Kinetics of Water Transfer Between the LCST and UCST Thermoresponsive Blocks in Diblock Copolymer Thin Films Monitored by In Situ Neutron Reflectivity. Issue 3 (4th December 2022)

• Record Type: Journal Article
• Authors: Hu, Neng; Lin, Li; Metwalli, Ezzeldin; Bießmann, Lorenz; Philipp, Martine; Hildebrand, Viet; Laschewsky, Andre; Papadakis, Christine M.; Cubitt, Robert; Zhong, Qi; Müller‐Buschbaum, Peter
• Is Part Of: Advanced materials interfaces. Volume 10:Issue 3(2023)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-12-04
• Subjects: block copolymer -- dual thermoresponsive -- kinetic water transfer -- neutron reflectivity -- thin film; Materials science -- Periodicals; 620.11
• DOI: 10.1002/admi.202201913
• Languages: English
• ISSNs: 2196-7350

Abstract

Abstract: The kinetics of water transfer between the lower critical solution temperature (LCST) and upper critical solution temperature (UCST) thermoresponsive blocks in about 10 nm thin films of a diblock copolymer is monitored by in situ neutron reflectivity. The UCST‐exhibiting block in the copolymer consists of the zwitterionic poly(4‐((3‐methacrylamidopropyl)dimethylammonio)butane‐1‐sulfonate), abbreviated as PSBP. The LCST‐exhibiting block consists of the nonionic poly(N‐isopropylacrylamide), abbreviated as PNIPAM. The as‐prepared PSBP80 ‐ b ‐PNIPAM400 films feature a three‐layer structure, i.e., PNIPAM, mixed PNIPAM and PSBP, and PSBP. Both blocks have similar transition temperatures (TTs), namely around 32 °C for PNIPAM, and around 35 °C for PSBP, and with a two‐step heating protocol (20 °C to 40 °C and 40 °C to 80 °C), both TTs are passed. The response to such a thermal stimulus turns out to be complex. Besides a three‐step process (shrinkage, rearrangement, and reswelling), a continuous transfer of D2 O from the PNIPAM to the PSBP block is observed. Due to the existence of both, LCST and UCST blocks in the PSBP80 ‐ b ‐PNIPAM400 film, the water transfer from the contracting PNIPAM, and mixed layers to the expanding PSBP layer occurs. Thus, the hydration kinetics and thermal response differ markedly from a thermoresponsive polymer film with a single LCST transition. Abstract : In situ neutron reflectivity is applied to investigate the kinetics of water transfer between the lower critical solution temperature (LCST) and upper critical solution temperature (UCST) thermoresponsive blocks in diblock copolymer thin films. The UCST type block profoundly influences the thermal response and final state of the diblock copolymer thin films, which possess implications for the investigation of complex transitional behaviors of such films.