A mild and quantitative route towards well-defined strong anionic/hydrophobic diblock copolymers:Synthesis and aqueous self-assembly

Block copolymers that accommodate both hydrophobic and ionic elements are interesting materials for numerous applications, such as stabilizing agents, lubricants and proton-exchange membranes. Frequently these copolymers are based on weak polyelectrolytes, but the pH-dependent charge density restricts their use to a limited pH window. Although strong polyelectrolytes do not suffer this problem, the most commonly employed post-modification approach limits the choice of the hydrophobic component, as harsh reaction conditions are usually involved. Moreover, this method often results in incomplete functionalization of the precursor copolymer. To avoid these difficulties a mild route was developed that is based on a hydrophobic protected poly(3-sulfopropyl methacrylate) intermediate that enables the preparation of well-defined strong anionic polyelectrolytes. The potential of this method was demonstrated by synthesizing hydrophobic/strong anionic diblock copolymers, and their self-assembly in aqueous solution was studied

Protected Poly(3-sulfopropyl methacrylate) Copolymers:Synthesis, Stability, and Orthogonal Deprotection

Because of their permanent charge, strong polyelectrolytes remain challenging to characterize, in particular, when they are combined with hydrophobic features. For this reason, they are typically prepared through a postmodification of a fully hydrophobic precursor. Unfortunately, these routes often result in an incomplete functionalization or otherwise require harsh reaction conditions, thus limiting their applicability. To overcome these problems, in this work a strategy is presented that facilitates the preparation of well-defined strong polyanions by starting from protected 3-sulfopropyl methacrylate monomers. Depending on the chemistry of the protecting group, the hydrophobic precursor could be quantitatively converted into a strong polyanion under nucleophilic, acidic, or basic conditions. As a proof of concept, orthogonally protected diblock copolymers were synthesized, selectively deprotected, and allowed to self-assemble in aqueous solution. Further conversion into a fully water-soluble polyanion was achieved by deprotecting the second block as well

Hierarchical structure formation in supramolecular comb-shaped block copolymers

Vanwege hun ketenachtige structuur vormen mengsels van chemisch verschillende homopolymeren gescheiden fases, net als water en olie. In blokcopolymeren zijn twee (diblok) of meer (multiblok) van zulke macromoleculen covalent aan elkaar gekoppeld, waardoor het onmogelijk is om op macroscopisch niveau te ontmengen. Als gevolg hiervan vindt fasescheiding van blokcopolymeren op moleculair niveau plaats. Door het molecuulgewicht of de samenstelling te veranderen kan fasescheiding van diblokcopolymeren leiden tot spontane vorming van verschillende soorten geordende structuren, met hun grootte variërend tussen de 10 en 100 nm. Voorbeelden hiervan zijn lamellaire, cylindrische en bolvorminge structuren. Door de complexiteit van de macromoleculaire architectuur te verhogen, verkrijgt men over het algemeen complexer fasegedrag. Structuren gevormd in multiblokcopolymeersystemen zijn bijvoorbeeld door zowel theoretische als experimentele onderzoeksgroepen grondig bestudeerd. Doordat hun synthese echter zeer ingewikkeld is, zijn er alternatieve, minder veeleisende routes nodig voor toepassingen in de nanotechnologie. Supramoleculaire chemie is een van deze methodes. Door lineaire diblokcopolymeren te combineren met kleine, organische oppervlakte-actieve stoffen, kunnen kamvormige polymeren worden bereid door deze twee componenten simpelweg te mengen. Vaak leidt dit tot de vorming van multiblokachtige hiërarchische structuren (d.w.z. structuurvorming binnen een andere structuur). Het werk dat in dit proefschrift wordt beschreven focust zich op de synthese en zelf-assemblage van een nieuwe klasse supramoleculaire materialen, de zogenaamde dubbele-kam diblokcopolymeren. Microfasescheiding van deze complexen resulteerde in verschillende nieuwe, unieke hiërarchische morfologieën welke niet eerder werden gezien in blokcopolymeer-gebaseerde materialen. Daarnaast kwam het gevonden fasegedrag goed overeen met eerder ontwikkelde theoretische modellen

Recent Developments and Practical Feasibility of Polymer-Based Antifouling Coatings

