Synthesis, helical conformation, and infrared emissivity property study of optically active substituted polyacetylenes derived from serine

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Novel optically active and racemic poly(N-propargylamides) bearing tyrosine pendants (LPT, DPT, and RPT) were synthesized and characterized. The polymers possessed moderate molecular weights and were thoroughly soluble in common organic solvents. The secondary structure of these three polymers in chloroform was studied and the results indicated that LPT and DPT could adopt helical structures with predominantly one-handed screw sense according to their intense Cotton effect and large specific rotation values, while RPT adopted random coiled polymer chain. The amide groups could form amide-amide hydrogen bonds to engender the twist of dihedral angle and the strong steric repulsion of phenol groups might have the opposite effect on the helix. The helical structure of the optically active polymers were conclusively constructed and stabilized by the optimization of intra-and intermolecular hydrogen bonding and steric repulsion of the side chains. Moreover, the infrared emissivity values of LPT and DPT at 30 8C were 0.682 and 0.671, which were much lower than RPT. LPT and DPT also showed superior heat resistance due to their unique helical conformation.

Optically active tyrosine‐containing poly(N‐propargylamides): Synthesis, helical conformation, and infrared emissivity study

Zhang

Hang

et al. 2017

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Infrared emissivity property study and conformational analysis of helical polysilane

Zhang

Zhou

et al. 2018

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Left and right single-handed helical polysilane (L-HPS and D-HPS) and racemic helical polysilane (R-HPS) were synthesized by the Wurtz-type coupling reaction. The chiral dichloro(methoxycarbonyl ethyl propyl ether)methylsilane monomers applied in copolymerization were derived from methyl D/L-lactate. The obtained polymers were characterized by 1 H and 13 C nuclear magnetic resonance, Fourier transform infrared spectroscopy, ultraviolet-visible spectroscopy, circular dichroism spectroscopy, gel permeation chromatography and X-ray diffraction. Infrared emissivity (IRE) values were also investigated. Compared to R-HPS, L-HPS, and D-HPS, a pair of mirror image, showed higher crystallinity, better thermal stability, and lower IRE (8-14 mm) at the values of 0.592 and 0.576, respectively. The higher regular secondary structure of HPSs was attributed to the formation of intermolecular hydrogen bonds. To further study the configurations of L-HPS, D-HPS, and R-HPS, rotational isomeric state scheme with molecular dynamics simulation have been utilized.

Evaluation of maleic acid‐based copolymers containing polyoxyethylene ether as inhibitors for CaCO₃ scale

Wang

Zhu

Liu

et al. 2019

Polymer scale inhibitors have been widely used to reduce the loss caused by mineral scaling in circulating cooling water systems. In this article, four maleic acid‐based copolymers [hydrolyzed polymaleic anhydride (HPMA)‐AEO] containing different fatty alcohol polyoxyethylene ether (such as AEO‐9, AEO‐10, AEO‐15, and AEO‐20) are prepared by the way of free‐radical copolymerization and characterized using Fourier transform infrared (FTIR), 1H NMR, and gel permeation chromatographic (GPC) techniques. The effects of HPMA‐AEO on CaCO3 scale are studied in several aspects (such as dose, Ca2+ concentration, temperature, inhibition time, pH, the ratio of EO:carboxyl, and the relative supersaturation of CaCO3 solution) by static experiments. The CaCO3 scaling process with dosing of HPMA‐AEO‐9 is investigated under dynamic tests. CaCO3 deposits and precipitate in the presence of HPMA‐AEO‐9 are analyzed using scanning electronic microscope (SEM) and X‐ray diffraction (XRD). The results show that the performance of HPMA‐AEO against CaCO3 scale highly depends upon the ratio of EO:carboxyl; the introduction of AEO group can significantly improve the performance of HPMA‐AEO to tolerate high alkalinity, high hardness, and high temperature; the presence of HPMA‐AEO‐9 can obviously affect the CaCO3 scaling process on the tube wall through interfering with nucleation process and crystal growth process and significantly alter the surface morphology and crystal form of CaCO3 deposits. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47470