Morphology Evolution of Polymeric Assemblies Regulated with Fluoro-Containing Mesogen in Polymerization-Induced Self-Assembly

5 years ago

Morphology Evolution of Polymeric Assemblies Regulated with Fluoro-Containing Mesogen in Polymerization-Induced Self-Assembly

Yen Wei, Meng Huo, Yiyang Zhang, Min Zeng, Jinying Yuan, Lei Liu

Mesogen-containing amphiphilic block copolymers have shown extremely abundant self-assembly behaviors because of the liquid crystalline (LC) alignment within the assemblies. However, development of an understanding of the self-assembly behaviors of these amphiphilic LC polymers is still constrained by the low assembly concentration and complex kinetic effects. Polymerization-induced self-assembly (PISA) is a powerful technique to prepare polymer assemblies at high solids content with good repeatability. Taking advantage of PISA, we systematically study the self-assembly behaviors of a series of mesogen-containing triblock copolymers poly(2-dimethylaminoethyl methacrylate)-b-poly(benzyl methacrylate)-b-poly(2-perfluorooctylethyl methacrylate) (PDMA-b-PBzMA-b-PFMA), which are prepared by seeded reversible addition–fragmentation chain transfer dispersion polymerization of FMA with PDMA-b-PBzMA micelles or vesicles as the seeds. When PDMA-b-PBzMA micelles are used, the morphology of the PDMA-b-PBzMA-b-PFMA assemblies evolves from spheroid to phase-segregated sphere, followed by phase-segregated spheroid, and eventually to cylinder, while the assemblies undergo a vesicle-to-micelle transition with a framboidal intermediate when PDMA-b-PBzMA vesicles are used as the seeds. These spherical micelles further fuse to cylinders or large spheres depending on the DPs of PBzMA and PFMA blocks. The LC ordering of the PFMA blocks is examined by differential scanning calorimetry and X-ray diffraction; the microphase segregation between PFMA and PBzMA blocks is studied with TEM and atomic force microscopy. These experiments evince that the formation of the ellipsoidal and cylindrical micelles is driven by the LC alignment of PFMA blocks, while the microphase segregation between PFMA and PBzMA blocks complicates the ultimate morphology through modulating the size of PFMA nanodomains. The interplay of the hydrophobic interaction among PBzMA blocks, lipophobic interaction, and LC ordering of PFMA blocks thus generates the above self-assembly behaviors.

Publisher URL: http://dx.doi.org/10.1021/acs.macromol.7b01437

DOI: 10.1021/acs.macromol.7b01437