Accessing chemically recyclable polyamides via geminal dimethyl substitution

The development of new chemically recyclable polymers could serve as a means of reducing the plastic pollution and alleviating global energy crisis and monomer design strategy has driven the innovation in this field. In this contribution, alpha-dimethyl substituted caprolactam (alpha-DMCL) and gamma-dimethyl substituted caprolactam (gamma-DMCL) were prepared to evaluate the substitution position effect on chemical recyclability and material performance in polycaprolactam (PCL) system. The introduction of geminal dimethyl substitution to e-caprolactam (CL) at alpha and gamma position could change the thermal and mechanical properties of the resulting polyamides P(alpha-DMCL) and P (gamma-DMCL). Remarkably, thermal depolymerization of P(gamma-DMCL) in presence of potassium caprolactamate (CL-K) could be carried out at 200 degrees C and converted to gamma-DMCL in 91% yield. The recovered gamma-DMCL was capable of repolymerization to P(gamma-DMCL) without a decrease in reactivity, demonstrating the proof-of-concept recyclability of P(gamma-DMCL).