**5. Biodestruction**

440 Polyurethane

complexes. In particular chelate structure of copper ion (2+) complexes with PGU is confirmed in (Hubina et al., 2010). Using results of (Bergman et al., 2008; Hubina et al., 2010)

Analysis influence of cross-linking degree of PGU on complexing metal ions with functional groups of PGU demonstrated that variation of hydroxyl and urethane groups balance in the

Peculiarities of "PGU-copper ion" complex formation were studied using electron paramagnetic resonance method (EPR). Copper ions were introduced into PGU matrix via pumping of 0,1M water solution of CuSO4 through column filled with PGU60 (the way it described above for dynamic sorption conditions). Then metal-containing PGU sample was dried and the EPR spectra of bivalent copper were recorded. Fig. 8 demonstrates EPR

Recorded spectra are characterized with anisotropy of g-factor and appearance of hyperfine structure in the region of g║ that is usually concerned to tetragonal chelate complexes of bivalent copper. Hyperfine structure components are broadened as a result of superposition of signals from tetragonal copper complexes which can differ both in symmetry distortion and in nearest chemical surrounding. Integral intensity of obtained EPR spectra depends on the balance of hydroxyl and urethane group in PGU while electron spin parameters are almost unchanged. That points on preferable interaction of metal cation with one of the components of PGU. This conclusion corresponds with the regularities of bivalent copper

system allows to achieve effective control over holding metal ions in PGU matrix.

spectrum of dried PGU60 after interaction with copper sulfate water solution.

ion complexing with mono saccharides.

scattering.

**Figure 8.** The representative EPR spectrum of copper containing PGU

Experimental analysis of influence of metal ions on water molecules self diffusion process in swelled polysaccharide gel was carried out by the method of quasi-elastic neutron

we can assume that cobalt ions also form chelate structures with PGU.

Used plastics utilization had become an important problem. One of the ways of polymer and in particular of polyurethane waste reclamation is biodegradation of plastic. The ability to biodegradation was analized on the PGU exposed in the medium of common soil microorganisms association as well as into the medium of resistive microbial association isolated from soils polluted by chlorine-organic pesticides. (Hubina et al., 2009). There were explored biodegradable properties of two types of PGU20: based on microbial polysaccharide xanthan (PGU20) and methylcellulose (PGU20-cellulose).

Polyglucanurethanes: Cross-Linked Polyurethanes Based on Microbial Exopolysaccharide Xanthan 443

Other type of PGU destruction is observed in natural medium (fig. 10 Spectrum 2). It is approved by redistribution of intensities of valence vibrations of C-O-C groups comparing with initial PGU and by absence of prominent changes in area of amide II. The band at 805 cm-1 responding to intercycle C-O-C bonds disappears. It is accompanied by increasing of intensity of the band responding to free OH-group (3430 cm-1) and C-H bonds (2850 and 2920 cm-1).

Another evidence of sufficient urethane bonds destruction in PGU20 in aggressive medium is seen on microphoto of PGU films after aggressive destruction (Fig. 11). There can be distinguished fibrous polymer elements, usual for fibrous of initial polysaccharide xanthan, which formed after urethane destruction. This effect is absent on the micro photos of PGU

 1 2 3 1 – initial polysaccharide fibers; 2 - effect of aggressive microbial medium; 3 – effect of natural microbial medium. **Figure 11.** Micro images of PGU films after contact with natural and aggressive microbial mediums

IR spectra of PGU20-cellulose present the difference between this polymer biodestruction

In particular, the intensity of the band in area 1600 – 1660 cm-1 falls both for natural medium and aggressive one. (Fig.13 stectra 2 and 3). Intensity of 809 cm-1 band decreases (valence vibrations of intercycle bonds C-O-C) after exposure of PGU20-cellulose in natural microbial medium (Fig.12 spectrum 2) differing from intensity of this band in PGU20-cellulose spectrum after contact with aggressive medium. Bands corresponding to symmetric and

Efficient difference in biodestruction character of PGU20-xanthan and PGU20-cellulose allows conclude that xanthan based PGU is destructed mainly in its saccharide side-chains

IR data correlate with results of TGA analysis. Table 3 shows difference in character of TG, DTG and DTA curves for PGU20-cellulose after contact with aggressive and natural medium. On DTG curves of PGU20-cellulose after natural and aggressive medium it is seen that stage of thermal destruction in temperature interval 200 – 300 oC is moved into district of higher temperatures while in PGU40-xanthan this stage is splitted and differs for natural

asymmetric vibrations of saccharide groups C-O-C are nearly unchanged.

