Silver Oxide Mediated Monotosylation of Poly(ethylene glycol) (PEG): Heterobifunctional PEG via Polymer Desymmetrization

Heterobifunctional poly(ethylene glycol)s (PEGs) are key structures for bioconjugation in the context of the “PEGylation” strategy to enhance blood circulation times of, for example, peptide drugs or “stealth” liposomes. The formation of heterobifunctional PEGs from symmetric PEG diols is challenging because of limited yields of the targeted monofunctional product and difficulties associated with separation steps. On the basis of a detailed comparison of reaction conditions, we have investigated a “polymer desymmetrization” strategy to maximize the yields of monofunctional PEG tosylate. The tosylation reaction in the presence of the heterogeneous catalyst silver oxide and potassium iodide i…

Monofunctional metathesis polymers via sacrificial diblock copolymers.

Rod–coil copolymers from oligo(p-benzamide) foldamers

Self assembling rod–coil copolymers were synthesized in which oligo(p-benzamide) rods up to the octamer were prepared via iterative solution synthesis employing the acid labile 2,4-dimethoxybenzyl amide protective group.

Hydroxyfunctional oxetane-inimers with varied polarity for the synthesis of hyperbranched polyether polyols via cationic ROP

Pencil Lead as a Matrix for MALDI-ToF Mass Spectrometry of Sensitive Functional Polymers

With the increase in complexity of functional polymers in recent years, MALDI-ToF has become an important tool for gaining precise information on polymer functionality, end groups, and, in special cases, molecular weights. Here we describe how pencil lead, deposited by simply drawing with a regular pencil onto conventional MALDI-ToF targets, can be used as a very attractive matrix for MALDI-ToF mass spectrometry of synthetic polymers. Highly sensitive polymers such as silyl hydride functional poly(styrene), poly(butadiene), and poly(isoprene) have been investigated using conventional MALDI-ToF matrices as well as pencil lead. In all cases, the use of pencil lead prevented oxidation of the h…

Rapid Synthesis and MALDI-ToF Characterization of Poly(ethylene oxide) Multiarm Star Polymers

Multiarm PEO star polymers with a purely aliphatic polyether structure have been synthesized using hyperbranched polyglycerol (PG) with different molecular weights as a multifunctional initiator. Different degrees of deprotonation of the initiator were studied with respect to molecular weight control. The results show that the degree of deprotonation is a crucial parameter for the synthesis of well-defined polymers with controlled molecular weights. Partial deprotonation of the PG hydroxyl groups (5-8%) was proven to represent an optimum for the synthesis of star polymers with molecular masses close to the theoretical values. Molecular weights of the stars ranged between 9 000 and 30000g · …

Supramolecular Linear-g-Hyperbranched Graft Polymers: Topology and Binding Strength of Hyperbranched Side Chains

Complex, reversible hyperbranched graft polymer topologies have been obtained by spontaneous self-assembly. Well-defined adamantyl- and β-cyclodextrin-functionalized polymers were employed to generate linear-g-(linear–hyperbranched) supramolecular graft terpolymers. For this purpose the synthesis of monoadamantyl-functionalized linear polyglycerols (Ada-linPG) and hyperbranched polyglycerols (Ada-hbPG) as well as poly(ethylene glycol)-block-linear polyglycerol (Ada-PEG-b-linPG) and poly(ethylene glycol)-block-hyperbranched poly(glycerol) (Ada-PEG-b-hbPG) block copolymers was established. Isothermal titration calorimetry (ITC) with β-cyclodextrin revealed a shielding effect of hyperbranched …

Methods of protein surface PEGylation under structure preservation for the emulsion-based formation of stable nanoparticles

Proteins show remarkable versatility as multifunctional materials for therapeutic applications. They can be easily modified with the toolkit of bioorganic chemistry and are particularly attractive because of their degradability and biocompatibility. Herein, we evaluate different methods for the attachment of multiple PEG chains on the surface of the enzyme lysozyme. For this, we activated standard 2 kDa mPEG chains with four different electrophilic groups and tested their ability to react with different amino acids on the surface of our model protein. The aim was to find an effective and at the same time mild modification method that preserves the native structure and activity of the enzyme…

Living Polymer Chains with Predictable Molecular Weight and Dispersity via Carbanionic Polymerization in Continuous Flow: Mixing Rate as a Key Parameter

Aiming at systematic variation of the parameter dispersity, Đ (or “polydispersity”), living polymers with predictable dispersity (Đ = 1.15–2.20) and controlled molecular weights (Mn = 3200–18 500 g mol–1) were prepared via carbanionic polymerization. The approach relies on a continuous flow reactor equipped with a tangential four-way jet micromixing device. By varying the total flow rate, the mixing efficiency of the initiator (sec-BuLi) and the corresponding vinyl monomers is controlled, resulting in polymers with predefined dispersity, while the number-average molecular weight, Mn, is kept constant. In this manner living polystyrene (PS), poly(p-methylstyrene) (PpMeS), and poly(2-vinylpyr…

Monofunktionalisierte Metathesepolymere durch Abbau von Diblockcopolymeren

ABA Triblock Copolymers Based on Linear Poly(oxymethylene) and Hyperbranched Poly(glycerol): Combining Polyacetals and Polyethers

The synthesis of hyperbranched-linear-hyperbranched ABA triblock copolymers based on a linear poly(oxymethylene) (POM) block and hyperbranched poly(glycerol) (hbPG) blocks is described. The polymers containing a polyacetal polyether structure were prepared from linear bishydroxy-functional POM macroinitiators, obtained by cationic ring-opening polymerization of trioxane and 1,3-dioxolane as a comonomer with formic acid as a transfer agent and subsequent hydrolysis of the formate group. Partial deprotonation of the resulting hydroxyl groups permitted “hypergrafting” of glycidol by anionic ring-opening multibranching polymerization (ROMBP). With respect to the hyperbranched blocks, the obtain…

Multihydroxyl-Functional Polystyrenes in Continuous Flow

We describe the synthesis of end-functionalized polystyrenes by living anionic polymerization in a microstructured reactor via termination by acetal-protected functional epoxides. Initiation of styrene polymerization by alkyllithium takes place in a micromixing device with efficient heat and mass transfer properties. A newly developed continuous polymerization−termination sequence enabled quantitative functionalization of the living carbanions by nucleophilic displacement with different, specifically designed glycidyl ethers (ethoxy ethyl glycidyl ether (EEGE), 1,2-isopropylidene glyceryl glycidyl ether (IGG), and trans-2-phenyl-1,3-dioxane glycidyl ether (PDGE)). Upon acidic hydrolysis the…

A Combined DPE/Epoxide Termination Strategy for Hydroxyl End-Functional Poly(2-vinylpyridine) and Amphiphilic AB2-Miktoarm Stars

Systematic investigation of functional core variation within hyperbranched polyglycerols

A novel series of hyperbranched polyether polyols with various n-alkyl amine cores (mono- and bifunctional) and photoactive cores (benzylamine and 1-naphthylmethylamine) have been prepared. Polymerization of glycidol was carried out in two ways, starting directly from primary amine initiators and from bisglycidolized amine initiators. NMR spectroscopy and size exclusion chromatography (SEC) showed good control over the molecular weights only, when bisglycidolized amines were used. Molecular weights and polydispersity of the hyperbranched polyglycerols prepared with these initiator-cores were in the range of 1600 to 8400 g/mol and of 1.5 to 2.5, respectively. MALDI-ToF mass spectrometry conf…