Thermoreversible Order−Order Transition of a Triblock Copolymer Containing a Mesogen‐Jacketed Liquid Crystalline Polymer with a Re‐Entrant Phase Behavior

Abstract

Poly{2,5-bis[(4-butoxyphenyl)-oxycarbonyl]styrene} (PBPCS) with a re-entrant phase behavior is used to synthesize a new kind of ABC triblock copolymers (triBCPs), poly. Two well-defi ned triBCPs D 120 S 100 B 50 and D 120 S 100 B 120 with different molecular weights (MWs) and narrow MW distributions are synthesized by sequential atom transfer radical polymerization. The volume fractions of PDMS, PS, and PBPCS in D 120 S 100 B 50 are 0.24, 0.26, and 0.50, respectively, while the values in D 120 S 100 B 120 are 0.14, 0.16, and 0.70, respectively. At low temperatures, PBPCS is amorphous. Both samples form a core-shell hexagonally packed cylindrical (CSH) morphology. At high temperatures, PBPCS in the triBCPs can form a liquid crystalline (LC) phase, the transformation of which can induce an order−order transition (OOT) of D 120 S 100 B 120 . The nanostructure changes from a CSH structure to a three-phase-four-layer lamellar structure, and the transition is thermoreversible. The sequence of the OOT is opposite to that of a coil−coil−coil triBCP. The unusual LC behavior of PBPCS plays an important role on the thermoreversible morphological transition of the triBCP.

Self-assembly in rod/coil block copolymers: Degenerate behavior under nonconfinement

“…When χ AB N is increased to 12 or decreased to 8 at f rod = 0.4, the region of the phase diagram of stability and degenerate behavior apparently decreased. The emergence of the NCSLM is very much dependent on χ AB N. In π-conjugated coil/coil/rod ABC triblock copolymers containing a mesogen-jacketed liquid crystalline polymer, the core-shell hexagonally packed cylinder/lamella transition emerges with increasing the temperature, [58] and the transition sequence is in reasonable agreement with that of NCSLM/CSLM transition. Consequently, it is expected that NCSLM may be observed in the experiment.…”

Synthesis and Self-Assembly of Silicon-Containing Azobenzene Liquid Crystalline Block Copolymers

“…Incorporating liquid-crystalline (LC) mesogens into BCPs produces LCBCPs which can form “structure-in-structure” hierarchical morphologies, that is, ordered LC phases within the microphase-separated domains. , The LC behavior not only enhances the immiscibility or chemical incompatibility between two blocks to increase the tendency for microphase-separation but also offers an effective way to switch the morphologies and orientation of the microphase-separated nanostructures by modulating the alignment of the LC mesogens via changes in temperature, solvents, magnetic field, and light illumination. − As an example, LCBCPs can experience diverse order-to-order transitions (OOTs) triggered by the LC phase transition in addition to the temperature-induced OOTs typical for BCPs that are attributed to the temperature-dependent χ. − In particular, azobenzene LC mesogens present a photoswitchable configuration change between cis and trans, that is, forming the low-energy trans configuration under visible light or heat treatment but the cis isomer upon irradiation with UV light . Thus, light of different wavelengths can be utilized to manipulate the orientation of azobenzene-containing LCBCPs. − For example, the cylindrical morphology of azobenzene photoresponsive LCBCPs can be transformed from random or in-plane orientation to out-of-plane vertical alignment under light irradiation. ,− …”