Polyglycerols as Multi-Functional Platforms: Synthesis and Biomedical Applications

The remarkable and unique characteristics of polyglycerols (PG) have made them an attractive candidate for many applications in the biomedical and pharmaceutical fields. The presence of multiple hydroxy groups on the flexible polyether backbone not only enables the further modification of the PG structure but also makes the polymer highly water-soluble and results in excellent biocompatibility. In this review, the polymerization routes leading to PG with different architectures are discussed. Moreover, we discuss the role of these polymers in different biomedical applications such as drug delivery systems, protein conjugation, and surface modification.

Selective polymerization of epoxides from hydroxycarboxylic esters: expediting controlled synthesis of α-carboxyl-ω-hydroxyl polyethers

Selective ring-opening polymerization of ethylene/propylene oxide from hydroxyl-functionalized carboxylic esters is achieved by use of metal-free Lewis pair catalysts. Subsequently, quantitative in situ hydrolysis is conducted to afford well-defined α-carboxyl-ω-hydroxyl polyethers which are highly valuable for bioconjugation but usually synthesized by much more tedious and costly routes.

Probing the Nanoscopic Thermodynamic Fingerprint of Paramagnetic Ligands Interacting with Amphiphilic Macromolecules

Self-assembly of macromolecules with ligands is an intricate dynamic process that depends on a wide variety of parameters and forms the basis of many essential biological processes. We elucidate the underlying energetic processes of self-assembly in a model system consisting of amphiphilic core-shell polymers interacting with paramagnetic, amphiphilic ligand molecules from temperature-dependent continuous wave electron paramagnetic resonance (CW EPR) spectroscopy subsequent to spectral simulation. The involved processes as observed from the ligands’ point of view are either based on temperature-dependent association constants (K_A,j,k) or dynamic rotational regime interconversion (IC) constants (K_IC,j,k). The interconversion process describes a transition from Brownian (b₁) towards free (b₂) diffusion of ligand. Both processes exhibit non-linear van’t Hoff (lnK vs. T⁻¹) plots in the temperature range of liquid water and we retrieve decisive dynamic information of the system from the energetic fingerprints of ligands on the nanoscale, especially from the temperature-dependent interconversion heat capacity (∆C°_P,IC).

Tunable dynamic hydrophobic attachment of guest molecules in amphiphilic core–shell polymers

In this study, synthesis and dynamic properties of amphiphilic core–shell polymers are reported as monitored through their interaction with small amphiphilic ligands. Our findings point to a most complex self-assembling nature of those host and guest molecules.

Polymerization of Ethylene Oxide, Propylene Oxide, and Other Alkylene Oxides: Synthesis, Novel Polymer Architectures, and Bioconjugation

The review summarizes current trends and developments in the polymerization of alkylene oxides in the last two decades since 1995, with a particular focus on the most important epoxide monomers ethylene oxide (EO), propylene oxide (PO), and butylene oxide (BO). Classical synthetic pathways, i.e., anionic polymerization, coordination polymerization, and cationic polymerization of epoxides (oxiranes), are briefly reviewed. The main focus of the review lies on more recent and in some cases metal-free methods for epoxide polymerization, i.e., the activated monomer strategy, the use of organocatalysts, such as N-heterocyclic carbenes (NHCs) and N-heterocyclic olefins (NHOs) as well as phosphazene bases. In addition, the commercially relevant double-metal cyanide (DMC) catalyst systems are discussed. Besides the synthetic progress, new types of multifunctional linear PEG (mf-PEG) and PPO structures accessible by copolymerization of EO or PO with functional epoxide comonomers are presented as well as complex branched, hyperbranched, and dendrimer like polyethers. Amphiphilic block copolymers based on PEO and PPO (Poloxamers and Pluronics) and advances in the area of PEGylation as the most important bioconjugation strategy are also summarized. With the ever growing toolbox for epoxide polymerization, a "polyether universe" may be envisaged that in its structural diversity parallels the immense variety of structural options available for polymers based on vinyl monomers with a purely carbon-based backbone.

Aliphatic Polyethers: Classical Polymers for the 21st Century

Polyethers-polymers with the structural element (R'-O-R)n in their backbone--are an old class of polymers which were already used at the time of the ancient Egyptians. However, still today these materials are highly important with applications in all areas of our life, reaching from the automotive and paper industry to cosmetics and biomedical applications. In this Review, different aliphatic polyethers like poly(epoxide)s, poly(oxetane)s, and poly(tetrahydrofuran) are discussed. Special emphasis is placed on the history, the polymerization techniques (industrially and in academia), the properties, the applications as well as recent developments of these materials.

Recent advances in glycerol polymers: chemistry and biomedical applications

Glycerol polymers are attracting increased attention due to the diversity of polymer compositions and architectures available. This article provides a brief chronological review on the current status of these polymers along with representative examples of their use for biomedical applications. First, the underlying chemistry of glycerol that provides access to a range of monomers for subsequent polymerizations is described. Then, the various synthetic methodologies to prepare glycerol-based polymers including polyethers, polycarbonates, polyesters, and so forth are reviewed. Next, several biomedical applications where glycerol polymers are being investigated including carriers for drug delivery, sealants or coatings for tissue repair, and agents possessing antibacterial activity are described. Fourth, the growing market opportunity for the use of polymers in medicine is described. Finally, the findings are concluded and summarized, as well as the potential opportunities for continued research efforts are discussed.

Synthesis of conductive polyaniline-modified polymers via a combination of nitroxide-mediated polymerization and “click chemistry”

A new strategy for graft copolymerization of aniline onto polystyrene by a multi step process is suggested.