Effects of Molecular Weight Reduction on Brittle–Ductile Transition and Elastic Yielding Due to Noninvasive γ Irradiation on Polymer Glasses

Incorporation of [3H]orotic acid into low-molecular-weight nRNA of rat liver, fractionated on polyacrylamide gels, increased 6-12h after partial hepatectomy and 6h after γ-irridation at 2000 R. The incorporation of orotic acid was particularly increased into the 4.5S, 5S and approx. 10S nRNA fractions. If the irradiation was given after 6h of regeneration and RNA was isolated from the nucleus 12h after hepatectomy then the incorporation of orotic acid into these low-molecular-weight nRNA components was greater than after hepatectomy or irradiation alone.

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Fundamental studies on cationic polymerizations: Molecular weights and molecular weight distributions of polyisobutylenes produced by γ-irradiation (free ions) and chemical catalysis (ion pairs)

Journal of Polymer Science Part A-1 Polymer Chemistry ◽

10.1002/pol.1971.150090608 ◽

1971 ◽

Vol 9 (6) ◽

pp. 1551-1561 ◽

Cited By ~ 22

Author(s):

Joseph P. Kennedy ◽

Akihiro Shinkawa ◽

Ffrancon Williams

Keyword(s):

Molecular Weight ◽

Ion Pairs ◽

Γ Irradiation ◽

Molecular Weights ◽

Chemical Catalysis ◽

Molecular Weight Distributions ◽

Free Ions ◽

Weight Distributions ◽

Cationic Polymerizations

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Effect of Irradiation on the Molecular Weight, Structure and Apparent Viscosity of Xanthan Gum in Aqueous Solution

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.239-242.2632 ◽

2011 ◽

Vol 239-242 ◽

pp. 2632-2637 ◽

Cited By ~ 1

Author(s):

Yan Jie Li ◽

Yi Ming Ha ◽

Feng Wang ◽

Yong Fu Li

Keyword(s):

Aqueous Solution ◽

Molecular Weight ◽

Apparent Viscosity ◽

Irradiation Dose ◽

Xanthan Gum ◽

Gel Permeation Chromatography ◽

Uv Spectra ◽

X Ray Diffraction ◽

Γ Irradiation ◽

Radiation Chemical

Xanthan gum samples were irradiated in aqueous solution at different doses (0-120 kGy) of 60Co γ-rays. The changes of molecular weight and structures of irradiated xanthan gum samples were investigated and characterized by using gel permeation chromatography(GPC), X-ray diffraction (XRD), fourier-transform infrared spectra (FTIR), ultraviolet–visible spectral (UV–vis) analysis and rheometer. Results showed the molecular weight decreased gradually with increasing irradiation dose. The radiation chemical yields G(d) of xanthan gum was 26.55. FTIR spectra and XRD indicated that γ-irradiation introduced no significant changes into the structure and crystal texture, but UV spectra showed a distinct absorption peak at about 265 nm, increasing with irradiation dose, which was attributed to the formation of carbonyl groups or double bond. Apparent viscosity of xanthan gum solution decreased with increasing irradiation dose and remain basically constant with the prolonging of shear time after irradiation.

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Influence of the polymer molecular weight on the microstructure of hybrid materials prepared by γ-irradiation

Radiation Physics and Chemistry ◽

10.1016/j.radphyschem.2014.06.023 ◽

2015 ◽

Vol 106 ◽

pp. 126-129 ◽

Cited By ~ 3

Author(s):

Joana J.H. Lancastre ◽

António N. Falcão ◽

Fernanda M.A. Margaça ◽

Luís M. Ferreira ◽

Isabel M. Miranda Salvado ◽

...

Keyword(s):

Molecular Weight ◽

Hybrid Materials ◽

Polymer Molecular Weight ◽

Γ Irradiation

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Environmentally Sensitive Luminescence Reveals Spatial Confinement, Dynamics and Their Molecular Weight Dependence in a Polymer Glass

10.26434/chemrxiv.14637756.v1 ◽

2021 ◽

Author(s):

Stephen Picken ◽

Georgy Filonenko

Keyword(s):

Molecular Weight ◽

Molecular Probes ◽

Key Factors ◽

Polymer Glasses ◽

Polymer Glass ◽

Irregular Structure ◽

Glassy Materials ◽

Environmentally Sensitive ◽

Induced Defects ◽

The Impact

Polymer glasses have an irregular structure. Among the causes for such complexity are the chemically distinct chain end-groups that are the most abundant irregularities in any linear polymer. In this work we demonstrate that chain end induced defects allow polymer glasses to create confined environments capable of hosting small emissive molecules. Using environmentally sensitive luminescent complexes we show that the size of these confinements depends on molecular weight and can dramatically affect the photoluminescence of free or covalently bound emissive complexes. We confirm the impact of chain end confinement on the bulk glass transition in poly(methyl acrylate) and show that commonly observed T<sub>g</sub> changes induced by the chain ends should have a structural origin. Finally, we demonstrate that size and placement of luminescent molecular probes in pMA can dramatically affect the probe luminescence and its temperature dependence suggesting that polymer glass is a highly irregular and complex environment marking its difference with conventional small molecule solvents. Considering the ubiquity of luminescent glassy materials, our work lays down a blueprint for designing them with structural considerations in mind, ones where packing density and chain end size are key factors.

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Effect of Additive on Hardness and Brittleness in Polycarbonate Films

Volume 10: Mechanics of Solids and Structures, Parts A and B ◽

10.1115/imece2007-42728 ◽

2007 ◽

Author(s):

Suresh Ahuja

Keyword(s):

Molecular Weight ◽

Elastic Modulus ◽

Polymer Surfaces ◽

Contact Deformation ◽

Nano Indentation ◽

Chain Mobility ◽

Brittle Ductile Transition ◽

Different Strains ◽

Number Of Segments ◽

Weight Number

Hardness and modulus of a polymer composite is known to depend on its structure, molecular weight, number of segments between entanglements and additives (filler). Nano-indentation is used increasingly as a powerful tool to determine hardness and visco-elastic modulus of polymer surfaces linear, cross-linked or composites. Hysitron Nanoindenter was used in our investigation of contact deformation of surfaces of filled polycarbonates supported on aluminum substrate. Bar coatings of polymer films were made from solution and dried all at 110C for half an hour. The results show that filled polycarbonate gives higher hardness than unfilled polycarbonate, which can give significantly different temperature dependence depending on molecular weight of the polycarbonate and structure of the filler. Depending on the type of filler and its concentration, the polycarbonate composite exhibits brittle-ductile transition at different strains. This behavior is analyzed in terms of chain mobility and free volume in the composite.

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