Hierarchical ordering and multilayer structure of poly(ε-caprolactone) end-functionalized by a liquid crystalline unit: role of polymer crystallization

Abstract

End functionalization is an effective avenue to develop polymers with specific functions. Microphase separation between the polymer segment and the end group can lead to end-functionalized polymers organizing into ordered structures; this behavior is more significant for crystallizable end-functionalized polymers. However, the role of polymer crystallization in the ordering organization of end-functionalized polymers remains unclear. Herein, we synthesized end-functionalized poly(ε-caprolactone) (PCL) with the liquid crystalline (LC) 4-hexyloxy-4′-cyanobiphenyl terminal, denoted LC-PCL. We demonstrated that the structural organization of LC-PCL was governed by the polymer composition and PCL crystallization. LC-PCL with a short PCL block organized in a smectic-like bilayer structure. LC-PCL with a medium PCL block length assembled in multilayers comprised of alternating PCL lamellae and LC layer; however, the formation of the LC layer was prohibited when the crystallization of PCL was fast. LC-PCL with a long PCL block only formed PCL lamellae, similar to conventional semicrystalline polymers. This study provides deep insight into the hierarchical structural organization of semicrystalline end-functionalized polymers.