ABA type liquid crystalline triblock copolymers by combination of living cationic polymerizaition and ATRP: synthesis and self-assembly

Abstract

Lamellar and hexagonal-coil-cylinder self-assembled structures of ABA type triblock copolymers containing mesogen-jacketed liquid crystalline polymer (MJLCP) as the rod block, and polyisobutylene (PIB) as the coil middle block were discovered. PIB was synthesized by living cationic polymerization of isobutylene initiated by 1,4-bis(2-chloro-2-propyl)benzene (p-DCC), and then a small amount of styrene was introduced at the end of the PIB chains to form the difunctional PIB macroinitiator with -CH 2 CH(C 6 H 5 )Cl end groups for further atom transfer radical polymerization (ATRP). 2,5-Bis[(4-methoxyphenyl)oxycarbonyl]styrene (MPCS) was block-copolymerized from the difunctional PIB macroinitiators at 110 C. The molecular characterization of the triblock copolymers was performed with 1 H NMR, 13 C NMR, gel permeation chromatography (GPC), and thermogravimetric analysis (TGA). Their phase structures and transitions were investigated by differential scanning calorimetry (DSC), small angle X-ray scattering (SAXS), and polarized optical microscopy experiments. It was demonstrated that the triblock copolymers formed lamellar structures at moderate rod fractions and hexagonal coil cylinders in the rod matrix at high rod fractions. The d-spacing of the microphase-separated structures was influenced by the liquid crystalline phase of rod-like PMPCS blocks.

Hierarchically ordered ABA triblock copolymer with large difference in glass transition temperatures of the two blocks

“…Interestingly, as shown by the SAXS results in Figure , when the samples are heated above the temperature at which the LC phase starts to develop and are then cooled to ambient temperature, the lamellar structures remain, with an increase in the d ‐spacing. This can be mainly attributed to the increase in the chain length of PMVBP caused by the conformational change from a wormlike chain to a rod‐like one following the phase transition from the amorphous state to the LC phase . The inconsistency of nonequilibrium morphologies and close‐equilibrium morphologies obtained from solvent annealing and thermal annealing, respectively, may also cause the difference in lamellar spacing.…”

“…Rod‐coil BCPs containing PMPCS can form hierarchical structures, for example, a “bilayer smectic A” structure was observed with the rigid PMPCS columns aligned parallel to the lamellar normal . ABA‐type rod‐coil‐rod triblock copolymer PMPCS‐ b ‐PIB‐ b ‐PMPCS, which was synthesized with the combination of living cationic polymerization and atom transfer radical polymerization, forms hierarchical structures when the temperature is increased to 160 ° C at which the PMPCS block enters into the LC phase . However, some MJLCP‐based rod‐coil BCP systems studied previously have glass transition temperatures ( T g 's) that are not dramatically different, which may limit their applications in certain fields.…”

Ordered nanostructures at two different length scales mediated by temperature: A triphenylene‐containing mesogen‐jacketed liquid crystalline polymer with a long spacer

“…Solution NMR experiments, mass spectroscopy, elemental analysis, gel permeation chromatographic (GPC) measurements, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), polarized light microscopy (PLM), small‐angle X‐ray scattering (SAXS), and one‐dimensional (1D) and two‐dimensional wide‐angle X‐ray diffraction (WAXD) experiments were performed according to the procedures previously described …”

Synthesis of Telechelic and Three-Arm Polytetrahydrofuran-block-amylose

“…Block copolymers offer interesting structures, which can be applied extensively in a lot of areas, such as printings, paintings, nano‐scale electronic devices, and drug delivery systems . Therefore, it becomes a point of interest to study whether the amylose complex formation can also be applied to a wider range of block copolymers, such as stars, dimers, triblock, comb‐shaped, or branched polymers.…”