LINEAR AND STAR-SHAPED HYBRID POLYMERS .4. PHOSPHOROLYTIC SYNTHESES WITH DI-FUNCTIONAL, OLIGO-FUNCTIONAL AND MULTIFUNCTIONAL PRIMERS

Studies on preparation of linear, star-, and comb-shaped polymers carrying amylose chains of uniform length grown by synthesis with potato phosphorylase are reported. Binding of malto-oligosaccharide primers (A) to different supports (B) was performed by the reaction of aldonolactone or N-(2-aminoethyl)aldonamide derivatives of malto-oligosaccharides with carriers respectively containing NH2 or CO2H groups. Synthetic products were converted into the tricarbanilate derivatives, and their hydrodynamic behavior was studied by light-scattering and viscosity measurements. The molecular-weight distribution was examined by 10-MPa l.c. Phosphorolytic syntheses with difunctional primers, A-B-A [with B = oligo(methylene) or oligo(oxyethylene)], proceed in the same way as with monofunctional primers. Both chain ends are elongated equally to amyloses of uniform length. Oligofunctional primers, (A)xB with x = 3, 4, and 6, lead to a mixture of components differing in the number of long branches, but with the amylose chains all having approximately uniform lengths. Compounds with two branches are preferentially formed. The results are discussed with regard to (a) the restrictions of the potato phosphorylase and (b) a model in which two primer ends from the oligofunctional substrate molecule are simultaneously bound to the active centers of the phosphorylase dimer. Compared with these densely packed primers, malto-oligomers attached to a linear backbone chain of poly(vinylamine) are attacked more easily. This can be explained by a greater flexibility of the poly(vinylamine) chain.