Multiblock copolymers (MBCs) are an emerging class of synthetic polymers that exhibit different macromolecular architectures and behaviours to those of homopolymers or di/triblock copolymers. Owing ...to the rapidly expanding field of synthetic methodologies applied in the field of polymer chemistry, sequenced controlled MBCs are becoming the new functional materials of this decade. MBCs can now be synthesised with precision and control unlike before and yet some of the synthetic limitations remain a challenge. In this review article, we summarise the various synthetic methodologies that have been reported to date with recent advances in different polymerisation techniques and applications.
Multiblock copolymers (MBCs) are an emerging class of synthetic polymers that exhibit different macromolecular architectures and behaviours to those of homopolymers or di/triblock copolymers.
Thermoresponsive polymers are gaining increasing interest for numerous applications especially in the biomedical and nanotechnology fields. The thermoresponsive behaviour of polymers has been ...extensively studied in pure water or water/organic solvent systems, however, temperature-induced phase transitions in other organic solvents are less common. Polymers in organic solvents exhibit a broad range of temperature-driven solution behaviours, from LCST and UCST, to sol-gel transitions, to micellization processes, among others, with potential applications as smart materials in electronics, in the lubricant industry, and in the biomedical field. This review article will focus on the thermoresponsive behaviour of polymers in different classes of organic solvents and mixtures thereof to emphasize and demonstrate the versatility and potential of these polymers.
Polymers does not only show phase transition in aqueous solutions but they also do in organic solvents, which is the focus of this review article.
Star-shaped glycopolymers provide very high binding activities toward lectins. However, a straightforward synthesis method for the preparation of multi-arm glycopolymers in a one-pot approach has ...been challenging. Herein, we report a rapid synthesis of well-defined multi-arm glycopolymers via Cu(0)-mediated reversible deactivation radical polymerization in aqueous media. d-Mannose acrylamide has been homo- and copolymerized with NIPAM to provide linear arms and then core cross-linked with a bisacrylamide monomer. Thus, the arm length and core size of multi-arm glycopolymers were tuned. Moreover, the stability of multi-arm glycopolymers was investigated, and degradation reactions under acidic or basic conditions were observed. The binding activities of the obtained multi-arm glycopolymers with mannose-specific human lectins, DC-SIGN and MBL, were investigated via surface plasmon resonance spectroscopy. Finally, the encapsulation ability of multi-arm glycopolymers was examined using DHA and Saquinavir below and above the lower critical solution temperature (LCST) of P(NIPAM).
Lectins are omnipresent carbohydrate binding proteins that are involved in a multitude of biological processes. Unearthing their binding properties is a powerful tool toward the understanding and ...modification of their functions in biological applications. Herein, we present the synthesis of glycopolymers with a brush architecture via a "grafting from" methodology. The use of a versatile 2-oxazoline inimer was demonstrated to open avenues for a wide range of 2-oxazoline/acrylamide bottle brush polymers utilizing aqueous Cu-mediated reversible deactivation radical polymerization (Cu-RDRP). The polymers in the obtained library were assessed for their thermal properties in aqueous solution and their binding toward the C-type animal lectins dendritic cell-specific intercellular adhesion molecule-3-grabbing nonintegrin (DC-SIGN) and mannose-binding lectin (MBL) via surface plasmon resonance spectrometry. The encapsulation properties of a hydrophobic drug-mimicking compound demonstrated the potential use of glyco brush copolymers in biological applications.
Click reactions are utilized widely to modify chain ends and side groups of polymers while click polymerizations based on step‐growth polymerization of bifunctional monomers have recently attracted ...increased attention of polymer chemists. Herein, the combination of two highly efficient click reactions, namely para‐fluoro‐thiol click and thiol‐bromo substitution reactions, is demonstrated to form fluorinated polymers with tuned hydrophobicity owing to the nature of the dithiol linker compound. The key compound in this study is 2,3,4,5,6‐pentafluoro benzyl bromide that provides the combination of thiol click reactions. The thiols used here are 4,4‐thiobisbenzenthiol, 2,2'‐(ethylenedioxy) diethanethiol, and 1,2‐ethanedithiol that allow tuning of the properties of obtained polymers. The step‐growth click reaction conditions are optimized by screening the effect of reaction temperature, base, solvent, and stochiometric ratio of the compounds. Thermal properties and hydrophobicity of synthesized polymers are determined via water contact angle, thermogravimetric analysis and differential scanning calorimetry measurements, showing thermal stability up to 300 °C, glass transition temperatures ranging from −25 to 82 °C and water contact angles ranging from 55 to 90 °C.
A new method for the synthesis of a series of fluorinated polymers using commercially available dithiol compounds and 2,3,4,5,6‐pentafluoro benzyl bromides is reported. The step‐growth polymerization can proceed at room temperature while based on the nucleophilicity of dithiol compounds, the completion could be reached in 10 min. Obtained polymers have a good thermal resistance up to 300 °C and hydrophobic character is measured by water contact angle measurements.
