Preparation and distorted cylindrical morphology of block copolymers consisting of flexible and semiflexible blocks

• Published in: Polymer journal Vol. 53; no. 12; pp. 1361 - 1369
• Main Authors: Doi, Yuya, Takano, Atsushi, Matsushita, Yushu
• Format: Journal Article
• Language: English
• Published: Tokyo Nature Publishing Group 01.12.2021
• Subjects: Anionic polymerization; Block copolymers; Cross-sections; Domains; Fractionation; Isocyanates; Liquid crystals; Molecular weight distribution; Polymerization; Polystyrene resins; Size exclusion chromatography; Small angle X ray scattering; Transmission electron microscopy
• ISSN: 0032-3896; 1349-0540
• DOI: 10.1038/s41428-021-00530-x

Diblock copolymers consisting of flexible polystyrene and semiflexible poly(n-hexyl isocyanate), P(S-b-HIC)s, were prepared by anionic polymerization, followed by size-exclusion chromatography (SEC) fractionation. Two P(S-b-HIC) samples having PHIC volume fractions (ΦPHIC) of 0.18 and 0.31, sufficiently high molecular weights (Mn,PS and Mn,PHIC are both larger than 10 kg/mol), and narrow molecular weight distributions (Mw/Mn < 1.05) were obtained. The microphase-separated structures of the two P(S-b-HIC) samples were investigated by transmission electron microscopy (TEM) and small- and wide-angle X-ray scattering (SAXS and WAXS). TEM and SAXS show that both the P(S-b-HIC) samples exhibit hexagonally packed cylindrical structures but different cross-sectional shapes; namely, P(S-b-HIC)-0.18 has a round-shaped cross-section while P(S-b-HIC)-0.31 has a distorted cross-section. From the WAXS measurements, P(S-b-HIC)-0.31 exhibits a sharp peak at q* = 3.9 nm−1, which is different from that of a nematic PHIC homopolymer that has a peak at q* = 4.6 nm−1. These results indicate that the PHIC blocks in P(S-b-HIC)-0.31 align obliquely to the interface in the columnar domain.Diblock copolymers consisting of flexible polystyrene and semiflexible poly(n-hexyl isocyanate), P(S-b-HIC)s, were prepared by anionic polymerization, followed by SEC fractionation. The microphase-separated structures of two P(S-b-HIC)s with ΦPHIC = 0.18 and 0.31, were investigated by TEM, SAXS and WAXS. Both two P(S-b-HIC)s exhibited hexagonally packed cylindrical structures but different cross-sectional shapes, namely, P(S-b-HIC)-0.18 has a round-shaped cross-section, while P(S-b-HIC)-0.31 has a distorted one. The latter could originate from the liquid crystalline structures of the PHIC blocks in cylindrical domains, which align obliquely to the interface of the domains.