Core−Shell Cylinder Morphology in Poly(styrene-<i>b</i>-1,3-cyclohexadiene) Diblock Copolymers

David, Jennifer; Gido, Samuel P.; Hong, Kunlun; Zhou, Jing; Mays, Jimmy W.; Tan, Nora Beck

doi:10.1021/ma9810722

Cited by 37 publications

(36 citation statements)

References 23 publications

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“…The core-shell cylinder nanostructure from the selfassembly of BCPs has also been found in polystyrene-blockpoly(1,3-cyclohexadiene) (PS-PCHD) BCPs by Gido and coworkers ( Figure 17). [58] It is remarkable to recognize that the PS-PCHD BCPs also possess a chiral entity (i.e., PCHD). Unlike ABC achiral triblock terpolymers or their blends, in which the formation of the core-shell cylinder nanostructure is controlled by relative incompatibilities, [14][15][16] we speculate that the core-shell cylinder nanostructure of self-assembly PS-PLLA BCP Ã is induced by the formation of specific configurations of PLLA chains due to the correspondence of chiral entities interacting with the immiscibility of constituted blocks.…”

Section: Crystallization-induced Stretching Of the H ã Phasementioning

confidence: 99%

Novel Nanostructures from Self‐Assembly of Chiral Block Copolymers

Chen

Chiang

2009

Macromol. Rapid Commun.

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A diblock copolymer system constituting both achiral and chiral blocks, polystyrene-block-poly(L-lactide) (PS-PLLA), was designed for the examination of chiral effects on the self-assembly of block copolymers (BCPs). A unique phase with three-dimensional hexagonally packed PLLA helices in PS matrix, a helical phase (H*), can be obtained from the self-assembly of PS-rich PS-PLLA with volume fraction of PLLA f PLLAv = 0.34, whereas no such phase was found in racemic polystyrene-block-poly(D.L-lactide) (PS-PLA) BCPs. Moreover, various interesting crystalline PS-PLLA nanostructures can be obtained by controlling the crystallization temperature of PLLA (T(c,PLLA) ), leading to the formation of crystalline helices (PLLA crystallization directed by helical confined microdomain) and crystalline cylinders (phase transformation of helical nanostructure dictated by crystallization) when T(c,PLLA) < T(g,PS) (the glass transition temperature of PS) and T(c,PLLA) ≧ T(g,PS) , respectively. As a result, a spring-like behavior of the helical nanostructure can be driven by crystallization so as to dictate the transformation (i.e., stretching) of helices and to result in crystalline cylinders. For PS-PLLA with PLLA-rich fraction (f PLLAv = 0.65), another unique phase, a hexagonally packed core-shell cylinder phase with helical sense (CS*), in which the PS microdomains appear as shells and PLLA microdomains appear as matrix and cores, can be found in the self-assembly of PLLA-rich PS-PLLA BCPs. The formation of those novel phases: helix and core-shell cylinder is attributed to the chiral effect on the self-assembly of BCPs, so we named this PS-PLLA BCP as chiral BCP (BCP*). For potential applications of those materials, the spring-like behavior with thermal reversibility might provide a method for the design of switchable nanodevices, such as nanoscale actuators. In addition, the PLLA blocks can be hydrolyzed. After hydrolysis, helical nanoporous PS bulk and PS tubular texture can be obtained and used as templates for the formation of nanocomposites.

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Section: Crystallization-induced Stretching Of the H ã Phasementioning

confidence: 99%

Novel Nanostructures from Self‐Assembly of Chiral Block Copolymers

Chen

Chiang

2009

Macromol. Rapid Commun.

