Prediction of polymer densities

Krevelen, D.W. Van; Hoftyzer, P. J.

doi:10.1002/app.1969.070130506

Cited by 70 publications

(53 citation statements)

References 17 publications

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“…For amorphous murein a density of 1.24 g/ cm3 was estimated. The applied group increments used to estimate the amorphous density of murein were taken from an analysis of linear polymers [18]. Therefore, the estimated density of 1.24 g/cm3 can only be used as a very rough approximation.…”

Section: The State Of Order Of Mureinmentioning

confidence: 99%

On the Secondary and Tertiary Structure of Murein

Labischinski

Barnickel

Bradaczek

et al. 1979

European Journal of Biochemistry

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X-ray diffraction, density measurements, and stereochemical data were used in order to disclose the architecture of murein, the rigid component of almost all bacterial cell walls. Dry densities of 1.38 -1.39 g/cm3 were observed for Micrococcus luteus and Staphylococcus aureus. The X-ray data for gram-positive (S. uureiis, M . luteus) and gram-negative (Escherichia cofi) strains were almost identical, showing, in addition to some diffuse scattering with broad maxima corresponding to Bragg values of 0.22 and 0.45 nm, two sharp peaks indicating periodicities of about 0.7 and 0.94 nm. These latter periodicities were not found in whole bacteria but emerge immediately after breakage of the whole cells. In gram-positive species a weak oriented reflex at 4.2 nm appeared, while all other reflexes remain ring-shaped. Diffraction patterns obtained under the influence of humidity and certain metal ions showed strong variations in the position of the 0.45-nm ha1 0.These data, together with stereochemical considerations, invalidate the hitherto advanced models of a chitin-like structure of the glycan chains in murein. Instead, the following model proposed and discussed here is consistent with the experimental data. The structure is made up of layers, which in S. aureus and M . luteus are separated by about 4.2 nm. The layers are more or less randomly rotated against each other. The sugar chains run parallel to these layers and, hence, to the surface of the cell wall. They do not possess a twofold screw axis as in chitin or cellulose. Thus, the peptide strands protude from the glycan chain axis in different directions. The peptide strands seem to assume fairly rigid conformations and to be mainly responsible for the regular layer-like arrangement of murein.The main skeletal component of most bacterial cell walls is a unique polymer called peptidoglycan (murein). The murein of gram-positive bacteria has a multilayered arrangement and makes up about 50 % of the cell wall weight, whereas the murein of gramnegative bacteria is probably monolayered, representing only about 5-10% of the cell wall weight [l].The glycan chains are composed of alternating sequences of N-acetylglucosamine and N-acetylmuramic acid. The peptide part is built up by alternating Dand L-amino acids, including a y-bond for D-glutamic acid (Fig. 1) [2-41.The subunits are linked together by p(1-4)-glycosidic bonds in the glycan part and can be crossParts of this paper were presented at the IV. International Conference on Small-Angle Scattering of X-Rays and Neutrons in Gatlinburg/U.S. A., October 1977. linked by peptide bonds between the free amino group of the diamino acid and the carboxyl group of the D-alanine of another peptide strand which, in this case, loses its second D-alanine. The cross-linkage COCH..

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Section: The State Of Order Of Mureinmentioning

confidence: 99%

On the Secondary and Tertiary Structure of Murein

Labischinski

Barnickel

Bradaczek

et al. 1979

European Journal of Biochemistry

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“…Amorphous density was estimated by the method proposed by Van Krevelen. 24 The degrees of crystallinity calculated were 65 and 46% for unpoled samples 3 and 5 and 72 and 56% for poled samples, respectively. that this increase in degree of crystallinity for poled samples may be due to the ordered crystal structure.…”

Section: Poled Samplementioning

confidence: 93%

Curie Transition in Poled and Unpoled Copolymer of Vinylidene Fluoride and Tetrafluoroethylene

Murata

1987

Polym J

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ABSTRACT:Copolymers of vinylidene fluoride (VDF) and tetrafiuoroethylene (TeFE) with TeFE content ranging from 17.8 to 30."imol% were studied by thermal, dynamic mechanical, and thermally stimulated current measurements. Below the melting point, a small endotherm was observed in differential thermal analysis. Corresponding to the endotherm, a crystalline relaxation, designated as r;, was observed by mechanical measurements. It was inferred that the endotherm and the r; mechanical relaxation were due to the Curie transition. The Curie points of these copolymers were about 50 K lower than those of VDF-trifiuoroethylene (TrFE) copolymers with the same VDF content. In X-ray measurements, it was confirmed that these copolymers took the all-trans crystal structure similar to that of PVDF form I of which the crystal lattice expanded in aand b-axis directions and was disordered in the c-axis repeat in comparison with that for VDFTrFE copolymers. The Curie temperature for poled samples increased by

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“…Groh and Zimmerman plotted the ratio of molar refraction, R L , to molar volume, V L , for different atoms present in organic polymers [4] using previously published data [5][6][7]. In spite of the broad range of values for each atom, due to different binding structures, and varying chemical environments, it is apparent that fluorine and to a lesser extent oxygen lower the refractive index of a compound [8].…”

Section: Lorentz-lorenz Equation and Correlation Model Of Groh And Zimentioning

confidence: 99%

Electrooptical Light-Management Material: Low-Refractive-Index Hydrogels

Chang

Holguin

2007

The Journal of Adhesion

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A prototype synthetic hydrogel that has a low refractive index (< 1.35) and is optically clear has been developed [1]. The refractive index is a key feature in the application of optical polymers, and this hydrogel is particularly useful for light-transmitting devices. The ultraviolet-light-curable hydrogel formulation contains more than 90% water (plus water-soluble oligomers, photoinitiator, and surfactant). UV cures it instantly at 425 mJ=cm 2 at a thickness of less than 10 mm, giving a firm hydrogel with a modulus of 2.3 Â 10 3 dyn=cm 2 . This hydrogel has utility in light-management applications.

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Prediction of polymer densities

Cited by 70 publications

References 17 publications

On the Secondary and Tertiary Structure of Murein

On the Secondary and Tertiary Structure of Murein

Curie Transition in Poled and Unpoled Copolymer of Vinylidene Fluoride and Tetrafluoroethylene

Electrooptical Light-Management Material: Low-Refractive-Index Hydrogels

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