Hierarchical Structures in a Main-Chain/Side-Chain Combined Liquid Crystalline Polymer with a Polynorbornene Backbone and Multi-Benzene Side-Chain Mesogens

A series of main-chain/side-chain combined liquid crystalline polymers (MCSCLCPs) with a polynorbornene backbone and multi-benzene mesogens in the side chain, PNbnPP (n = 2, 6, 10), were synthesized through a controllable polymerization method: ring-opening metathesis polymerization (ROMP). Differential scanning calorimetry, polarized light microscopy, and one-/two-dimensional wide-angle X-ray diffraction were utilized to investigate the phase behavior of PNbnPP. Experimental results reveal that the two fundamentally different liquid crystalline (LC) building blocks—the mesogen-jacketed LC polymer main chain and the multi-benzene calamitic mesogens in the side chain—compete and promote with each other, leading to a complex phase behavior. Because of the coupling effect between the rigid core and the pendants (multi-benzene mesogens) of PNb2PP with a short spacer, PNb2PP forms a simple smectic phase. On the other hand, owing to the decoupling effect of the long spacers, at low temperatures PNb6PP and PNb10...