Ring-Opening Polymerization of Bicyclic Lactams

1 Polymerization of Bicyclic Lactams Having a Bicyclo 3.2. l joctane Skeleton 

The anionic polymerization of 58 shows typical equilibrium polymerization behavior. From the temperature dependence of the equilibrium monomer concentration, the thermodynamic parameters for the polymerization of 58 in dimethyl sulfoxide were evaluated to be AHSS = -23.8 1.5 kJ/mol and ASss = — 71.5 + 4.2 kJ/mol deg (subscript ss refers to a solution state). [67] The ceiling temperature for 1 mol/L solution is about 60 °C. The enthalpy change in the polymerization of 58 is considerably larger than those for monocyclic lactams, pyrrolidone and piperidone, but no quantitative comparison of these data can be made, because the reported data refer to different experimental conditions. The significant entropy decrease in the polymerization is ascribable to the presence of the six-membered tetrahydropyran ring in the repeating unit. 

Anionic polymerization of 58 activated by N-benzoyl lactam proceeds without side reactions. Since side reactions in the anionic polymerization of lactams are mainly caused by protonabstraction, the pKa value for the bridge-head methine proton adjacent to the lactam-carbonyl group in 58 must be higher than that for the a-methylene protons in 2-pyrrolidone. This is because the former monomer has a rigid bicyclic structure. 

A monodisperse polyamide was prepared by the anionic polymerization of 58 using its N-benzoyl derivative and potassium pyrroridonate as the activator and 

In the presence of a cationic initiator such as trifluoromethanesulfonic acid and boron trifluoride etherate, 58, gave a mixture of dimers and higher oligomers. [69] On the basis of structural analyses of the dimers prepared from the racemic and optically active monomers, it was concluded that the cationic oligomerization involved protonation onto the amide nitrogen of 58 followed by selective scission of the C(5)—N(6) bond, while the C(5)—0(8) bond remained intact. 

---

The condensation polymers (105) have been prepared (80JOC5325) by ring-opening polymerization of bicyclic lactam (101), the urethanes (102) and (103) and urea (104 Scheme 28). The polymerizability of these monomers, compared with the inertness of isomers (106)... 

---