New characterization methods for block copolymers and their phase behaviors

Abstract

In this feature article, we briefly review the new methods we have utilized recently in the investigation of morphology and phase behavior of block copolymers. We first describe the chromatographic fractionation method to purify block copolymers from their side products of mainly homopolymers or block copolymer precursors inadvertently terminated upon addition of the next monomer in the sequential anionic polymerization. The chromatographic method is extended to the fractionation of the individual block of diblock copolymers which can yield the diblock copolymer fractions of different composition and molecular weight, which also have narrower distributions in both molecular weight and composition. A more detailed phase diagram could be constructed from the set of block copolymer fractions without the need of acquiring many block copolymers each prepared by anionic polymerization. The fractions with narrow distribution in both molecular weight and composition exhibit better long-range ordering and sharper phase transition. Next, epitaxial relationships between two ordered structures in block copolymer thin film is discussed. We employed the direct visualization method, transmission electron microtomography (TEMT) to scrutinize the grain boundary structure.

Structural characterization of the Fddd phase in a diblock copolymer thin film by electron microtomography

“…A strong tendency to align the densest plane of the minor phase parallel to the film plane and substantially different phase behaviors relative to the bulk state have been reported. [18][19][20][21][22][23][24][25] The highly periodic nanopatterns obtained from block copolymers in the film have been exploited for potential applications. [26][27][28][29][30] By virtue of the network structure, the Fddd phase is a potential candidate for devices which need large surface channels or a substantial skeleton structure such as membranes or photo-voltaic systems.…”

Rapid Generation of Block Copolymer Libraries Using Automated Chromatographic Separation

“…16 Pioneering work by Chang and co-workers demonstrated the feasibility of separating BCPs by composition in one- 16 and two-dimensional 17,18 experiments with the phase behavior of polystyreneblock-polyisoprene being examined over a limited range of compositions (≈10% in f A ) and on a small scale (≈100 mg). 19,20 However, the manual optimization of separation conditions is generally not a trivial task and requires complex injection sequences, programmed temperature ramps, and/or the identification of critical conditions to minimize molecularweight effects. 21 In contrast, this report establishes an operationally simpler, automated chromatography technique that can be applied to a wide variety of BCP chemistries and provides scalability for the rapid and precise exploration of phase behavior.…”

“…This strategy obviates the need to directly synthesize multiple materials and leads to more uniform dispersity among the sample library . Pioneering work by Chang and co-workers demonstrated the feasibility of separating BCPs by composition in one- and two-dimensional , experiments with the phase behavior of polystyrene- block -polyisoprene being examined over a limited range of compositions (≈10% in f A ) and on a small scale (≈100 mg). , However, the manual optimization of separation conditions is generally not a trivial task and requires complex injection sequences, programmed temperature ramps, and/or the identification of critical conditions to minimize molecular-weight effects …”

Fractionation of poly(dimethyl siloxane) by interaction chromatography

“…12 Thus established IC separation condition can be applied for their block copolymers and mixtures with facility. 13 In this study, we would like to add one more important commercial polymers, poly(dimethyl siloxane) (PDMS) in the list. PDMS is the most widely used silicon-containing polymer and a variety of chemically modified PDMS are produced commercially.…”