Evaluation of the Interaction Parameter for Poly(solketal methacrylate)-block-polystyrene Copolymers

• DOI: 10.1021/acs.macromol.7b02221
• Publication Date: 2018-01-23T20:05:48Z
• Authors: Duk Man Yu; Jose Kenneth D. M...; Hyeyoung Kim; Jaewon Choi; Alexander E. Ribbe; Javid Rzayev; Thomas P. Russell
• Keywords: Small-angle X-ray scattering; Polystyrene; Degree of polymerization; Lipid microdomain; Flory–Huggins solution theory

A series of symmetric poly(solketal methacrylate-b-styrene) (PSM-b-PS) copolymers with varying molecular weights that can transform a hydrophobic PSM block to hydrophilic poly(glycerol monomethacrylate) (PGM) through an acid hydrolysis were investigated. This simple chemical transformation significantly enhances the segmental interaction parameter (χ), enabling phase-mixed copolymer (BCP) microphase separate without any additives. Temperature-dependent small-angle X-ray scattering (SAXS) measurements as function degree polymerization (16 ≤ N 316) and conversion conducted characterize order-to-disorder transition (ODT) behavior well lamellar microdomain features. Using mean-field correlation-hole analysis scattering, χ value for PS was determined PGM. For 100% PGM, found be given by = 0.3144 + 36.91/T, 0.438 at 25 °C, which is ∼13 times larger in magnitude than PSM-b-PS (∼0.035 °C) calculated using 118 Å3 reference volume. With this large increase χ, even smallest synthesized PGM-b-PS underwent separation, allowing us achieve center-to-center spacing (commonly referred full pitch) 5.4 nm, obtained lowest weight sample (Mn 2200 g/mol, 16).