Nanostructured poly(ethylene oxide)-like dendron-block-linear poly(ethylene-alt-propylene) copolymers: design, synthesis, and thermal and assembling properties

作者：Song Jie; Cho Byoung Ki^*

来源：Soft Matter, 2012, 8(12): 3419-3428.

DOI：10.1039/c2sm07240h

A series of self-assembling dendron-coil block copolymers with well-defined molecular structures were prepared via a divergent method. The hydrophilic and hydrophobic blocks are composed of PEO-like dendrons and poly(ethylene-alt-propylene) (PEP) linear coils, respectively. A dendron-coil, 2G-2400 (2G and 2400 indicate the dendron generation and PEP molecular weight, respectively), showed a melting transition of the peripheral PEO chains. In contrast, the dendron-coils containing the 3rd generation dendron did not show any melting transition because of the plasticization effect of the tri(ethylene oxide) branches. Due to the strong immiscibility between the PEO-like dendron and PEP blocks, diverse microphase-separated morphologies were observed. 2G-2400 displayed a lamellar mesophase with an interdigitated dendron packing structure. For the larger 3rd generation dendron series, A15 micellar cubic (Pm3n space group), hexagonal columnar, and lamellar morphologies were revealed depending on the PEP coil length and/or temperature. For the columnar mesophases, the molecular wedge angles (alpha) were calculated to be 46.8 degrees and 34.6 degrees for 3G-2400 and 3G-3400, respectively. This suggests that the longer PEP coil of 3G-3400 is conformationally more deformed in the columnar structure. As a consequence, the columnar phase was transformed into an interdigitated lamellar structure as the temperature increased. This order to order transition is a reversal of the well-known phase sequence of linear block copolymers. This unusual morphological behavior is mainly attributed to the unique molecular arrangement associated with non-conventional dendron-coil chain architecture.

• 出版日期2012