Molecular modelling of ring-opening polymerisation of lactamimide-containing macrocyclic esters

Abstract

The molecular modelling of anionic (MeO– initiated) and cationic (H+ initiated) polymerisation of lactamimide‐containing macrocyclic esters has been carried out at PM3 and HF/3‐21G levels of theory. It was found that it is strain release that drives the polymerisation of these macrocycles. Most likely that entropy gain on the ring‐opening can not compensate entropy loss on polymer formation due to the relative rigidity of cyclic molecules. Methanolate initiated anionic polymerisation will not lead to high molecular weight product due to the side reactions involving the attack of growing anionic species at carbonyls of lactamimide moiety, while the cationic polymerisation should proceed smoothly provided that polymerisation temperature is less than ceiling temperature.

1‐amino‐4,5‐8‐naphthalenetricarboxylic acid‐1,8‐lactam‐4,5‐imide‐containing macrocycles: synthesis, molecular modelling and polymerization

“…Taking advantage of having well‐defined unique cyclic structures and not a mixture of cyclic oligomers, it is possible to correlate their polymerizability with the ring strain of prepared macrocycles, since, as has been shown recently, the ROP of lactamimide‐containing macrocycles is due to strain release not entropy gain 16. The isodesmic reaction approach has been adopted to estimate the ring strain 20.…”

“…The polymerization of synthesized macrocycles was carried out in the molten state at 260–270 °C for 2.5 h under a nitrogen flow. Since the lactam cycle of the lactamimide moiety is sensitive to either nucleophilic or electrophilic attack,16 thermally driven ROP was used. Both biphenyl‐containing macrocycles ( LI2Bph and LI4Bph ) readily underwent ROP producing the corresponding polymers (Scheme ).…”

“…The macrocyclic monomer technique could be a promising new approach to the synthesis of polylactamimides via reactive processing of macrocyclic monomers. A recent theoretical study of ROP of lactamimide‐containing macrocycles showed that this process is enthalpy‐driven,16 unlike macrocylcic polycarbonates where the polymerization proceeds owing to the entropy gain on ring‐opening 17. However, Kricheldorf et al recently discussed the formation of cyclic polyesters as a kinetically controlled reaction 18.…”