Hyperbranched PEG by Random Copolymerization of Ethylene Oxide and Glycidol

The synthesis of hyperbranched poly(ethylene glycol) (hbPEG) in one step was realized by random copolymerization of ethylene oxide and glycidol, leading to a biocompatible, amorphous material with multiple hydroxyl functionalities. A series of copolymers with moderate polydispersity ($\overline {M} _{{\rm w}} /\overline {M} _{{\rm n}} $ < 1.8) was obtained with varying glycidol content (3-40 mol-%) and molecular weights up to 49 800 g mol(-1) . The randomly branched structure of the copolymers was confirmed by (1) H and (13) C NMR spectroscopy and thermal analysis (differential scanning calorimetry). MTS assay demonstrated low cell toxicity of the hyperbranched PEG, comparable to the highly…

Ferrocenyl Glycidyl Ether: A Versatile Ferrocene Monomer for Copolymerization with Ethylene Oxide to Water-Soluble, Thermoresponsive Copolymers

The first ferrocene-containing epoxide monomer, ferrocenyl glycidyl ether (fcGE), is introduced. The monomer has been copolymerized with ethylene oxide (EO). This leads to electroactive, water-soluble, and thermoresponsive poly(ethylene glycol) (PEG) derived copolyethers. Anionic homo- and copolymerization of fcGE with EO was possible. Molecular weights could be varied from 2000 to 10 000 g mol–1, resulting in polymers with narrow molecular weight distribution (Mw/Mn = 1.07–1.20). The ferrocene (fc) content was varied from 3 to 30 mol %, obtaining water-soluble materials up to 10 mol % incorporation of the apolar ferrocenyl comonomer. Despite the steric bulk of fcGE, random copolymers were …

Water-Soluble “Poly(propylene oxide)” by Random Copolymerization of Propylene Oxide with a Protected Glycidol Monomer

Hydrophilic, functional poly(propylene oxide) (PPO) copolymers were prepared by anionic random copolymerization of propylene oxide with the protected glycidyl derivative ethoxy ethyl glycidyl ether (EEGE). The monobenzyl-protected ethylene glycol initiator 2-(benzyloxy)ethanol was used to initiate the polymerization because it allows for the introduction of hydroxyl groups at both ends of the polymer chain. Acidic deprotection permitted selective removal of the acetal protecting groups in the chain or alternatively orthogonal deprotection of the terminal hydroxyl group by catalytic hydrogenation. A series of narrowly distributed hydroxyl-functional PPO copolymers (Mw/Mn < 1.07–1.25 g mol–1)…

Organobase-Catalyzed Synthesis of Multiarm Star Polylactide With Hyperbranched Poly(ethylene glycol) as the Core

Multiarm star copolymers consisting of the polyether-polyol hyperbranched poly(ethylene glycol) (hbPEG) as core and poly(L-lactide) (PLLA) arms are synthesized via the organobase- catalyzed ring-opening polymerization of lactide using hbPEG as a multifunctional macroinitiator. Star copolymers with high molecular weights up to 792 000 g mol−1 are prepared. Detailed 2D NMR analysis provides evidence for the attachment of the PLLA arms to the core and reveals that the adjustment of the monomer/initiator ratio enables control of the arm length. Size exclusion chromatography measurements show narrow molecular weight distributions. Thermal analysis reveals a lower glass transition temperature, me…

Hyperbranched Poly(propylene oxide): A Multifunctional Backbone-Thermoresponsive Polyether Polyol Copolymer

Backbone-thermoresponsive hyperbranched poly(propylene oxide)-based polyether polyols have been synthesized by anionic ring-opening copolymerization of glycidol and propylene oxide. The number of functional hydroxyl end groups and the lower critical solution temperature (LCST) can be readily adjusted by varying the comonomer ratio. Molecular weights in the range of 1200-2000 g/mol were achieved. Hyperbranched polyether polyols with LCST values between 24 and 83 °C can be obtained in a convenient one-step reaction.

