, Y. W. Chiang, Y. S. Sun, Macromolecules 55 , 2130 (2022). Fig. 2 : (a,b) NR experimental curves (open circles) and fitted curves (red lines) and (c,d) corresponding SLD profiles of B 75 D 25 x (x = 4 and 17) films with a thickness of 162 nm that were annealed at 270 °C. The SLD values of the dPS layers and PMMA PLs are also shown in (c) and (d). Moreover, the d-spacing values are depicted in (c) and (d) for visual guidance. [Reproduced from Ref. 1]