Phosphazene/Lewis Acids as Highly Efficient Cooperative Catalyst for Synthesis of High‐Molecular‐Weight Polyesters by Ring‐Opening Alternating Copolymerization of Epoxide and Anhydride

Abstract

The synthesis of high‐molecular‐weight polyesters via the ring‐opening alternating copolymerization (ROAC) of cyclic anhydrides and epoxides using organocatalysts remains a major challenge. In this context, the organic cyclic trimeric phosphazene base (CTPB) was used as an efficient catalyst for the ROAC of phthalic anhydride (PA) with epoxides. It was found that the activity and PA conversion dramatically increased with the addition of triethyl borane (TEB) as a cocatalyst, even a small amount of TEB, for example, 5 mol % relative to CTPB. The molecular structures of obtained polyesters were characterized by nuclear magnetic resonance (1H NMR, 13C NMR) and matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI TOF), which demonstrated the formation of perfectly alternating polyesters with unimodal and narrow molecular weight distributions. Different molecular weight polyesters (up to 118.5 kg mol−1) were facilely prepared by reducing the loading of CTPB and TEB, while the polymerizations were fast (turnover frequency, TOF up to 500 h−1). Thermal analysis of the resulting polymers indicated that the alternating polyesters were amorphous, and their Tgs increased with the increment of molecular weights. © 2020 Wiley Periodicals, Inc. J. Polym. Sci. 2020, 58, 803–810

Synthesis of Diverse Polycarbonates by Organocatalytic Copolymerization of CO2 and Epoxides: From High Pressure and Temperature to Ambient Conditions

“…[36] Recently,three phosphazenes (CTPB,C 3 N 3 -Py-P 3 and C 3 N 3 -Me-P 3 as shown in Scheme 1) with tunable basicity and structures have been successfully developed in our group and showed high efficiencyf or ROPs of various cyclic monomers. [55][56][57][58][59][60][61][62][63] In this study,t hese phosphazenes in combination with TEB were tested as binary organocatalytic pair for copolymerization of CO 2 with different epoxides (Schemes 1a nd 2) under various conditions.…”

“…Theo btained polymer was further analyzed by 1 HNMR (Figure 1) and 13 CNMR (Figure S4). According to 1 HNMR analysis,there is no signal at 3.5-4.0 ppm, which is assigned to polyether (PCHO), [56] thus implying that PCHC with > 99 % carbonate linkages was produced. GPC analysis (Figure S5) shows a M n of 15.4 kDa with ab imodal distribution ( = 1.26).…”

Recent Developments in Ring-Opening Copolymerization of Epoxides With CO2 and Cyclic Anhydrides for Biomedical Applications

“…Compared with organometallic catalysts, the metal-free Lewis pair catalysts are easy to synthesize and often commercially available (Pappuru and Chakraborty, 2019;Hong, 2021). By adjusting the acidity, basicity, and steric effects, the Lewis acidbase pair can have excellent catalytic performance (Figure 8) (Zhang et al, 2020b). This section only summarizes the very recent highlights.…”

A Facile Fabrication of Lysosome-Targeting pH Fluorescent Nanosensor Based on PEGylated Polyester Block Copolymer

“…Due to the advantageous features of this ROCOP, such as atom-economic, enriched monomer resources and mild reaction conditions, it has become an effective and promising strategy for the synthesis of biocompatible polyesters [42][43][44][45]. By taking advantage of this versatile ROCOP, various polyesters with tunable structures, functionalities and good biocompatibility can be successfully synthesized [46][47][48][49]. In fact, based on this type of ROCOP, a serials of functionalized polyester-based amphiphilic polymers have been well developed.…”

“…In comparison with the most reported methods to prepare polymeric fluorescent pH nanosensors through the abovementioned radical copolymerization or ROAC of cyclic lactone monomers, the ROCOP of epoxides and anhydrides may presents many advantages, such as facile preparation, wide availability of raw materials, flexible design, polymer structure with tunable functionalities, etc. [41,44,47] Meanwhile, the fabricated polymeric pH nanosensors via the ROCOP of epoxides and anhydrides also exhibits many benefits over others, including good biocompatibility, good cell permeability, better potential biodegradability and tunable structure and function, etc. [41,44,47] Thus, if the ROCOP of epoxides and anhydrides, hydrophilic modifications and decoration with fluorescent dyes can be realized together, the attractive polymeric pH nanosensors with advantageous properties may be fabricated conveniently and effectively by a novel approach.…”