Final Report: Aqueous Processing of Biodegradable Materials from Renewable ResourcesEPA Grant Number: R826117
Title: Aqueous Processing of Biodegradable Materials from Renewable Resources
Investigators: McCarthy, Stephen P. , Koroskenyi, Balint , Zhang, Jinwen
Institution: University of Massachusetts - Lowell
EPA Project Officer: Richards, April
Project Period: November 1, 1997 through October 31, 2000 (Extended to December 31, 2001)
Project Amount: $300,004
RFA: Technology for a Sustainable Environment (1997) RFA Text | Recipients Lists
Research Category: Nanotechnology , Sustainability , Pollution Prevention/Sustainable Development
The objective of this research project was to obtain intermediate products for commercial bulk applications, in areas such as packaging or health care, from naturally available, abundant, raw materials such as chitosan and konjac, which are inherently biodegradable and environmentally friendly. The focus was to find potential comparable alternatives for the petroleum-based conventional polymeric materials, which are not prone to biological degradation and, therefore, are a growing concern for environmental pollution today. The research focused specifically on ?green? conversion processes, which cause minimal impact on the environment in terms of utilization of hazardous chemicals, energy, and water. The conversion of raw materials into products should mainly involve aqueous processing techniques such as aqueous chemistry, extrusion, and film casting from aqueous solutions.
Research conducted in the period covered by this report included the preparation of chitosan hollow fibers for bile acid sequestrants; synthesis of aminated polysaccharide derivatives for cholesterol-lowering drugs, which could be used alone or in combination with the chitosan hollow fiber; and comparison of different polysaccharides, mainly konjac, for natural hypoglycemic agents. Another specific goal of the project was the synthesis of biodegradable polymers in solvent-free or aqueous systems, using microwave radiation as the energy source to extend green chemistry throughout the entire life cycle of biodegradable polymeric materials.
Chitosan samples of different degree of acetylation have been successfully prepared. Because the degree of substitution (DS) probably has a critical effect on the bile acid binding power, it is important to investigate the optimum value. Animal studies on chitosan samples of varying degree of acetylation (DS = 5, 20, 30, 40) are in progress. For the hollow fiber spinning, a spinning line is being built and fiber spinning will be tested in the future.
Konjac has been successfully acetylated to a high degree (up to DS = 2.6). The water absorbency was thereby reduced from 16 g/g to about 4-5 g/g. If the product retained its cholesterol-lowering property, it would be an excellent candidate for a corresponding drug. Animal studies on a sample of DS=2.5 to determine its ability to bind cholesterol is currently in progress. If the cholesterol-lowering property is reduced with reduced water absorbency, further optimization of the degree of acetylation may be required. This will be conveniently done by varying the reaction time or the temperature.
A method has been elaborated for the efficient grafting of konjac with polyacrylics. Although significant increase in the water absorbency has not yet been observed, appropriate modification of the product should result in a superabsorbent. Further investigations in this direction will be conducted. The degree of grafting and the extent of crosslinking will be varied.
The simplest way of crosslinking konjac is evidently the esterification of the hydroxyl groups with a diacid. Because the water absorbency of acylated with succinic anhydride is reduced at higher DS values, this method fails to provide the desired superabsorbent. However, acylation of konjac with succinic acid under different conditions may result in the formation of a network of high water absorbency. For example, acylation with succinyl chloride in the presence of a base seems to be a promising approach. Further studies are in progress. Crosslinking also can be accomplished by esterifying the hydroxyl groups of konjac with carboxylic side groups of a polymer such as poly(acrylic acid). However, poly(acrylic acid) is not biodegradable; therefore, little would be gained over the currently used superabsorbents. Polymers of hydroxy acids with carboxylic side groups, however, seem to be excellent candidates. A study on the possible application of malic acid, whose polymer is biodegradable, has been initiated.
The microwave-assisted synthesis of various biodegradable polysaccharides gave superior results for both polysaccharide derivatives and polyesters. Successful derivatization of polysaccharides has been achieved using microwave radiation. Relatively high DS values were obtained without the use of hazardous organic solvents with various reagents. Although acetylation is limited due to the rapid escape of acidic anhydride from the reaction system, succinates of medium DS can be prepared even in the absence of solvent. Carboxymethylation was conducted both with chloroacetic acid and glyoxylic acid to obtain considerable extent of substitution. The results are very promising, and point in the direction of the possibility of even higher DS after adequate modification of the apparatus. Refluxing the highly volatile components would likely allow more extensive reactions. The efficiency of energy utilization and the reduction of reaction time are evident. The method is superior to conventional heating for the synthesis of derivatives of low or medium DS, even without modification of a commercially available microwave oven. Amination of starch proved more successful than conventional heating, resulting in a nearly twofold increase in the DS value in significantly reduced reaction time. Amination of chitosan in alkaline medium only led to medium DS values, probably due to reduced swelling at high pH.
Journal Articles on this Report : 2 Displayed | Download in RIS Format
|Other project views:||All 4 publications||2 publications in selected types||All 2 journal articles|
||Koroskenyi B, McCarthy S. Synthesis of acetylated konjac glucomannan and effect of degree of acetylation on water absorbency. Biomacromolecules 2001;2(3):824-826.||
||Koroskenyi B, McCarthy SP. Microwave-assisted solvent-free or aqueous-based synthesis of biodegradable polymers. Journal of Polymers and the Environment 2002;10(3):93-104.||