New bio-polyamides from terpenes: a-pinene and (+)-3-carene as valuable resources for lactam production
The synthesis and polymerization of two v-lactams and two e-lactams derived from the terpenes a-pinene and (+)-3-carene are reported. The new biopolymers can be considered as polyamide 2 (PA2) and polyamide 6 (PA6)-types with aliphatic stereoregular side chains, which lead to remarkable new properties. The macromolecules are investigated by gel permeation chromatography (GPC), nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC), and infrared (IR). The (+)-3-carene-derived PA6-type is of particular interest, since it reaches a molecular weight of over 30 kDa, which is the highest value for lactam-based polyamides derived from terpenes reported to date. Additionally, a glass transition temperature (Tg) of 120 °C is observed, surpassing the glass transition temperature of PA6 by 60 °C. The absence of a melting point (Tm) indicates high amorphicity, another novelty for terpene-based polyamides, which might give transparent bio-polyamides access to new fields of application.