Thermoreversible Networks

Abstract

This series presents critical reviews of the present and future trends in polymer and biopolymer science including chemistry, physical chemistr;6 physics and material science. It is addressed to all scientists at universities and in industry who wish to help abreast of advances in the topics covered.As a rule, contributions are specially commissioned. The editors and publishers will, however, always be pleased to receive suggestions and supplementary information. Papers are accepted for,,Advances in Polmyer Science" in English.In references Advances in Polymer Science is abbreviated Adv. Polym. Sci. and is cited as a journal. This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, re-use of illustrations, recitation, broadcasting, reproduction on microfilms or in other ways, and storage in data banks. Duplication of this publication or parts thereof is only permitted under the provisions of the German Copyright Law of September 9, 1965, in its current version, and permission for use must always be obtained from Springer-Verlag. Violations are liable for prosecution under the German Copyright Law. © Springer-Verlag Berlin Heidelberg 1997 Printed in GermanyThe use ofregisterednames, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. ForewordMacromolecular science and engineering as a separate discipline has existed for no more than seventy-five years, and has undoubtedly been one of the major scientific growth areas in the 2oth century. We now appreciate that the term represents the study of all aspects of high molecular weight species, from the synthesis and characterisation of plastics and rubbers, to the interpretation of the structure and function of biological material from an understanding of molecular physics and chemistry.For many years most physical and chemical studies on polymeric materials had to be carried out on biopolymers, since no synthetic polymers existed, except as a 'mistake' in the bottom of an organic chemist's flask! Indeed, the first synthetic resins were manufactured some fifty years before there was any real understanding of their polymeric nature. Nowadays, it is taken almost for granted that the mechanical properties of a wide range of polymeric materials are a natural consequence of their long-chain structure.Much work is still concerned with essentially linear polymers, from their synthesis to the characterisation as melts or glasses. However, also polymer gels and networks have always been of major interest and technological importance. Historically, at least, polymer networks can be divided into two main classes, chemically cross-linked materials (including bulk elastomers) and 'entanglement systems'. The latter are formed by the topological interaction of polymer chains, either in the melt or in solution when the...

Self-healing slip pulses and the friction of gelatin gels

“…We thus measure shear moduli in the kPa range, which depend on the gel composition as shown in Table 1. Although gelatin forms physical gels which are known to strengthen with time by constantly forming new crosslinks [16], no evolution of G is measured, up to experimental precision (≃ 5%), during the course of an experiment. This must certainly be assigned to the fact that bulk ageing is logarithmic only, while the duration of an experimental run (≤ 1 hour) is short on the scale of the previous history (≃ 20 hours).…”

Solvent control of crack dynamics in a reversible hydrogel

“…Gelatin gels are constituted of denatured (coil) collagen chains, held together by crosslinks made of segments of three-stranded helices stabilized by hydrogen bonds 5 . This network, swollen by the aqueous solvent, which controls its (undrained) bulk modulus, is responsible for the finite shear modulus µ, of order a few kPa.…”

Unassociated Molecular Chains in Physically Crosslinked Gellan Gels

“…[3][4][5][6][7][8][9][10][11][12][13][14][15][16] The gelation of gellan is remarkably enhanced by the addition of cations in aqueous solutions, since the gellan molecules possess carboxyl groups in the repeating unit. 11,12 Potassium, rubidium and cesium ions are categorized as gel-promoting cations.…”