Modification dextran with

Protocol for the Modification of Dextran with Chloroacetic Acid... 

The conversion of dextran with 1,2-epoxy-3-phenoxypropane, epoxyoctane or epoxydodecane may be exploited for the preparation of amphiphilic dextran derivatives. Polymeric surfactants prepared by hydrophobic modification of polysaccharides have been widely studied, starting with the pioneering work of Landoll [261]. Neutral water-soluble polymeric surfactants can be obtained by reaction of dextran with 1,2-epoxy-3-phenoxypropane in 1 M aqueous NaOH at ambient temperature (Fig. 35, [229,233]). The number n of hydrophobic groups per 100 Glcp units varies between 7 and 22 depending on the reaction conditions. 2-Hydroxy-3-phenoxy propyl dextran ethers (DexP) behave like classical associative polymers in aqueous solution. In dilute solution, the intrinsic viscosity decreases significantly whereas... 

More recently, thiolated dextran was synthesised by modification of dextran with 4-nitrophenyl chloroformate in DMSO/pyridine in the presence of DMAP at 0 °C yielding a carbonate (content 6%), which can be substituted with cystamine. Subsequent reduction yields the thiolated dextran containing between 1 and 4% thiol moieties (Fig. 57) [370]. 

Polyelectrolyte and non-polyelectrolyte acrylamide random copolymers and graft copolymers of dextran with acrylamide were synthesized to evaluate the effects of polymer composition and structure on viscosity modification and solution behavior in water and brine. Polymer solution rheological behavior and precipitation properties were measured. 

A wide variety of solution condensation systems were devised and tested including one and two liquid combinations and salt-containing systems. Only the system using the stannane dissolved in DMSO and dextran with sodium hydroxide in water yielded the desired modified cellulosic product (Table 1). Other results indicate that the presence of a strong base is conducive to effecting the modification of the cellulose. The DMSO systems had the NaOH present only as a largely undissolved solid. Further studies should consider the use of DMSO, DMF, etc. soluble strong bases such as triethylenediamine. 

The following protocol illustrates the modification of a dextran polymer with chloroace-tic acid. 

Dextran derivatives containing carboxyl- or amine-terminal spacer arms may be prepared by a number of techniques. These derivatives are useful for coupling amine- or carboxylate-containing molecules through a carbodiimide-mediated reaction to form an amide bond (Chapter 3, Section 1). Amine-terminal spacers also can be used to create secondary reactive groups by modification with a heterobifunctional crosslinking agent (Chapter 5). 

This type of modification process has been used to form sulfhydryl-reactive dextran polymers by coupling amine spacers with crosslinkers containing an amine reactive end and a thiol-reactive end (Brunswick et al., 1988 Noguchi et al., 1992). The result was a multivalent sulfhydryl-reactive dextran derivative that could couple numerous sulfhydryl-containing molecules per polymer chain. 

Modification of dextran polymers with 1,4-butanediol diglycidyl ether results in ether derivatives of the dextran hydroxyl groups, which then contain hydrophilic spacers with terminal epoxy functions (Figure 25.16). 

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