Well defined m-A(BC) n 'miktobrush' terpolymers were synthesized utilizing the alternating radical copolymerization of two hydrophobic and incompatible macromonomer (MM) building blocks; a maleimide (MI) end functionalized poly(methyl-caprolactone) block (MI-PMCL) or 'C' and a styrene (Sty) end functionalized poly(perfluoro propylene oxide) block (Sty-PFPO) or 'F'. Polymerizations were mediated by a poly(ethylene oxide) (PEO) functionalized reversible addition-fragmentation chain transfer (RAFT) agent (PEO-CTA) or 'O' to control the chain growth of the MMs from the O block to form O(CF) n ''miktobrush'' terpolymers. The synthesis of a range of well defined m-O(CF) n terpolymers with various compositions was achieved by changing the feed of MMs. All building blocks and brush polymers were characterized by nuclear magnetic resonance (NMR) spectroscopy, size exclusion chromatography (SEC) and elemental analyses. This new strategy offers a powerful route towards a block polymer architecture that can enable the formation of multi-domain hierarchical nanostructures with features on multiple length scales due to the incompatibility and unique connectivity of the building blocks incorporated.Block polymers can spontaneously self-assemble into welldefined nanostructures in block selective solvents and in the bulk, offering a powerful 'bottom up' approach towards precisely engineered materials for many diverse applications including; microelectronics, 1 tissue engineering, 2 drug delivery and water purification. 3 The increased understanding of self-assembled block polymers with varied architectures is of both fundamental and technological importance. 4 Towards this goal, AB diblock copolymers have been studied in depth. 5-7 Adding more blocks and functional groups to AB diblock copolymers increases architectural and functional complexity and can lead to more exotic self-assembled morphologies. 8,9 For instance, in a solvent selective for the A block, an ABC triblock terpolymer will form 'multicompartment micelles' whereby the two solvophobic (and incompatible) B and C blocks will produce two separate nanoscopic core domains. 10,11 If the chemistry of the microphase separated domains (B and C) is sufficiently different, multicompartment micelles can facilitate the storage of distinct small molecules within their separate core domains, thus enabling simultaneous storage and delivery of multiple incompatible payloads. 12 Linear ABC terpolymers, 13-19 linear BAC or ACB terpolymers, 20 side chain grafted ABC terpolymers or 'polysoaps', 21-23 miktoarm star m-ABC terpolymers, 24-30 and blends of block polymers 31-36 have been pursued as multicompartment micelle systems by various research groups. In each case, the connection point of the solvophobic B and C chains relative to the solvophilic corona forming block, A influences the micelle morphology to a great extent, although factors such as the solvophobicity and overall terpolymer composition play important roles. 5,11 In m-ABC terpolymers, three mutually immiscible blocks are...
The aqueous self-assembly of μ-A(BC) n mikto brush terpolymers has been studied using dynamic light scattering and cryogenic transmission electron microscopy. In this system, the A block is hydrophilic poly(ethylene oxide), “O”, the B block is hydrophobic poly(methylcaprolactone), “C”, and the C block is hydrophobic and oleophobic poly(perfluoropropylene oxide), “F”. Two terpolymers were examined: one with an average of about two C blocks and two F blocks and another with an average of about three C blocks and two F blocks. In both cases, the total molar mass is near 40 kg mol –1 , and the volume fraction of the single O block is greater than 50% of the whole. Both samples form multicompartment micelle structures with subdivided solvophobic cores of C and F domains. The morphologies observed are generally analogous to those previously observed for the self-assembly of μ-ABC mikto arm star terpolymers, namely, “raspberry” and “hamburger” micelles; however, an intriguing multicompartment polymersome morphology with compartmentalized solvophobic bilayers is also observed. These results are interpreted in terms of the relative strengths of the competing interactions among the three blocks and the solvent and in terms of the constraints imposed by the mikto brush architecture.
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