Detailed Cyclization Pathways Identification of Polyacrylonitrile and Poly(acrylonitrile-co-itaconic acid) by in Situ FTIR and Two-Dimensional Correlation analysis

Abstract

In situ Fourier transform infrared spectroscopy (in situ FTIR) and two-dimensional (2D) correlation analysis were applied to investigate the cyclization pathways of polyacrylonitrile homopolymer (PAN) and poly­(acrylonitrile-co-itaconic acid) (PAI) during thermal treatment under argon atmosphere. The cyclization pathways for PAN and PAI at different temperatures were summarized based on the 2D correlation analysis. According to the cyclization pathways, the cyclization of PAN was divided into three stages. The vital role of the ends of original PAN chains, especially the conjugated nitrile, in initiating cyclization by the free radical mechanism was verified. A part of IA in PAI chains first converted into anhydride, and then the formed anhydride rather than the carboxyl group initiated cyclization first. The ionic mechanism mainly initiated cyclization at 220 °C and below. Both for PAN and PAI, the length of cyclic structures from the free radical mechanism was ca. three repeated six-membered rings, but that from the ionic mechanism was ca. eight repeated six-membered rings.

Quantification of the ion transport mechanism in protective polymer coatings on lithium metal anodes

“…Self-cyclization of PAN is an attractive approach to form chemical cross-linking between the PAN segments. 13,14 Conventionally, selfcyclization of PAN is initiated at temperatures above 200 C, [15][16][17] and the resulting cross-link density only varies in a narrow range (e.g. 1.5-2.5 Â 10 À4 mol cm À3 ) regardless of the heating time.…”

Investigation of the Cyclization Mechanism of Poly(acrylonitrile-co-ethylenesulfonic acid) Copolymer during Thermal Oxidative Stabilization by In Situ Infrared Spectroscopy

“…In the current studies, it is commonly recognized that H of the hydroxyl group directly transfers to the neighboring N of CN in P(AN-co-IA) copolymers. 20,21 According to this direct cyclization mechanism, the process of the cyclization reaction of P(AN-co-ESA) was performed as shown in Figure 9 hydrogen bond and SO bond do not change before the nitrile group.…”

Macromolecular Chain Structure Regulation of AN–MA–IA Aqueous Copolymerization with a Water-Soluble Azo Initiator AIBA

“…10 According to the existing research, IA is the most efficient acidic comonomer for the two corresponding carboxylic groups. 11 Compared with the free radical mechanism, the ionic mechanism can reduce the cyclization reaction rate with a controllable exothermal heat at a relatively low and uniform reaction temperature, thereby obtaining a precursor with less structural defects. 12 The content and sequence distribution of the comonomer IA in the PAN copolymer considerably influence the AN segment length, which affects the molecular weight of the PAN and the TOS process.…”

“…PAN copolymers contain a small amount of comonomers, e.g., methyl acrylate (MA), methyl methacrylate (MMA), itaconic acid (IA), and acrylic acid (AA), to overcome the disadvantages of the PAN homopolymer, such as the low processability and high exothermic heat generation during thermal oxidative stabilization (TOS). , Among these comonomers, acidic comonomers contain carboxyl groups, which can change the free radical mechanism to the ionic mechanism of the cyclization reaction during TOS . According to the existing research, IA is the most efficient acidic comonomer for the two corresponding carboxylic groups . Compared with the free radical mechanism, the ionic mechanism can reduce the cyclization reaction rate with a controllable exothermal heat at a relatively low and uniform reaction temperature, thereby obtaining a precursor with less structural defects …”