Solid-state polymerization of butadienes. Crystal structure and solution properties of a stereoregular amphoteric 1,4-trans-polybutadiene

The double salt 1 consisting of the hydrochloride of 6-amino-2,4-trans-hexadienoic acid and cadmium chloride in a 2:1 stoichiometry polymerizes in the crystalline state if exposed to UV or γ irradiation. A stereoregular polymeric ampholyte is formed in an extended chain macroconformation, embedded in an inorganic matrix. The crystal structure of the polymerized crystals and the solution properties of the polymer are reported. Polymerized crystals are triclinic, space group P1 , a = 7.2144 Å, b = 7.2447 Å, c = 18.5936 Å, α = 104.49°, β = 96.631°, γ = 95.706°, Z = 2. The structure consists of 2-dimensional layers of polymer and inorganic CdCl₆ octahedra alternatively stacked in the third dimension. The cadmium ions can be separated from the polymer by a precipitation as insoluble CdS. After separation from the inorganic material the polymer is soluble in strong acids and bases and insoluble in neutral water. From viscosity measurements of alkaline solutions of the polymer, an average molar mass of 4 × 10⁴ g/mol can be deduced. The polymer selectively adsorbs divalent transition metal ions if suspended in an aqueous solution of transition metal salts. The structure of the resulting polymer–metal complexes is discussed.