Hyperbranched Polyglycerols with Elevated Molecular Weights: A Facile Two-Step Synthesis Protocol Based on Polyglycerol Macroinitiators

Employing transfer-dominated branching radical telomerisation (TBRT) and atom transfer radical polymerisation (ATRP) to form complex polyester-polymethacrylate branched-linear star copolymer hybrids via orthogonal initiation

TBRT and ATRP are orthogonal initiation chemistries used in vinyl polymerisations. Here, we present the first combination of these techniques to readily create high molecular weight branched polyester macroinitiators capable of forming star copolymers from a range of methacrylate monomers.

Hyperbranched Polymers: Recent Advances in Photodynamic Therapy against Cancer

Hyperbranched polymers are a class of three-dimensional dendritic polymers with highly branched architectures. Their unique structural features endow them with promising physical and chemical properties, such as abundant surface functional groups, intramolecular cavities, and low viscosity. Therefore, hyperbranched-polymer-constructed cargo delivery carriers have drawn increasing interest and are being utilized in many biomedical applications. When applied for photodynamic therapy, photosensitizers are encapsulated in or covalently incorporated into hyperbranched polymers to improve their solubility, stability, and targeting efficiency and promote the therapeutic efficacy. This review will focus on the state-of-the-art studies concerning recent progress in hyperbranched-polymer-fabricated phototherapeutic nanomaterials with emphases on the building-block structures, synthetic strategies, and their combination with the codelivered diagnostics and synergistic therapeutics. We expect to bring our demonstration to the field to increase the understanding of the structure-property relationships and promote the further development of advanced photodynamic-therapy nanosystems.

Quasilinear polyglycidols by triethyborane-controlled anionic polymerization of unprotected glycidol

In this study, quasilinear polyglycidols (PG)s with ultralow degree of branching (DB) could be synthesized through anionic polymerization of glycidol carried out in the presence of triethylborane (TEB). PGs with DB ≤ 0.10, and molar masses up to 40 kg mol^-1 could be indeed obtained using mono- or trifunctional ammonium carboxylates as initiator and under slow monomer addition conditions. The synthesis of degradable PGs through ester linkages obtained by copolymerization of glycidol with anhydride is also described. PG-based amphiphilic di- and triblock quasilinear copolymers were also derived. The role played by TEB is discussed and a polymerization mechanism is proposed.

Controlled Synthesis of Dendrite-like Polyglycerols Using Aluminum Complex for Biomedical Applications

This work describes a one-pot synthesis of dendrite-like hyperbranched polyglycerols (HPGs) via a ring-opening multibranching polymerization (ROMBP) process using a bis(5,7-dichloro-2-methyl-8-quinolinolato)methyl aluminum complex (1) as a catalyst and 1,1,1-tris(hydroxymethyl)propane/trimethylol propane (TMP) as an initiator. Single-crystal X-ray diffraction (XRD) analysis was used to elucidate the molecular structure of complex 1. Inverse-gated (IG)¹³C NMR analysis of HPGs showed degree of branching between 0.50 and 0.57. Gel permeation chromatography (GPC) analysis of the HPG polymers provided low, medium, and high-molecular weight (M _n) polymers ranging from 14 to 73 kDa and molecular weight distributions (M _w/M _n) between 1.16 and 1.35. The obtained HPGs exhibited high wettability with water contact angle between 18 and 21° and T _g ranging between -39 and -55 °C. Notably, ancillary ligand-supported aluminum complexes as catalysts for HPG polymerization reactions have not been reported to date. The obtained HPG polymers in the presence of the aluminum complex (1) can be used for various biomedical applications. Here, nanocomposite electrospun fibers were fabricated with synthesized HPG polymer. The nanofibers were subjected to cell culture experiments to evaluate cytocompatibility behavior with L929 and MG63 cells. The cytocompatibility studies of HPG polymer and nanocomposite scaffold showed high cell viability and spreading. The study results concluded, synthesized HPG polymers and composite nanofibers can be used for various biomedical applications.

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.

A shish-kebab-like supramolecular polymer and its light-responsive self-assembly into nanofibers

We report a shish-kebab-like supramolecular polymer (SKSP) and its light-responsive self-assembly into nanofibers.

