VARIATIONS IN PHYSICAL-CHEMICAL PROPERTIES OF BLOCK-COPOLYMER CHITOSAN WITH METHYL ACRYLATE DURING BIODEGRADATION UNDER THE ACTION OF ASPERGILLUS TERREUS - Biochemistry and Biotechnology: Research and Development - page 127

to the temperatures of PMA destruction (Figure 4 and 5, Table 1). It is not surprising since
biodestruction of the blocks of a natural polymer is the first to take place. In this case, the
temperatures t dest1 almost coincide, while t dest2 of the PMA decreases by 55 о С (series No.2)
and 61.5 о С (series No.1). Variations in t dest of the PMA in the block-copolymer can point to
partial destruction of its synthetic fragments as well.
m- mass of combusted substance; ∆t - temperature rise in the experiment with the
correction for heat exchange; q par. , q ct , q(HNO 3 ), q с , - corrections for the energy of
combustion of paraffin, cotton thread, the energy of formation of HNO 3 water solution, and
incomplete combustion of carbon, respectively; Δ c U,-energy of combustion of the studied
substance under the conditions of a calorimetric bomb.

Table 2. The results of experiments on determining the energy of CHS
combustion at 25 о С

q par ,
J

q ct ,
J

q(HN
O 3 ), J

q с ,
J

− Δ c U,
J/g

m, g ∆t, J

0.2155 5
0.2379 1
0.2644 4
0.2420 7

2.523305
2.572280
2.591835
2.570570

33120.7
33455.4
33184.2
33263.4

36.0
32.1
31.5
33.8

10.0
14.7
12.3
8.8

28.8
35.1
39.3
32.8

19577.6
19401.5
19602.3
19764.0

Среднее значение 19586.4±83.7

C ONCLUSION

1. The comparison of physical-chemical properties of chitosan, its block-copolymer

with methyl acrylate, and the CHS/PMA mixture showed that the polysaccharide
does not practically affect the synthetic component, while PMA yields variations in
the temperature of the chitosan relaxation transitions. The MA blocks in the
copolymer decrease the temperature of the β-transition and increase the temperature
of vitrification of the ordered CHS microregions. As far as the mixture is concerned,
PMA blocks the oscillations of pyranose rings of CHS and, thus, suppresses the β-
transition of the latter.

2. The investigations performed using the DTA method revealed variations in physical-

chemical properties of the CHS/MA block-copolymer under the action of Aspergillus
terreus. In this case, chitosan is the first to be reprocessed by micromycetes, since it
is the temperatures of the chitosan relaxation processes that change most
substantially. The effect of Aspergillus terreus also manifests itself in the formation
of a new relaxation process at t<0оС. It should be also noted that the effect of
micromycetes on the CHS/MA block polymer yields a more substantial change in its
physical-chemical properties in case of a direct action of micromycetes (series No.2)
since both the flocci of the fungi and the products of their vital life penetrate into the
copolymer. An important sign of the micromycete action on chitosan is the
disappearance of endothermic maxima of its destruction on the thermograms and the
appearance of endothermic maxima of PMA destruction. A decrease in the
temperature of the second endothermic maximum of the PMA destruction by 60-