Optical activity measurements in solids 7. Polylactides and poly(β‐hydroxybutyrates)

Bartus, Jan; Weng, Dexi; Vogl, Otto

doi:10.1002/pi.1994.210340413

Cited by 15 publications

(13 citation statements)

References 10 publications

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“…A positive dichroic band occurs at k = 210 nm as it is known for optically active polylactides. [29,30] This Cotton effect can be attributed to the n -p* absorption of the ester group. [31] The intensity/concentration coefficient of the CD band corresponds with those found for poly(llactide)s of high optical purity, [30] indicating that there is no evident racemisation during the polymerization process.…”

Section: Resultsmentioning

confidence: 99%

Optically Active Supramolecular Poly(L-lactide)s End-Capped with Terpyridine

Heller

Schubert

2001

Macromol. Rapid Commun.

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Section: Resultsmentioning

confidence: 99%

Optically Active Supramolecular Poly(L-lactide)s End-Capped with Terpyridine

Heller

Schubert

2001

Macromol. Rapid Commun.

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“…We have now developed and perfected the general method for measuring the optical activity of inorganic crystals in suspension (in addition to the single crystal measurement) 15–22. We also measured synthetic macromolecules in solution and suspension, found excellent agreement of the data, when all the conditions of measurements were optimized 6–9…”

Section: Crystallizationmentioning

confidence: 94%

Trends in survival after diagnosis with hematologic malignancy in adolescence or young adulthood in the United States, 1981‐2005

Pulte

Gondos

Brenner

2009

Cancer

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The creation of chirality on Earth and the development of chiral life have been discussed in this highlight. Convincing evidence for the introduction of chirality on Earth is still fragmentary. We believe that by a combination of chiral crystallization and formation of helical polymers with preferred chiral conformational structure is the key to this question. This concept of macromolecular asymmetry has inspired ideas and resulted in possible rules for how chiral life as we know it, could have been introduced. These investigations needed the understanding of the requirements for chiral crystallization, for the stereochemistry of the initial formation of helical polymers, the measurements of optical activity of solids and their coordination with the fundamentals of chirality. Spacial modeling of the “oligo‐crystallization” of sodium chlorate led to the conception of “isotactic” linear crystallization, which involves helical propagation. It seems to require unequal sizes of the cations and anions, which, by branching propagation leads to three‐dimensional chiral crystal formation. Linear “isotactic” propagation of crystallization seems to be equivalent to stereo and conformational specific polymerization. One and a half turns of the helix seems to be required for stereo‐ and conformational specificity, that is, between the pentamer and hexamer in chloral polymerization (11/3 or nearly 4/1 helix) and between trimer and tetramer for the sodium chlorate crystal (2/1 helix). © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

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“…47 In this case, the electric vector is nearly perpendicular to the surface and interacts almost exclusively with the normal component (z) of the transition moments of molecules. The determination of the spectral dependence of the optical constants of the polylactide monolayer (n x , n y , n z , k x , k y , and k z ) was performed using an n ∞ value (refraction index in the visible) of 1.47 48 and an estimated film thickness of 15 Å. Although this estimated film thickness does not allow the determination of the absolute values of n and k, it nevertheless…”

Section: Methodsmentioning

confidence: 99%

Determination of Molecular Orientation in Biaxially Oriented Ultrathin Films

et al. 2004

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Biaxial orientation in ultrathin films is characterized by a preferential orientation of the main molecular axis in the plane of the film in addition to its orientation with respect to the normal of the film. In this paper, analytical expressions allowing the calculation of the molecular orientation in biaxially oriented films from their anisotropic optical constants are presented for the first time. These expressions have been used to calculate the molecular orientation in multilayers of poly(γ-benzyl-L-glutamate) and to determine the angles between the main molecular axis and the different transition moments used (R angles). Using the optical constants determined by Buffeteau et al.1 for PBG multilayers, we have found that the tilt angle of the PBG helices with respect to the monolayer normal is 89°and that the azimuthal angle in the plane is 57°. The calculated R angles for the carbonyl stretching mode of the ester group and the amide I and amide II modes of the amide group are 49, 34 and 74°, respectively. The analytical expressions presented in this paper have also been used to calculate the molecular orientation in Langmuir-Blodgett monolayers of an equimolar blend of poly(D-lactide) and poly(L-lactide). The optical constants of a monolayer of the polylactide mixture determined using p-and s-polarized transmittance and p-polarized reflection-absorption infrared spectra have shown that the polylactide helices have a tilt angle of 81°and an azimuthal angle of 56°.

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Optical activity measurements in solids 7. Polylactides and poly(β‐hydroxybutyrates)

Cited by 15 publications

References 10 publications

Optically Active Supramolecular Poly(L-lactide)s End-Capped with Terpyridine

Optically Active Supramolecular Poly(L-lactide)s End-Capped with Terpyridine

Trends in survival after diagnosis with hematologic malignancy in adolescence or young adulthood in the United States, 1981‐2005

Determination of Molecular Orientation in Biaxially Oriented Ultrathin Films

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