Abstract
ABSTRACTAn array of branched poly(ɛ‐caprolactone)s was successfully synthesized using an one‐pot inimer promoted ring‐opening multibranching copolymerization (ROCP) reaction. The biorenewable, commercially available yet unexploited comonomer and initiator 2‐hydroxy‐γ‐butyrolactone was chosen as the inimer to extend the use of 5‐membered lactones to branched structures and simultaneously avoiding the typical tedious work involved in the inimer preparation. Reactions were carried out both in bulk and in solution using stannous octoate (Sn(Oct)2) as the catalyst. Polymerizations with inimer equivalents varying from 0.01 to 0.2 were conducted which resulted in polymers with a degree of branching ranging from 0.049 to 0.124. Detailed ROCP kinetics of different inimer systems were compared to illustrate the branch formation mechanism. The resulting polymer structures were confirmed by 1H, 13C, and 1H‐13C HSQC NMR and SEC (RI detector and triple detectors). The thermal properties of polymers with different degree of branching were investigated by DSC, confirming the branch formation. Through this work, we have extended the current use of the non‐homopolymerizable γ‐butyrolactone to the branched polymers and thoroughly examined its behaviors in ROCP. © 2016 The Authors. Journal of Polymer Science Part A: Polymer Chemistry Published by Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 1908–1918
Highlights
Introducing branches to polymers provides materials with distinctly different properties compared to analogous linear polymers, including both a reduction in viscosity and an increase in flexibility.[1]
The commercially available and biobased 5-membered lactone, aOHcBL, was chosen to introduce the concept of using 5-membered lactones in branched polymers and to facilitate statistical branching and to avoid the multistep synthesis generally associated with the preparations of inimers used
The multibranching ring-opening multibranching copolymerization (ROCP) system kinetics were studied in detail to explore whether good control over the Sn(Oct)2-catalyzed ROCP for the inimer-monomer system could be achieved and to determine if the chemical and physical properties of the resulting materials are tunable
Summary
Introducing branches to polymers provides materials with distinctly different properties compared to analogous linear polymers, including both a reduction in viscosity and an increase in flexibility.[1]. We assume that the high molecular weight is due to the ring-opening of cBL, which acted as a branch unit and that the secondary alcohol in the inimer initiates polymerization.
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