Effect of structure on polymerizability: Olefin polysulfone formation

Polymerizability in the thermodynamic sense is measured by the free energy of polymerization. The effect of structure on polymerizability can be measured in two ways: (1) we may compare standard free energies (which are directly related to equilibrium monomer concentrations) at a given temperature; or (2) we may compare the temperatures at which the actual free energy changes are zero for a chosen monomer concentration. These temperatures are termed “ceiling temperatures” Tc and have been determined for the 1:1 copolymerization of sulfur dioxide S. with a wide variety of unsaturated compounds M, under the standard conditions [M] [S] = 27 mole2.1−2(binary mixture, mole fraction of M approximately 0.09). The polymers have the general formula magnified image Tc was determined by extrapolating the photochemical rate‐temperature relation to zero rate. In the straight chain 1‐olefin series Tc falls from ethylene (gt;135°) to propylene 90°, to butene‐1 64°, and thereafter remains approximately constant with increasing chain length. With 2‐olefins there is a progressive decrease from butene 34°, to pentene 8°, to heptene −38°. Branching invariably lowers Tc and the effect is greatest when the branching is at the double bond: thus isobutene 4°, 3‐methylbutene‐1 36°, 4,4‐dimethylpentene‐1 14°. 2‐Ethyl substitution of a 1‐olefin, or 2, 3 or 4 substitution of a 2‐olefin results in inability to react at any temperature down to −80°. Cyclic olefins have Tc considerably higher than the corresponding 2‐olefins: cyclopentene 102°, cyclohexene 24°. A number of allyl compounds have also been investigated. Tc is related to the heat and entropy of polymerization by the relation Tc = Delta;H/ΔS and in eight cases values of ΔH and ΔS have been obtained. A change of structure mainly affects ΔH. Estimated equilibrium monomer concentrations in polysulfone formation and in vinyl polymerization at 25°C. are summarized.