Characterization of diblock copolymer order-order transitions in semidilute aqueous solution using fluorescence correlation spectroscopy

The temperature and pH-dependent diffusion of poly(glycerol monomethacrylate)-block-poly(2-hydroxypropyl methacrylate) nanoparticles prepared via polymerization-induced self-assembly in water is characterized using fluorescence correlation spectroscopy (FCS). Lowering the solution temperature or raising the solution pH induces a worm-to-sphere transition and hence an increase in diffusion coefficient by a factor of between four and eight. FCS enables morphological transitions to be monitored at relatively high copolymer concentrations (10% w/w) compared to those required for dynamic light scattering (0.1% w/w). This is important because such transitions are reversible at the former concentration, whereas they are irreversible at the latter. Furthermore, the FCS data suggest that the thermal transition takes place over a very narrow temperature range (less than 2 °C). These results demonstrate the application of FCS to characterize order-order transitions, as opposed to order-disorder transitions. The temperature and pH-dependent diffusion of poly(glycerol monomethacrylate)-block-poly(2-hydroxypropylmethacrylate)- nanoparticles in water is characterized using fluorescence correlation spectroscopy. Lowering either the solution temperature or pH induces a worm-to-sphere transition and hence an increase in diffusion coefficient by a factor of between four and eight

Highly Tunable Nanostructures in a Doubly pH-Responsive Pentablock Terpolymer in Solution and in Thin Films

Multiblock 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

Asymmetric copolymers: synthesis, properties, and applications of gradient and other partially segregated copolymers

This is an accepted manuscript of an article published by Wiley in Macromolecular Rapid Communications, available online: https://doi.org/10.1002/marc.201800357 The accepted version of the publication may differ from the final published version.Asymmetric copolymers are a class of materials with intriguing properties. They can be defined by a distribution of monomers within the polymer chain that is neither strictly segregated, as in the case of block copolymers, nor evenly distributed throughout each chain, as in the case of statistical copolymers. This definition includes gradient copolymers as well as block copolymers that contain segments of statistical copolymer. In this review, different methods to synthesize asymmetric copolymers are first discussed. The properties of asymmetric copolymers are investigated in comparison to those of block and random counterparts of similar composition. Finally, some examples of applications of asymmetric copolymers, both academic and industrial, are demonstrated. The aim of this review is to provide a perspective on the design and synthesis of asymmetric copolymers with useful applications.This research was financially supported by the ASYMCOPO Project, an international collaborative research project of the Deutsche Forschungsgemeinschaft (DFG, Germany) and the Agence Nationale de la Recherche (ANR, France); DFG project: GU 1685/1-1 (J. Z., C. G. S. and U. S. S.) and ANR project ANR-15-CE08-0039 (S. H.). C. G. S. and U. S. S. thank the Center for Excellence “PolyTarget” (SFB 1278, project Z01) of the Deutsche Forschungsgemeinschaft (DFG, Germany) for financial support. B. F. M. acknowledges the financial support from Consejo Nacional de Ciencia y Tecnologia (CONACyT, Mexico) to pursue her PhD.Published versio