INTRODUCTION:

Biodegradable polymers have been widely investigated nowadays. Carbohydrate polymers specifically polyesters are most studied biodegradable polymers. Synthesis and Characterization of biodegradable low molecular weight aliphatic esters and their delivery in protein delivery systems is recently studied by some workers (Zhou et al., 2004). Polymers based on carbohydrates have emerged as exciting topic of polymer research due to worldwide focus on sustainable materials. Almost all walks of life needs paradigmatic shift from petroleum and non renewable source towards sustainable materials. The polymers based on carbohydrates dates back to as early as the 1930s. Reppe was the first to synthesis vinyl saccharide monomer. He synthesized ethers from glucose and fructose by alkali catalyzed addition of protected sugars to acetylene (Reppe; 1930). Functionalization of polymers has emerged as another important area of research in polymer science and technology. The polymers containing carbohydrates are useful in various fields like pharmacological and biomedical applications (Kobayashi et al; 1985), in synthetic fibers like nylon type from 1,6- diaminosugars and dibasic acids (Bird et al; 1960).

Very few workers have worked on polymers synthesized from maleic anhydride (Vaidya and Bhattacharya, 1993; Dontulwar et al, 2006). The esters of carbohydrates are completely soluble in water and found to be sutaible in detergent formulation (Dontulwar et al; 2006). The detergent made out of acid slurry cause harm to aquatic flora and fauna. Acid slurry has petroleum origin. The detergents of petroleum origin are responsible for foaming and eutrophication. By using biodegradable polymers in detergent formulation the above said problem of water pollution can be minimized to a greater extent. In our earlier work, we discussed the synthesis of biodegradable polymers from sorbitol, white dextrine and maleic anhydride (Dontulwar et al, 2006) and starch, glycerol and maleic anhydride (Dontulwar et al, 2006).

The present work encompasses the synthesis of polymer from starch, glycerol, sorbitol, maleic anhydride as precursor using water as solvent and HCl as catalyst in order to see its application in detergent formulation. The application of this polymer will be presented elsewhere.

MATERIALS AND METHODS:

A glass reactor fitted with stirrer, heating mantle and condenser was used for the synthesis of polymers. The temperature control of 2ºC was achieved by using an efficient temperature regulator. A constant water supply through a condenser helps to control reactor temperature. Initially stoichiometric quantity (Table 1) of starch, glycerol, sorbitol, maleic anhydride was added in the reactor. Hydrochloric acid was used as a catalyst. About 200 ml of water was added to get free flowing homogenous paste. The temperature was raised to 120ºC slowly and steadily in the intervals of 0.5 hour. The reaction was continued for 3.5 hour till the desired molecular weight was achieved. The consistency of the paste was maintained by adding additional water after 0.5 hour. At the end of this period, the reaction was stopped and the prepared polymer was collected in a glass-stoppered bottle with least air gap. The cooking schedule of the polymer synthesis is given in Table 2. The final yield of the product was weighed. The molecular weight of the polymer was determined by viscosity average method using Redwood viscometer. The acid value and the sap value and other physical constants were determined by standard methods (Bacher, 1960). The polymer formed was believed to be an ester of carbohydrate which was corroborated by spectral studies. The biodegradable evidence was obtained through BOD and COD studies. The COD of the synthesized polymer was found to be 1124829.87 mg/g of the polymer. For BOD study, the bacteriological seed was brought from bacteriological reactor of food industry and preserved at 37^oC in laboratory. The seed was activated by adding the nutrients as phosphate buffer, dextrose and ammonium chloride in sufficient quantity. The seed was then aerated for 48 hours and multiplied. This activated seed was inoculated or added to dilute polymer sample (0.241g in 500 ml water) for analysis and subsequent BOD of the dissolved resin was estimated for 10 days. The results are described in Table 5.

Table 1: Stoichiometric proportion of components in polymer synthesis

Sr. No.	Raw Material	Concentration (%)
1	Starch	30.78
2	Glycerol	26.92
3	Sorbitol	26.92
4	Maleic Anhydride	15.38
5	Water as solvent	1000 ml (Total)

Table 2: Cooking schedule of polymer

Time	Temperature (^oC)	Remarks
00:00	Room Temperature	600 g water added and batch started
00:30	48	-
01:00	75	-
01:30	95	-
02:00	100	-
02:10	101	300 g water added
02:30	103	Thickening of batch started
02:40	105	200 g water added
02:50	106	300 g water added
03:00	108	Batch Turned viscous
03:10	108	-
03:30	116	Batch terminated

RESULTS AND DISCUSSION:

