Bio-based semi-interpenetrating networks with nanoscale morphology and interconnected microporous structure

Creating new bio-based sustainable polymeric materials with similar or better performance than the petroleum-based counterparts  has recently received considerable attention. It will have a significant positive impact on the environment and the sustainable polymer industry. This review article shows a relatively new method based on simultaneous in-situ polymerization and compatibilization of bio-based plant oil and biodegradable thermoplastic polymer to prepare semi-interpenetrating polymer networks (SINs) with unusual nano-scale morphology and interconnected porous structure will be summarized. The SINs were synthesized via cationic polymerization of tung oil in a homogenous solution of poly(ε-caprolactone) as a biodegradable, semi-crystalline, and biocompatible thermoplastic polymer. The degrees of miscibility, nanostructure morphology, and crystallinity was found to be composition-dependent. This relatively new blending method created  a two-phase nanoscale morphology as small as 100 nm for blends with PCL contents of 20 and 30 wt.%. For higher PCL contents (e.g., 50 wt.% PCL blend), a co-continuous, interconnected microscale two-phase morphology was detected. The microporous structure of the SINs was also changed as a function of composition. For example, the interconnectivity and pore size was considerably decreased with increasing PCL content. Furthermore, a considerable decrease in the crystallization kinetics of PCL was observed as the PCL content is higher than or equal to 30 wt.%. While on the other hand, the crystallization kinetics accelerated significantly for 50 wt.%. This novel, low-cost strategy for preparing bio-based SINs with nanoscale morphology and interconnected three-dimensional cluster structures and desired properties should be widely used for creating new polymer systems.