Formation and Evolution of sp2 Hybrid Conjugate Structure of Polyacrylonitrile Precursor during Stabilization

Abstract

The generated sp2 hybrid conjugate structure of a C atom, which resulted from the chemical reaction affected by temperature and time, is an effective six-membered ring planar structure of the final carbon fiber. This kind of hybrid conjugate structure determined the formation of the final structure and mechanical properties of carbon fiber. In this paper, the formation and evolution of sp2 hybrid conjugated structures of PAN precursor during thermal stabilization were investigated by Raman, UV-vis and 13C-NMR methods. The results indicated that with the increase of stabilization temperature, the degree of the sp2 hybrid conjugated structure of stabilized PAN fiber increases “linearly”, while the content of the sp2 hybrid carbon atoms increases with “S-type”. The final sp2 hybrid conjugated ring structure is mainly composed of single-ring, double-ring, triple-ring, and double-bond structures. Compared with the time factor, the temperature effect plays a decisive role in the formation of the sp2 hybrid conjugate structure.

A comparative investigation of the synergistic correlation (mechanical-hydrophobicity/hydrophilicity vs. structural behaviors) of a series of surface-metalized polyacrylonitrile fibers by silver nanoparticles (AgPAN): An in-situ surface metallization protocol

“…This absorption band was assigned with the n- π* transitions of C-O and C-N groups in the polymeric matrix. 76 From the spectrum of the same sample (Figure S1(a)), it can show that weak bands at wavelength of ˜ 247 nm and ˜ 60 nm represented a π- π* transition and n- π* transition of C=O and C=C bonds, 48,77 respectively. Whitford et al 48 reported that an absorption peak in the ultraviolet region of 265–275 nm with varying intensity attributed to the PAN chromophore.…”

A preparation strategy for multicolor carbon dots embedded in silicone for latent fingermarks and detection of AcO−

“…The longer the absorption peak is, the larger the electron delocalization structure the CDs may have, which is consistent with the phenomenon that the fluorescence of the CDs changes from blue to red. 45,46 In Fig. 1B, the fluorescence of CDs separated by different polar solvents ranges from 439 nm to 615 nm.…”

Effect of ambient atmosphere on the formation and evolution of conjugated structure of pre-oxidized polyacrylonitrile

“…Relevant scholars have put forward that the characteristic structure formed during the pre-oxidation process included C=C, C=N and aromatic heterocyclic conjugated groups, which could be characterized and analyzed by UV-vis spectroscopy [27,28]. This was because the absorption wavelength of UV-vis absorption spectrum was usually in the range of 200-800 nm, and it could significantly characterize the n-π * and π-π * orbital transitions of unsaturated bond conjugated systems.…”