Synthesis of random terpolymers and determination of reactivity ratios of N‐carboxyanhydrides of leucine, β‐benzyl aspartate, and valine

Abstract

The copolymerization and terpolymerization of leucine‐N‐carboxyanhydride, β‐benzyl aspartate‐ N‐carboxyanhydride, and valine‐N‐carboxyanhydride in dioxane, initiated with triethylamine, were investigated to determine the random nature of the terpolymer composition for potential applications as targeting drug delivery carriers. 1H NMR was used to obtain the actual monomer compositions of the polymers. The reactivity ratio of each monomer was determined with Fineman–Ross, Kelen–Tüdös, and nonlinear least‐squares curve‐ fitting methods. The product of the estimated reactivity ratios from the monomers in the binary copolymerizations indicated that random polymers were predominantly formed. On the basis of the reactivity ratios determined from the binary copolymers, Alfrey–Goldfinger equations were used to estimate the compositions of the terpolymers. There was no statistical difference between the actual monomer compositions and the calculated compositions of the terpolymers; this validated the reactivity ratios estimated by Fineman–Ross, Kelen–Tüdös, and nonlinear least‐squares curve‐ fitting methods. Therefore, the poly(leucine‐β‐Bzl‐ aspartate‐valine) synthesized in this study was primarily a random terpolymer. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 317–325, 2004

Tunable mechano-responsive organogels by ring-opening copolymerizations of N-carboxyanhydrides

“…1c), the calculated numbers of repeat units from 1 H NMR spectroscopy showed linear correlations with the theoretical numbers of repeat units, which were obtained according to the feed ratios of the two monomers and the ratios of monomers to macroinitiator, indicating that BLG and Gly NCA monomers had similar reactivities and were fully consumed during the polymerizations. 20 …”

Kinetic Investigations on Microwave-Assisted Statistical Terpolymerizations of 2-Oxazoline Monomers

“…Up to this moment, only few kinetic investigations were reported on free radical statistical terpolymerizations, whereby no good control over the monomer distribution in single polymer chains could be achieved due to the use of the uncontrolled polymerization method. [35][36][37][38][39] In addition, one example of kinetic investigations on controlled nitroxide-mediated free radical terpolymerizations was reported to result in well-defined polymers, but the monomer distribution throughout the chains was not determined. [40] As such, detailed kinetic investigations on the monomer incorporation and, thus, the monomer distribution have not been determined for living or controlled statistical terpolymerizations.…”

Terpolymerization kinetics of amino acid N‐carboxy anhydrides

“…43,45 The results obtained from this approach are given in Table 5. The predicted values are in very good agreement with the experimental data, thus validating the copolymerization parameters calculated for the binary systems and supporting the experimental results for the terpolymer composition.…”

“…44 Wamsley et al investigated the terpolymerization of Leu-NCA/ Asp(Bzl)-NCA/Val-NCA by determining the copolymerization parameters of the binary mixtures (with 1 H-NMR spectroscopy) and comparing the experimentally obtained terpolymer composition with the predicted composition. 43 No kinetic data of the progress of a terpolymerization is available to date.…”

“…Nuclear magnetic resonance (NMR) ( 1 H-NMR or 15 N-NMR) has also been used to study amino acid NCA polymerization kinetics. [42][43][44] While it is able to distinguish between certain amino acids, it is limited by the fact that it only allows the study of small numbers of monomers due to significant overlap of signals in more complex copolymerization. To address this, we have recently reported a procedure through which we were able to follow the Additional Supporting Information may be found in the online version of this article.…”