Copolymer Based on Polyglycerol-Acrylate-Lactate as Potential Water Viscosifier and Surfactant for Enhanced Oil Recovery

Polymer and surfactant flooding are widely applied processes in enhanced oil recovery (EOR) in which viscous polymers or surfactants aqueous solutions are introduced in oil reservoirs to rise the recovery of the remaining oil. In this regard, one of the challenges of EOR practices is the use of efficient but low-cost viscosifier and surfactant polymers. This work is aimed at synthesizing a polyglycerol derived from the biodegradable and nontoxic monomer, glycerol, and evaluating the effect of its copolymerization on rheological and interfacial properties, which were tested in water and brine for the former and in the water/oil system for the last properties. The copolymers were synthesized using a polyglycerol backbone, acrylic acid, lactic acid, and oleic acid. The chemical structure of copolymers was characterized by Fourier transform infrared spectroscopy (FT-IR), thermogravimetry (TG), and differential scanning calorimetry (DSC). The viscosity and the interfacial tension (IFT) of polymeric solutions were tested. Thus, the viscosity and surface performance of the prepared polymer solutions in distilled water and brine were analyzed according to the structure of the synthesized polymers. The results showed that the synthesized polymers modified water viscosity and surface tension between water and oil. The developed polymers could be candidates for applications in enhanced oil recovery and related applications.

Mucin-Inspired, High Molecular Weight Virus Binding Inhibitors Show Biphasic Binding Behavior to Influenza A Viruses

Multivalent binding inhibitors are a promising new class of antivirals that prevent virus infections by inhibiting virus binding to cell membranes. The design of these inhibitors is challenging as many properties, for example, inhibitor size and functionalization with virus attachment factors, strongly influence the inhibition efficiency. Here, virus binding inhibitors are synthesized, the size and functionalization of which are inspired by mucins, which are naturally occurring glycosylated proteins with high molecular weight (MDa range) and interact efficiently with various viruses. Hyperbranched polyglycerols (hPGs) with molecular weights ranging between 10 and 2600 kDa are synthesized, thereby hitting the size of mucins and allowing for determining the impact of inhibitor size on the inhibition efficiency. The hPGs are functionalized with sialic acids and sulfates, as suggested from the structure of mucins, and their inhibition efficiency is determined by probing the inhibition of influenza A virus (IAV) binding to membranes using various methods. The largest, mucin-sized inhibitor shows potent inhibition at pm concentrations, while the inhibition efficiency decreases with decreasing the molecular weight. Interestingly, the concentration-dependent IAV inhibition shows a biphasic behavior, which is attributed to differences in the binding affinity of the inhibitors to the two IAV envelope proteins, neuraminidase, and hemagglutinin.

Mega macromolecules as single molecule lubricants for hard and soft surfaces

A longstanding goal in science and engineering is to mimic the size, structure, and functionality present in biology with synthetic analogs. Today, synthetic globular polymers of several million molecular weight are unknown, and, yet, these structures are expected to exhibit unanticipated properties due to their size, compactness, and low inter-chain interactions. Here we report the gram-scale synthesis of dendritic polymers, mega hyperbranched polyglycerols (mega HPGs), in million daltons. The mega HPGs are highly water soluble, soft, nanometer-scale single polymer particles that exhibit low intrinsic viscosities. Further, the mega HPGs are lubricants acting as interposed single molecule ball bearings to reduce the coefficient of friction between both hard and soft natural surfaces in a size dependent manner. We attribute this result to their globular and single particle nature together with its exceptional hydration. Collectively, these results set the stage for new opportunities in the design, synthesis, and evaluation of mega polymers.

Synthetic globular polymers of several million molecular weight are expected to exhibit unique properties but are difficult to synthesize. Here the authors synthesize such dendritic polymers that show unique lubrication properties and act as molecular ball bearings due to their 3D compact structure, size, solubility, hydration and low intrinsic viscosities.

