Selectively Deuterated Poly(ϵ-caprolactone)s: Synthesis and Isotope Effects on the Crystal Structures and Properties

Dongsook Chang, Tianyu Li, Lengwan Li, Jacek Jakowski, Jingsong Huang, Jong Kahk Keum, Byeongdu Lee, Peter V. Bonnesen, Mi Zhou, Sophya Garashchuk, Bobby G. Sumpter, Kunlun Hong

Research output: Contribution to journalArticlepeer-review

21 Scopus citations

Abstract

Selective deuteration is an important tool for many analytical techniques including neutron scattering and spectroscopies. However, the availability of deuterated materials is limited because of the challenges in their synthesis. Here, we report the synthesis of partially and fully deuterated ϵ-caprolactone monomers and their corresponding polymers, poly(ϵ-caprolactone)s (PCLs), and the investigation of isotope effects on their crystalline structures and physical properties. Deuteration of PCLs leads to smaller crystal lattices and volumes compared to protiated PCLs by the amount proportional to the deuteration levels. The linear trend suggests that the volume isotope effect in PCL is primarily governed by the vibrations of C-D and C-H bonds. The large intrachain contraction of deuterated PCLs compared to that of polyethylene reported in the literature can be ascribed to the presence of polar ester groups in PCLs. Deuterated PCLs also display lower melting temperatures than protiated PCLs proportional to their deuteration levels because of weaker intermolecular interactions in deuterated polymers. FTIR spectroscopy, with support from density functional theory calculations, shows large red shifts of the stretching and bending frequencies of C-D versus C-H bonds as dictated by their relative reduced masses 13/7, and to a smaller degree for the C=O stretching frequency. This work is among the very few studies comparing the effects of partial versus full deuteration on the structures and properties in semicrystalline polymers. These results not only advance our understanding of isotope effects in polymeric materials but also provide an important avenue to design polymers with desirable properties.

Original languageEnglish
Pages (from-to)9393-9404
Number of pages12
JournalMacromolecules
Volume51
Issue number22
DOIs
StatePublished - Nov 27 2018

Funding

FundersFunder number
National Science Foundation1655740

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