Atom Transfer Radical Polymerization for Biorelated Hybrid Materials

Aluminum Tralen Complex Meditated Reversible-Deactivation Radical Polymerization of Vinyl Acetate

The Al^III(tralen)Cl complex (tralenH₂ = N,N'-di(cyclohepta-2,4,6-trien-1-one-2-yl)-1,2-diaminobenzene) has been synthesized and applied to mediate the reversible-deactivation radical polymerization (RDRP) of vinyl monomers. The polymerization of unconjugated monomers such as vinyl acetate (VAc) and N-vinylpyrrolidone (NVP) with Al^III(tralen)Cl showed the living characters of linearly increased molecular weight with conversion and formation of block copolymer. However, the control manners in the polymerization of conjugated monomers like acrylates and styrene were limited. The electron paramagnetic resonance (EPR) spectrum indicated that Al^III(tralen)BArF (BArF = tetrakis(3,5-trifluormethylphenyl)borate) and propagating radicals formed a paramagnetic dormant species, possibly PVAc-Al^III(tralen)BArF, via the single-electron transfer to the tralen ligand.

DNA-Polymer Nanostructures by RAFT Polymerization and Polymerization-Induced Self-Assembly

Nanostructures derived from amphiphilic DNA-polymer conjugates have emerged prominently due to their rich self-assembly behavior; however, their synthesis is traditionally challenging. Here, we report a novel platform technology towards DNA-polymer nanostructures of various shapes by leveraging polymerization-induced self-assembly (PISA) for polymerization from single-stranded DNA (ssDNA). A "grafting from" protocol for thermal RAFT polymerization from ssDNA under ambient conditions was developed and utilized for the synthesis of functional DNA-polymer conjugates and DNA-diblock conjugates derived from acrylates and acrylamides. Using this method, PISA was applied to manufacture isotropic and anisotropic DNA-polymer nanostructures by varying the chain length of the polymer block. The resulting nanostructures were further functionalized by hybridization with a dye-labelled complementary ssDNA, thus establishing PISA as a powerful route towards intrinsically functional DNA-polymer nanostructures.

Fully oxygen-tolerant atom transfer radical polymerization triggered by sodium pyruvate

ATRP (atom transfer radical polymerization) is one of the most robust reversible deactivation radical polymerization (RDRP) systems. However, the limited oxygen tolerance of conventional ATRP impedes its practical use in an ambient atmosphere. In this work, we developed a fully oxygen-tolerant PICAR (photoinduced initiators for continuous activator regeneration) ATRP process occurring in both water and organic solvents in an open reaction vessel. Continuous regeneration of the oxidized form of the copper catalyst with sodium pyruvate through UV excitation allowed the chemical removal of oxygen from the reaction mixture while maintaining a well-controlled polymerization of N-isopropylacrylamide (NIPAM) or methyl acrylate (MA) monomers. The polymerizations of NIPAM were conducted with 250 ppm (with respect to the monomer) or lower concentrations of CuBr2 and a tris[2-(dimethylamino)ethyl]amine ligand. The polymers were synthesized to nearly quantitative monomer conversions (>99%), high molecular weights (M n > 270 000), and low dispersities (1.16 < Đ < 1.44) in less than 30 min under biologically relevant conditions. The reported method provided a well-controlled ATRP (Đ = 1.16) of MA in dimethyl sulfoxide despite oxygen diffusion from the atmosphere into the reaction system.

The rise of bio-inspired polymer compartments responding to pathology-related signals

Self-organized nano- and microscale polymer compartments such as polymersomes, giant unilamellar vesicles (GUVs), polyion complex vesicles (PICsomes) and layer-by-layer (LbL) capsules have increasing potential in many sensing applications. Besides modifying the physicochemical properties of the corresponding polymer building blocks, the versatility of these compartments can be markedly expanded by biomolecules that endow the nanomaterials with specific molecular and cellular functions. In this review, we focus on polymer-based compartments that preserve their structure, and highlight the key role they play in the field of medical diagnostics: first, the self-assembling abilities that result in preferred architectures are presented for a broad range of polymers. In the following, we describe different strategies for sensing disease-related signals (pH-change, reductive conditions, and presence of ions or biomolecules) by polymer compartments that exhibit stimuli-responsiveness. In particular, we distinguish between the stimulus-sensitivity contributed by the polymer itself or by additional compounds embedded in the compartments in different sensing systems. We then address necessary properties of sensing polymeric compartments, such as the enhancement of their stability and biocompatibility, or the targeting ability, that open up new perspectives for diagnostic applications.

Enlightening advances in polymer bioconjugate chemistry: light-based techniques for grafting to and from biomacromolecules

Photochemistry has revolutionized the field of polymer-biomacromolecule conjugation. Ligation reactions necessitate biologically benign conditions, and photons have a significant energy advantage over what is available thermally at ambient temperature, allowing for rapid and unique reactivity. Photochemical reactions also afford many degrees of control, specifically, spatio-temporal control, light source tunability, and increased oxygen tolerance. Light-initiated polymerizations, in particular photo-atom-transfer radical polymerization (photo-ATRP) and photoinduced electron/energy transfer reversible addition-fragmentation chain transfer polymerization (PET-RAFT), have been used for grafting from proteins, DNA, and cells. Additionally, the spatio-temporal control inherent to light-mediated chemistry has been utilized for grafting biomolecules to hydrogel networks for many applications, such as 3-D cell culture. While photopolymerization has clear advantages, there are factors that require careful consideration in order to obtain optimal control. These factors include the photocatalyst system, light intensity, and wavelength. This Perspective aims to discuss recent advances of photochemistry for polymer biomacromolecule conjugation and potential considerations while tailoring these systems.

Low Ppm Atom Transfer Radical Polymerization in (Mini)Emulsion Systems

In the last decade, unceasing interest in atom transfer radical polymerization (ATRP) has been noted, especially in aqueous dispersion systems. Emulsion or miniemulsion is a preferred environment for industrial polymerization due to easier heat dissipation and lower production costs associated with the use of water as a dispersant. The main purpose of this review is to summarize ATRP methods used in emulsion media with different variants of initiating systems. A comparison of a dual over single catalytic approache by interfacial and ion pair catalysis is presented. In addition, future development directions for these methods are suggested for better use in biomedical and electronics industries.

Superhydrophilicity and strong salt-affinity: Zwitterionic polymer grafted surfaces with significant potentials particularly in biological systems

In recent years, zwitterionic polymers have been frequently reported to modify various surfaces to enhance hydrophilicity, antifouling and antibacterial properties, which show significant potentials particularly in biological systems. This review focuses on the fabrication, properties and various applications of zwitterionic polymer grafted surfaces. The "graft-from" and "graft-to" strategies, surface grafting copolymerization and post zwitterionization methods were adopted to graft lots type of the zwitterionic polymers on different inorganic/organic surfaces. The inherent hydrophilicity and salt affinity of the zwitterionic polymers endow the modified surfaces with antifouling, antibacterial and lubricating properties, thus the obtained zwitterionic surfaces show potential applications in biosystems. The zwitterionic polymer grafted membranes or stationary phases can effectively separate plasma, water/oil, ions, biomolecules and polar substrates. The nanomedicines with zwitterionic polymer shells have "stealth" effect in the delivery of encapsulated drugs, siRNA or therapeutic proteins. Moreover, the zwitterionic surfaces can be utilized as wound dressing, self-healing or oil extraction materials. The zwitterionic surfaces are expected as excellent support materials for biosensors, they are facing the severe challenges in the surface protection of marine facilities, and the dense ion pair layers may take unexpected role in shielding the grafted surfaces from strong electromagnetic field.