**3.3 Infrared analysis**

The IR spectra of xylans (**Figure 5**), and more particularly of 4-Omethylglucuronoxylans, have been studied in detail by Marchessault and Liang (1962) (see [33]) and more recently by Kacurakovaet*coll*. (2000) (see [34]). The absorption bands appearing in the figure and listed in the table are characteristic of xylans of type (1 → 4), with a maximum absorption band at 1044 cm−1, corresponding to the vibrations of elongation of the ring bonds and C-OH bonds. The weak, but very clear band at 896 cm−1 is characteristic of glycosidic type bonds [35].

**Figure 2.**

*Scheme of fractionalizationof 4-O-methylglucuronoxylans (MGX) from chestnut wood.*

#### **Figure 3.**

*Structure of 4-O-methylglucuronoxylan extracted from Castanea sativa.*


**321**

**4. The results**

*FT-IR spectra of xylan.*

**Figure 5.**

**Figure 4.** *1*

*H NMR spectra of xylan (D2O).*

are calculated from 1

The synthesis of the biodegradable xylan-g-PLLA copolymers is carried out at atmospheric pressure by opening the L-lactide ring and the DMAc/LiClxylan solution (0.2 g/l) in the presence of DMAP as catalyst. The degree of substitution and the degree of polymerization express the efficiency of the grafting reaction. They

number of grafted PLLA chains per repeat unit which is calculated by comparing the integration of the 3 protons of the terminal CH3 with the equatorial proton H5 of xylose. The medium DP, meanwhile, is calculated by comparing the integration of internal CH3s with terminal CH3s. The yield is defined as the ratio between the

It should be noted that the DS and the DP show that the latter both increase with the amount of L-lactide and the DMAP and decrease beyond the 16 h time.

weight of plastic film and the initial weight of polysaccharide.

H NMR spectra. The medium DS is defined as the medium

*Chemical Modification of Xylan*

*DOI: http://dx.doi.org/10.5772/intechopen.94208*

#### **Table 1.**

*Chemical shifts of glycosidic residues of xylan (D2O).*

#### *Chemical Modification of Xylan DOI: http://dx.doi.org/10.5772/intechopen.94208*

*Biotechnological Applications of Biomass*

**3.2 RMN**

The result of 1

**3.3 Infrared analysis**

products. This MGX is represented in **Figure 3**.

Xyl/4-*O*-MeGlcA ratio was found: 6.1. However, concerning the size of the extracted molecules, a DP of about 200 was found which is a typical result for this kind of

4-Omethylglucuronoxylans, have been studied in detail by Marchessault and Liang (1962) (see [33]) and more recently by Kacurakovaet*coll*. (2000) (see [34]). The absorption bands appearing in the figure and listed in the table are characteristic of xylans of type (1 → 4), with a maximum absorption band at 1044 cm−1, corresponding to the vibrations of elongation of the ring bonds and C-OH bonds. The weak, but very clear band at 896 cm−1 is characteristic of glycosidic type bonds [35].

The IR spectra of xylans (**Figure 5**), and more particularly of

*Scheme of fractionalizationof 4-O-methylglucuronoxylans (MGX) from chestnut wood.*

*Structure of 4-O-methylglucuronoxylan extracted from Castanea sativa.*

H 4,48 (7,5)

*Chemical shifts of glycosidic residues of xylan (D2O).*

*H NMR spectra of xylan (D*2*O) is presented in* **Table 1** and **Figure 4**.

**Chemical shifts in ppm (J en Hz) 1 2 3 4 5**

3,79 4,10 (4,5; 11,5);

3,38 (11,0)

3,55 (9,0)

3,29 (8,2)

**320**

**Table 1.**

**Figure 2.**

**Figure 3.**

**Glycoside residues**

(1 → 4)- D-Xylp <sup>1</sup>

**Figure 4.** *1 H NMR spectra of xylan (D2O).*

**Figure 5.** *FT-IR spectra of xylan.*

#### **4. The results**

The synthesis of the biodegradable xylan-g-PLLA copolymers is carried out at atmospheric pressure by opening the L-lactide ring and the DMAc/LiClxylan solution (0.2 g/l) in the presence of DMAP as catalyst. The degree of substitution and the degree of polymerization express the efficiency of the grafting reaction. They are calculated from 1 H NMR spectra. The medium DS is defined as the medium number of grafted PLLA chains per repeat unit which is calculated by comparing the integration of the 3 protons of the terminal CH3 with the equatorial proton H5 of xylose. The medium DP, meanwhile, is calculated by comparing the integration of internal CH3s with terminal CH3s. The yield is defined as the ratio between the weight of plastic film and the initial weight of polysaccharide.

It should be noted that the DS and the DP show that the latter both increase with the amount of L-lactide and the DMAP and decrease beyond the 16 h time. In addition, it has been proven that DMAP is used as a hyper nucleophilia catalyst which is 104 times more active than pyridine [10], this is more favorable when the reaction time is longer, favoring depolymerization reactions. The maximum conditions for having a larger DS and DP are: 16 h, 8 eq/OH, 1 eq/OH.
