TABLE OF CONTENTS Let us consider solution of the direct problem of estimation of the properties of polymers based on their chemical structure on an example of natural polymers. The specific features of these polymers are the following:
These polymers contain cyclic non-aromatic structures with a large number of OH-groups able to form hydrogen bonds.
Hydrogen bonds in these polymers may be formed both between neighboring chains and in the range of a single chain, and even in a single repeat unit. The scheme representing these interactions is shown in Figure 41. The presence of interchain and intrachain (including intra-unit) hydrogen bonds depends on the steric factor - dislocation of OH-groups in relation to the plane of circles.
Many high-molecular compounds, including cellulose, degrade thermally at heating before the process of devitrification is onset. Consequently, the glass transition temperature (the most important characteristic for polymers) may not be determined experimentally.
Many natural high-molecular compounds possess different units, i.e. contain fragments of different chemical nature in their chains.
In this Section, we will discuss application of the approach developed for estimating the physical properties of polymers based on their chemical structure to natural high-molecular compounds, which possess quite complicated but well studied chemical structure.
Table A-1-1 indicates chemical structures of 16 fragments of hemicelluloses structures, most often met in the structure of natural polymers. Of special attention is the fact that in some cases, despite the identical gross-formula, these fragments included in polymeric chains involve different physical properties of natural polymers. For example, for...
