Abstract
The anionic ring-opening polymerization of carbazole-containing monomers, (9-carbazolylmethyl)thiirane (M1) and (3,6-di-tert-butyl-9-carbazolylmethyl)thiirane (M2), with hexanethiol or pentaerythritol tetrakis(3-mercaptopropionate) (PETMP) as initiators and 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) as catalyst at 20 °C in tetrahydrofuran or N,N-dimethylformamide as solvents has been studied. The polymerization of these monomers proceeds in a living fashion affording linear and star-shaped polymers with controlled molecular weight (Mn = 4000–15,000 g mol−1) and relatively low polydispersity (Đ < 1.3). It was demonstrated that end-capping of polymers by trifluoroacetic anhydride allowed to protect thiol end groups from oxidative coupling, which typically leads to the broadening of molecular weight distribution of the synthesized polymers. The thermal, photophysical and electrochemical properties of the synthesized linear and star-shaped polymers were estimated.
Highlights
Poly(N-vinylcarbazole) is one of the extensively studied photoconductive polymers due to its application as hole transporting host in polymer light emitting diodes [1,2,3,4]
The BF3OEt2-coinitiated cationic polymerization of this monomer leads to polymers with Mn = 2860 g mol−1 and Đ = 4.5 [2], while anionic polymerization in the presence of BuLi as initiator results in poly-(9-(thiiran-2-ylmethyl)9H-carbazole) with slightly higher molecular weight (Mn = 5800 g mol−1) but still high polydispersity (Đ = 4.4) [29]
We report on living anionic ring-opening polymerization of two thiirane derivatives containing carbazole group, (9carbazolylmethyl)thiirane (M1) and (3,6-di-tert-butyl-9-carbazolylmethyl)thiirane (M2) (Scheme 1) using 1,5,7-triazabicyclo[4.4.0] dec-5-en (TBD) as catalyst in conjunction with hexanethiol and pentaerythritol tetrakis(3-mercaptopropionate) (PETMP) as initiators
Summary
Poly(N-vinylcarbazole) is one of the extensively studied photoconductive polymers due to its application as hole transporting host in polymer light emitting diodes [1,2,3,4]. The use of controlled radical polymerization technique allowed to prepare well-defined homopolymers [16,17,18], end-functionalized polymers as well as block copolymers [19,20,21] and even star polymers [22] These examples are still limited to the polymerization of carbazole-containing (meth)acrylates and styrenes [23,24,25,26,27]. The BF3OEt2-coinitiated cationic polymerization of this monomer leads to polymers with Mn = 2860 g mol−1 and Đ = 4.5 [2], while anionic polymerization in the presence of BuLi as initiator results in poly-(9-(thiiran-2-ylmethyl)9H-carbazole) with slightly higher molecular weight (Mn = 5800 g mol−1) but still high polydispersity (Đ = 4.4) [29]
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