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“…Recently, poly(1,3‐cyclohexadiene) (PCHD) and its derivatives have attracted increasing attention, because of their physical, chemical, and electrical properties 1–30. The special structure of the main chain with the six‐membered rings directly connected to each other offers a unique characteristic of PCHDs.…”

Section: Introductionmentioning

confidence: 99%

Early administration of abciximab bolus in the emergency department improves angiographic outcome after primary PCI as assessed by TIMI frame count: Results of the early ReoPro administration in myocardial infarction (ERAMI) trial

Gabriel

Oliveira

Silva

et al. 2006

Cathet Cardio Intervent

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“…A similar core-shell cylinder phase has been seen upon the self-assembly of diblock copolymers of PS-b-poly(1,3-cyclohexadiene) (PS-PCHD) by Gido and co-workers. [20] It is worth noting that the PS-PCHD block copolymers also possess a chiral entity (i.e., PCHD). Also, in ABC triblock copolymers and their blends, the formation of the core-shell cylinder microstructure is controlled by the relative incompatibilities of the different segments.…”

mentioning

confidence: 99%

Tubular Nanostructures from Degradable Core–Shell Cylinder Microstructures in Chiral Diblock Copolymers

Chen

Chiang

et al. 2006

Advanced Materials

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Nature uses the self-assembly of molecules as a tool for structuring substances. [1,2] Biological architectures are formed by the interplay between secondary forces, such as hydrophobic, hydrogen-bonding, steric, and electrostatic interactions, to achieve different levels of organization, i.e., morphologies at different length scales. Mimicking these motifs found in Nature, helical morphologies at different length scales, ranging from helical chain conformations and helical aggregates to helical agglomerates, are amongst the most fundamental and interesting textures found in organic systems. [2][3][4][5][6][7][8][9] The chirality of organic compounds is thought to be one of the main origins for the formation of helical textures, and is used as a secondary interaction to assemble chiral molecules and macromolecules into hierarchical structures with a helical sense.[4] The self-assembly of block copolymers has been extensively studied because of their fascinating phase behavior. Nanoscale microstructures with distinct microphases can be obtained simply by chemically attaching immiscible polymer chains together as block copolymers.[10] Recently, a well-organized, three dimensionally packed nanohelical phase has been obtained by the self-assembly of chiral block copolymers, polystyrene-b-poly(L-lactide) (PS-PLLA) with PS-rich fractions.[11a] The hexagonally packed nanohelical microstructure of PLLA in the PS matrix exhibits a springlike response upon stimulation. Moreover, the self-assembled nanohelices have been transformed into cylinders by crystallization and shear.The stress-induced formation of cylinders has been found to be thermally reversible through undulation upon annealing, which could potentially enable the manipulation and switching of these helical microstructures.[11b] The morphology of the PLLA helical microstructure in the PS matrix is attributed to a combination of chirality and the immiscibility of the constituent blocks. Intuitively, hierarchical structures with a helical sense for the achiral block might be expected in the phase diagram of block copolymers, namely PS-PLLA with PLLArich fractions. Interestingly, a bulk core-shell cylinder microstructure is formed from the self-assembly of PLLA-rich PS-PLLA. Unlike the core-shell cylinder microstructure observed in ABC triblock copolymers, [12][13][14][15][16] this unique tubular texture of the achiral block is attributed to the chiral effect induced by the chiral block. Consequently, a scrolling mechanism has been proposed to interpret the formation of the core-shell cylinder microstructure, which is assembled from a hierarchical structure with a helical sense. Moreover, tubular nanostructures can be simply obtained by hydrolyzing the degradable PLLA block from the core-shell cylinder microstructure. As a complementary approach for the formation of nanotubes from triblock and tetrablock copolymer systems, [17] the self-assembly of chiral diblock copolymers with a degradable character may also provide an easy and convenient way to fabricate tub...

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Core−Shell Cylinder Morphology in Poly(styrene-b-1,3-cyclohexadiene) Diblock Copolymers

Cited by 37 publications

References 23 publications

Novel Nanostructures from Self‐Assembly of Chiral Block Copolymers

Novel Nanostructures from Self‐Assembly of Chiral Block Copolymers

Early administration of abciximab bolus in the emergency department improves angiographic outcome after primary PCI as assessed by TIMI frame count: Results of the early ReoPro administration in myocardial infarction (ERAMI) trial

Tubular Nanostructures from Degradable Core–Shell Cylinder Microstructures in Chiral Diblock Copolymers

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