Abstract
AbstractMultiblock copolymers with charged blocks are complex systems that show great potential for enhancing the structural control of block copolymers. A pentablock terpolymer PMMA‐b‐PDMAEMA‐b‐P2VP‐b‐PDMAEMA‐b‐PMMA is investigated. It contains two types of midblocks, which are weak cationic polyelectrolytes, namely poly(2‐(dimethylamino)ethyl methacrylate) (PDMAEMA) and poly(2‐vinylpyridine) (P2VP). Furthermore, these are end‐capped with short hydrophobic poly(methyl methacrylate) (PMMA) blocks in dilute aqueous solution and thin films. The self‐assembly behavior depends on the degrees of ionization α of the P2VP and PDMAEMA blocks, which are altered in a wide range by varying the pH value. High degrees of ionization of both blocks prevent structure formation, whereas microphase‐separated nanostructures form for a partially charged and uncharged state. While in solutions, the nanostructure formation is governed by the dependence of the P2VP block solubility of the and the flexibility of the PDMAEMA blocks on α, in thin films, the dependence of the segregation strength on α is key. Furthermore, the solution state plays a crucial role in the film formation during spin‐coating. Overall, both the mixing behavior of the 3 types of blocks and the block sequence, governing the bridging behavior, result in strong variations of the nanostructures and their repeat distances.
Highlights
The nanostructure of the pentablock terpolymer M18D170V209D170M18 is investigated in aqueous solutions and in thin films in dependence on the charge states of the D and V blocks with the aim of relating the self-assembled solution structures to the nanostructures in thin films, which are prepared from these solutions
Www.afm-journal.de in aqueous solution and in thin film geometry is investigated in dependence on the charge state of the polymer
Compared to triblock copolymers with only one weak polyelectrolyte central block, such as poly(methyl methacrylate) (PMMA)-b-poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA)-b-PMMA,[63] the charge distribution along the polymer chain is not random, but segmental. We find that this has a remarkable influence on the self-assembly behavior of the polymer and offers great control
Summary
Block copolymers have gained increasing amount of attention and research interest over the past couple of decades due to their ability to self-assemble into a plethora of different structures in solution, in the bulk and in confined geometry.[1,2,3] Applications include, among many others, drug delivery,[4,5] injectable hydrogels,[6,7,8] membranes,[9,10] litho graphy,[11,12,13] sensors,[14,15] organic photovoltaics,[16] and batteries.[17,18] For many of these applications, a precise knowledge and control of their nanostructure and degree of order are imperative for best performance. We investigate a pentablock terpolymer with two chemically different types of charged blocks that are pH-responsive with a focus on the influence of the charge state of the polymer on the microphase separation and self-assembly behavior in aqueous solutions and in dry thin films. [56,57]).[27,36] confinement and surface tension effects in the thin film geometry might induce an alignment of the nanodomains The investigation of both aqueous solutions and the thin films prepared from these solutions combined with a determination of the charge states of the blocks in films gives a broad view of the nanostructure formation and allows us to draw conclusions about the charge-dependent self-assembly behavior of pentablock terpolymers. In the Experimental Section, the polymer synthesis, sample preparation and experimental methods are outlined
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