While nature has optimized its antifouling strategies over millions of years, synthetic antifouling coatings have not yet reached technological maturity. For an antifouling coating to become technically feasible, it should fulfill many requirements: high effectiveness, long-term stability, durability, ecofriendliness, large-scale applicability, and more. It is therefore not surprising that the search for the perfect antifouling coating has been going on for decades. With the discovery of metal-based antifouling paints in the 1970s, fouling was thought to be a problem of the past, yet its untargeted toxicity led to serious ecological concern, and its use became prohibited. As a response, research shifted focus toward a biocompatible alternative: polymer-based antifouling coatings. This has resulted in numerous advanced and innovative antifouling strategies, including fouling-resistant, fouling-release, and fouling-degrading coatings. Here, these novel and exciting discoveries are highlighted while simultaneously assessing their antifouling performance and practical feasibility

Bioinspired Underwater Adhesives by Using the Supramolecular Toolbox

Nature has developed protein-based adhesives whose underwater performance has attracted much research attention over the last few decades. The adhesive proteins are rich in catechols combined with amphiphilic and ionic features. This combination of features constitutes a supramolecular toolbox, to provide stimuli-responsive processing of the adhesive, to secure strong adhesion to a variety of surfaces, and to control the cohesive properties of the material. Here, the versatile interactions used in adhesives secreted by sandcastle worms and mussels are explored. These biological principles are then put in a broader perspective, and synthetic adhesive systems that are based on different types of supramolecular interactions are summarized. The variety and combinations of interactions that can be used in the design of new adhesive systems are highlighted

Enhanced stability of complex coacervate core micelles following different core-crosslinking strategies

Complex coacervate core micelles (C3Ms) are formed by mixing aqueous solutions of a charged (bio)macromolecule with an oppositely charged-neutral hydrophilic diblock copolymer. The stability of these structures is dependent on the ionic strength of the solution; above a critical ionic strength, the micelles will completely disintegrate. This instability at high ionic strengths is the main drawback for their application in, e.g., drug delivery systems or protein protection. In addition, the stability of C3Ms composed of weak polyelectrolytes is pH-dependent as well. The aim of this study is to assess the effectiveness of covalent crosslinking of the complex coacervate core to improve the stability of C3Ms. We studied the formation of C3Ms using a quaternized and amine-functionalized cationic-neutral diblock copolymer, poly(2-vinylpyridine)-block-poly(ethylene oxide) (QP2VP-b-PEO), and an anionic homopolymer, poly(acrylic acid) (PAA). Two different core-crosslinking strategies were employed that resulted in crosslinks between both types of polyelectrolyte chains in the core (i.e., between QP2VP and PAA) or in crosslinks between polyelectrolyte chains of the same type only (i.e., QP2VP). For these two strategies we used the crosslinkers 1-ethyl-3-(3′-dimethylaminopropyl)carbodiimide hydrochloride (EDC) and dimethyl-3,3′-dithiopropionimidate dihydrochloride (DTBP), respectively. EDC provides permanent crosslinks, while DTBP crosslinks can be broken by a reducing agent. Dynamic light scattering showed that both approaches significantly improved the stability of C3Ms against salt and pH changes. Furthermore, reduction of the disulphide bridges in the DTBP core-crosslinked micelles largely restored the original salt-stability profile. Therefore, this feature provides an excellent starting point for the application of C3Ms in controlled release formulations

Scalable Fabrication of Reversible Antifouling Block Copolymer Coatings via Adsorption Strategies

Fouling remains a widespread challenge as its nonspecific and uncontrollable character limits the performance of materials and devices in numerous applications. Although many promising antifouling coatings have been developed to reduce or even prevent this undesirable adhesion process, most of them suffer from serious limitations, specifically in scalability. Whereas scalability can be particularly problematic for covalently bound antifouling polymer coatings, replacement by physisorbed systems remains complicated as it often results in less effective, low-density films. In this work, we introduce a two-step adsorption strategy to fabricate high-density block copolymer-based antifouling coatings on hydrophobic surfaces, which exhibit superior properties compared to one-step adsorbed coatings. The obtained hybrid coating manages to effectively suppress the attachment of both lysozyme and bovine serum albumin, which can be explained by its dense and homogeneous surface structure as well as the desired polymer conformation. In addition, the intrinsic reversibility of the adhered complex coacervate core micelles allows for the successful triggered release and regeneration of the hybrid coating, resulting in full recovery of its antifouling properties. The simplicity and reversibility make this a unique and promising antifouling strategy for large-scale underwater applications