Two-Dimensional Folded Chain Crystals of a Synthetic Polymer in a Langmuir−Blodgett Film

Kumaki, Jiro; Kawauchi, Takehiro; Yashima, Eiji

doi:10.1021/ja050457e

Cited by 124 publications

(152 citation statements)

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“…This model satisfies the AFM results, the stoichiometry of it-and st-PMMAs, as well as the reported helical structures of each component, that is, the it-and st-PMMAs. The double-stranded helical structure was proposed for it-PMMA Synthesis and structures of helical polymers E Yashima on the basis of an XRD analysis 94 and was further proved by highresolution AFM of an it-PMMA LB film, 95 whereas st-PMMA is reported to form a crystalline inclusion complex gel with specific organic solvents, such as toluene, resulting in a 74/4 helical structure with a helical pitch of 0.885 nm, in which solvents are encapsulated in the sufficiently large cavity (B1 nm) of the inner helix. 96,97 This helical structure is almost identical to that of the st-PMMA component of the triple-stranded helical stereocomplex (Figure 13b).…”

Section: Synthesis and Structures Of Helical Polymers E Yashimamentioning

confidence: 99%

Synthesis and structure determination of helical polymers

Yashima

2010

Polym J

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During the last decade, remarkable progress in developing synthetic helical polymers with a controlled helical sense has been achieved. However, the exact helical structures of most of the already prepared synthetic helical polymers remain unsolved. In this review, the recent progress in the synthesis of helical polymers and their structural determination, including helical pitch and handedness based on X-ray diffraction and spectroscopic measurements, together with high-resolution atomic force microscopy, is described. Polymer Journal (2010) 42, 3-16; doi:10.1038/pj.2009 Keywords: atomic force microscopy; circular dichroism; helical polymer; helical structure; X-ray diffractionThe helix is a unique structure as observed in nature from microscopic to macroscopic levels and is inherently chiral. Inspired by biological helices, such as DNA and proteins, chemists have been challenged to synthesize helical polymers with a controlled helical sense that aims not only to mimic biological helical structures but also to develop chiral materials for the separation of enantiomers and asymmetric catalysis. [1][2][3][4][5][6][7][8][9][10][11][12] The history of synthetic helical polymers with optical activity extends back to the 1960s when Pino and Lorenzi 13 investigated the structural and chiroptical properties of isotactic vinyl polymers prepared by the polymerization of a-olefins bearing optically active substituents. Although helical polyolefins are totally dynamic in nature and consist of short helical segments separated by frequently occurring helical reversals among disordered, random coil conformations, 14 this study was significant in the field of synthetic helical polymers, from which a number of helical polymers have been synthesized.On the basis of the pioneering studies by Nolte et al., 15 Okamoto et al. 16 and Green et al., 17 the existing synthetic helical polymers that exhibit an optical activity solely because of their macromolecular helicity can be classified into two categories with respect to their helix inversion barriers, that is, static and dynamic helical polymers (Figure 1). 9,12 Optically active helical polymers, such as poly(triphenylmethyl methacrylate) (1), 16 poly(t-butyl isocyanide) (2) 15 and polychloral (3), 18 have a sufficiently high helix inversion barrier and belong to the family of static helical polymers. Therefore, these helical polymers with either a right-or left-handed helix can be prepared by the helix-sense-selective polymerization of the corresponding achiral monomers using chiral catalysts or initiators under kinetic control. On the other hand, dynamic helical polymers, such as polyisocyanates (8) 17 and polysilanes (9), 19 possess a very low helix inversion barrier.As a consequence, they consist of interconvertible right-and lefthanded helical segments separated by rarely occurring helical reversals, as demonstrated by Green et al.,6,20,21 so that a preferred-handed helical conformation can be induced in the presence of a small amount of chiral residues at the pendant 6 or ter...

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Section: Synthesis and Structures Of Helical Polymers E Yashimamentioning

confidence: 99%

Synthesis and structure determination of helical polymers

Yashima

2010

Polym J

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“…Specifically, AFM and STM measurements have been performed for various PMMA types on mica and highly ordered pyrolytic graphite (HOPG) [110,111,230,231], finding tacticity-dependent configurations of so-called folded-chain crystals. Remarkably, this is also the case for atactic PMMA (Fig.…”

Section: Tem Measurementsmentioning

confidence: 99%

Development of an Ultrafast Low-Energy Electron Diffraction Setup

Gulde

2015

Springer Theses

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“…[10][11][12] The presence of an interface can significantly affect the crystalline structure of materials, small molecules 13 and polymers 14,15 alike. The impact of geometrical confinement in forms of droplets, 16,17 thin films, 15,[18][19][20][21][22][23] adsorbed structures, 24,25 composite phases, [26][27][28] and blend patterns 14,29,30 on polymer crystals specifically have been comprehensively investigated.…”

Section: Introductionmentioning

confidence: 99%

Surface-Induced Frustration in Solid State Polymorphic Transition of Native Cellulose Nanocrystals

2017

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ABSTRACT. The presence of an interface generally influences crystallization of polymers from melt or from solution. Here, by contrast, we explore the effect of surface immobilization in a direct solid state polymorphic transition on individual cellulose nanocrystals (CNCs), extracted from a plant-based origin. The conversion from native cellulose I to cellulose III crystal occurred via a 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 2 host-guest inclusion of ethylene diamine inside the crystal. 60% reduction in CNC width (height) in atomic force microscopy images suggested that when immobilized on a flat modified silica surface, the stresses caused by the inclusion or the subsequent regeneration resulted in exfoliation, hypothetically between the van der Waals bonded sheets within the crystal. Virtually no changes in dimensions were visible when the polymorphic transition was performed to non-immobilized CNCs in bulk dispersion. With reservations and by acknowledging the obvious dissimilarities, the exfoliation of cellulose crystal sheets can be viewed as analogous to exfoliation of 2D structures like graphene from a van der Waals stacked solid. Here, the detachment is triggered by an inclusion of a guest molecule inside a host cellulose crystal and the stresses caused by the firm attachment of the CNC on a solid substrate, leading to detachment of molecular sheets or stacks of sheets.

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Two-Dimensional Folded Chain Crystals of a Synthetic Polymer in a Langmuir−Blodgett Film

Cited by 124 publications

References 10 publications

Synthesis and structure determination of helical polymers

Synthesis and structure determination of helical polymers

Development of an Ultrafast Low-Energy Electron Diffraction Setup

Surface-Induced Frustration in Solid State Polymorphic Transition of Native Cellulose Nanocrystals

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