Cationic polymerization of 1,2‐epoxy‐3‐nitropropane in the presence of ethylene glycol, 2 Higher oligodiols: Discrepancies with the activated monomer mechanism

The cationic polymerization of 1,2‐epoxy‐3‐nitropropane (ENP) in the presence of ethylene glycol and boron trifluoride etherate is studied. The reaction was performed by adding the monomer stepwise in the reaction medium, so that the instantaneous mole ratio [ENP]/[OH] was below one, in order to favor the Activated Monomer Mechanism (AMM). We have shown previously that polymerization proceeds via AMM during the first two steps of the reaction (M̄n < 350). In this paper, we present our results concerning the subsequent stages. In addition to the expected molecules containing one ethylene glycol unit per chain $ [{ H {--} ( O}{ CHR}{ CH}₂ {--} )_p { OCH}₂ { - CH}₂ { O {--} ( CH}₂{ CHR}{ O{--} )}_q { H (R} = { CH}₂ { NO}₂ )] $ we find also some α,ω‐ENP oligodiols which do not contain any ethylene glycol unit $ [{ H {--} ( O}{ CH}₂{ CHR}{--} )_i { OH} $ , some mono‐ or diethoxylated oligomers $ { [C}₂ { H}₅ {--} ({ O}{ CH}₂{ CHR{--} )}_i { OH} $ and $ { C}₂ { H}₅ {--} ({ O}{ CH}₂{ CHR{--} )}_i { OC}₂ { H}₅ ] $ and some cyclics. The experimental hydroxyl concentration exceeds that introduced through the ethylene glycol used. Primary OH groups are present and the average molecular weight is limited to 500. The viscosity of the reaction medium decreases significantly when the polymerization is terminated, or simply when the medium is put in contact with atmospheric water.