New approaches to advanced polymers by selective cellulose functionalization

Abstract

The uniform structure of cellulose, combined with its hydrophilicity, biocompatibility, chirality, and structure-forming capacity, as well as its broad synthetic potential, make the design of cellulose-based advanced materials a challenge for polysaccharide research. The synthesis of new cellulose products with regiocontrolled pattern of functionalization and of well defined supramolecular nanoscale architectures is a highlight in recent cellulose chemistry. The present feature will discuss regioselective functionalization of cellulose and cellulose derivatives with respect to reactivity of the polymer depending on molecular and supramolecular structure. Experimental examples of functionalization via ester intermediates of controlled stability as well as via protecting or activating ether groups are described and the efficiency of the reaction routes and procedures is evaluated. Moreover, problems and progress in techniques of product analysis and structure-property relationships as well as potential applications of regioselectively functionalized cellulosics are presented together with a discussion of possible future developments in cellulose chemistry. Acta Polymer., 48,277-297 0 VCH Verlagsgesellschaft mbH, D-6945 1 Weinheim 1997 0323-7648/97/0808-0277$17.50+.50/0 ' 278 Klemm, Heinze, Philipp, Wagenknecht Acta Polymer., 48,277-297 (1997) Fig. 5. Electron microscopic pictures (TEM) of typical cellulose samples: acotton linters, b -spruce sulfite pulp (from Fink et al.

Synthesis and structure characterization of 2,3‐ O‐ carboxymethylcellulose

“…For example, the tritylation of cellulose has become a well-known and useful method for selective protection of primary hydroxyl groups in this field [7][8][9] . In the course of our studies in the field of polysaccharides 10,11) one of recent research goals is the development of synthesis pathways for a controlled functionalization of the macromolecules both within the AGU and along the polymer chains. In the present paper we wish to report a new attempt to control the functionalization pattern by reacting the secondary hydroxyl groups of 6-O-protected triphenylmethylcellulose products via induced phase separation processes exemplified by the preparation of carboxymethylcellulose (CMC).…”

Structures of regenerated cellulose films revealed by grazing incidence small-angle x-ray scattering

“…For the design of advanced materials, synthetic modification of cellulose has been conducted to introduce various functionalities. 6 Substitution of some hydroxyl protons causes drastic changes in the physical properties: in fact, silylated cellulose derivatives are often soluble in nonpolar solvents due to the significant reduction in the intermolecular hydrogen bonding. 7,8 For example, Wegner and co-workers 9,10 demonstrated that Langmuir monolayers of trimethylsilylcellulose ͑TMSC͒ could be transferred onto a hydrophobized substrate by the Langmuir-Blodgett ͑LB͒ method.…”

Concepts for preparation of novel regioselective modified cellulose derivatives sulfated, aminated, carboxylated and acetylated for hemocompatible ultrathin coatings on biomaterials

“…In other hemocompatibility tests, the sulfate groups in the C-2/3 position of cellulose are much more effective in confering anticlotting activity on the molecule than those in 6 position. [19] However reverse results are reported in regioselectice sulfated chitin derivatives in comparable positions [24] for interpreting the results one has to take into account the validity and comparability of the used tests for antithrombogenicity and athrombogenity for biomaterials and the results of our planed total study. Low level of complement activation is also important for a high standard of hemocompatibility.…”

“…Only more recent synthetic reactions have used the regioselective concepts for preparing more defined derivatives. There are exellent reviews for preparing cellulose derivatives and recently for preparing regioselectively sulfated cellulose by Klemm et al [18][19] In contrast to this chitosan derivatives with more defined arranged functional groups in the repeating units were synthesized prior to the cellulose derivatives. The earliest attempt at sulfation of chitosan was that of Karrer et al [20] The product had a DS of 1.7.…”

“…Recently it was shown by Nishimura et al [24] that 2, 3 regioselectively disulfated Chitosan showed low anticoagulant properties whereas 2, 3 regioselectively disulfated cellulose showed high anticoagulant properties. [19] However, comparable high anticoagulant properties of that of HE have never been reached.…”