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Photoinduced Strain‐Assisted Synthesis of a Stiff‐Stilbene Polymer by Ring‐Opening Metathesis Polymerization
Author(s) -
Krishnan Baiju P.,
Xue Lulu,
Xiong Xinhong,
Cui Jiaxi
Publication year - 2020
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.202002418
Subject(s) - photoisomerization , romp , polymerization , metathesis , photochemistry , polymer , polymer chemistry , materials science , ring opening metathesis polymerisation , isomerization , chemistry , catalysis , organic chemistry , composite material
Developing a novel strategy to synthesize photoresponsive polymers is of significance owing to their potential applications. We report a photoinduced strain‐assisted synthesis of main‐chain stiff‐stilbene polymers by using ring‐opening metathesis polymerization (ROMP), activating a macrocyclic π‐bond connected to a stiff‐stilbene photoswitch through a linker. Since the linker acts as an external constraint, the photoisomerization to the E ‐form leads to the stiff‐stilbene being strained and thus reactive to ROMP. The photoisomerization of Z ‐form to E ‐form was investigated using time‐dependent NMR studies and UV/Vis spectroscopy. The DFT calculation showed that the E ‐form was less stable due to a lack of planarity. By the internal strain developed due to the linker constraint through photoisomerization, the E ‐form underwent ROMP by a second generation Grubbs catalyst. In contrast, Z ‐form did not undergo polymerization under similar conditions. The MALDI‐TOF spectrum of E ‐form after polymerization showed the presence of oligomers of >5.2 kDa.