{"title":"Vacuum-Pumping Induced Crystallographic Anisotropy of Poly(dimethylsiloxane) Oil under Capillary Confinement","authors":"Xiang Shi","doi":"10.1021/acs.cgd.4c00916","DOIUrl":null,"url":null,"abstract":"Investigating the low-temperature crystallization behavior of liquid polysiloxanes poses a significant challenge. To address this issue, a custom low-temperature chamber with specialized sample holders was meticulously constructed and integrated with a laboratory X-ray diffraction apparatus, enabling time-resolved wide-angle X-ray diffraction (WAXD) measurements of linear poly(dimethylsiloxane) (PDMS) oil and cross-linked PDMS film during cooling and heating. Under vacuum pumping and capillary confinement, the linear silanol-terminated PDMS oil demonstrates significant crystalline orientation at low temperatures when the crystalline index surpasses 10%, with the recorded 2D diffraction patterns showing heterogeneous azimuthal intensity distributions. The presence of crystallographic anisotropy is strongly influenced by the experimental vacuum pumping rather than the millimeter-scale capillary confinement. Unlike the strain-induced alignment of crystalline planes observed in stretched PDMS film, the vacuum-pumping-induced crystallographic anisotropy in linear PDMS oil measured within a capillary only results in a minimal or partial lamellar orientation. This alignment will cause crystalline chain segments to pack parallel to the incident X-ray beam direction and fold within the <i>a-c</i> plane. These findings are expected to enhance low-temperature X-ray analysis techniques for liquid samples and facilitate future crystallographic investigations of polysiloxane materials.","PeriodicalId":34,"journal":{"name":"Crystal Growth & Design","volume":null,"pages":null},"PeriodicalIF":3.2000,"publicationDate":"2024-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Crystal Growth & Design","FirstCategoryId":"92","ListUrlMain":"https://doi.org/10.1021/acs.cgd.4c00916","RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"CHEMISTRY, MULTIDISCIPLINARY","Score":null,"Total":0}
引用次数: 0
Abstract
Investigating the low-temperature crystallization behavior of liquid polysiloxanes poses a significant challenge. To address this issue, a custom low-temperature chamber with specialized sample holders was meticulously constructed and integrated with a laboratory X-ray diffraction apparatus, enabling time-resolved wide-angle X-ray diffraction (WAXD) measurements of linear poly(dimethylsiloxane) (PDMS) oil and cross-linked PDMS film during cooling and heating. Under vacuum pumping and capillary confinement, the linear silanol-terminated PDMS oil demonstrates significant crystalline orientation at low temperatures when the crystalline index surpasses 10%, with the recorded 2D diffraction patterns showing heterogeneous azimuthal intensity distributions. The presence of crystallographic anisotropy is strongly influenced by the experimental vacuum pumping rather than the millimeter-scale capillary confinement. Unlike the strain-induced alignment of crystalline planes observed in stretched PDMS film, the vacuum-pumping-induced crystallographic anisotropy in linear PDMS oil measured within a capillary only results in a minimal or partial lamellar orientation. This alignment will cause crystalline chain segments to pack parallel to the incident X-ray beam direction and fold within the a-c plane. These findings are expected to enhance low-temperature X-ray analysis techniques for liquid samples and facilitate future crystallographic investigations of polysiloxane materials.
期刊介绍:
The aim of Crystal Growth & Design is to stimulate crossfertilization of knowledge among scientists and engineers working in the fields of crystal growth, crystal engineering, and the industrial application of crystalline materials.
Crystal Growth & Design publishes theoretical and experimental studies of the physical, chemical, and biological phenomena and processes related to the design, growth, and application of crystalline materials. Synergistic approaches originating from different disciplines and technologies and integrating the fields of crystal growth, crystal engineering, intermolecular interactions, and industrial application are encouraged.