This critical review covers the recent progress in the research of mesogen-jacketed liquid crystalline polymers (MJLCPs), special side-on side-chain liquid crystalline polymers with very short spacers or without spacers. MJLCPs can self-organize into supramolecular columnar phases with the polymer chains aligned parallel to one another or smectic phases with the backbones embedded in the smectic layers. The semi-rigid rod-like MJLCP with a tunable rod shape in both length and diameter provides an excellent building block in designing novel rod-coil liquid crystalline block copolymers which can self-assemble into hierarchical supramolecular nanostructures depending on the competition between liquid crystal formation and microphase separation (229 references).

A remarkably rich variety of nanophase-separated structures and various order–order transitions are observed in a series of low-molecular weight (MW) rod–coil block copolymers (BCPs) with the rod blocks of different lengths (L Rod’s). The rod–coil diblock copolymer studied herein is poly(dimethylsiloxane)-b-poly{2,5-bis[(4-methoxyphenyl)oxycarbonyl]styrene} (PDMS-b-PMPCS), in which PMPCS is a rod-like polymer and exhibits an MW-dependent liquid crystalline (LC) phase behavior. When the polymerization degree of the PMPCS rod block (N Rod) is less than 32 (L Rod < 8 nm), the PMPCS block is always amorphous in the entire temperature range. And the corresponding PDMS-b-PMPCS BCPs with N Rod from 11 to 29 and the volume fraction of the PMPCS rod (f Rod) from 43% to 67% self-assemble into various equilibrium nanostructures after annealed at temperatures above the glass transition temperatures of the PMPCS blocks. When N Rod = 11 and f Rod = 43%, the BCP forms a lamellar structure (LAM); when N Rod = 15 and f Rod = 51%, the BCP forms a double gyriod structure (GYR) ; when N Rod = 20 and f Rod = 57%, the BCP forms a GYR structure after annealed below 180 °C and transforms to the Fddd structure after annealed above 180 °C; when N Rod = 29 and f Rod = 67%, the nanostructure of the BCP after annealed below 180 °C is hexagonally packed cylinders (HEX) and changes to a body centered cubic structure (BCC) after annealed above 180 °C. When N Rod > 32 (L Rod > 8 nm), the PMPCS rod block is amorphous at low temperatures and transforms to a stable columnar LC phase after annealed at high temperatures. Correspondingly, the PDMS-b-PMPCS BCP with N Rod = 44 and f Rod = 75% forms a HEX structure after annealed at lower temperatures at which the PMPCS block is amorphous, and the nanostructure transforms to LAM after the sample is annealed at higher temperatures at which the PMPCS block enters into the LC phase. Therefore, only by a small change of the rod length in the low-MW PDMS-b-PMPCS rod–coil BCPs, various nanostructures including LAM, GYR, Fddd, HEX, and BCC are obtained. In addition, by increasing annealing temperatures, GYR-to-Fddd and HEX-to-BCC transitions are observed in the BCPs with the amorphous PMPCS, and a HEX-to-LAM transition occurs in the BCP when the LC PMPCS block undergoes an isotropic-to-LC phase transformation.

A tough double-network (DN) ion gel composed of chemically cross-linked poly­(furfuryl methacrylate-co-methyl methacrylate) (P­(FMA-co-MMA)) and physically cross-linked poly­(vinylidene fluoride-co-hexafluoropropylene) (P­(VDF-co-HFP)) networks with 80 wt % of ionic liquid (IL) was fabricated via a one-pot method. This ion gel exhibits excellent mechanical strength and considerable ionic conductivity, which can be used as a solid gel electrolyte. Upon an adjustment of the weight ratio of P­(FMA-co-MMA) to P­(VDF-co-HFP) and the content of the cross-linker, remarkably robust DN ion gel (failure tensile stress 660 kPa, strain 268%; failure compressive stress 17 MPa, strain 85%) was obtained. The high mechanical strength is attributed to the chemical/physical interpenetrating networks. The rigid chemically cross-linked P­(FMA-co-MMA) network dissipates most of the loading energy, and the ductile physically cross-linked P­(VDF-co-HFP) network provides stretchability for the whole gel. More importantly, the P­(FMA-co-MMA) network is formed by dynamic covalent bonds that can undergo a thermally reversible reaction, giving the gel a unique and effective thermal healing capability. Furthermore, with the high content of IL, the DN ion gel possesses a high ionic conductivity of 3.3 mS cm–1 at room temperature, which is higher than those of most solid polymer electrolytes and comparable to those of commercial organic liquid electrolytes.