Pincer-like Polymers Based on Methylenebis-salicylic Acid
Abstract Generated abstract
Methylenebis-salicylic acid is examined as a monomer capable of polycondensation with difunctional reagents to give pincer-like polyamide structures that can form intracomplex compounds with heavy metal salts. The authors prepare methylenebis-salicylic acid, condense it with ethylenediamine, and characterize the resulting fractions by melting behavior, viscosity in sulfuric acid, nitrogen content, estimated degree of polymerization, solubility, thermal stability, and X-ray diffraction. Treatment of the polyamide with copper acetate gives a dark-green, largely insoluble copper complex that is thermally stable and resistant to alkali, while concentrated acid releases copper into solution. X-ray data suggest that the initial polyamide is amorphous with limited ordering, whereas the copper complex is amorphous without detectable ordering.
Full Text
Pincer-like Polymers Based on Methylenebis-salicylic Acid
L. I. Aristov, N. E. Molodykh
(Presented by the scientific seminar of the organic departments)
Methylenebis-salicylic acid (I) is capable of entering into a polycondensation reaction with difunctional compounds, forming compounds of the polyamide and polyester type (II). The latter can react with salts of heavy metals with the formation of intracomplex high-molecular-weight compounds (III). The chemistry of the process may be represented by the following scheme:
\[ 2\,\mathrm{HO{-}C_6H_4{-}COOH} + \mathrm{CH_2O} \longrightarrow \mathrm{HO{-}C_6H_3(COOH){-}CH_2{-}C_6H_3(COOH){-}OH} \qquad \mathrm{I} \]
\[ \mathrm{HO{-}C_6H_3(COOH){-}CH_2{-}C_6H_3(COOH){-}OH} + \mathrm{NH_2CH_2CH_2NH_2} \longrightarrow \left[ \begin{array}{c} \mathrm{HO{-}C_6H_3{-}CH_2{-}C_6H_3{-}OH}\\ \mathrm{\ \ \ \ \vert\ \ \ \ \ \ \ \ \ \ \ \ \vert}\\ \mathrm{-OC\ \ \ \ \ \ \ \ \ \ \ CONH{-}NH{-}}\\ \mathrm{\ \ \ \ \ \ \ \ \ \ \ \ \ \vert}\\ \mathrm{\ \ \ \ \ \ \ \ \ \ \ CH_2{-}CH_2} \end{array} \right]_n \qquad \mathrm{II} \]
\[ \left[ \begin{array}{c} \mathrm{HO{-}C_6H_3{-}CH_2{-}C_6H_3{-}OH}\\ \mathrm{\ \ \ \ \vert\ \ \ \ \ \ \ \ \ \ \ \ \vert}\\ \mathrm{-OC\ \ \ \ \ \ \ \ \ \ \ CONH{-}NH{-}}\\ \mathrm{\ \ \ \ \ \ \ \ \ \ \ \ \vert}\\ \mathrm{\ \ \ \ \ \ \ \ \ \ \ CH_2{-}CH_2} \end{array} \right]_n + \mathrm{MeA} \longrightarrow \left[ \begin{array}{c} \mathrm{HO{-}C_6H_3{-}CH_2{-}C_6H_3{-}O\!\to\!Me}\\ \mathrm{\ \ \ \ \vert\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \swarrow}\\ \mathrm{-OC\ \ \ \ \ \ \ \ \ \ \ CONH\ \ NH{-}}\\ \mathrm{\ \ \ \ \ \ \ \ \ \ \ \ \vert\ \ \vert}\\ \mathrm{\ \ \ \ \ \ \ \ \ \ \ CH_2{-}CH_2} \end{array} \right]_n \qquad \mathrm{III} \]
However, an intracomplex compound may also be formed through the terminal groups of salicylic acid.
E. I. Orlov gives, for methylenebis-salicylic acid, a melting point of \(238^\circ\mathrm{C}\) (I). When salicylic acid was heated with formaldehyde in concentrated hydrochloric acid for 12 hours, a substance was obtained which, after appropriate purification, had a melting point of \(242^\circ\mathrm{C}\), molecular weight by Rast 296 (theoretical — 288). Calculated: C — 62.5%, H — 4.18%. Found: C — 62.87%, H — 4.5%.
The condensation product of methylenebis-salicylic acid with 20% ethylenediamine hydrate is a white powder with melting points of different fractions from 170 to \(220^\circ\mathrm{C}\). Relative
The viscosity of 0.2% solutions of the fractions in concentrated sulfuric acid at \(20^\circ\mathrm{C}\) is 1.0117–1.0177. The nitrogen content in the various fractions of polymer (II) ranges from 6.25 to 7.72%, which corresponds to \(n = 7\text{–}8\) and an average molecular weight of 2000–2500. When an aqueous-alcoholic solution of copper acetate is added to a solution of the polyamide in dimethylformamide, a dark-green precipitate separates. The substance possesses considerable thermal stability. On holding for 12 hours at \(200^\circ\mathrm{C}\), the change in weight is 0.5% per hour. At \(260^\circ\) on a block, the substance does not melt but changes color. The compound obtained is practically insoluble in most organic solvents. It dissolves only slightly (1.82%, 4.3%, 6.2%), respectively, in dimethylformamide, pyridine, and a 1 N sodium hydroxide solution. The complex is stable in alkaline solutions, but under the action of concentrated acid the copper passes into solution.
The X-ray diffraction pattern of (II), recorded on a URS-50-I apparatus with a copper anode at a current of 7 \(\mu\mathrm{A}\) and a voltage of 20 kV over the range \(2\Theta = 4\text{–}42^\circ\), shows that the substance has an amorphous structure with a certain degree of ordering in the structure (a halo at \(2\Theta = 24^\circ\)); the X-ray diffraction pattern of III, recorded under the same parameters, indicates an amorphous structure of the polymer with no ordering of the structure.
The interaction of this compound with other metals and the properties of the compounds obtained are being studied.
REFERENCES
- E. I. Orlov. Formaldehyde, Its Production, Properties, and Applications. ONTI, Khimteoret., 84, 1935.