Starch employed in this study is a cornstarch purchased from Sigma-Aldrich Chemical Company. Other chemicals used for the synthesis were purchased from SigmaAldrich Chemical Company, and they were used as received without further purification. Natural clay (montmorillonite, MMT) and two commercial organoclays (Cloisite 30B and Cloisite 15A) used in the preparation of nanocomposites were provided by Southern Clay Products. EVOH contained 27 mol % of ethylene units.
- Synthesis of Chemically Modified Starch
- Preparation of Blends and Nanocomposites based on Modified Starch
- Characterization Methods
Synthesis of Anionically Modified Starch with Hexanoyl Group (AS-LF)
5 g of natural starch (NS) was added to a flask containing 150 ML isopropyl alcohol. The reaction mixture was vigorously stirred at room temperature for 60 min upon the addition of aqueous NaOH solution (10 ML, 5%). Sodium chloroacetate with a predetermined amount (based on the desired DS) was then added into the reaction mixture, and the temperature of the reactor was raised to 55 oC. The reaction was stopped after 6 h by pouring the reaction mixture into a beaker containing ethanol. The modified starch was precipitated from the ethanol. Then the product was filtered off. The anionically modified starch (AS) was stirred in anhydrous ethanol for at least 24 h and dried in a vacuum oven at 50 oC for 24h.
5g of dried AS was added to a flask containing 80 ML pyridine. The suspension was vigorously stirred at 115 oC for 60 min. The reaction system was connected to a condenser cooled by water. Hexanoyl chloride with a predetermined amount (based on desired DS) was added dropwise into the reaction mixture, and the temperature of the reactor was kept at 115 oC for 6 h. The reaction mixture was poured into a beaker containing ethanol. The product (AS-LF) was precipitated from the ethanol and filtered off. The product was stirred in anhydrous ethanol for at least 24 h and dried in a vacuum oven at 60 oC for 24 h.
Synthesis of Anionically Modified Starch with Benzoyl Group (AS-B)
5 g of dried AS was added to a flask containing 80 ML pyridine. The suspension was vigorously stirred at 115 oC for 60 min. The reaction system was connected with a condenser cooled by water. Benzoyl chloride with a predetermined amount (based on desired DS) was added dropwise into the reaction mixture, and the temperature of the reaction was kept at 115 oC for 6 h. The reaction mixture was poured into a beaker containing ethanol. The product (AS-B) was precipitated from the ethanol and filtered off. The product was stirred in anhydrous ethanol for at least 24 h and dried in a vacuum oven at 100 oC for 12 h.
Synthesis of Cationically Modified Starch with Hexanoyl Group (CS-LF)
5 g of natural starch was added to a flask containing 100 ML aqueous NaOH solution (5%). The reaction mixture was vigorously stirred at room temperature for 60 min. Then glycidyltrimethylammonium chloride with a predetermined amount (based on the desired DS) was added dropwise into the reaction mixture, and the temperature of the reaction was raised to 60 oC. The reaction was stopped after 6 h by pouring the reaction mixture into a beaker containing ethanol. The product (CS) was precipitated from the ethanol and filtered off. The CS was stirred in anhydrous ethanol for at least 24 h and dried in a vacuum oven at 50 oC for at least 24 h.
5 g of CS was added to a flask containing 80 ML pyridine. The suspension was vigorously stirred at 115 oC for 60 min. The reaction system was connected with a condenser cooled by water. Hexanoyl chloride with a predetermined amount (based on desired DS) was added dropwise into the reaction mixture, and the temperature of the reaction was kept at 115 oC for 6 h. The reaction mixture was poured into a beaker containing ethanol. The product (CS-LF) was precipitated from the ethanol and filtered off. The product was stirred in anhydrous ethanol for at least 24 h and dried in a vacuum oven at 60 oC for 24 h.
Synthesis of Cationically Modified Starch with Benzoyl Group (CS-B)
5 g of CS was added to a flask containing 80 ML pyridine. The suspension was vigorously stirred at 115 oC for 60 min. The reaction system was connected with a condenser cooled by water. Benzoyl chloride with a predetermined amount (based on desired DS) was added dropwise into the reaction mixture, and the temperature of the reaction was kept at 115 oC for 6 h. The reaction mixture was poured into a beaker containing ethanol. The product (CS-B) was precipitated from the ethanol and filtered off. The product was stirred in anhydrous ethanol for 24 h and dried in a vacuum oven at 100 oC for 12 h.