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: London Nature Publishing Group UK 01.12.2021; Nature Publishing Group
• Subjects: 639/301/923/1028; 639/925/929; Anionic polymerization; Biomaterials; Bioorganic Chemistry; Block copolymers; Chemistry; Chemistry and Materials Science; Chemistry/Food Science; Cross-sections; Domains; Fractionation; Isocyanates; Liquid crystals; Molecular weight distribution; Original Article; Polymer Sciences; Polymerization; Polystyrene resins; Size exclusion chromatography; Small angle X ray scattering; Surfaces and Interfaces; Thin Films; 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 ( Φ PHIC ) of 0.18 and 0.31, sufficiently high molecular weights ( M n,PS and M n,PHIC are both larger than 10 kg/mol), and narrow molecular weight distributions ( M w / M n  < 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 Φ PHIC  = 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.