Double Strand Helix of Isotactic Poly(methyl methacrylate

Kusanagi, Hiroshi; Tadokoro, Hiroyuki; Chatani, Yôzô

doi:10.1021/ma60051a028

Cited by 156 publications

(106 citation statements)

References 3 publications

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“…A recurring motif in many diverse biopolymers is the helix. This structure has also been observed in synthetic polymers -for example, meta-phenylacetylene oligomers [1], and the isotactic form of poly(methyl methacrylate) [2] in various solvents. The occurrence of helical structures in polymers with substantially different monomer chemistries suggests an underlying generic behavior, which has prompted significant efforts to produce "minimal" models that naturally display helical structures [3,4,5,6].…”

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confidence: 56%

Helical Structures from an Isotropic Homopolymer Model

2006

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We present Monte Carlo simulation results for square-well homopolymers at a series of bond lengths.Although the model contains only isotropic pairwise interactions, under appropriate conditions this system shows spontaneous chiral symmetry breaking, where the chain exists in either a left-or a right-handed helical structure. We investigate how this behavior depends upon the ratio between bond length and monomer radius.

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confidence: 56%

Helical Structures from an Isotropic Homopolymer Model

2006

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“…39 The thin films and methodology developed here The morphological description outlined above bears resemblance to the nucleation, growth, and facilitated rapid equilibrium as attested to by the morphological uniformity which was observed, substantial dehydration prior to primary nucleation is as of yet unclear, but as we will show and have clarified the morphological events associated with the crystal growth of DNA as they later, 37 this is associated with a progression of relate to hydration level. Diffraction work on multihelical forms of many DNA molecules, which these systems, as well as other DNAs of differing can be seen in several states of unwinding, and GC%, and alternative counterions (e.g., Li), may associated with crystal fronts.…”

Section: Discussionmentioning

confidence: 83%

The phase morphology and crystal growth habits of DNA fractions. Optical microscopy and light scattering

Monar

Phillips

1997

J. Polym. Sci. B Polym. Phys.

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Polydisperse DNA of reasonable molecular weights was prepared from a mammalian source via sonication and fractionation. A method for characterizing the molecular weight using gel electrophoresis is described. Quiescent crystallization was studied in thin films of one of the fractions induced by rapidly changing the hydration state isothermally. We report the occurrence of the semicrystalline nature of DNA. The crystal growth occurring via aggregates is best described as sheaves and spherulites from DNA gels in the relative humidity range (RH) corresponding to A‐DNA. These habits exhibit primary nucleation and secondary growth, which closely resemble those of melt‐crystallized, synthetic macromolecules and, in a follow‐up report, will be shown to be lamellar in nature. Small, needle‐like crystals are observed for B‐DNA hydration levels, and are unstable at lower hydration levels. A transformation from needle to lamellar crystals can occur, even when the primary nucleation of lamellar forms is otherwise absent at that hydration level, through a cylindrical phase exhibiting selective reflection of colored bands. The hydration level plays, in part, the role of the supercooling in this system and the long‐known hysteresis in the formation and dissolution of the A‐DNA (crystals) can now be viewed in light of those factors known to operate in semicrystalline systems. A morphological phase diagram is developed and is in accord with the known physical evidence. Because this preparation and these morphological observations are without precedence, substantial detail into methodology is included for this first article in the series. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1843–1854, 1997

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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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Double Strand Helix of Isotactic Poly(methyl methacrylate

Cited by 156 publications

References 3 publications

Helical Structures from an Isotropic Homopolymer Model

Helical Structures from an Isotropic Homopolymer Model

The phase morphology and crystal growth habits of DNA fractions. Optical microscopy and light scattering

Synthesis and structure determination of helical polymers

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