Search results for "End-group"
showing 10 items of 93 documents
A Facile Two-Step Route to Branched Polyisoprenes via ABn-Macromonomers
2007
A facile two-step synthesis for branched poly(isoprene)s (PI) based on polyaddition of AB n -type macromonomers is described. The synthesis of the macromonomers was achieved by anionic polymerization of isoprene and subsequent end-capping of the polymers by addition of chlorodimethylsilane to the living carbanions. This led to PI-based macromonomers with narrow polydispersity (M w /M n < 1.15) and molecular weights in the range of 1700 -22100 g mol -1 . Synthesis of the branched polymers was carried out by a hydrosilylation-based polymerization of the macromonomers. Characterization via SEC, SEC-MALLS, coupled SEC-viscosimetry and 1 H-NMR-spectroscopy supported the formation of branched str…
Evaluating chemical ligation techniques for the synthesis of block copolypeptides, polypeptoids and block copolypept(o)ides: a comparative study
2015
In this work, we describe the synthesis of block copolypeptides, polypeptoids and block copolypept(o)ides by chemical ligation techniques. Polysarcosine (PSar), poly(N-e-trifluoroacetyl-L-lysine) (PLys(TFA)) and poly(γ-benzyl-L-glutamate) (PGlu(OBzl)) homopolymers of different polarities and end group functionalities but with similar average degrees of polymerization (Xn = 50 and 100) could be obtained by ring opening polymerization (ROP) of α-amino acid N-carboxyanhydrides (NCA) and postpolymerization modification reactions. In the next step, these polymers were applied to copper(I)-catalyzed azide–alkyne coupling (CuAAC), strain-promoted azide–alkyne coupling (SPAAC) and native chemical l…
A road less traveled to functional polymers: epoxide termination in living carbanionic polymer synthesis.
2010
Functional polymers possess tremendous potential both in academia and in industry. In particular, oxiranes offer manifold possibilities for the introduction of single hydroxyl or multiple orthogonal functionalities in carbanionic polymerization. Here, we present a brief overview of the fascinating possibilities arising from the employment of common as well as individually designed epoxide derivatives for the synthesis of end-functional polymers. Continuous flow techniques can be utilized for the rapid generation and screening of precisely defined hydroxyl-modified polymers. The utilization of functionalized polymers as precursors for the formation of complex macromolecular architectures (e.…
Multihydroxyl-Functional Polystyrenes in Continuous Flow
2010
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…
Pencil Lead as a Matrix for MALDI-ToF Mass Spectrometry of Sensitive Functional Polymers
2007
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…
Hetero-Telechelic Dye-Labeled Polymer for Nanoparticle Decoration
2009
The synthesis of poly(methyl methacrylate) (PMMA) exhibiting one fluorescent dye (Texas Red) and one methyl disulfide end group is described. It is shown that the latter end group enabled the exchange of both oleic amine on gold nanoparticles (AuNP) and of oleic acid on CdSe/ZnS quantum dots (QD), allowing for a phase transfer of both types of nanoparticles (NP) from hexane into dimethylformamide due to the solubility provided by the PMMA chains. For AuNP, a fluorescence quenching of the dye was found due to fluorescence resonance energy transfer (FRET) from the dye to the AuNP, while QDs caused a fluorescence enhancement by FRET from the QD to the attached dyes. Due to the hetero-telecheli…
Versatile ω-end group functionalization of RAFT polymers using functional methane thiosulfonates
2009
Five different polymers, poly[methyl methacrylate] (PMMA), poly[lauryl methacrylate] (PLMA), poly[diethylene glycol methacrylate] (PDEGMA), poly[N-iso-propylacrylamide] (PNIPA), and poly[styrene] (PS) prepared by the RAFT process and thus terminated with dithioesters were aminolyzed in the presence of S-3-butynyl methane thiosulfonate (MTS), which was synthesized in two steps. Analysis of the polymers by 2D NMR, UV–vis absorbance, and gel permeation chromatogra-phy revealed them to quantitatively carry acetylene end groups connected with disul-fide bridges, indicating that functional MTS reagents can be employed for end group functionalization of RAFT polymers. This versatile method is of ad…
Thiol-functionalized ROMP polymers via Sacrificial Synthesis
2009
The synthesis of well-defined and highly functionalized thiol-functionalized polymers has been accomplished via the ring-opening metathesis polymerization (ROMP). A sacrificial synthesis-based approach was chosen for this interesting functional group since it has proven to give precise control over molecular weight and selective placement of end-groups on a different functionality before. Thiol-functionalized ROMP-polymers were successfully synthesized employing thioacetal monomers, which can be cleaved by hydrogenation leaving the desired thiol group behind. The placement of this highly reactive functional group at one chain end of a poly(norborneneimide) is demonstrated by analytical meth…
Facilitating polymer conjugation via combination of RAFT polymerization and activated ester chemistry
2010
The synthesis of block copolymers via polymer conjugation of well-defined building blocks offers excellent control over the structures obtained, but often several coupling strategies need to be explored to find an efficient one depending on the building blocks. To facilitate the synthesis of polymers with adjustable functional end-groups for polymer conjugation, we report on the combination of activated ester chemistry with RAFT polymerization using a chain transfer agent (CTA) with a pentafluorophenyl ester (PFP-CTA), which allows for flexible functionalization of either the CTA prior to polymerization or the obtained polymer after polymerization. Different polymethacrylates, namely PMMA, …
Synthesis and characterization of bisalkylated polysarcosine-based lipopolymers
2019
The use of PEGylated lipids for the synthesis of stealth liposomes and lipid formulations for nucleic acid delivery has promoted the development of nanoparticle based drugs for cancer therapy, and chronic diseases. Moreover, several other nanomedicines based on these materials have advanced into clinical trails. This enormous success, however, has recently been compromised by the occurrence of immune responses towards PEG, which render pharmacokinetics and can substantially reduce the therapeutic efficiency of drugs. Therefore, alternatives for PEGylated lipids with comparable or even identical solution properties are required. In this work, we report the synthesis of polysarcosine based li…