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Unusual reversible elastomeric gels from Nostoc commune

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Nostoc commune cyanobacteria grow in extreme conditions of desiccation and nutrient-poor soils. Their colonies form spherical gelatinous bodies are composed of a variety of polysaccharides that allow them to store water and nutrients. In this paper, we study this type of biological gel that shows characteristics of both chemical and physical gels. The structure of this gel was assessed by means of scanning electron microscopy, plate-plate rheometry, Fourier transform infrared spectroscopy and absorption/desorption tests. The storage modulus of this gel was found to be frequency independent, as is usual for chemical gels. The stress sweeps showed a reversible stress softening behaviour that was explained in terms of the physical nature of the interactions of this network. The high density of physical crosslinks probably allows this physical network to behave as a highly elastomeric chemical network, limiting the relaxation of individual chains. On the other hand, reversibility is associated with the physical nature of its bonds.

This article originally appeared in International Journal of Biological Macromolecules 97, 2017, Pages 411-417.

Sign up or log in to your free Materials Today account to download the full article.

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Sign up or log in to your free Materials Today account to download the full article.

Nostoc commune cyanobacteria grow in extreme conditions of desiccation and nutrient-poor soils. Their colonies form spherical gelatinous bodies are composed of a variety of polysaccharides that allow them to store water and nutrients. In this paper, we study this type of biological gel that shows characteristics of both chemical and physical gels. The structure of this gel was assessed by means of scanning electron microscopy, plate-plate rheometry, Fourier transform infrared spectroscopy and absorption/desorption tests. The storage modulus of this gel was found to be frequency independent, as is usual for chemical gels. The stress sweeps showed a reversible stress softening behaviour that was explained in terms of the physical nature of the interactions of this network. The high density of physical crosslinks probably allows this physical network to behave as a highly elastomeric chemical network, limiting the relaxation of individual chains. On the other hand, reversibility is associated with the physical nature of its bonds.

This article originally appeared in International Journal of Biological Macromolecules 97, 2017, Pages 411-417.

Sign up or log in to your free Materials Today account to download the full article.

Source: https://www.materialstoday.com/biomaterials/features/unusual-reversible-elastomeric-gels-from-nostoc/

Metal

Celebrating 100 years of polymer science


Celebrating 100 years of polymer science

The year 2020 marks the 100th anniversary of a milestone paper published in 1920 by Hermann Staudinger (Über Polymerisation. Ber. Dtsch. Chem. Ges. 1920;53:1073–85) in which he introduced the groundbreaking hypothesis of the existence of long chain molecules, consisting of a large number of covalently linked monomeric units. This paper, and Staudinger’s subsequent papers on the topic, can be considered as a foundation of the field of macromolecular chemistry and polymer science.

To celebrate the 100th Anniversary of the 'Macromolecular Hypothesis', Progress on Polymer Science has invited world leaders in polymer science and engineering to share their insights in the form of reviews, trends, or perspectives on the current, past and future developments in macromolecular chemistry. These contributions have been made available in 'open access' format and we, the Editors of Progress in Polymer Science, invite you to explore these perspectives on what the future of the field might hold.

Read Special Issue

Republished by Plato

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Celebrating 100 years of polymer science

The year 2020 marks the 100th anniversary of a milestone paper published in 1920 by Hermann Staudinger (Über Polymerisation. Ber. Dtsch. Chem. Ges. 1920;53:1073–85) in which he introduced the groundbreaking hypothesis of the existence of long chain molecules, consisting of a large number of covalently linked monomeric units. This paper, and Staudinger’s subsequent papers on the topic, can be considered as a foundation of the field of macromolecular chemistry and polymer science.

To celebrate the 100th Anniversary of the ‘Macromolecular Hypothesis’, Progress on Polymer Science has invited world leaders in polymer science and engineering to share their insights in the form of reviews, trends, or perspectives on the current, past and future developments in macromolecular chemistry. These contributions have been made available in ‘open access’ format and we, the Editors of Progress in Polymer Science, invite you to explore these perspectives on what the future of the field might hold.

Read Special Issue

Source: https://www.materialstoday.com/polymers-soft-materials/news/celebrating-100-years-of-polymer-science/

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Metal

China’s coal consumption expected to reach 2.9 billion mt in 2020

Zhang Hong stated that China’s coal consumption in 2020 will likely amount to 2.9 billion mt.

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Zhang Hong, vice secretary of the China National Coal Association (CNCA), stated at the 2020 China Coal and Coke Industry Conference held in Shenzhen that China’s coal consumption in 2020 will likely amount to 2.9 billion mt, while supply and production of coal will basically remain in equilibrium.

As previously reported by SteelOrbis, in the January-September period this year China’s raw coal output amounted to 2.79 billion mt, declining by 0.1 percent year on year. In September alone, China’s raw coal output totaled 330 million mt, down 0.9 percent year on year, 0.8 percentage points bigger than the rate of decline recorded in August.

Source: https://www.steelorbis.com/steel-news/latest-news/chinas-coal-consumption-expected-to-reach-29-billion-mt-in-2020-1169692.htm

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Metal

Vehicle output and sales in China expected to fall by four percent in 2020

Chen Shihua has forecast that vehicle output and sales in China in 2020 will likely decrease by around four percent year on year.

Republished by Plato

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Chen Shihua, vice secretary of the China Association of Automobile Manufacturers (CAAM), has forecast that vehicle output and sales in China in 2020 will likely decrease by around four percent year on year.

In the January-September period this year, production and sales of automotive vehicles in China totaled 16.957 million units and 17.116 million units, down 6.7 percent and 6.9 percent year on year, according to CAAM. This means that output and sales will gradually rebound in October-December, thereby reducing the decrease rate for the full year to four percent.

However, vehicle output and sales in 2021 will likely increase slightly due to the expected economic growth.

Source: https://www.steelorbis.com/steel-news/latest-news/vehicle-output-and-sales-in-china-expected-to-fall-by-four-percent-in-2020-1169689.htm

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