Synthesis and Interfacial Behavior of Polystyrene−Polysaccharide Diblock Copolymers

• Published in: Macromolecules Vol. 36; no. 6; pp. 1982 - 1987
• Main Authors: Bosker, W. T. E, Ágoston, K, Cohen Stuart, M. A, Norde, W, Timmermans, J. W, Slaghek, T. M
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 25-03-2003
• Subjects: adsorption; Applied sciences; block; Exact sciences and technology; Natural polymers; Physicochemistry of polymers; polymers; Starch and polysaccharides; Monolayer; Condensation reaction; Interface pressure; Amino group; End group; Air water interface; Experimental study; Dextran; Chemical modification; Preparation; Diblock copolymer; Oside polymer; Styrene polymer; Hysteresis; Conformation; Amphiphilic polymer; Styrene copolymer
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/ma020925u

Linear block copolymers of polystyrene and polysaccharide were synthesized using a block synthesis method with amino-terminated polystyrene and sodium cyanoborohydride as reducing agent. Different types of polysaccharides, dextrans, and maltodextrins with various molecular weights were used. IR spectroscopy indicated a successful coupling. Yields of reaction are 75−95 wt %. Attempts to couple long dextrans (M w > 6000 Da) were not successful. Interfacial pressure measurements of monolayers of the copolymers on water showed interfacial behavior typical for amphiphilic compounds and different from the starting compounds, confirming the coupling reaction. Time-dependent hysteresis occurs between successive compression and expansion cycles. This is, to a large extent, due to the slow adsorption/desorption of the polysaccharide chains at the air−water interface and the formation of aggregates of copolymer at the interface. Aggregates are mainly formed by H-bonds between adjacent polysaccharide chains. The relaxation time for hysteresis, determined for polystyrene−dextran copolymer, was 85 min.