Influence of Molecular Architecture and Chain Flexibility on the Phase Map of Polystyrene-block-poly(dimethylsiloxane) Brush Block Copolymers

Abstract

We report the microphase-separated morphologies of model bottlebrush block copolymers (BBCPs) over a wide range of architectural design parameters. Densely grafted polystyrene-block-poly­(dimethylsiloxane) (PS-b-PDMS) BBCPs rapidly self-assemble into ordered lamellar, cylindrical, and deformed spherical morphologies depending on the volume fraction (f), side chain length (N sc), and overall backbone length (N bb). The microstructure was characterized by using electron microscopy and X-ray scattering. An experimental phase map is constructed, describing the dependence of morphologies and order–order transitions with respect to the design parameters. A lamellar morphology is primarily observed at symmetric f, while ordered cylindrical and deformed spherical morphologies appear at asymmetric f. The relative flexibility of the PS-b-PDMS backbone facilitates the accessibility of morphologies with curved interfaces and exceptionally large domain spacing. We also find that the breadth of the lamellar window decreases with increasing backbone length and side-chain asymmetry. These findings provide a comprehensive experimental description of the PS-b-PDMS BBCPs and provide insight into the rich phase behavior of this class of macromolecules.

Confinement and Processing Can Alter the Morphology and Periodicity of Bottlebrush Block Copolymers in Thin Films

“…36,45−48 An important result from the work so far is that compared with the linear case, the phase window for lamellae is expanded in the case of approximately symmetric side chain lengths, although asymmetric side chains or long backbones both appear to enable phases with more curvature (cylinders/spheres). 47 Linear BCPs in a thin film geometry have been studied extensively, in large part because of their potential for nanopatterning applications. In a thin film, the interactions between the polymer and the confining surfaces dictate the orientation of the BCP.…”

“…Self-consistent field theory (SCFT) calculations have proposed that the backbones are oriented perpendicular near the BBCP interface, but that their orientations become significantly less correlated with increasing distance from the interface . There have been initial efforts to map out the bulk phase diagrams of BBCPs, a daunting task due to the number of tunable parameters. ,− An important result from the work so far is that compared with the linear case, the phase window for lamellae is expanded in the case of approximately symmetric side chain lengths, although asymmetric side chains or long backbones both appear to enable phases with more curvature (cylinders/spheres) …”

Diversity-Oriented Synthesis of Graft Copolymer Silicones Enables Exceptionally Broad Thermomechanical Property Windows through Pendant-Mediation

“…Graft copolymers, which feature polymeric side chains attached to a polymer backbone, offer greater structural complexity than traditional linear (co)polymers, with parameters such as backbone length, sidechain sequence, [1][2][3][4][5] sidechain length, 6 grafting density, 7,8 and block lengths 9 de ning their unique bulk properties [10][11][12][13][14] and self-assembled morphologies [15][16][17][18][19][20][21] and enabling their application as optical materials, 22,23 elastomers, [24][25][26][27][28] drug delivery systems, 29,30 biomimetics, 27,31−34 and more. [35][36][37][38] Nevertheless, despite enormous recent interest in their synthesis and properties, most studies of graft copolymers to date have involved either homopolymers or copolymers derived from two different polymer side chains arranged in either block or statistical sequences; the potential for combining graft polymer segments with small-molecule comonomers, leveraging only the latter to tune material properties, has been much less explored.…”

Theory of Y‐ and Comb‐Shaped Polymer Brushes: The Parabolic Potential Framework

“…Such microphase segregated materials are being actively studied because of the possibility to control their optical and mechanical properties by tuning architectural parameters of constituent branched polymer blocks. [18][19][20][21][22][23][24][25][26][27][28] The paper is organized as follows. In Section 2 we present the general parabolic potential framework for arbitrary polymer architecture.…”