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Physically Adsorbed Block Copolymers as Neutral Layers
Du Yeol Ryu(류두열),이우섭,김영식,조승연,안형주 한국고분자학회 2021 한국고분자학회 학술대회 연구논문 초록집 Vol.46 No.1
A physically adsorbed layer of PS-b-PMMA can effectively act as an excellent neutral layer towards the overlying PS-b-PMMA film which is completely identical to itself. The surface neutrality is valid when the correlation length (ξ) of the adsorbed layer is shorter that the domain spacing (L0) of the BCP. Subsequently, we proved that this approach can also be applied in the case of high-χ PS-b-P2VP. Based on the order-to-disorder transition behavior of the overlying PS-b-P2VP film, surface neutrality provided by the physically adsorbed PS-b-P2VP layer with its optimal thickness was even better than that of the adsorbed P(S-r-2VP) random copolymers. Our strategy enables the preparation of a high-quality neutral layer for BCP nanopatterning without any necessity of the specially designed random copolymer mats or brushes.
Temperature−Pressure Superposition in SANS χ for an A-<i>b</i>-B Diblock Copolymer
Lee, Jumi,Ryu, Du Yeol,Cho, Junhan American Chemical Society 2011 Macromolecules Vol.44 No.7
<P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/mamobx/2011/mamobx.2011.44.issue-7/ma102102x/production/images/medium/ma-2010-02102x_0003.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ma102102x'>ACS Electronic Supporting Info</A></P>
Ahn, Hyungju,Naidu, Sudhakar,Ryu, Du Yeol,Cho, Junhan WILEY-VCH Verlag 2009 Macromolecular Rapid Communications Vol.30 No.6
<P>The phase behavior of a weakly interacting binary system composed of deuterated polystyrene (dPS) and poly(n-hexyl methacrylate) (PnHMA) was investigated by the turbidity measurement for the binary blend, and by small angle X-ray scattering (SAXS) and depolarized light scattering for the block copolymers. For the binary dPS/PnHMA blend, a new phase diagram involving both the upper critical solution transition (UCST) and lower critical solution transition (LCST) was observed by the delicate control of molecular weights between dPS and PnHMA. Whereas for the block copolymers such as dPS-block-PnHMA and PS-block-PnHMA, an order-to-disorder transition (ODT) on heating was observed within the experimental temperature range depending on the molecular weight. This coexistence of both a UCST and LCST in the dPS/PnHMA blend consequently represents the experimental evidence that the corresponding (d)PS-b-PnHMAs possess not only ODT, but also lower disorder-to-order transition (LDOT) character driven by a compressibility difference, although the latter is hindered by thermal degradation.</P><P> <img src='wiley_img/10221336-2009-30-6-MARC200800646-gra001.gif' alt='wiley_img/10221336-2009-30-6-MARC200800646-gra001'> </P>
Kim, Minjung,Park, Sungmin,Ryu, Du Yeol,Kim, Kyungkon Elsevier 2016 Polymer Vol.103 No.-
<P><B>Abstract</B></P> <P>The thermal stability of organic photovoltaics (OPVs) is greatly enhanced by using an interdiffused polymer/fullerene bilayer (ID-BL) as a photoactive layer. The solutions of poly[[9-(1-octylnonyl)-9H-carbazole-2,7-diyl]-2,5-thiophenediyl-2,1,3-benzothiadiazole-4,7-diyl-2,5-thiophenediyl] (PCDTBT) and phenyl-C<SUB>71</SUB>-butyric-acid-methyl ester (PCBM) are sequentially deposited to form the ID-BL. For comparison, a single photoactive layer consisting of mixed domains of PCDTBT and PCBM (MX-SL) is prepared by depositing blended solution of PCDTBT and PCBM, which is the most widely used method for fabricating OPVs. After applying thermal stress at 80 °C for 10 days, the OPV utilizing the ID-BL photoactive layer maintained 97.2% of its initial efficiency, whereas the efficiency of the OPV utilizing the MX-SL photoactive layer decreased to 37.5% of its initial efficiency. The glazing angle X-ray diffraction (GIXRD) and Flory-Huggins interaction parameter analysis reveal that the ordered domain size of PCDTBT in ID-BL is greater than that of the MX-SL and the ordered domain is maintained after the thermal stress test. These findings imply that mixing of the PCDTBT and PCBM domains does not occur due to the enhanced ordering of PCDTBT in ID-BL during the thermal stress test. Meanwhile, the domain size of PCDTBT in MX-SL is reduced due to further mixing of the PCDTBT and PCBM domains during the thermal stress test, which deteriorates the optimized bulk heterojunction (BHJ) morphology. These results show that efficient and thermally stable OPVs can be realized by utilizing the ID-BL photoactive layer prepared by the sequential solution deposition.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Thermal stability of OPV was enhanced by using interdiffused polymer/fullerene bilayer. </LI> <LI> The bilayer exhibited high morphological stability during thermal stress test. </LI> <LI> BHJ morphology was deteriorated for polymer:fullerene blend film under thermal stress. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>