Hyo Jeong Kim, Yeamsuksawat Thanakorn, Dae Eon Jung, Youngho Eom
{"title":"Rheological study on lower critical solution temperature behavior of organo-soluble cyano-substituted p-aramid in isotropic phase","authors":"Hyo Jeong Kim, Yeamsuksawat Thanakorn, Dae Eon Jung, Youngho Eom","doi":"10.1007/s13367-024-00088-z","DOIUrl":null,"url":null,"abstract":"<div><p>Poly(2-cyano-<i>p</i>-phenylene terephthalamide) (CY-PPTA) has garnered significant interest as a promising precursor for super <i>p</i>-aramid fibers because of its organosolubility in <i>N</i>,<i>N</i>-dimethyl acetamide/lithium chloride (DMAc/LiCl) while conserving the superior properties of the resultant fibers. However, CY-PPTA has been reported to exhibit abnormal phase behavior owing to the strong dipole–dipole interactions induced by the cyano groups. Herein, we rheologically study the isotropic phases of CY-PPTA/DMAc solutions with respect to the concentration and temperature and compare them with those of CY-PPTA/sulfuric acid (H<sub>2</sub>SO<sub>4</sub>) solutions. In the isotropic region, the CY-PPTA solutions yield a higher power-law exponent of the dynamic viscosity (<i>η'</i>) versus concentration of 6.0 (<i>ηʹ</i> ~ <i>c</i><sup>6.0</sup>) in the DMAc system than that in H<sub>2</sub>SO<sub>4</sub> (<i>ηʹ</i> ~ <i>c</i><sup>3.2</sup>). Moreover, the CY-PPTA/DMAc solutions exhibit a lower critical solution temperature (LCST) behavior with increasing temperature, in contrast with the upper critical solution temperature in H<sub>2</sub>SO<sub>4</sub>. Consequently, the viscosity and exponent of the CY-PPTA/DMAc solutions increase at elevated temperatures. As shown by the Cole–Cole plot, the heterogeneity in the DMAc system becomes worse. The LCST of the CY-PPTA solution is ascribed to the intermolecular interactions between the highly polar cyano groups, which are negligible in H<sub>2</sub>SO<sub>4</sub>.</p></div>","PeriodicalId":683,"journal":{"name":"Korea-Australia Rheology Journal","volume":null,"pages":null},"PeriodicalIF":2.2000,"publicationDate":"2024-03-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Korea-Australia Rheology Journal","FirstCategoryId":"5","ListUrlMain":"https://link.springer.com/article/10.1007/s13367-024-00088-z","RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"MECHANICS","Score":null,"Total":0}
引用次数: 0
Abstract
Poly(2-cyano-p-phenylene terephthalamide) (CY-PPTA) has garnered significant interest as a promising precursor for super p-aramid fibers because of its organosolubility in N,N-dimethyl acetamide/lithium chloride (DMAc/LiCl) while conserving the superior properties of the resultant fibers. However, CY-PPTA has been reported to exhibit abnormal phase behavior owing to the strong dipole–dipole interactions induced by the cyano groups. Herein, we rheologically study the isotropic phases of CY-PPTA/DMAc solutions with respect to the concentration and temperature and compare them with those of CY-PPTA/sulfuric acid (H2SO4) solutions. In the isotropic region, the CY-PPTA solutions yield a higher power-law exponent of the dynamic viscosity (η') versus concentration of 6.0 (ηʹ ~ c6.0) in the DMAc system than that in H2SO4 (ηʹ ~ c3.2). Moreover, the CY-PPTA/DMAc solutions exhibit a lower critical solution temperature (LCST) behavior with increasing temperature, in contrast with the upper critical solution temperature in H2SO4. Consequently, the viscosity and exponent of the CY-PPTA/DMAc solutions increase at elevated temperatures. As shown by the Cole–Cole plot, the heterogeneity in the DMAc system becomes worse. The LCST of the CY-PPTA solution is ascribed to the intermolecular interactions between the highly polar cyano groups, which are negligible in H2SO4.
期刊介绍:
The Korea-Australia Rheology Journal is devoted to fundamental and applied research with immediate or potential value in rheology, covering the science of the deformation and flow of materials. Emphases are placed on experimental and numerical advances in the areas of complex fluids. The journal offers insight into characterization and understanding of technologically important materials with a wide range of practical applications.