Synthesis and characterization of a model carbon-chain polymer substituted by two esters on every third atom via anionic ring-opening polymerization of a cyclopropane-1,1-dicarboxylate

Abstract

SUMMARY Ultrapure diethyl 1,l-cyclopropanedicarboxylate (1) undergoes ring-opening polymerization when placed in the presence of small amounts of sodium thiophenolate (2) at temperatures above 80°C, and leads to the synthesis of a carbon-chain polymer substituted on every third carbon atom by ethyl ester substituents. 1 polymerizes also in the presence of 2 generated in situ from thiophenol and metallic sodium, but does not polymerize in the presence of metallic sodium alone. Polymerizations are slow and require high concentrations in monomer and initiator to obtain reasonable polymerization times. In spite of the high temperatures used in some experiments (up to 130"C), no structural subunit resulting from side reactions was detected, presumably due to the high stability of the propagating malonate --carbanion. Polymers of narrow molecular weight distribution were obtained at both 80 and 130°C (M,.,/Mn < 1,14), and absolute degrees of polymerization increased with polymer yields. These results were rationalized on the basis of a quasi-living polymerization mechanism. Thermal properties of poly( 1) were determined by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). Poly(1) is stable up to 275°C and is a micro-crystalline polymer insoluble in most typical solvents, with the noticeable exception of chloroform and dichloromethane.

Control of End Groups in Anionic Polymerizations Using Phosphazene Bases and Protic Precursors As Initiating System (XH-ButP4 Approach): Application to the Ring-Opening Polymerization of Cyclopropane-1,1-Dicarboxylates

“…Polymerizations of electrophilic cyclopropanes such as 1 are typically initiated by soft nucleophiles such as cyanide or thiolate anions . Several reports have already established that thiophenolates PhSM (with M = Li, Na, K, or tetraalkylammonium (R 4 N)) are particularly convenient as initiators in the polymerization of 1 , yielding full conversion of the ring-opened adduct, with higher initiation rate constants than those observed for the propagation step and without side reactions. ,, In a recent report, we established that the Bu t P 4 /PhSH couple generated an excellent initiator in situ, requiring lower reaction temperatures for the initiation step than those typically needed with alkali metal thiophenolates ( k p = 5.8 × 10 −4 L·mol −1 ·s −1 in THF at 60 °C for the Bu t P 4 /PhSH initiator vs k p = 2.0 × 10 −4 L·mol −1 ·s −1 in DMSO at 130 °C for a sodium thiophenolate initiator (Figure S1 in the Supporting Information)) . As a result, the thiophenolate anions, and more specifically the Bu t P 4 /PhSH couple, will be used in this study as a benchmark to evaluate the efficiencies of other Bu t P 4 /XH couples, as well as the possibility of controlling the nature of the other end group via an end-capping reaction.…”

Design of Optimized Reaction Conditions for the Efficient Living Anionic Polymerization of Cyclopropane‐1,1‐Dicarboxylates

“…As malonates act as transfer agent during the polymerization, their occurrence prevents a perfect control over the molecular weights. We have had very good experiences with a synthetic procedures for 1 that involves dialkyl malonate, 1,2‐dibromoethane, potassium carbonate, and DMSO . In most cases, pure 1 can be obtained according to this procedure, completely free of starting malonate as long as the reaction and work‐up procedures are strictly observed.…”

“…Over the past two decades, our group has been describing the living anionic polymerization of activated cyclopropanes in about fifteen research papers . The ring‐opening polymerization of cyclopropanes was not a new concept at the time we started investigating the issue, but previous attempts had always led to oligomers, with broad to very broad molecular weight distributions .…”

“…Conditions that have so far been found to polymerize 1 livingly can be schematically divided into two sets, depending on the type of counterion associated to the malonate RC(COOR) − carbanion on the growing chain. One set involves simple alkali ions, while the other one implicates the large tBuP 4 H + phosphazenium cation derived from the protonation of tBuP 4 superbase (see Scheme for a mechanism) . Both systems have their pros and cons.…”

Structure and Morphology of Poly(diethyl trimethylene-1,1-dicarboxylate) Crystals

“…In this contribution, we investigate poly(diethyl trimethylene-1,1-dicarboxylate), or PDTD, a polytrimethylene polymer for which the side substituents are ethyl ester (X = Y = −COOC 2 H 5 ). Details of the synthesis and characterization of this and similarly substituted polymers have been recently reported. , The complete chemical structure of the PDTD molecules, including the terminal groups, is Ph−S−[CH 2 CH 2 CX 2 ] n −H.…”