The synthesis of polymer from starch, glycerol, sorbitol, and maleic anhydride was performed in the presence of HCl as catalyst at 120^oC. The physiochemical properties are shown in Table 3. Figs. 1 and 2 show the IR and NMR spectra, respectively, of the synthesized polymer. The IR spectrum of the polymer is given in Fig 1. The various prominent peaks of the IR spectra observed for the polymer are given Table 4. The peak at 3402.3 cm^-1 is due to O-H stretching. The peak at 3402.3 cm^-1 shows the presence of –OH groups in the polymer molecule. The peak at 2935.9 cm^-1 is revealing the =C-H stretching. We have two peaks at 1720.2 cm^-1 and 1221.1 cm^-1 respectively which are the characteristics peaks for ester group. These two peaks i.e. at 1720.2 cm^-1 and 1221.1 cm^-1 combine confirm the presence of O ll –O-C- group in the polymer. The peak at 1637.1 cm-1 is due to C=C stretching. The presence of esteric group was later on confirmed by NMR spectra (Fig 2). The prominent NMR (Fig 2) peaks are observed in 3.38-3.768 ppm range suggest the presence of an esteric proton in the polymer. This peak along with peak at 2935.9 cm-1 (=C-H stretch) in IR spectra is giving confirmation to the idea of presence of –C=C-H group in the polymer. Thus the IR and NMR spectroscopy proved the presence of O ll -O -C -CH group in the polymer. This study supports the predicted chemical reaction i.e. esterification and presence of an esteric group. The carbohydrate polymer formed out of starch, glycerol, sorbitol, and maleic anhydride was studied in order to see the its biodegradable nature. The results (Table 5) show 22% degradation of BOD on first day which increases to 60% on the 6th day. The results also show the drastic degradation which was compared with normal BOD estimation of 6 (Fig. 3). The application of the synthesized polymer with respect to detergent formulation was checked by HLB value. The HLB value of 11.88 is indicative of the use of the polymer in detergent formulation and in some cases for paints, inks and emulsions, etc. The polymer is soluble in water and NaOH and insoluble in organic solvent xylene and alcohol and is partially soluble in alcohol-water (1:1) mixture.

Table 3: Physico-chemical properties of polymer

Sr. No.	Polymer Property	Observation
1	Acid value of the polymer	57.1
2	pH value	2.00
3	Saponification value	385.35
4	Solid (%)	64
5	Colour	White
6	Solubility of polymer In water In xylene In alcohol+water In NaOH solution	Soluble Insoluble Partially soluble Soluble
7	HLB of Polymer	11.88
8	MW of the polymer	1863

Figure 1: I.R. spectra of polymer

Table 4: The prominent peaks of the IR spectra of polymer

Peaks (cm^-1)	Groups
3402.3	O-H stretching
2935.9	C-H stretching
1720.0	C stretching
1637.1	C=C stretching
1221.1	C-O stretching
771.4
922.7	=C-H bending
1041.4

Figure 2: NMR spectra of polymer

Table 5: Biodegradation study of the polymer

Sr. No.	Particulars	Concentration (mg/g)
Sr. No.	Particulars	BOD at 20^oC	COD	BOD:COD
1	After 1^st day	248962.65	1124829.87	0.2213
2	After 2^nd day	298755.18	-	0.2656
3	After 3^rd day	622406.63	-	0.5533
4	After 4^th day	634854.77	-	0.5644
5	After 5^th day	647302.90	-	0.5754
6	After 6^th day	672199.17	-	0.5976
7	After 7^th day	647302.90	-	0.5754
8	After 8^th day	622406.63	-	0.5533
9	After 9^th day	398340.20	-	0.3542
10	After 10^th day	373443.98	-	0.3320

Figure 3: Trend of BOD with Time

The polymer with M. W. 1863 g/mol was synthesized by direct condensation using HCl as catalyst. The polymer was an ester based on starch, glycerol, sorbitol, and maleic anhydride. The polymer was biodegradable in nature. The polymer can be used in the detergent formulation, paints, inks, emulsions, etc. The polymer was soluble in water and NaOH.

REFERENCES:

1. Bacher Mehlem V.C. (1960), The analysis of Fats and Oils , Garrard Publication, Champaign- Illionois pp 105 ( For the acid value)

2. Bacher Mehlem V.C. (1960), The analysis of Fats and Oils , Garrard Publication, Champaign- Illionois pp 299-308 ( For the sap value)

3. Bird , T.P.; Black, W. A.P., Dewar, E. and Rutherford, D. (1960) Chemical Industry (London), 1331

4. Dontulwar, J.R.; Borikar, D. K.; Gogte, B.B., Carbohydrate Polymers, 63 (2006) 375-378

5. Dontulwar, J.R.; Borikar, D. K.; Gogte, B.B., Carbohydrate Polymers, 65 (2006) 207-210

6. Kobayashi, K.; Sumitoma, H. and Ina, Y. (1985) Polymer Journal, 17,567-575

7. Reppe, W. (1930) DRP 584840,714490

8. Vaidya, U. R. and Bhattchrya, M. (1993), PCT Int. Application WO 9323456

9. Zhou, S.; Deng, X.; Li, X.; Jia w.; Liu. L. (2004), J. Appl. Polymer Sc., 91, 1848-1856

Received on 11.04.2011 Modified on 02.05.2011

Asian J. Research Chem. 4(7): July, 2011; Page 1084-1086