Multi-block copolymers offer a plethora of exciting properties, easily tuned by modulating parameters such as monomer composition, block length, block number and dispersity. Here, we demonstrate a ...highly efficient one-pot synthesis of such materials by combining copper-mediated reversible-deactivation radical polymerisation (Cu-RDRP) with thiol-bromo post-polymerisation modification. Specifically, the use of bifunctional bromo initiators and bisthiol compounds furnishes hydrophilic, hydrophobic and amphiphilic architectures in less than 10 minutes via a step growth-type mechanism. Furthermore, the degradation characteristics of the obtained polymers are demonstrated in oxidative, methylating and high temperature environments. The rate of degradation and nature of the end-group is shown to vary with the choice of bisthiol linker and other reaction conditions.
Thioacrylates are a novel class of monomers that have been shown to be polymerisable. However, knowledge of their polymerisation behaviour in metal mediated radical polymerisation is limited, ...although the thioester functionality allows efficient post modifications. In this report, findings on the polymerisation of thioacrylates
via
SET-LRP conditions are presented. In a set of carefully monitored optimisation reactions, low conversions were observed when CuBr
2
was employed, which is due to the complexation of the thioester with Cu catalyst. Nevertheless, once CuBr
2
is replaced with an iron based deactivator, full conversion for the homopolymerisation of ethyl thioacrylate is achieved. In a next step, the polymerisation conditions for an ethyl thioacrylate and a methyl acrylate block copolymer are optimised. The obtained block copolymer was subjected to an amidation reaction to obtain an all-acrylic copolymer, consisting of an acrylate, a thioacrylate and an acrylamide.
Ethyl thioacrylate was polymerised
via
Cu-RDRP and subjected to amidation to obtain the first "all-acrylic" copolymer.
We synthesised a library of linear 2-(dimethylaminoethyl) methacrylate polymers (PDMAEMA) as an alternative to polyacrylamide flocculants and used them for flocculation of freshwater microalgae ...Chlorella vulgaris. The dose required to induce flocculation (17.2–23.5 mg L−1) was found to be independent of the molecular weight (MW) of the polymer. ζ-potential measurements indicated that flocculation occurred primarily through a charge neutralisation mechanism. Surface charge reversal of the microalgal-PDMAEMA particles and resulting dispersion restabilization was observed for high MW PDMAEMA, but not for low MW PDMAEMA. We hypothesized that charge reversal was a result of partial absorbance of long polymers to the cell surface, resulting in charged loops and tails that emerge from the cell surface. This was confirmed and visualized using AFM, which revealed an increase in surface roughness of cells when high MW PDMAEMA was added in high dose, but not when low MW PDMAEMA was used. Dispersion restabilization could be partially prevented by stepwise addition of the high MW PDMAEMA.
•PolyDMAEMA was proven to be an effective flocculant for Chlorella vulgaris.•Polymer molecular weight did not affect dose required to induce flocculation.•AFM showed attachment of polymer on microalgal cells.•Dispersion restabilization can be avoided by stepwise addition of polymer.
Carbohydrate-binding proteins (lectins) play vital roles in cell recognition and signaling, including pathogen binding and innate immunity. Thus, targeting lectins, especially those on the surface of ...immune cells, could advance immunology and drug discovery. Lectins are typically oligomeric; therefore, many of the most potent ligands are multivalent. An effective strategy for lectin targeting is to display multiple copies of a single glycan epitope on a polymer backbone; however, a drawback to such multivalent ligands is they cannot distinguish between lectins that share monosaccharide binding selectivity (e.g., mannose-binding lectins) as they often lack molecular precision. Here, we describe the development of an iterative exponential growth (IEG) synthetic strategy that enables facile access to synthetic glycomacromolecules with precisely defined and tunable sizes up to 22.5 kDa, compositions, topologies, and absolute configurations. Twelve discrete mannosylated “glyco-IEGmers” are synthesized and screened for binding to a panel of mannoside-binding immune lectins (DC-SIGN, DC-SIGNR, MBL, SP-D, langerin, dectin-2, mincle, and DEC-205). In many cases, the glyco-IEGmers had distinct length, stereochemistry, and topology-dependent lectin-binding preferences. To understand these differences, we used molecular dynamics and density functional theory simulations of octameric glyco-IEGmers, which revealed dramatic effects of glyco-IEGmer stereochemistry and topology on solution structure and reveal an interplay between conformational diversity and chiral recognition in selective lectin binding. Ligand function also could be controlled by chemical substitution: by tuning the side chains of glyco-IEGmers that bind DC-SIGN, we could alter their cellular trafficking through alteration of their aggregation state. These results highlight the power of precision synthetic oligomer/polymer synthesis for selective biological targeting, motivating the development of next-generation glycomacromolecules tailored for specific immunological or other therapeutic applications.
PDF
