Hyperbranched poly(2-oxazoline)s via bisfunctional crosslinker

Hyperbranched polymers are an interesting type of polymeric structure as they possess useful features for a range of applications. They have been used for small molecule storage and transport owing to the existence of their large number of end groups that can be used for further functionalisation. In this study, we introduce a bisfunctional 2-oxazoline based crosslinker to synthesise hyperbranched poly(2-oxazoline)s with molar mass ranging from 3.2 kDa to 22 kDa. Furthermore, to control the degree of crosslinking, an end-capping agent was added at the beginning of the polymerisation in order to prevent uncontrolled branching and subsequent gelation. Moreover, advanced viscosity gel permeation chromatography was used to compare the degree of branching present in each polymer, and the lower critical solution temperature of each branched polymer was measured, with transition temperatures ranging from 44 °C to 70 °C

Single-chain glycopolymer folding via host-guest interactions and its unprecedented effect on DC-SIGN binding

Reversible self-folding actions of natural biomacromolecules play crucial roles for specific and unique biological functions in Nature. Hence, controlled folding of single polymer chains has attracted significant attention in recent years. Herein, reversible single-chain folded glycopolymer structures in α-shape with different density of sugar moieties in the knot were created. The influence of folding as well as the sugar density in the knot was investigated on the binding capability with lectins, such as ConA, DC-SIGN and DC-SIGNR. The synthesis of triblock glycocopolymers bearing β-CD and adamantane for the host-guest interaction and also mannose residues for the lectin interaction was achieved using the reversible addition-fragmentation chain transfer (RAFT) polymerization technique. The reversible single-chain folding of glycopolymers was achieved under a high dilution of an aqueous solution and the self-assembled folding was monitored by 2D nuclear overhauser enhancement spectroscopy (NOESY) NMR and dynamic light scattering. The lectin binding profiles consistently provided an unprecedented effect of single chain folding as the single-chain folded structures enhanced greatly the binding ability in comparison to the unfolded linear structures

A detailed study on understanding glycopolymer library and Con A interactions

Synthetic glycopolymers are important natural oligosaccharides mimics for many biological applications. To develop glycopolymeric drugs and therapeutic agents, factors that control the receptor-ligand interaction need to be investigated. A library of well-defined glycopolymers has been prepared by the combination of copper mediated living radical polymerization and CuAAC click reaction via post-functionalization of alkyne-containing precursor polymers with different sugar azides. Employing Concanavalin A as the model receptor, we explored the influence of the nature and densities of different sugars residues (mannose, galactose, and glucose) on the stoichiometry of the cluster, the rate of the cluster formation, the inhibitory potency of the glycopolymers, and the stability of the turbidity through quantitative precipitation assays, turbidimetry assays, inhibitory potency assays, and reversal aggregation assays. The diversities of binding properties contributed by different clustering parameters will make it possible to define the structures of the multivalent ligands and densities of binding epitopes tailor-made for specific functions in the lectin-ligand interaction. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2588–259

Detailed GPC analysis of poly(N-isopropylacrylamide) with core cross-linked star architecture

Core cross-linked star shaped polymers possess unique physical properties that can be utilized as drug transporters for biomedical applications. However, detailed analysis of these polymer structures is not straightforward. Herein, we employ multi-detector gel permeation chromatography (GPC) to elucidate structural features of cross-linked stars prepared from the polymerisation of NIPAM via Cu(0)-mediated Reversible Deactivation Radical Polymerisation. Furthermore, we aim to show how varying the arm length and the core size of the star polymers can not only affect their structural properties but also their capacity to encapsulate drug-like molecules

Poly(2-oxazoline) with pendant hydroxyl groups via a silyl ether-based protecting group

