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Investigation of Tacticity and Living Characteristics of Photoredox‐Mediated Metal‐Free Ring‐Opening Metathesis Polymerization
Author(s) -
Pascual Laura M. M.,
Goetz Adam E.,
Roehrich Adrienne M.,
Boydston Andrew J.
Publication year - 2017
Publication title -
macromolecular rapid communications
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.348
H-Index - 154
eISSN - 1521-3927
pISSN - 1022-1336
DOI - 10.1002/marc.201600766
Subject(s) - tacticity , norbornene , polymer chemistry , polymerization , ring opening metathesis polymerisation , polymer , copolymer , monomer , materials science , metathesis , composite material
This study investigated the microstructures of polymers produced via photoredox‐mediated metal‐free ring‐opening metathesis polymerization. Polynorbornene, poly( exo ‐dihydrodicyclopentadiene), and poly( endo ‐dicyclopentadiene) were found to have cis olefin contents of 23%, 24%, and 28%, respectively. Additionally, the cis / trans ratio remained consistent during the course of norbornene polymerization. Polymer tacticity was evaluated by quantitative 13 C NMR spectroscopy, which revealed each polymer to be largely atactic. Specifically, the three polymers were estimated to be 33%, 58%, and 55% syndiotactic, respectively. In parallel, this study also explored the ability to produce diblock copolymers from norbornene and exo ‐dihydrodicyclopentadiene. Successful diblock copolymerization was achieved using either monomer order. In each case, however, the results suggested to us that chain–chain coupling (increased molecular weight) and irreversible termination (dead chains observed during attempted chain extension) occurred when reaction times were extended.