Topochemically Modified Cellulose

• Published in: Cellulose (London) Vol. 10; no. 3; pp. 237 - 250
• Main Authors: Sipahi-Sağlam, E, Gelbrich, M, Gruber, E
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Nature B.V 01-09-2003
• Subjects: Acrylamide; Block copolymers; Cellulose; Chemical reactions; Coupling (molecular); Crystalline cellulose; Crystallites; Grafting; Hydrazones; Initiators; Macromolecules; Organic chemistry; Polydimethylsiloxane; Polyethylenes; Polymerization; Slurries; Substrates
• ISSN: 0969-0239; 1572-882X
• DOI: 10.1023/A:1025151701985

Selective topochemical reactions were carried out on particles of micro-crystalline cellulose. For this purpose these crystallites were chemically activated via hydrazone linkages at the reducing ends. Macromolecules, carrying reactive end groups, were attached to the reactive cellulose crystallites by coupling reactions (‘grafting to’ method). Amino-terminated polyethylene glycols and polydimethylsiloxanes were coupled to crystallites carrying phenyl carboxylic functions at their front faces. The cellulose-block-polydimethylsiloxane copolymer exhibits a pronounced tendency to form specific super-structures in slurries and films made from it. After freeze drying, layer structures are observable with the naked eye. Alternatively a radical polymerization of acrylamide could be started from the substrate surface after attaching reactive initiators (‘grafting from’ method). Both methods lead to selectively grafted cellulose particles. This was confirmed by SEC measurements after degrafting the attached polymers. A higher graft density resulted from radical polymerization due to the distinctly higher molecular weights obtained in this way. However, these grafted products did not form any special super-structures.