(containing D-mannose, D- glucuronic acid and D-glucose).

sample after destruction in natural microbial medium .

and biodestruction of PGU20-xanthan (Fig. 12)

and aggressive medium.

The resistant microbial association with working name "Micros" was isolated from soil polluted by chlorine-organic pesticides. This association has high destructive activity with respect to chlorine-organic, organic-phosphorous, simm-triazine and other pesticide groups. It was supposed, that "Micros" is able to specialize to exotic substratum and could decompose polyglukanurethane systems due to utilization of this polymer as carbon or nitrogen source. To compare destruction of the PGU by common soil microorganisms the soil native-born microbial association was isolated from pollution-free chernozem soil. It has never contacted with pollutants in soil.

Changes in polymer structure after exposure in microbial medium were analyzed by FTIR spectroscopy, optical microscopy and thermogravimetry. Fig presents IR – spectra of PGU20 after contact with aggressive and natural microbial medium. Evaluation of redistribution of bonds in destructed PGU was provided by analysis of the location, width and intensity of valence vibrations band of C-O-C intercycle group of polysaccharide (805 cm-1) and also by analysis of location and intensity of band amide II) in PGU urethane bridges (1600 1660 cm-1).

In PGU spectrum after the sample contact with aggressive medium (spectrum 3 fig 10) it is seen resolving of complex band at 1600 – 1660 cm-1 (N-H vibrations) comparing to initial PGU20 spectrum (Fig.10 spectrum 1). This may be caused by destruction of essential part of urethane bonds of PGU in aggressive medium.

**Figure 10.** IR spectra of PGU20 based on xanthan 1 – initial PGU, 2 – PGU after contact with natural microbial medium, 3 – PGU after contact with aggressive microbial medium

Other type of PGU destruction is observed in natural medium (fig. 10 Spectrum 2). It is approved by redistribution of intensities of valence vibrations of C-O-C groups comparing with initial PGU and by absence of prominent changes in area of amide II. The band at 805 cm-1 responding to intercycle C-O-C bonds disappears. It is accompanied by increasing of intensity of the band responding to free OH-group (3430 cm-1) and C-H bonds (2850 and 2920 cm-1).

442 Polyurethane

cm-1).

to biodegradation was analized on the PGU exposed in the medium of common soil microorganisms association as well as into the medium of resistive microbial association isolated from soils polluted by chlorine-organic pesticides. (Hubina et al., 2009). There were explored biodegradable properties of two types of PGU20: based on microbial

The resistant microbial association with working name "Micros" was isolated from soil polluted by chlorine-organic pesticides. This association has high destructive activity with respect to chlorine-organic, organic-phosphorous, simm-triazine and other pesticide groups. It was supposed, that "Micros" is able to specialize to exotic substratum and could decompose polyglukanurethane systems due to utilization of this polymer as carbon or nitrogen source. To compare destruction of the PGU by common soil microorganisms the soil native-born microbial association was isolated from pollution-free chernozem soil. It has

Changes in polymer structure after exposure in microbial medium were analyzed by FTIR spectroscopy, optical microscopy and thermogravimetry. Fig presents IR – spectra of PGU20 after contact with aggressive and natural microbial medium. Evaluation of redistribution of bonds in destructed PGU was provided by analysis of the location, width and intensity of valence vibrations band of C-O-C intercycle group of polysaccharide (805 cm-1) and also by analysis of location and intensity of band amide II) in PGU urethane bridges (1600 1660

In PGU spectrum after the sample contact with aggressive medium (spectrum 3 fig 10) it is seen resolving of complex band at 1600 – 1660 cm-1 (N-H vibrations) comparing to initial PGU20 spectrum (Fig.10 spectrum 1). This may be caused by destruction of essential part of

**Figure 10.** IR spectra of PGU20 based on xanthan 1 – initial PGU, 2 – PGU after contact with natural

microbial medium, 3 – PGU after contact with aggressive microbial medium

polysaccharide xanthan (PGU20) and methylcellulose (PGU20-cellulose).

never contacted with pollutants in soil.

urethane bonds of PGU in aggressive medium.

