Isomerization of Linear to Hyperbranched Polymers: Two Isomeric Lactones Converge via Metastable Isostructural Polyesters to a Highly Branched Analogue

Grant W. Fahnhorst, Daniel E. Stasiw, William B. Tolman, Thomas R. Hoye

Research output: Contribution to journalArticlepeer-review

4 Scopus citations

Abstract

We report here the Zn(II)-catalyzed convergence of two metastable and isostructural polyesters to an isomeric polymer having a hyperbranched architecture. Ring-opening transesterification polymerization (ROTEP) of 4-carbomethoxyvalerolactone (CMVL) under Brønsted catalysis is known to give the linear polyester PCMVL. We show here that this can be isomerized to the equilibrated (and highly branched) polyester EQ-PCMVL. Analysis of the fragments obtained from eliminative degradation of EQ-PCMVL were critical in the formulation of its structure. The isomerization of PCMVL to EQ-PCMVL is a direct consequence of the presence of the second ester functional group in the CMVL ester-lactone, a rarely studied class of monomer. Zn(II)-catalysis of the ROTEP of the isomeric β-lactone, 2-(2-carbomethoxyethyl)propiolactone (isoCMVL), as well as isomerization of the isostructural linear homopolymer derived from that isomeric monomer, led to the same EQ-PCMVL. These results suggest a new strategy for the introduction of branching into various polyesters.

Original languageEnglish (US)
Pages (from-to)1144-1148
Number of pages5
JournalACS Macro Letters
Volume7
Issue number10
DOIs
StatePublished - Oct 16 2018

Bibliographical note

Funding Information:
Financial support for this work was provided by the Center for Sustainable Polymers at the University of Minnesota, an NSF-supported Center for Chemical Innovation (CHE-1413862). Some of the NMR data were obtained with an instrument whose purchase was enabled by the NIH Shared Instrumentation Grant Program (S10OD011952).

Publisher Copyright:
Copyright © 2018 American Chemical Society.

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