Carbohydrates, modified

Carbohydrates occur in every living organism. The sugar and starch in food and the cellulose in wood, paper, arid cotton are nearly pure carbohydrates. Modified carbohydrates form part of the coating around living cells, other carbohydrates are part of the nucleic acids that carry our genetic information, and still others are used as medicines. 

Polythiophenes functionalized with monosaccharides have been evaluated for their ability to detect the influenza virus and E. coli (Baek et al. 2000). Copolymers of thiophene acetic acid 10 and carbohydrate-modified thiophenes 11 have been prepared via iron(III) chloride mediated polymerization. Addition of influenza virus to a sialic acid containing copolymer resulted in a blue shift of the polymer absorption maximum, resulting in an orange to red chromatic transition. Mannose-containing polythiophenes underwent color changes upon the addition of the lectin ConA or E. coli cells that contain cell surface mannose-binding receptors. A similar biotinylated pol5hhiophene afforded a streptavidin responsive material (Paid and Leclerc 1996). 

K. H. Dotz and E. G. da Silva, Carbohydrate-modified fused pyranosylidene complexes via radical addition of epoxides to unsaturated metal carbenes, Tetrahedron, 56 (2000) 8291-8299. 

Molecular switches based on the dihydroazulene-vinylheptafulvene system are discussed in Chapter 3. Chiroptical switching was achieved with a carbohydrate-modified chiral polyazuleneJ721... 

Treatment Weight reduction (if necessary) is of primary Importance. Dietary restriction of controlled carbohydrate, modified fat, low alcohol consumption. If necessary, drug therapy includes niacin and/or gemfibrozil (or clofibrate), or lovastatin (or mevastatin). 

Table III lists a number of selected references that describe the formulation of resins or adhesives at each intersection in Figure 1. PF, UF, UF modified with phenolics, and PF modified with nitrogenous compounds (e.g., urea) have not been included, because they do not contain carbohydrates and because they are in common use. The resin and adhesive systems that have been investigated most recently are those formed by the combination of carbohydrates with PF, both with and without the addition of a nitrogenous compound. Our attempts at the Forest Products Laboratory to use carbohydrate modified PF to bond wood are discussed in Chapter 25.

Carbohydrate-Modified Phenol-Formaldehyde Resins Formulated at Neutral Conditions... 

In this study, up to about 50% of the phenol-formaldehyde was replaced with carbohydrates and the modified resins used to bond wood veneer panels. The carbohydrate modified resins were formulated and cured under neutral conditions. The resins bond wood with acceptable dry- and wet-shear strengths, and wood failures. Reducing as well as nonreducing carbohydrates can be used as modifiers. The carbohydrate modifiers are being incorporated into the resin via ether linkages between the hydroxyls of the carbohydrate and methylol groups in the phenol-formaldehyde resin. The resins formulated under neutral conditions are very light in color. 

In an earlier paper (2), we determined that carbohydrates could replace a significant portion of the phenol-formaldehyde resin used for bonding plywood veneer. Carbohydrates from renewable resources such as wood can replace up to 50% of the phenol and formaldehyde in resins formulated under basic conditions without significant loss of bond quality. Two-ply, Douglas-fir-veneer panels bonded with these carbohydrate-modified resins have shear strengths approximately equivalent to those for panels bonded with unmodified phenol-formaldehyde resin. 

Water extraction studies of the carbohydrate modified resins in the earlier study indicate that a portion of the carbohydrate is apparently incorporated into the final cured resin. The absolute amount of modifier incorporated into the cured resin increases with the amount initially added during resin formulation. IR studies indicated that the carbohydrate derivative is probably incorporated into the resin via ether linkages. 

CONNER ET AL. Carbohydrate-Modified Phenol—Formaldehyde Resins 359... 

Color of Bond Line. Two-ply veener panels bonded with carbohydrate-modified resins formulated under neutral conditions had bond lines that are extremely light colored in contrast to the dark red-black color characteristic of resins cured under basic conditions. The color ranges from a light yellow-tan with unmodified and xylose-modified resins to a medium tan with the prehy-drolyzate modified resins. These resins would therefore be suited for bonding wood used for decorative purposes. 

Viscosity of Neutral Resins. The neutral resins, both unmodified and carbohydrate-modified, were very viscous. The resins have a consistency of taffy candy. This might present problems in their utilization with present commercial equipment, although equipment for applying foamed resins might be suitable. 

G. Jonas, R. Stadler, Acta Polymer., 1994, 45, 14-20. Carbohydrate modified polysiloxanes II. Synthesis via hydrosUation of mono-, di-and oligosaccharide aUylglycosides . 

K. Loos, G. Jonas, R. Stadler, Macromol. Chem. Phys. 2001,202,3210-3218, Carbohydrate Modified Polysiloxanes, 3. Solution Properties of carbohydrate-PolysUoxane conjugates in Toluene . 

M. Haupt, S. Knaus, T. Rohr, H. Gruber, J. Macromol. Sci. Pure Appl. Chem. 2000, A37(4), 323-341. Carbohydrate modified polydimethylsiloxanes. Part 1. Synthesis and Characterization of carbohydrate silane and siloxane building blocks ... 

D. Henkensmeier, B. C. Abele, A. Candussio, J. Thiem, Macromol. Chem. Phys., 2004, 205, 1851-1857. Synthesis and characterization of terminal carbohydrate modified polydimethylsiloxanes . 

R. Wagner, L. Richter, Y. Wu, J. Weissmuller, J. Reiners, K.-D. Klein, D. Schaefer, S. Stadt-muller, in Organosificon Chemistry 111 From Molecules to Materials, N. Auner, J. Weis, Eds, 1998, 510-514. Carbohydrate-modified sfioxane surfactants The effect of substructures on the wetting behavior on non polar solid surfaces. 

Doetz, K H, Ehlenz, R, Carbohydrate-modified metal carbenes synthesis and first applications, Chem. Eur. J., 3, 1751-1756, 1997. 

Kellam B, Drouillat B, Dekany G, Starr MS, Toth I (1998) Synthesis and in vitro evaluation of lipoamino acid and carbohydrate-modified enkephalins as potential antinoceptive agents. Int JPharm 161 55-64... 

Summary The wetting behavior of liquid siloxanes and aqueous solutions of carbohydrate-modified siloxane surfactants on perfluorinated surfaces has been investigated. Siloxanyl moieties in surfactants level off to a large extent the influences of other structural elements. The donor-acceptor portions of the surface tension and the interfacial tension solid/liquid converge and amount to about 1-2 mN/m. The contact angle is not a linear function of the surface tension. It results from the superposition of surface tension and interfacial tension solid/liquid, both independent of each other. 

For that purpose carbohydrate-modified siloxane surfactants bearing four independent structural elements (i) siloxanyl moiety (si), (ii) spacer (sp), (iii) carbohydrate unit (ch) and (iv) modifying element (mo) have been synthesized [4, 5, 6]... 

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