1‐allyloxy‐2‐hydroxy‐propyl‐starch: Synthesis and characterization

New reactive unsaturated starch derivatives, 1‐allyloxy‐2‐hydroxy‐propyl‐starches (AHP‐starches), were synthesized by the reaction of waxy maize starch (WMS) and amylose‐enriched maize starch (AEMS) with allyl glycidyl ether in a heterogeneous alkaline suspension containing NaOH and Na₂SO₄. The degree of substitution (DS) was determined by ¹H NMR spectroscopy, and a DS of 0.20 ± 0.01 was found for both AHP‐WMS and AHP‐AEMS, respectively. The AHP derivatives of WMS and AEMS were further characterized with ¹H and ¹³C NMR. It was shown that the AHP substitution was located on the C‐6 hydroxyl group of the glucose residues in the starch. The substitution pattern of the AHP groups along the polymer chain was randomly clustered, as determined by enzymatic digestion using pullulanase, α‐amylase, and amyloglucosidase, followed by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry analysis of the digestion products. With X‐ray diffraction and scanning electron microscopy, no changes in the granular morphology and crystallinity between the unmodified starches and AHP‐starches were detected. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2734–2744, 2007