Can Hyperbranched Polymers Entangle? Effect of Hydrogen Bonding on Entanglement Transition and Thermorheological Properties of Hyperbranched Polyglycerol Melts

Melt rheology and thermal phase transition of a series of hyperbranched polyglycerol samples (hbPG) (DB ≈ 60%) in a broad molecular weight range (Mn = 600–440 000 g/mol) were investigated and correlated to both molecular weight and nature of the end group (hydroxyl vs permethylated and trimethylsilylated). The well-characterized and defined flexible polyethers are particularly suitable to shed light on the linear viscoelastic behavior with respect to (i) hyperbranched topology and (ii) hydrogen bond interactions, particularly in comparison to the perfectly linear polyglycerol counterparts studied recently [Osterwinter, C.; Macromolecules 2015, 48, 119−130]. We present a detailed examination…

Biodegradable pH-Sensitive Poly(ethylene glycol) Nanocarriers for Allergen Encapsulation and Controlled Release

In the last decades, the number of allergic patients has increased dramatically. Allergen-specific immunotherapy (SIT) is the only available cause-oriented therapy so far. SIT reduces the allergic symptoms, but also exhibits some disadvantages; that is, it is a long-lasting procedure and severe side effects like anaphylactic shock can occur. In this work, we introduce a method to encapsulate allergens into nanoparticles to avoid severe side effects during SIT. Degradable nanocarriers combine the advantage of providing a physical barrier between the encapsulated cargo and the biological environment as well as responding to certain local stimuli (like pH) to release their cargo. This work int…

How Structure-Related Collapse Mechanisms Determine Nanoscale Inhomogeneities in Thermoresponsive Polymers

Continuous wave electron paramagnetic resonance (CW EPR) spectroscopy on the amphiphilic spin probe TEMPO in solutions of selectively chosen functional, thermoresponsive poly(propylene oxide) (PPO)- and poly(ethylene oxide) (PEO)-based copolymers of both linear and branched structure is used to elucidate their host–guest interactions and inverse phase transitions. Three different fundamental types of host–guest interactions between probes and polymers could be correlated to the phase transition mechanisms (supported by MD simulations), evidencing that these proceed via nanoscale inhomogeneities of the polymers. Because of their ability to host small amphiphilic guest molecules, thermorespon…

Die vielen Gesichter des Poly(ethylenglykol)s

Poly(ethylenglykol) ist in unserem Leben allgegenwartig. Wir begegnen diesem biokompatiblen und hervorragend wasserloslichen Polymer, meist ohne dass uns dies bewusst ist, in fast allen Bereichen des alltaglichen Bedarfs: Von Haut- und Haarpflegeartikeln, uber Kosmetik- und Styling-Produkten bis hin zu Lebensmitteln und Medikamenten. Selbst in der maritimen Militartechnologie und bei der Konservierung geborgener Kulturguter wird es eingesetzt. Dieser Artikel beschaftigt sich mit der Darstellung, den teils uberraschenden Eigenschaften und der Anwendung dieses strukturell simplen, aber faszinierend vielseitigen Polymers.

Correlations between Ion Conductivity and Polymer Dynamics in Hyperbranched Poly(ethylene oxide) Electrolytes for Lithium-Ion Batteries

Poly(ethylene oxide)s with varying degrees of hyperbranching are effective at preventing the crystallization of PEO and lead to approximately a 100-fold increase in the Li-ion conductivity below 50 °C as compared with linear PEO. The Li-ion conductivities, which increase further upon permethylation of the hydroxyl termini, are found to correlate quantitatively with the fast segmental dynamics of PEO as measured by inelastic neutron scattering.

Systematic Variation of the Degree of Branching (DB) of Polyglycerol via Oxyanionic Copolymerization of Glycidol with a Protected Glycidyl Ether and Its Impact on Rheological Properties

Hyperbranched Poly(ethylene glycol) Copolymers: Absolute Values of the Molar Mass, Properties in Dilute Solution, and Hydrodynamic Homology

Hyperbranched poly(ethylene glycol) copolymers were synthesized by random anionic ring-opening multibranching copolymerization of ethylene oxide with glycidol as a branching agent, leading to poly(ethylene glycol) structure with glycerol branching points. Extending the available range of molar masses by novel synthesis strategies, a limited extent of control over the degree of polymerization was achieved by variation of the solvent in this copolymerization. Generally, absolute molar mass characterization of hyperbranched polymers still represents an unresolved challenge. A series of the hyperbranched poly(ethylene glycol)-co-(glycerol) copolymers (hbPEGs) of a wide range of molar masses (14…

Hyperbranched aliphatic polyether polyols

Hyperbranched polymers, dendritic macromolecules with branch-on-branch structures, have become an important polymer class since the early 1990s. They combine several advantages of the perfectly branched dendrimers with easy accessibility, typically in a one-step synthesis. Hyperbranched polyethers are a particularly interesting class of chemically stable and often biocompatible materials. Multifunctional hyperbranched polyethers with controllable molar mass and comparably low polydispersities can been prepared using hydroxyl-functional epoxides or oxetanes for polymerization via anionic and cationic polymerization mechanisms. Here, we review the progress in the preparation, characterization…

Stereocomplex Formation in Polylactide Multiarm Stars and Comb Copolymers with Linear and Hyperbranched Multifunctional PEG