Starch acetalation

Starch Acetalation with Aldehyde-amine, Aldehyde-amide... 

Starch Acetalation with Aldehyde-Amine, Aldehyde-Amide, and Aldehyde-Phenol Resins... 

Specific acetalation can be performed on starch dialdehyde. Unlike starch, acetalated by aldehydes, the aldehydo groups on starch dialdehyde lead to the formation of acetals with alcohols. Acetals are formed randomly along the macrochain, moreover, 1,4-dioxane rings (25 and 26) also formed as a result of new, hemiacetal bonds.425,426 In such a manner, an allylated derivative was prepared with the use... 

Mercaptolysis of starch dialdehyde occurs upon reaction with thiolacetic acid.525 It is possible that acetalation and crosslinking are involved in making a size consisting of starch dialdehyde, starch, and boric acid.526... 

A wide variety of reaction conditions have been proposed for the reaction of starch with aldehydes. Early studies entailed use of alkaline solutions, perhaps in order to gelatinize starch.1276 Because of the known behavior of aldehydes in alkaline media (Cannizzaro disproportionation and aldol condensations of aldehydes with active active a-methylene groups), this reaction has no simple outcome. However, a process of acetalation in alkaline solutions was subsequendy patented.1293 An exothermic reaction was observed within 3 4 min using an excess of formaldehyde. It was also reported that a,(3-unsaturated aldehydes reacted readily in slightly basic media.1294... 

Starch dialdehyde acetalated with pullulan was applied as a cathode-mix binder in dry-cell batteries1363 and in contact lenses.1364 It was also reported that starch dialdehyde, after animation with ethylenediamine and crosslinking with 1,5-pentandial, immobilized trypsin.1411 This preparation was proposed as a component of wound dressing. 

Preparation of a chlorostarch for improved pigment retention in paper has been reported.2278 Acetalation of chlorinated starches was described573 as a procedure for producing a high-strength paper size. 

Reaction conditions necessary to carry out the modifications described earlier in this section usually result in some decomposition of amylose and amylopectin, even when simple substitution, addition, or crosslinking are involved. As a rule, graft copolymerization produces derivatives of significantly increased molecular weight. Starch grafting usually entails etherification, acetalation, or esterification of starch with vinyl monomers to introduce a reaction site for the further formation of a copolymeric chain. Such a chain would typically consist of either identical or different vinyl monomers (block polymers), or it may be grafted onto another polymer altogether. 

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