Preparation of Chitin/Polystyrene Hybrid Materials by Efficient Graft Copolymerization Based on Mercaptochitin

Abstract

Graft copolymerization of styrene onto mercaptochitin has been examined. Chitin was first tosylated to give tosylchitin, which was subsequently transformed into mercaptochitin. Athough the graft copolymerization was carried out in suspension, it proceeded efficiently to give chitin derivatives having polystyrene branches, a novel type of hybrid materials composed of a natural polysaccharide and a synthetic polymer. Under appropriate conditions, the grafting percentage reached 970%, indicating the high efficiency of the mercaptochitin as an initiator for the polymerization of styrene. The resulting graft copolymers exhibited glass transition phenomena at 115 °C and showed high swelling in organic solvents as a result of the introduction of polystyrene branches. Hydrolytic degradation of the chitin main chain allowed the isolation of the side chains, and the polystyrene isolated from the graft copolymer with a grafting percentage of 940% had Mn, Mw, and Mw/Mn values of 9.74 × 10 4 , 2.55 × 10 5 , and 2.62. These values indicate that the ratio of the mercapto groups actually used for initiating graft copolymerization was 4%, and a polystyrene chain attached on average to every 45 pyranose units.

Preparation and graft copolymerisation of thiolated β-chitin and chitosan derivatives

“…Kurita et al have reported the successful polymerisation of grafted chitin copolymers using 6-mercaptochitin from a-chitin as the trunk polymer Kurita, Hashimoto, Yoshino et al, 1996;Kurita et al, 2002). It was proposed that chitin copolymers could also be formed from related polymers prepared here, although these samples displayed lower DS values than those prepared by Kurita.…”

“…Thiolated chitosan polymers have been investigated for their metal binding capacity and selectivity (Cárdenas, Orlando, & Edelio, 2001;Lasko, Pesic, & Oliver, 1993), as macroinitiators for graft copolymerisation (Kurita, Hashimoto, Ishii, & Mori, 1996;Kurita, Hashimoto, Yoshino, Ishii, & Nishimura, 1996;Kurita, Inoue, & Harata, 2002) and for drug delivery and wound healing (Bernkop-Schnürch, Hornof, & Guggi, 2004;Guggi, Langoth, Hoffer, Wirth, & Bernkop-Schnürch, 2004;Hornof, Kast, & Bernkop-Schnürch, 2003;Hoyer, Schlocker, Krum, & Bernkop-Schnürch, 2008;Krauland, Guggi, & Bernkop-Schnürch, 2006;Masuko et al, 2005;Matsuda, Kobayashi, Itoh, Kataoka, & Tanaka, 2005;Werle & BernkopSchnürch, 2008). The thiol functional groups (R-SH) in the polymer can enhance the mucoadhesive properties of chitosan by forming disulfide bonds (RASASAR 0 ) with cysteine residues in proteins .…”

“…These materials are therefore suitable for drug delivery in a variety of physical forms such as gels, powders and films. The thiol groups can also dissociate to give hydrogen and sulfur free radicals which can initiate polymerisation with vinyl monomers like styrene and methyl methacrylate (MMA) Kurita, Hashimoto, Yoshino et al, 1996;Kurita et al, 2002).…”

“…One chitin derivative which has received attention for graft copolymerisation is 6-mercaptochitin. This derivative contains a thiol group in the 6-position which can easily react with vinyl monomers like styrene and MMA to form comb-like copolymers Kurita, Hashimoto, Yoshino et al, 1996;Kurita et al, 2002). Reaction at the 6-position leaves the amine free for further modifications.…”

Efficient Graft Copolymerization of 2-Methyl-2-oxazoline onto Tosyl- and Iodo-Chitins in Solution

“…6 However, the reactions have to be conducted under heterogeneous conditions in suspension owing to the insolubility of chitin and are thus generally poor in efficiency and reproducibility. Though insoluble, mercapto-chitin is a suitable radical initiator for styrene 7 and methyl methacrylate 8 to introduce side chains at the labile mercapto groups. As a new approach to graft copolymers, living poly(2-oxazoline)s were terminated t To whom all correspondence should be addressed.…”