Dendritic Polyglycerol Sulfate for Therapy and Diagnostics

Dendritic polyglycerol sulfate (dPGS) has originally been investigated as an anticoagulant to potentially substitute for the natural glycosaminoglycan heparin. Compared to unfractionated heparin, dPGS possesses lower anticoagulant activity but a much higher anticomplementary effect. Since coagulation, complement activation, and inflammation are often present in the pathophysiology of numerous diseases, dPGS polymers with both anticoagulant and anticomplementary activities represent promising candidates for the development of polymeric drugs of nanosized architecture. In this review, we describe the nanomedical applications of dPGS based on its anti-inflammatory activity. Furthermore, the application of dPGS as a carrier molecule for diagnostic molecules and therapeutic drugs is reviewed, based on the ability to target tumors and localize in tumor cells. Finally, the application of dPGS for inhibition of virus infections is described.

Hyperbranched polyglycerol derivatives exhibiting normal or abnormal thermoresponsive behaviours in water: facile preparation and investigation by turbidimetry and fluorescence techniques

Polymers exhibiting an abnormal thermoresponsive behaviour, in which increase in the polymer concentration in water leads to an increase in the phase transition temperature, are few, and no plausible strategy has been addressed to prepare these polymers. For illuminating a feasible common strategy to prepare polymers with an abnormal thermoresponsive behaviour, in this study, we systematically prepared a series of hyperbranched polyglycerol (HPG) derivatives through a facile esterification reaction between HPG and aliphatic acids having different carbon numbers (X). Turbidimetry measurements demonstrate that thermoresponsive HPGs can be obtained only when HPGs are conjugated with aliphatic units of X ≤ 8. The conjugation of HPG with aliphatic units of X ≤ 4 resulted in thermoresponsive HPGs with a normal thermoresponsive behaviour. For the preparation of thermoresponsive HPGs with an abnormal thermoresponsive behaviour, X should be controlled in the range of 5-8. Fluorescence measurements with nile red as the fluorescent probe demonstrate that the existence of relatively strong hydrophobic interaction is a key factor to ensure that the polymer exhibits an abnormal thermoresponsive behaviour in water. Moreover, turbidimetry and fluorescence techniques are complementary for measuring the phase transition behaviour and suitable for different polymer concentration regions.

Green Synthesis of Hyperbranched Polyglycerol at Room Temperature

In this work we report on a new method for the cationic polymerization of glycidol by citric acid at ambient and solvent free conditions. In this polymerization, citric acid is a proton donor and is able to incorporate in the structure of polyglycerol by reaction with the activated monomer. The molecular weight and degree of branching of the synthesized polymers are affected by the glycidol/citric acid molar ratios and reaction temperature. Due to the citric acid core of the hyperbranched polyglycerols, they are able to break down into the smaller segments at neutral or acidic conditions. Apart from citric acid, glycidol, and water, other reagents or organic solvents have not been used in the synthetic and purification processes. Taking advantage of the green synthesis and ability to cleave under physiological conditions, in addition to the intrinsic biocompatibility of polyglycerol, the synthesized polymers are promising candidates for future biomedical applications.

Hyperbranched polyglycerols: recent advances in synthesis, biocompatibility and biomedical applications

Hyperbranched polyglycerol is one of the most widely studied biocompatible dendritic polymer and showed promising applications. Here, we summarized the recent advancements in the field.

Solution-Stable Colloidal Gold Nanoparticles via Surfactant-Free, Hyperbranched Polyglycerol-b-polystyrene Unimolecular Templates

Hyperbranched polyglycerol-block-polystyrene copolymers, denoted HPG-b-PS, are synthesized and employed as a new and effective unimolecular template for synthesizing colloidal gold (Au) nanoparticles. The coordination of noble metal precursors with polyether within the inner HPG core and subsequent in situ reduction enables the formation of well-dispersed and stable PS-capped Au nanoparticles. The inner HPG core is produced via ring opening multibranching polymerization (ROMBP) and subsequently converted into atom transfer radical polymerization (ATRP) macroinitiators for the controlled growth of polystyrene (PS) arms possessing low polydispersity (PDI < 1.31). An initial investigation into the templating parameters of HPG-b-PS was undertaken by producing templates with different arm numbers (98 and 117) and different PS chain lengths (i.e., molecular weight = 3500-13400 g/mol). It was found that the PS chain length and solvent conditions affect the quality of the resulting PS-capped colloidal Au nanoparticles. This work demonstrates, for the first time, a simple, lower-cost approach for templating nonpolar solvent-soluble PS-capped Au nanoparticles on the order of 10-30 nm in diameter.

