Equilibrium Anionic Polymerization of p-lsopropyl-α-methylstyrene in Tetrahydrofuran

Abstract

The equilibrium anionic polymerization of p-isopropyl-α-methylstyrene in tetrahydrofuran with potassium and sodium-naphthalene complex as initiators has been investigated in the temperature range of -20 to +20° C by use of high-vacuum techniques. The comparison of these results with those obtained previously for the equilibrium polymerization of α-methyl-styrene revealed that, because of the p- substituted bulkier isopropyl group in the monomer, the values of δG_c, the free-energy change upon the polymerization of 1 mole of liquid monomer to 1 base-mole of liquid amorphous polymer of infinite chain length, are slightly higher in the present studies. The values of ΔH_c and ΔS ^ccomputed from the plots of ΔG_c /RT versus 1/T yielded values which are lower than that for the α-methylstyrene-THF system. The effect of p-substitution is also observed in the higher values of the monomer equilibrium concentration [M] and lower values of β[β = x_ms-x_sp (V_m/V_s)].

where x_ms and x are monomer-solvent and solvent-polymer interaction parameters, respectively, and V_m /V_s is molar volume ratio of monomer to solvent. The values of x_ms for the p-isopropyl-α-methylstyrene-THF system increase regularly with increasing temperature, whereas in α-methylstyrene-THF system the increase in x^ms was not that marked