[PDF] Glass Formation Behavior Of Model Ionomers eBook

Author : Dihui Ruan
Publisher :
Page : 61 pages
File Size : 20,80 MB
Release : 2015
Category : Ionomers
ISBN :

GET BOOK

Ionomers - polymers with bonded ionic groups - are important because of their wide applications in various fields. The glass formation behavior of ionomers has direct impact on their properties and performance, and therefore demands a deeper understanding. The ionic groups collapse into distributed ionic aggregates in the ionomers. The region surrounding the aggregates shows dynamic suppression among uncharged polymer chains, and the size of this region is correlated to chains' persistence length. This phenomenon is a consequence of the fact that there is bond connectivity between aggregates and polymers, which differs from materials with only non-bonded interfaces, like composites. Here, we perform molecular dynamics simulations of model ionomers to test this conventional view and propose a fundamental reconsideration of grafted micro-phase materials like ionomers. Based on our results, the covalent grafts are not the central factor determining linear segmental dynamics and glass formation. Instead, we find that they are equivalent to strong physical attractions, as in ungrafted nanocomposites and nanoconfined glass-formers, where near-interface mobility suppression is mediated by cooperative rearrangements intrinsic to glass-forming liquids, rather than by a unique covalent `tethering effect'. This conclusion indicates the need for a revised understanding of glass formation and segmental dynamics in materials incorporating covalent grafting.

Author : Michel Pineri
Publisher : Springer Science & Business Media
Page : 579 pages
File Size : 14,5 MB
Release : 2012-12-06
Category : Science
ISBN : 9400938292

GET BOOK

Ionomers, that is polymers containing a low concentration of charged units along the chain, have been the subject of increasing interest during the past twenty years. The presence of ionic groups in the poly mer changes some of its properties dramatically. Increases in the modu lus and the viscosity of several orders of magnitude have been observed, and changes in the glass transition of hundreds of degrees are possible. In addition, diffusion coefficients can be modified drastically. These changes are due primarily to the presence of reversible ionic cross links in these materials. Because of the low dielectric constant of most organic polymers, the ions or ionic dipoles tend to aggregate ; this aggregation process, however, is limited, because the ionic groups are covalently bonded to the organic chain. Host of the fundamental research done on these materials has been devoted to a determination of the extent of association, the structure of the aggregates, the limi ting factors, and the correlations between molecular and supermolecular structure and the resul ting properties.

Author : Michel Pineri
Publisher : Springer Science & Business Media
Page : 608 pages
File Size : 50,47 MB
Release : 1987-05-31
Category : Science
ISBN : 9789027724588

GET BOOK

Proceedings of the NATO Advanced Research Workshop, Villard de Lans, France, June 15-21, 1986

Author : Shulamith Schlick
Publisher : CRC Press
Page : 326 pages
File Size : 37,2 MB
Release : 1996-01-15
Category : Science
ISBN : 9780849376481

GET BOOK

The molecular structure and composition of ionomers lead to a complex superposition of properties of organic chains and of polyelectrolytes. The potential use of this class of polymers in applications such as surfactants, ion selective membranes in electrochemical processes, coatings, fuel cells and batteries has sparked a vast amount of research.

Author : Christoph Schick
Publisher : Springer
Page : 796 pages
File Size : 44,68 MB
Release : 2016-06-28
Category : Technology & Engineering
ISBN : 3319313290

GET BOOK

In the past decades, the scan rate range of calorimeters has been extended tremendously at the high end, from approximately 10 up to 10 000 000 °C/s and more. The combination of various calorimeters and the newly-developed Fast Scanning Calorimeters (FSC) now span 11 orders of magnitude, by which many processes can be mimicked according to the time scale(s) of chemical and physical transitions occurring during cooling, heating and isothermal stays in case heat is exchanged. This not only opens new areas of research on polymers, metals, pharmaceuticals and all kinds of substances with respect to glass transition, crystallization and melting phenomena, it also enables in-depth study of metastability and reorganization of samples on an 1 to 1000 ng scale. In addition, FSC will become a crucial tool for understanding and optimization of processing methods at high speeds like injection molding. The book resembles the state-of-the art in Thermal Analysis & Calorimetry and is an excellent starting point for both experts and newcomers in the field.

Author : M.R. Tant
Publisher : Springer Science & Business Media
Page : 524 pages
File Size : 37,35 MB
Release : 2012-12-06
Category : Technology & Engineering
ISBN : 940091461X

GET BOOK

Polymers have achieved an enviable position as the class of materials having the highest volume of production, exceeding that of both metals and ceramics. The meteoric rise in the production and utilization of polymers has been due to advances in polymer synthesis which allow the creation of specific and well-defined molecular structures, to new knowledge concerning the relationships between polymer structure and properties, and to an improved understanding of how processing can be used as a tool to develop morphological features which result in desired properties. Polymers have truly become 'engineered materials' in every sense of the term. Polymer scientists and engineers are forever seeking to modify and improve the properties of synthetic polymeric systems for use in specific applications. Towards this end they have often looked to nature for advice on how to design molecules for specific needs. An excellent illustration of this is the use of noncovalent bonding (ionic, hydrogen, and van der Waals) in lipids, proteins, and nucleic acids, where these noncovalent bonds, acting both intra and intermolecularly, precisely control the structure and thus the function of the entire system. The utilization of ionic bonding, in particular in man-made polymers has attracted widespread interest in recent years, since ionic interactions exert a similar strong influence on the structure and properties of these synthetic systems.

Author : Ole Fejerskov
Publisher : John Wiley & Sons
Page : 641 pages
File Size : 18,43 MB
Release : 2009-03-16
Category : Medical
ISBN : 1444309285

GET BOOK

The second edition of Dental Caries: the Disease and its Clinical Management builds on the success of the prestigious first edition to present an unrivaled resource on cariology. The clinical thrust of the first edition is widened and strengthened to include coverage of the disease in all its variety, from eruption of the first primary tooth to the prevalent forms of the disease in older patients. The centrality of caries control and management to the dental health of all populations is further emphasized, as the book goes beyond the successful treatment of carious lesions to demonstrate the long-term consequences of the non-operative and therapeutic techniques employed.