Polyacrylamide-Based Block Copolymer Bearing Pyridine Groups Shows Unexpected Salt-Induced LCST Behavior

Thermal-responsive block copolymers are a special type of macromolecule that exhibit a wide range of applications in various fields. In this contribution, we report a new type of polyacrylamide-based block copolymer bearing pyridine groups of polyethylene glycol-block-poly(N-(2-methylpyridine)-acrylamide; Px) that display distinct salt-induced lower critical solution temperature (LCST) behavior. Unexpectedly, the phase-transition mechanism of the salt-induced LCST behavior of Px block copolymers is different from that of the reported LCST-featured analogues. Moreover, their thermo-responsive behavior can be significantly regulated by several parameters such as salt species and concentration, urea, polymerization degree, polymer concentration and pH values. This unique thermal behavior of pyridine-containing block copolymers provides a new avenue for the fabrication of smart polymer materials with potential applications in biomedicine.

Polystyrene-b-Poly(2-(Methoxyethoxy)ethyl Methacrylate) Polymerization by Different Controlled Polymerization Mechanisms

Functional polymers have been an important field of research in recent years. With the development of the controlled polymerization methods, block-copolymers of defined structures and properties could be obtained. In this paper, the possibility of the synthesis of the functional block-copolymer polystyrene-b-poly(2-(methoxyethoxy)ethyl methacrylate) was tested. The target was to prepare the polymer of the number average molecular weight (Mn) of approximately 120 that would contain 20–40% of poly(2-(methoxyethoxy)ethyl methacrylate) by mass and in which the polymer phases would be separated. The polymerization reactions were performed by three different mechanisms for the controlled polymerization—sequential anionic polymerization, atomic transfer radical polymerization and the combination of those two methods. In sequential anionic polymerization and in atomic transfer radical polymerization block-copolymers of the desired composition were obtained but with the Mn significantly lower than desired (up to 30). The polymerization of the block-copolymers of the higher Mn was unsuccessful, and the possible mechanisms for the unwanted side reactions are discussed. It is also concluded that combination of sequential anionic polymerization and atomic transfer radical polymerization is not suitable for this system as polystyrene macroinitiator cannot initiate the polymerization of poly(2-(methoxyethoxy)ethyl methacrylate).

Poly(Ethylene Glycol-block-2-Ethyl-2-Oxazoline) as Cathode Binder in Lithium-Sulfur Batteries

Functional binders constitute a strategy to overcome several challenges that lithium-sulfur (Li-S) batteries are facing due to soluble reaction intermediates in the positive electrode. Poly (ethylene oxide) (PEO) and poly (vinylpyrrolidone) (PVP) are in this context a previously well-explored binder mixture. Their ether and amide groups possess affinity to the dissolved sulfur species, which enhances the sulfur utilization and mitigates the parasitic redox shuttle. However, the immiscibility of PEO and PVP is a concern for electrode stability. Copolymers comprising ether and amide groups are thus promising candidates to improve the stability the system. Here, a series of poly (ethylene glycol-block-2-ethyl-2-oxazoline) with various block lengths is synthesized and explored as binders in S/C composite electrodes in Li-S cells. While the electrochemical analyses show that although the sulfur utilization and capacity retention of the tested electrodes are similar, the integrity of the as-cast electrodes can play a key role for power capability.

Dispersible Conjugated Polymer Nanoparticles as Biointerface Materials for Label-Free Bacteria Detection

Fast and efficient identification of bacterial pathogens in water and biological fluids is an important issue in medical, food safety, and public health concerns that requires low-cost and efficient sensing strategies. Impedimetric sensors are promising tools for monitoring bacteria detection because of their reliability and ease-of-use. We herein report a study on new biointerface-based amphiphilic poly(3-hexylthiophene)-b-poly(3-triethylene-glycol-thiophene), P3HT-b-P3TEGT, for label-free impedimetric detection of Escherichia coli (E. coli). This biointerface is fabricated by the self-assembly of P3HT-b-P3TEGT into core-shell nanoparticles, which was further decorated with mannose, leading to an easy-to-use solution-processable nanoparticle material for biosensing. The hydrophilic block P3TEGT promotes antifouling and prevents nonspecific interactions, while improving the ionic and electronic transport properties, thus enhancing the electrochemical-sensing capability in aqueous solution. Self-assembly and micelle formation of P3HT-b-P3TEGT were analyzed by 2D-NMR, Fourier transform infrared, dynamic light scattering, contact angle, and microscopy characterizations. Detection of E. coli was characterized and evaluated using electrochemical impedance spectroscopy and optical and scanning electron microscopy techniques. The sensing layer based on the mannose-functionalized P3HT-b-P3TEGT nanoparticles demonstrates targeting ability toward E. coli pili protein with a detection range from 10³ to 10⁷ cfu/mL, and its selectivity was studied with Gram(+) bacteria. Application to real samples was performed by detection of bacteria in tap and the Nile water. The approach developed here shows that water/alcohol-processable-functionalized conjugated polymer nanoparticles are suitable for use as electrode materials, which have potential application in fabrication of a low-cost, label-free impedimetric biosensor for the detection of bacteria in water.

In Vitro and In Vivo Characterization of Biodegradable Reactive Isocyanate-Terminated Three-Armed- and Hyperbranched Block Copolymeric Tissue Adhesives

Tissue adhesives are an attractive class of biomaterials, which can serve as a treatment for meniscus tears. In this study, physicochemical and adhesive properties of novel biodegradable three-armed- and hyperbranched block copolymeric adhesives are evaluated. Additionally, their degradation in vitro and in vivo, and the tissue reaction after subcutaneous injection in rats are assessed. The developed adhesives have sufficient adhesive strength to meniscus tissue after curing (66-88 kPa). Networks based on the three-armed adhesive have tensile properties that are in the same range as human meniscus. After 26 weeks, networks based on the hyperbranched adhesive show a faster mass loss (25.4%) compared to networks prepared from the three-armed ones (5.5%). Both adhesives induce an inflammatory reaction, however, no necrosis and only initial toxic effects on peripheral tissues are observed. The proposed materials are suitable candidates for the use as resorbable tissue adhesives for meniscus repair.