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Industrial and household products, such as paints, inks and cosmetics usually consist of mixtures of macromolecules that are disperse in composition, in size and in monomer sequence. Identifying structure–function relationships for these systems is complicated, as particular macromolecular components cannot be investigated individually. For this study, we have addressed this issue, and have synthesized a series of five sequence-defined polyurethanes (PUs): one neutral-hydrophobic, one single-charged hydrophilic, one single-charged hydrophobic and two double-charged amphiphilic PUs (one symmetric and one asymmetric). These novel precision PUs – that were prepared by using stepwise coupling-deprotection synthetic protocols – have a defined composition, size and monomer sequence, where the chosen sequences were inspired by those that are abundantly formed in the production of industrial waterborne PU dispersions. By performing dynamic light scattering experiments (DLS), self-consistent field (SCF) computations and cryogenic transmission electron microscopy (cryo-TEM), we have elucidated the behavior in aqueous solution of the individual precision PUs, as well as of binary and ternary mixtures of the PU sequences. The double-charged PU sequences (‘hosts’) were sufficiently amphiphilic to yield single-component micellar solutions, whereas the two more hydrophobic sequences did not micellize on their own, and gave precipitates or ill-defined larger aggregates. Both the neutral-hydrophobic PU and the hydrophilic single-charged PU were successfully incorporated in the host micelles as guests, respectively increasing and reducing the micelle radius upon incorporation. SCF computations indicated that double-charged symmetric PUs stretch whilst double-charged asymmetric PUs are expelled from the core to accommodate hydrophobic PU guests within the micelles. For the ternary mixture of the double-charged symmetric and asymmetric hosts and the neutral-hydrophobic guest we have found an improved colloidal stability, as compared to those for binary mixtures of either host and hydrophobic guest. In another ternary mixture of precision PUs, with all three components not capable of forming micelles on their own, we see that the ensemble of molecules produces stable micellar solutions. Taken together, we find that the interplay between PU-molecules in aqueous dispersions promotes the formation of stable micellar hydrocolloids., In a novel synthetic approach, we have prepared sequence-defined waterborne polyurethanes and have studied their (co)-assembly to hydrocolloids; we find that especially the interplay between the sequences promotes the formation of stable micelles.

Structurally complex hierarchical block copolymer assemblies can be formed in solution via the interplay of multiple assembly pathways. Crystallizable block copolymers can undergo self-assembly, crystallization or phase separation in solution. By selecting appropriate solvency conditions (solvent and temperature) it is possible to induce an interplay between these processes resulting in a complex association behavior. This leads to the formation of assemblies with up to four levels of hierarchical organization. Furthermore, varying the copolymer composition enables to tune the formation mechanism and the morphology of the aggregates.

The assembly of oppositely charged block copolymers, containing small thermoresponsive moieties, was investigated as a function of salt concentration and temperature. Aqueous solutions of poly-[N-isopropylacrylamide]-b-poly[dimethylaminoethyl methacrylate] (NIPAM44-b-DMAEMA216) and PNIPAM-b-poly[acrylic acid]-b-PNIPAM (NIPAM35-b-AA200-b-NIPAM35) were mixed in equal charge stoichiometry, and analysed by light scattering (LS), NMR spectroscopy and small angle X-ray scattering (SAXS). At room temperature, two different micelle morphologies were found at different salt concentrations. At NaCl concentrations below 0.75 M, complex coacervate core micelles (C3M) with a PNIPAM corona were formed as a result of interpolyelectrolyte complexation. At NaCl concentrations exceeding 0.75 M, the C3M micelles inverted into PNIPAM cored micelles (PCM), containing a water soluble polyelectrolyte corona. This behavior is ascribed to the salt concentration dependence of both the lower critical solution temperature (LCST) of PNIPAM, and the complex coacervation. Above 0.75 M NaCl, the PNIPAM blocks are insoluble in water at room temperature, while complexation between the polyelectrolytes is prevented because of charge screening by the salt. Upon increasing the temperature, both types of micelles display a cloud point temperature (Tcp), despite the small thermoresponsive blocks, and aggregate into hydrogels. These hydrogels consist of a complexed polyelectrolyte matrix with microphase separated PNIPAM domains. Controlling the morphology and aggregation of temperature sensitive polyelectrolytes can be an important tool for drug delivery systems, or the application and hardening of underwater glues., The assembly of oppositely charged block copolymers, containing small thermoresponsive moieties, was investigated as a function of salt concentration and temperature.

We report the synthesis and self-assembly of a library of squaramide-based bolaamphiphiles with variable hydrophobic and hydrophilic domain sizes, consisting of varied aliphatic chains (n = 2 to 12 methylene repeat units) and linear oligo(ethylene glycol) (m = 11 to 36 repeat units), to understand their effect on the formation of supramolecular polymer nanoparticles. Systematic variation of the hydrophobic chain length show that a minimum hydrophobic domain is required to shield the squaramide units from water when a constant hydrophilic domain is maintained for self-assembly. By contrast, significant increases to the hydrophilic chain length of the bolaamphiphile, while keeping the hydrophobic domain constant, results in a transition from fibrillar to spherical nanoscale objects with an alteration in the aggregation mode of the monomers likely due to steric constraints of the oligo(ethylene glycol) chains. By understanding the self-assembly space achievable for these squaramide-based bolaamphiphiles through examining the interplay between various monomer features, we show their distinct effects on the formation of self-assembled nanoparticles with possibilities to modulate their shape and size in water for future applications in the biomedical area.

Self-assembly of block copolymers in solution is a topic of great interest in polymer science due to the potential for applications as a drug carrier system. In bulk, fully discrete polymers have been shown to self-assemble in extremely well-defined structures, but the effect of full discreteness on self-assembly in solution is less known. Furthermore, little is known about the effect of molar mass dispersity on crystallization driven self-assembly. Here, we investigate both the effects of dispersity and crystallinity on the self-assembly behavior of low molecular weight poly(lactic acid)-poly(ethylene glycol) block co-oligomers (BCOs) in solution. The results show that the introduction of dispersity and/or crystallinity does not significantly affect spherical and cylindrical morphologies, but vesicular structures are affected. The introduction of dispersity in amorphous vesicle forming BCOs lowers the reproducibility of preparations in solution. For crystalline BCOs, the introduction of dispersity leads to a clear decrease of ordering in bulk and it prevents crystallization of the lLA block in solution. This all arises already at a low dispersity (Đ ≤ 1.06), highlighting the effect of dispersity on assemblies of low MW BCOs. It also underlines the need to take dispersity into account when aiming for homogeneous well-defined structures in solution.