Relation between structure and thermal transitions in comb‐like polymers, 1. Poly(N‐n‐alkylmaleimide)s

Abstract

AbstractA series of nine poly(N‐n‐alkylmaleimide)s (PMIs) with the n‐alkyl side chain ranging in length from ethyl to octadecyl and including only the even members of the series was studied by differential scanning calorimetry (DSC) from 100 K to above the glass transition temperature. The nine members of the PMI series generally were found to exhibit a glass transition temperature (Tg), a sub‐glass transition temperature (sub‐Tg = Tγ), and, but only the four higher homologs a melting point (Tm) with the respective melting enthalpy (ΔHf). The glass transition of the amorphous members is directly related to the number of methylene groups (including terminal methyl) of the n‐alkyl side chain of the repeating unit. The values of Tg estimated according to a semi‐empirical equation are in good agreement with the experimental data. The melting points of the members of the series presenting crystallinity in the n‐alkyl side chain were analyzed. A good fit of a Garner plot by a least‐mean‐squares procedure is obtained with T = 408,0K, a = −6,26 and b = −2,03. The contribution to the heat of melting per methylene unit clearly demonstrates that the hexagonal paraffin crystal structure is present in the crystalline members, in agreement with X‐ray data. The data when analyzed by Jordan′s procedure show that only part of the n‐alkyl side chain is forming a crystal lattice.