Another evidence of sufficient urethane bonds destruction in PGU20 in aggressive medium is seen on microphoto of PGU films after aggressive destruction (Fig. 11). There can be distinguished fibrous polymer elements, usual for fibrous of initial polysaccharide xanthan, which formed after urethane destruction. This effect is absent on the micro photos of PGU sample after destruction in natural microbial medium .

1 – initial polysaccharide fibers; 2 - effect of aggressive microbial medium; 3 – effect of natural microbial medium. **Figure 11.** Micro images of PGU films after contact with natural and aggressive microbial mediums

IR spectra of PGU20-cellulose present the difference between this polymer biodestruction and biodestruction of PGU20-xanthan (Fig. 12)

In particular, the intensity of the band in area 1600 – 1660 cm-1 falls both for natural medium and aggressive one. (Fig.13 stectra 2 and 3). Intensity of 809 cm-1 band decreases (valence vibrations of intercycle bonds C-O-C) after exposure of PGU20-cellulose in natural microbial medium (Fig.12 spectrum 2) differing from intensity of this band in PGU20-cellulose spectrum after contact with aggressive medium. Bands corresponding to symmetric and asymmetric vibrations of saccharide groups C-O-C are nearly unchanged.

Efficient difference in biodestruction character of PGU20-xanthan and PGU20-cellulose allows conclude that xanthan based PGU is destructed mainly in its saccharide side-chains (containing D-mannose, D- glucuronic acid and D-glucose).

IR data correlate with results of TGA analysis. Table 3 shows difference in character of TG, DTG and DTA curves for PGU20-cellulose after contact with aggressive and natural medium. On DTG curves of PGU20-cellulose after natural and aggressive medium it is seen that stage of thermal destruction in temperature interval 200 – 300 oC is moved into district of higher temperatures while in PGU40-xanthan this stage is splitted and differs for natural and aggressive medium.

Polyglucanurethanes: Cross-Linked Polyurethanes Based on Microbial Exopolysaccharide Xanthan 445

New hydroxylcontaining polyurethane networks (polyglucanurethane) with various urethane group content were obtained based on microbial exopolysaccharide xanthan and latent blocked polyisocyanate using environment friendly technique. Obtained polyglukaneurethanes possess advanced thermal and chemical (both alkali and acid) resistance. Thermal resistance of PGU grows with increasing of urethane group amount. Were as with growth of urethane group

Study of properties of polyglucanuretanes reveals their ability to quantitative extraction of phenol and bivalent metal ions from water solution, while controlling sorption properties of the material with polysaccharide cross-linking degree. According to electron spectroscopy and EPR data the main mechanism of ion capture by polyglucanurethane consists in

Biodestruction research demonstrate that polyglucanurethane degradation in aggressive microbial media occurs via polysaccharide fragmentation due to urethane bonds cleavage. On the contrary microbial association that was isolated from pollution-free chernozem

But both in aggressive microbial association and in natural microbial association that was isolated from pollution-free soil the direct relation was observed between destruction process intensity and percentage of polysaccharide OH-group substitution in PGU. The lower percentage of OH-groups was substituted, the more intensive destruction process was

*Institute of Macromolecular Chemistry National Academy of Sciences of Ukraine, Ukraine* 

The authors acknowledge Prof. Gvozdiak R.I, Dr. Dankevich L. and Dr. Vocelko S. (Institute of microbiology and virology of NAS of Ukraine) for help in the study of polyglukanurethane biodegradation in various microbial environments and for providing of

Bergmann D., Furth G., Mayer Ch.Binding of bivalent cations by xanthan in aqueous solution. *International Journal of Biological Macromolecules*. 2008, Oct 1;43(3):245-51, 0141-

Crini G. Recent developments in polysaccharide-based materials used as absorbents in wastewater treatment. *Progress in Polymer Science.* 2005. V. 30, pp. 38 – 70, 0079-6700

content in the system the amount of absorbed water declines.

formation of "polymer-metal ion" chelate complexes.

disintegrate the polysaccharide chains predominantly.

**6. Conclusions** 

observed.

**Author details** 

**Acknowledgement** 

**7. References** 

8130

Nataly Kozak and Anastasyia Hubina

various producents microbial exopolysaccharides.

**Figure 12.** IR spectra PGU20-cellulose 1 – initial PGU20-cellulose; 2 – PGU after contact with natural microbial medium, 3 – PGU after contact with aggressive microbial medium.

**Table 3.** IR spectra of PGU40 and PGU-cellulose-20 after biodestruction
