Abstract
We investigated how the reactivity of epoxide and oxetane monomers in photoinitiated cationic polymerization is strongly influenced by their ability to form intramolecular hydrogen-bonding complexes with the Brønsted acids produced by the photoinitiator. In this paper, we highlight the importance of the thermal stability of the hydrogen-bonded complexes of the protonated monomers. We observed that the glycidyl ether structural motif (and its oxetane analog) is key for the formation of the complexes. Using temperature-controlled Fourier transform infrared (FTIR) with in situ ultraviolet irradiation, we performed a series of real-time FTIR experiments which support the hypothesis that the induction period is due to the thermal stability of the hydrogen-bonded complex. In particular, we focused on the photoinitiated cationic polymerization of bis(1-ethyl(3-oxetanil)methyl) ether ("di-oxetane", DOX) for the thermal stability study because it exhibits a prolonged induction period. Furthermore, it was possible to delay the cationic polymerization of DOX without causing autocatalytic polymerization if the temperature is kept lower than 30 °C. This is because the protonated monomer is stable and propagates very slowly at temperatures below 30 °C. On subsequent heating, the hydrogen-bonded complex of DOX loses its thermal stability, and the autocatalytic cationic polymerization of DOX occurs.
Original language | English |
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Pages (from-to) | 1158-1165 |
Number of pages | 8 |
Journal | Macromolecules |
Volume | 52 |
Issue number | 3 |
DOIs | |
Publication status | Published - 2019 Feb 12 |
Bibliographical note
Funding Information:This research was supported by NSF DMR Polymers Program (Award No. 1308917).
Publisher Copyright:
© 2019 American Chemical Society.
All Science Journal Classification (ASJC) codes
- Organic Chemistry
- Polymers and Plastics
- Inorganic Chemistry
- Materials Chemistry