Polyglycidol, Its Derivatives, and Polyglycidol-Containing Copolymers-Synthesis and Medical Applications

Polyglycidol (or polyglycerol) is a biocompatible polymer with a main chain structure similar to that of poly(ethylene oxide) but with a ⁻CH₂OH reactive side group in every structural unit. The hydroxyl groups in polyglycidol not only increase the hydrophilicity of this polymer but also allow for its modification, leading to polymers with carboxyl, amine, and vinyl groups, as well as to polymers with bonded aliphatic chains, sugar moieties, and covalently immobilized bioactive compounds in particular proteins. The paper describes the current state of knowledge on the synthesis of polyglycidols with various topology (linear, branched, and star-like) and with various molar masses. We provide information on polyglycidol-rich surfaces with protein-repelling properties. We also describe methods for the synthesis of polyglycidol-containing copolymers and the preparation of nano- and microparticles that could be derived from these copolymers. The paper summarizes recent advances in the application of polyglycidol and polyglycidol-containing polymers as drug carriers, reagents for diagnostic systems, and elements of biosensors.

Molecular dynamics simulation studies of hyperbranched polyglycerols and their encapsulation behaviors of small drug molecules

Computer simulation could disclose more details about the conformations of HPGs and their encapsulation behaviors of guest molecules.

Maleimide Glycidyl Ether: A Bifunctional Monomer for Orthogonal Cationic and Radical Polymerizations

A novel bifunctional monomer, namely maleimide glycidyl ether (MalGE), prepared in a four-step reaction sequence is introduced. This monomer allows for selective (co)polymerization of the epoxide group via cationic ring-opening polymerization, preserving the maleimide functionality. On the other hand, the maleimide functionality can be copolymerized via radical techniques, preserving the epoxide moiety. Cationic ring-opening multibranching copolymerization of MalGE with glycidol was performed, and a MalGE content of up to 24 mol% could be incorporated into the hyperbranched polymer backbone (Mn = 1000-3000 g mol(-1)). Preservation of the maleimide functionality during cationic copolymerization was verified via NMR spectroscopy. Subsequently, the maleimide moiety was radically crosslinked to generate hydrogels and additionally employed to perform Diels-Alder (DA) "click" reactions with (functional) dienes after the polymerization process. Radical copolymerization of MalGE with styrene (Mn = 5000-9000 g mol(-1)) enabled the synthesis of a styrene copolymer with epoxide functionalities that are useful for versatile crosslinking and grafting reactions.

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.

Facile synthesis of photolabile dendritic-unit-bridged hyperbranched graft copolymers for stimuli-triggered topological transition and controlled release of Nile red

Successive RAFT SCVP and ROP were used to generate novel hyperbranched graft copolymers with the ability for the photo-triggered degradation and accelerative release of hydrophobic dye.

Water-soluble and redox-responsive hyperbranched polyether copolymers based on ferrocenyl glycidyl ether

Hyperbranched polymers based on glycidol and ferrocenyl glycidyl ether are prepared, characterized, and their redox behavior in water is studied and quantified with Mößbauer spectroscopy.

Poly(styrene-graft-hyperbranched polyglycidol): synthesis and solution behavior of a hyperbranched polyelectrolyte

This work presents a three-step synthetic procedure to obtain a hypergrafted copolymer composed of a glassy backbone with flexible branched pendant segments. The polymer exhibited polyelectrolyte behavior and conformational changes prior to neutralization with LiBr salt.

Hydrogen peroxide-responsive anticancer hyperbranched polymer micelles for enhanced cell apoptosis

Hydrogen peroxide-responsive nanomicelles from hyperbranched polymers were developed for effective cancer therapy through enhanced apoptotic cell death.

Synthesis of hyperbranched polymers and their applications in analytical chemistry

This review focuses primarily on the recent developments in the synthesis of hyperbranched polymers and their application in analytical chemistry.