Programming viscosity in silicone oils
- Programmable oils feature tunable viscosity and therefore possess potential for technical improvements and innovative solutions in many lubricated applications. Herein, we describe the first assessment of the variability of rheological properties of light-programmable 9-anthracene ester-terminated polydimethylsiloxanes (PDMS-As), including implications that arise with UV-light as an external trigger. We applied a modified rheometer setup that enables the monitoring of dynamic moduli during exposure to UV-light. The reversible dimerization of anthracene esters is used to either link PDMS chains by UV-A radiation (365 nm) or cleave chains by UV-C radiation (254 nm) or at elevated temperatures (>130 degrees C). Thermal cleavage fully restores the initial material properties, while the photochemical cleavage of dimers occurs only to a limited extent. Prolonged UV radiation causes material damage and in turn reduces the range of programmable rheological properties. The incomplete cleavage contributes to a gradual buildup of viscosity overProgrammable oils feature tunable viscosity and therefore possess potential for technical improvements and innovative solutions in many lubricated applications. Herein, we describe the first assessment of the variability of rheological properties of light-programmable 9-anthracene ester-terminated polydimethylsiloxanes (PDMS-As), including implications that arise with UV-light as an external trigger. We applied a modified rheometer setup that enables the monitoring of dynamic moduli during exposure to UV-light. The reversible dimerization of anthracene esters is used to either link PDMS chains by UV-A radiation (365 nm) or cleave chains by UV-C radiation (254 nm) or at elevated temperatures (>130 degrees C). Thermal cleavage fully restores the initial material properties, while the photochemical cleavage of dimers occurs only to a limited extent. Prolonged UV radiation causes material damage and in turn reduces the range of programmable rheological properties. The incomplete cleavage contributes to a gradual buildup of viscosity over a course of several switching cycles, which we suggest to result from chain length-dependent reaction kinetics. Material property gradients induced during radiation due to attenuation of the light beam upon its passing through the oil layer have to be considered, emphasizing the need for proper mixing protocols during the programming step. The material in focus shows integrated photorheology and is suggested to improve the performance of silicone oils in friction systems.…
Author details: | Chris GäbertGND, Tobias Rosenstingl, Dominic LinslerGND, Martin DienwiebelORCiDGND, Stefan ReinickeORCiDGND |
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DOI: | https://doi.org/10.1021/acsapm.0c00794 |
ISSN: | 2637-6105 |
Title of parent work (English): | ACS applied polymer materials |
Subtitle (English): | reversible tuning of rheological properties in 9-anthracene ester-terminated polydimethylsiloxanes |
Publisher: | ACS Publications |
Place of publishing: | Washington, DC |
Publication type: | Article |
Language: | English |
Date of first publication: | 2020/11/18 |
Publication year: | 2020 |
Release date: | 2023/11/08 |
Tag: | anthracene; dimerization; light-programmable viscosity; lubricant; polysiloxane; reversible chain extension |
Volume: | 2 |
Issue: | 12 |
Number of pages: | 9 |
First page: | 5460 |
Last Page: | 5468 |
Funding institution: | Fraunhofer-Gesellschaft through the Cluster of Excellence "Programmable; Materials CPM" |
Organizational units: | Mathematisch-Naturwissenschaftliche Fakultät / Institut für Chemie |
DDC classification: | 5 Naturwissenschaften und Mathematik / 54 Chemie / 540 Chemie und zugeordnete Wissenschaften |
Peer review: | Referiert |