The introduction of a functionality onto a poly(2-oxazoline) (POx) chain has been widely explored, yet reports of POx bearing hydroxyl side chains in a well-defined manner have not. Here, we report a simple yet elegant approach for the synthesis of POx with pendant hydroxyl groups through use of silyl protecting groups. First, a hydroxyl group containing 2-oxazoline monomer was synthesized from ε-caprolactone, which on its own results in poorly defined polymers. Moreover, protecting the hydroxy group with silyl ether-based protecting group led to well-defined polymers with free hydroxyl groups on the side chains upon deprotection. Finally, copolymers with 2-ethyl-2-oxazoline resulted in polymers with tunable hydrophilicity, and copolymers with 2-n-propyl-2-oxazoline resulted in polymers with tunable thermoresponsive behavior in water

Thermoresponsive polymers in non-aqueous solutions

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

One-pot synthesis of amphiphilic multiblock poly(2-oxazoline)s via para-fluoro-thiol click reactions

A clickable initiator, pentafluoro benzyl bromide, has been investigated for the cationic ring opening polymerization of poly(2-oxazolines). Additionally, the clickable alpha end group was then utilized in a para-fluoro-thiol click reaction to synthesise linear diblock, tetrablock, multiblock copolymers as well as star shaped poly(2-oxazoline)s using dithiol compounds as terminating agents. Thus, a one-pot approach combining the para-fluoro-thiol click reaction and direct termination of the poly(2-oxazoline) living chain end with 4,4-thiobisbenzenethiol has been performed to prepare multiblock copolymers of poly(2-ethyl-2-oxazoline) (PEtOx) and poly((2-ethyl-2-oxazoline)-b-(2-methyl-2-oxazoline) (PEtOx-mb-PMeOx). All obtained polymers were characterized by Size Exclusion Chromatography (SEC), 1H Nuclear Magnetic Resonance (NMR) and Matrix-Assisted Laser Desorption/Ionization-Time of Flight (MALDI-ToF) mass spectrometry. Last but not least, the self-assembly properties of prepared amphiphilic polymers were studied with DLS and TEM. Nanoparticles with a diameter ranging from 184 nm to 250 nm were observed in TEM for PEtOx-mb-PMeOx copolymers

Microphase separation assisted reduction in the percolation threshold of MWCNT/block polymer composites

Block copolymers continue to attract a great deal of interest since they allow the formation of microphase-separated domains, useful for nanopatterning/templating. Herein, we present the drastic effect of microphase separation of a diblock copolymer on the electrical properties of polymer nanocomposites. Microphase-separated poly(styrene-b-2-ethylhexyl acrylate) (P(St-b-EHA)) block copolymers having different block lengths were synthesized and utilized as templates for multi-walled carbon nanotubes (MWCNTs). The percolation threshold of the films decreased from 0.46 to 0.19 vol.% with decreasing styrene phase fraction. More importantly, we observed a non-linear and unique reduction in percolation threshold with transforming phase into lamellar structures

Step-growth glycopolymers with a defined tacticity for selective carbohydrate–lectin recognition

Glycopolymers are potent candidates for biomedical applications by exploiting multivalent carbohydrate–lectin interactions. Owing to their specific recognition capabilities, glycosylated polymers can be utilized for targeted drug delivery to certain cell types bearing the corresponding lectin receptors. A fundamental challenge in glycopolymer research, however, is the specificity of recognition to receptors binding to the same sugar unit (e.g., mannose). Variation of polymer backbone chirality has emerged as an effective method to distinguish between lectins on a molecular level. Herein, we present a facile route toward producing glycopolymers with a defined tacticity based on a step-growth polymerization technique using click chemistry. A set of polymers have been fabricated and further functionalized with mannose moieties to enable lectin binding to receptors relevant to the immune system (mannose-binding lectin, dendritic cell-specific intercellular adhesion molecule-3-grabbing non-integrin, and dendritic and thymic epithelial cell-205). Surface plasmon resonance spectrometry was employed to determine the kinetic parameters of the step-growth glycopolymers. The results highlight the importance of structural complexity in advancing glycopolymer synthesis, yet multivalency remains a main driving force in lectin recognition