Mixed Esters of Amylose

Wolff, I. A.; Olds, David W.; Hilbert, Guido E.

doi:10.1021/ie50572a027

Cited by 19 publications

(6 citation statements)

References 2 publications

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“…The insertion of binary mixed acids to starch was first seen several decades ago for amylose with a combination of formic acid, acetic, propanoic and benzoic acids [19]. These processes imparted the film softer and moldable properties.…”

Section: Glass Transition Temperaturementioning

confidence: 99%

Preparation and Physical Properties of Starch Mixed Esters

Yang

Montgomery

2008

Starch Stärke

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The use of trifluoroacetic anhydride as a promoter for the preparation of mixed esters of granular starch is reported. Efficient esterification results in complete dissolution of the starch granules, which is attained without the use of an external heat source when trifluoroacetic anhydride was added incrementally to a starch slurry in the mixed carboxylic acids. Starch mixed esters are co-acetate/butyrate, co-acetate/hexanoate, co-acetate/octanoate, co-acetate/palmitate and co-acetate/butyrate/hexanoate/ octanoate/palmitate, each from a solution of the corresponding mixed acids. The products comprise a total degree of substitution . 2.5, as analyzed by gas-liquid or high-pressure liquid chromatographies. In each product the extent of acid substitution is the same as or close to the composition of the corresponding acid distribution in the reaction mixture. Films cast of the resulting mixed esters, together with the corresponding single acid esters, are analyzed for glass transition and tensile properties, as measured by a dynamic mechanical analyzer. Glass transition temperature and tensile modulus increase proportionally with the increased mole fraction of acetate within the starch mixed acids. Film elongation increases with increases of acyl chain length in all of the starch esters. The dependency of those properties on the relative distribution of acyl group is discussed.

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Section: Glass Transition Temperaturementioning

confidence: 99%

Preparation and Physical Properties of Starch Mixed Esters

Yang

Montgomery

2008

Starch Stärke

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“…The best known examples of highly substituted starch derivatives are esters containing acetate, fatty acid or mixed ester groups [15][16][17][18][19][20][21][22]. To achieve a high degree of substitution, reaction conditions are rather drastic, using organic solvents and acyl chlorides or anhydrides as esterifying agents and pyridine as a catalyst.…”

Section: Introductionmentioning

confidence: 99%

Effect of Reaction Conditions and Alkyl Chain Lengths on the Properties of Hydroxyalkyl Starch Ethers

Funke¹,

Lindhauer²

2001

Starch/Stärke

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Starch applications in the plastics industry have been investigated intensively for many years. Unfortunately, native starch is unsuitable for most applications in polymers, because of its hydrophilic and brittle character. Modification of native starch can be a solution of this problem.In our research programme we developed an environmentally friendly process for the preparation of starch derivatives with long hydrophobic side chains based on natural products derived from vegetable fats and oils on the one hand and amylomaize starch on the other hand. In this process modification is carried out by the addition of longchain 1,2-epoxyalkanes (chain lengths varying between 6-18 C atoms) to starch in an alkaline aqueous medium. Reaction yields and molar degrees of substitution depended on chain length, reaction time, temperature and catalyst concentration. Under optimised reaction conditions molar degrees of substitution of hydroxyalkyl starch ethers for theoretical molar substitution (MS) = 3.0 decreased from MS=1.8 (C 6 starch ether) to MS=0.2 (C 18 starch ether), respectively. Hydrophobic properties of starch products were measured in order to reveal structural effects obtained at different reaction conditions. Water solubility and water absorption properties of hydroxyalkyl starch ethers decreased with increasing chain length and number of hydroxyalkyl substituents. Thermal and thermoplastic properties of starch ethers were investigated in order to determine their potential use as biodegradable polymers in the plastics industry. As expected, thermoplasticity of starch ethers increased with increasing MS and increasing chain length of the hydroxyalkyl side groups. Scheme 1. Reaction scheme for the preparation of hydroxyalkyl starch ether (MS = 1).

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“…Amylose triacetate film, like that from cellulose acetate undergoes orientation (6) when drawn. Films from mixed esters of cellulose and amylose are also similar (8).…”

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confidence: 84%