In the following work I focused on the molecular modelling of polymethacrylic acid (PMA) with semiempirical methods. Completely protonated atactic and isotactic forms of PMA act very differently when dissolved in solution. The structure of chains of both forms of PMA differ greatly. While isotactic form can be present either in a helical or semicircular form, atactic form is only present in a semicircular form. Comparison of solvation energies shows that isotactic form is not solvated as well as the atactic form. This is in agreement with the experimental data. Next, I compared the structure and solvation of PMA in water and dimethyl sulfoxide (DMSO). The results for water and DMSO were very similar which is not what was expected, since isotactic form of PMA dissolves in DMSO, while it is insoluble in water. Lastly, I compared energies of interaction for dimers of both forms of PMA. The results showed greater interaction between two chains of isotactic form of PMA through potential hydrogen bonds when compared to the atactic form. This is in agreement with the experimental data, since less carboxylic groups are available for the formation of hydrogen bonds with the solvent, which in turn leads to less favourable solvation in solvents like water.
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