Strong Anionic/Charge-Neutral Block Copolymers from Cu(0)-Mediated Reversible Deactivation Radical Polymerization

Development of Polyampholyte Cellulose-Based Hydrogels for Diapers with Improved Biocompatibility

Non-biodegradable superabsorbent polymers (SAPs) in personal care products (PCPs) pose significant environmental and health concerns despite their high absorption capacity. The aim of this study was to develop cellulose-based hydrogels as a sustainable alternative to those conventional SAPs, taking advantage of cellulose properties such as biocompatibility, biodegradability, and hydrophilicity. A synthesized allyl cellulose (AC) derivative was copolymerized with unusual monomers used in the production of SAPs, and the influence of monomer ratios, crosslinking density, and the ratio of cellulose to monomers on the absorption capacity was investigated and optimized. The most promising hydrogels were fully characterized for the proposed application and compared with a commercial SAP extracted from a baby diaper. The cellulose-based hydrogels showed promising absorption capacities in synthetic urine (~15 g/g), and a high centrifuge retention capacity (12.5 g/g), which was only slightly lower than the commercial SAP. These new hydrogels exhibited excellent biocompatibility and outperformed the established commercial diaper SAP. This study represents a more sustainable alternative to conventional SAPs, potentially reducing health risks while increasing the bio-based content of PCPs. Further optimization of these hydrogels could transform the hygiene product industry, by providing a balance between performance and environmental sustainability.

Strong Anionic Fluorene Donor-Acceptor Copolyelectrolytes from Protected Hydrophobic Precursors

Conjugated polyelectrolytes (CPEs), materials that are defined by a π $\pi$ -conjugated backbone and charged ionic functional groups, are frequently prepared through direct polymerization of charged monomer species in aqueous media. This route is, however, often accompanied by labor-intensive work-up procedures, low yields, and ultimately results in materials that are difficult to characterize. To overcome these inconveniences, in this work protection chemistry is applied on sulfonate-functionalized fluorene monomers that are polymerized under standard Suzuki polycondensation conditions to obtain protected donor-acceptor copolymers. Treatment of the organo-soluble precursors under nucleophilic conditions resulted in quantitative removal of the protecting groups, thereby exposing the strong anionic functionalities. Unlike in other studies, the conjugated backbones remained unharmed during this process: the photophysical properties of the CPEs are identical to their hydrophobic precursors.

Influence of counterions on the thermal and solution properties of strong polyelectrolytes

Strong polyelectrolytes (i.e., macromolecules whose charge density is independent of the medium's pH) are invaluable assets in the soft matter toolbox, as they can readily disperse in aqueous media, complex to oppositely charged species - polymers and small molecules alike - and can be implemented in a plethora of applications, ranging from surface modification to chelating agents and lubricants. However, the direct synthesis of strong polyelectrolytes in a controlled fashion remains a challenging endeavour, and their in-depth characterisation is often limited. Additionally, producing a set of charged macromolecules with the same chain length but varying counterions would open doors towards a fine control of the polymer's chemistry and physical properties. Unfortunately, this either necessitates the direct polymerisation of several monomers with potentially varying reactivities, or a time-consuming ion exchange from a single batch. Herein we explore the facile and efficient production of strong polyanions through the deprotection of a poly(3-isobutoxysulphopropyl methacrylate) using a range of inorganic and organic iodide-containing salts. Owing to the contrasting nature of their counterions, the resulting polyanions exhibit a wide range of glass transition temperatures, which follow a non-monotonic trend with increasing counterion size. While all polymers readily dissolve in water, some can also be dissolved in non-aqueous media as well. This strategy, applied to block copolymers, permits the production of a library of amphiphilic macromolecules with consistent hydrophilic and hydrophobic blocks, yet varying nature of their polyanionic segments. All amphiphiles, regardless of their counterions, readily disperse in aqueous media and form well-defined micelles featuring a hydrophobic core and a charged hydrophilic shell, as evidenced by dynamic light scattering, ζ-potential and transmission electron microscopy. Additionally, a handful of block copolymers are capable of yielding polymer micelles in organic solvents, opening an avenue to the build-up of nanostructured soft matter in non-aqueous media.

Effect of Polyelectrolyte Charge Density on the Linear Viscoelastic Behavior and Processing of Complex Coacervate Adhesives

It is well-known that the phase behavior and physicochemical and adhesive properties of complex coacervates are readily tuneable with the salt concentration of the medium. For toxicity reasons, however, the maximum applicable salt concentration in biomedical applications is typically low. Consequently, other strategies must be implemented in order to optimize the properties of the resulting complex coacervates. In this work, the effect of the charge density of a strong polyanion on the properties of complex coacervates was studied. To control this charge density, statistical anionic/charge-neutral hydrophilic copolymers were synthesized by means of an elegant protection/deprotection strategy and subsequently complexed with a strong polycation. The resulting complexes were observed to have an increasing water content as well as faster relaxation dynamics, with either increasing salt concentration or decreasing charge density. Time-salt and time-salt-charge density superpositions could be performed and showed that the relaxation mechanism of the complex coacervates remained unchanged. When the charge density was decreased, lower salt concentration complexes became suitable for viscoelastic adhesion with improved injectability. Such complex coacervates are promising candidates for injectable biomedical adhesives.

Rationally designed block copolymer-based nanoarchitectures: An emerging paradigm for effective drug delivery

Various polymeric materials have been investigated to produce unique modes of delivery for drug modules to achieve either temporal or spatial control of bioactives delivery. However, after intravenous administration, phagocytic cells quickly remove these nanostructures from the systemic circulation via the reticuloendothelial system (RES). To overcome these concerns, ecofriendly block copolymers are increasingly being investigated as innovative carriers for the delivery of bioactives. In this review, we discuss the design, fabrication techniques, and recent advances in the development of block copolymers and their applications as drug carrier systems to improve the physicochemical and pharmacological attributes of bioactives.

One-Pot Synthesis of Strong Anionic/Charge-Neutral Amphiphilic Block Copolymers

Despite the ever more versatile polymerization techniques that are becoming available, the synthesis of macromolecules with tailored functionalities can remain a lengthy endeavor. This becomes more conspicuous when the implementation of incompatible chemistries (i.e., strong polyelectrolytes) within sequence-controlled polymers is desired, often requiring (i) polymerization, (ii) chain extension, and (iii) postpolymerization modification. Herein, we explore the production of strong anionic/charge-neutral block copolymers (BCPs) in a one-pot fashion. This straightforward three-step process includes the synthesis of a macroinitiator and chain extension via rapid and efficient photomediated atom transfer radical polymerization, followed by in situ deprotection to expose the polyanionic domains. The resulting BCPs, which are strong amphiphiles by nature, are capable of self-assembly in aqueous media, as evidenced by dynamic light scattering, small-angle X-ray scattering, ζ-potential measurements, and transmission electron microscopy. We further demonstrate the versatility of our methodology by producing several BCPs through sampling of a single reaction mixture, enabling the straightforward production of strong polymer amphiphiles.

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.