Controlling polymer architecture in the thermal hyperbranched polymerization of L-lysine

Because of the unequal reactivity of the two amine groups of L-lysine hydrochloride, thermal polymerization of this asymmetrical AB2 monomer results in hyperbranched polymers, which contain ?2.5 times more N?-linked linear compared to N?-linked linear structural units. This report discusses the feasibility of three approaches to control polymer architecture during the thermal hyperbranched polymerization of L-lysine hydrochloride. The reactivity of the more reactive ?-NH 2 group was modulated by introducing temporary protective groups that preferentially block the ?-NH2 position. This was achieved by (i) addition of o-vanillin to the polymerization, (ii) copolymerization of N?-benzylidene-L-lysine, and (iii) copolymerization of ?-amino-?-caprolactam. Analysis of the degree of branching (DB) and the average number of branches (ANB) of the obtained polymers did not provide evidence for any significant structural changes. Analysis of the distribution of structural units, in contrast, revealed major structural changes and indicated a rearrangement from N?-linked linear structural units to N ?-linked linear structural units upon addition of o-vanillin and N?-benzylidene-L-lysine. Unlike o-vanillin and N ?-benzylidene-L-lysine, ?-amino-?-caprolactam was found to be rather ineffective in modulating polymer architecture. © 2007 American Chemical Society.

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Harm-Anton Klok, Markus Scholl
2007
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https://infoscience.epfl.ch/record/112642?ln=fr

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Polymérisation

vignette|Le latex de ce ballon de baudruche est synthétisé par polymérisation. vignette|Structure du UHMWPE, un haut polymère avec n supérieur à . La polymérisation désigne la réaction chimique ou le

Lysine

La lysine (abréviations IUPAC-IUBMB : Lys et K) est un acide dont l'énantiomère L est l'un des aminés protéinogènes, et l'un des neuf acides aminés essentiels pour l'homme. Elle est codée sur les

American Chemical Society

L'American Chemical Society (ACS) (« Société américaine de chimie ») est une société savante basée aux États-Unis active dans le domaine de la recherche scientifique en chimie. Historique

The thermal polymerization of amino acids revisited; Synthesis and structural characterization of hyperbranched polymers from L-lysine

Harm-Anton Klok, Markus Scholl

This contribution reports on the synthesis of hyperbranched polylysines via thermal polymerization of L-lysine hydrochloride. Polymerization of L-lysine hydrochloride in the presence of one equivalent KOH at 150°C resulted in polymers with a number-average molecular weight of 4600 g/mol and a polydispersity of 2.6 after 48 h. The rate of polymerization could be significantly enhanced and the polymer molecular weight improved by carrying out the polymerization with 3 mol % of an amidation catalyst. Among the different catalysts that were investigated Zr(OnBu)4 was found to be the most effective. Unequivocal support for the branched architecture of the polymers was obtained from 1H NMR spectroscopy, which allowed the identification and quantification of the four different structural units that constitute the polymer, viz. Nα and Nε linked linear units, dendritic units and terminal units. The structure of the polymers was found to be relatively independent of the reaction conditions. The degree of branching and the average number of branches varied between 0.35-0.45 and 0.15-0.25, respectively. © 2007 Wiley Periodicals, Inc.

2007

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L-lysine dendronized polystyrene

Harm-Anton Klok

This paper reports the synthesis and characterization of a novel class of dendronized polymers which are based on styrene functionalized dendritic L-lysine macromonomers. Free radical polymerization of zeroth and first generation macromonomers afforded dendronized polymers with number-average degrees of polymerization (DP) between 50 and 240, corresponding to number-average molecular weights between 50 × 103 and 240 × 103 g/mol. In contrast, only short oligomers (DP = 5-15) were obtained on polymerization of the second generation dendritic L-lysine macromonomers. Molecularly resolved ATM images allowed first insight into the structure of these peptide dendronized polymers. Depending on the degree of polymerization, either rods, short rods, or globular structures were found. © 2005 American Chemical Society.

2005

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Synthesis and ring-opening (Co)polymerization of L-lysine N-carboxyanhydrides containing labile side-chain protective groups

Harm-Anton Klok

This contribution describes the synthesis and ring-opening (co)polymerization of several L-lysine N-carboxyanhydrides (NCAs) that contain labile protective groups at the ε-NH2 position. Four of the following L-lysine NCAs were investigated: Nε-trifluoroacetyl-L-lysine N-carboxyanhydride, Nε-(tert-butoxycarbonyl)-L-lysine N-carboxyanhydride, Nε-(9-fluorenylmethoxycarbonyl)-L-lysine N-carboxyanhydride, and Nε-nitroveratryloxycarbonyl)-L-lysine N-carboxyanhydride. In contrast to the harsh conditions that are required for acidolysis of benzyl carbamate moieties, which are usually used to protect the ε-NH2 position of L-lysine during NCA polymerization, the protective groups of the L-lysine NCAs presented here can be removed under mildly acidic or basic conditions or by photolysis. As a consequence, these monomers may allow access to novel peptide hybrid materials that cannot be prepared from ε-benzyloxycar-bonyl-L-lysine N-carboxyanhydride (Z-Lys NCA) because of side reactions that accompany the removal of the Z groups. By copolymerization of these L-lysine NCAs with labile protective groups, either with each other or with γ-benzyl-L-glutamate N-carboxyanhydride or Z-Lys NCA, orthogonally side-chain-protected copolypeptides with number-average degrees of polymerization ≤20 were obtained. Such copolypeptides, which contain different side-chain protective groups that can be removed independently, are interesting for the synthesis of complex polypeptide architectures or can be used as scaffolds for the preparation of synthetic antigens or protein mimetics. © 2003 Wiley Periodicals, Inc.

2003

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