Synthesis of High Molecular Weight Cyclic Poly(ε‐caprolactone)s of Variable Ring Size Based on a Light‐Induced Ring‐Closure Approach

Abstract

High molecular weight cyclic poly(ε-caprolactone)s (cPCLs) with variable ring size are synthesized via light-induced ring closure of α,ω-anthracene-terminated PCL (An-PCL-An). The ring size of cPCL is tunable simply by adjusting the polymer concentration from 10 to 100 mg mL(-1) in THF. The cyclo-addition via the bimolecular cyclization of An-PC-An is well characterized by a variety of analyses such as (1) H NMR and UV-vis spectroscopies, gel-permeation chromatography, and differential scanning calorimetry. The reversible dimerization of An induced by heating enables the cyclic PCL to have a switchable "on-off" capability. This novel light-induced ring-closure technique can be one of the most powerful candidates for producing various well-defined cyclic polymers in highly concentrated polymer solution.

Cyclic Polymers by Ring‐Closure Strategies

“…Also in 2015, Wang et al. used the photodimerization of anthracene for the preparation of cyclo ‐PCL, with the selected concentration conditions (0.01–0.1 mg mL −1 for M n ≈14 000 g mol −1 ) mainly affording high‐molecular‐weight cyclic oligomers rather than PCL monocycles …”

Precise Synthesis, Properties, and Structures of Cyclic Poly(ε-caprolactone)s

“…The synthesis of c -PCL bearing cycloadded anthracene units was reported (Scheme 2) [19]. α,ω -Anthracene-terminated linear PCLs were synthesized at 80~110 °C in toluene under argon atmosphere by a one-pot reaction composed of two steps.…”

“…A research effort was first made to develop synthetic methods of c -PCL. As a result, several synthetic schemes were reported [6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30]. The synthesized products were examined in terms of properties and structures [6,7,8,10,16,17,18,20,27,28,31,32,33,34,35].…”

Synthese cyclischer Polymere durch Ringschluss‐Strategien

“…Ebenfalls 2015 berichteten Wang et al. über die Anwendung der Photodimerisierung von Anthracen auf die Herstellung von cyclo ‐PCL, wobei unter den gewählten Konzentrationsbedingungen (0.01–0.1 mg mL −1 bei M n ≈ 14 000 g mol −1 ) vorwiegend cyclische Oligomere mit hohem Molekulargewicht anstelle von PCL‐Monocyclen erhalten wurden …”