“Chemically Shielded” Poly(ethylene oxide) Single Crystal Growth and Construction of Channel-Wire Arrays with Chemical and Geometric Recognitions on a Submicrometer Scale

Abstract

A series of poly(ethylene oxide)-block-polystyrene (PEO-b-PS) diblock copolymers were used to generate nucleation sites for the crystal growth of a homo-PEO fraction in solution. The numberaverage molecular weights of the PEO blocks (M n PEO ) were similar, and the number-average molecular weights of the PS blocks (Mn PS ) ranged from 4.6K to 17K g/mol. In PEO-b-PS/(chlorobenzene/octane) solutions, square-shaped single crystals bounded by four {120} planes were isothermally grown and observed with transmission electron and atomic force microscopy. A "sandwich" lamellar structure, constructed by a PEO single crystal layer covered by two tethered PS block layers on the top and bottom crystal basal surfaces, was found. These diblock copolymer single crystals were used as seeds to grow homo-PEO (M n PEO ) 56K g/mol) single crystals in amyl acetate. When the Mn PS in the block copolymer was 4.6K g/mol, the edges and corners of the {120} bounded PEO-b-PS single crystals served as nucleation sites to initiate the further growth of the homo-PEO single crystal. As the Mn PS of the block copolymers increased, the homo-PEO crystal growth was increasingly hampered along the {120} edges of the PEOb-PS single crystals. When the Mn PS of the block copolymer was 17K g/mol, only the four corners of the PEO-b-PS single crystal could still act as nucleation sites. The four edges were chemically "shielded" by the tethered PS blocks. This indicates that increasing the Mn PS led to a higher reduced tethering density of the PS blocks on both the basal surfaces of the PEO-b-PS single crystals. The repulsion generated among the tethered PS blocks caused the PS blocks located near and at the edges to advance along the [120] direction. Interestingly, this local environment only accepted the PEO-b-PS molecules but rejected the homo-PEO molecules from further growth. As a direct result of this study, novel channel-wire arrays on a submicrometer length scale having chemical and geometric recognitions could be fabricated via alternating crystal growth of PEO-b-PS and homo-PEO. This fabrication provided robustly controlled arrays with spacing down to 50 nm.

Fine fibrillar and rectangular/hexagonal ordered grains of poly(3-hexyl thiophene) and poly(ethylene glycol) developed by seeding technique

“…These major fronts constituted four sides of square of ideal and monolayer single crystal. This was in accordance with those that have been reported for homo-PEG and copolymer single crystals having PEG as crystalline substrate up to now [19,42,57,58].…”

“…Scanning force microscopy (SFM) images of the surfaces of PEO crystals revealed oriented fibril-like growth with increasing annealing temperature [15]. Recently, polymer single crystals and highly ordered structures have been employed in distinct potential applications including programmable assembly of nanoparticles [16], mimicking the natural bone nanostructures [17], magnetically recyclable catalyst support [18][19][20][21][22], templates to synthesize nanoparticle clusters [23,24], substrates for anisotropic deposition of Au nanoparticles [25], utilizable in semiconductor microelectronics and solid-state [26,27], ultrathin film systems [28], delivery systems for human papilloma virus-associated tumors [29][30][31], nano/micromotors [32,33], and photovoltaic devices [34].…”

Uniform patchy and hollow rectangular platelet micelles from crystallizable polymer blends

“…Although platelet BCP micelles offer much promise as functional, colloidally-stable 2D nanoobjects, synthetic approaches that allow access to low dispersities, dimensional control, and spatial control of functionality are limited. Recent advances include the formation of platelets from end-functionalized, crystallizable linear polymers (14,15) or hyperbranched analogs (16), which permits programmed nanoparticle attachment and patterning, and the creation of 2D assemblies from homopolymer crystals consisting of alternate rings of BCP and homopolymer (17,18). Lenticular platelet micelles can be formed by the growth of platelet-forming BCPs with a crystallizable poly(ferrocenyldimethylsilane) (PFS) core-forming block and a relatively short complementary corona-forming block (core : corona block ratio > 1:1) on addition to a solution containing cylindrical micelle seeds (19).…”

Two-dimensional assemblies from crystallizable homopolymers with charged termini

“…8,9 Recent advances have demonstrated the use of thiol-terminated crystalline homopolymers that allow the peripheral nanoparticle patterning on the 2D platelet, 10,11 as well as the fabrication of alternate rings of a homopolymer and BCP. 12,13 In a further advance, nanosheets formed by the crystallization of precursors containing silsesquioxane clusters bound to hyperbranched polymers can be fragmented into seeds using sonication which can be used to control the growth of 2D platelets on subsequent precursor addition. 14 We have shown that addition of a BCP with a crystallizable poly(ferrocenyldimethylsilane) (PFS) core-forming block 15 and a short complementary corona-forming block to seeds derived from the sonication of 1D cylindrical PFS BCP micelles allows access to lenticular platelet micelles.…”