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

Duk Man Yu, Jose Kenneth D. Mapas, Hyeyoung Kim, Jaewon Choi, Alexander E. Ribbe, Javid Rzayev, Thomas P. Russell

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45 Scopus citations

Abstract

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

Original languageEnglish
Pages (from-to)1031-1040
Number of pages10
JournalMacromolecules
Volume51
Issue number3
DOIs
StatePublished - 13 Feb 2018

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