Enormously Wide Range Cylinder Phase of Liquid Crystalline PEO-b-PMA(Az) Block Copolymer

Abstract

A series of amphiphilic liquid crystalline diblock copolymers, PEO m -b-PMA(Az) n , consisting of hydrophilic poly(ethylene oxide) and hydrophobic poly(methacrylate) moieties with side chains containing liquid crystalline (LC) azobenzene moieties, produced highly ordered microphaseseparated films with PEO cylinders aligned perpendicular to the smectic LC layer of azobenzene in the PMA(Az) matrix. In this paper, morphological phase diagrams of PEO m -b-PMA(Az) n diblock copolymers above and below the isotropic transition temperature of LC azobenzene (T iso ) are presented. The diagrams are based on small-angle X-ray scattering (SAXS) measurements of approximately 70 kinds of polymers with varying degrees of polymerization in each block. An asymmetric phase diagram described against the volume fraction of PEO ( f PEO ) was obtained at temperatures above and below T iso . The lamellar phase appears in the f PEO window 0.52 ≤ f PEO ≤ 0.78 above and below T iso . Besides, the wide window, 0.087 ≤ f PEO < 0.52, allows the PEO cylinder phase to form below T iso . In particular, the PEO sphere phase, observed above T iso , was completely eliminated through an order− order transition (OOT) to the PEO cylinder phase in the window 0.087 ≤ f PEO ≤ 0.23. Such a large expansion in the PEOcylinder-phase window could be attributed to the main chain of LC PMA(Az) being shorter than that of the flexible PEO chain, and LC azobenzene forming a smectic layer in the microphase separated system.

Ordered mesoporous crystalline titania with high thermal stability from comb-like liquid crystal block copolymers

“…Simultaneously, the azobenzene LC groups in the hydrophobic domains selforganize to form alignments vertical to hydrophilic domains, 39,49 which makes the cylindrical micelles more stable. Scheme 1 illustrates the proposed synthesis process.…”

Longitudinal and Lateral Integration of Conducting Polymer Nanowire Arrays via Block-Copolymer-Templated Electropolymerization

“…52 Three kinds of block copolymers with different molecular weights of each segment, PEO40-b-PMA(Az)17, PEO114-b-PMA(Az)45, and PEO272-b-PMA(Az)94, were adopted to achieve the size control of the PPy nanowire array (characterization of these polymers is described in Figures S1b-S1d 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 nanowire diameter of 7 nm, a periodicity of 13 nm, and a density of 4.4 × 10 12 wires/in. 2 , which has been never achieved before.…”

Chemically directed self-assembly of perpendicularly aligned cylinders by a liquid crystalline block copolymer

“…Several research studies have revealed the significant effects of LC ordering of the side-chains on the microphase separation due to homeotropic orientation of the liquid crystalline microdomains. [24][25][26][27][28] In contrast to the conventional non-LC block copolymers, the LC azobenzene mesogen-mesogen interaction functions as an additional elastic energy term (F LC ) in the expression of total free energy (F) of the PEO-b-PMA(Az) thin film system. PEO-b-PMA(Az), one of such block copolymers, consists of poly(ethylene oxide) (PEO) as a segment forming cylindrical microdomains, and poly(methacrylate) with azobenzene mesogens in the side chain (PMA(Az)) as a segment forming a matrix phase (Fig.…”

“…1). 27,28 Another advantage is the perpendicular orientation of the PEO hexagonal cylindrical microdomains to a substrate by just a thermal annealing process, which is due to homeotropic anchoring of the Az mesogens to the air/free interface. The total free energy of the system is given by the following equation.…”