By: Sarah Ackermann, MSc
Functional materials are molecules and materials that are designed to have specific physical, chemical, and mechanical properties for application to technological and social problems. In the ever-evolving field of functional molecules research, laboratory instruments like Differential Scanning Calorimetry (DSC) and Simultaneous Thermal Analysis (STA) have become indispensable tools. These instruments are used to determine thermal events, specific heat, and mass loss, providing critical data for researchers. Some groups working in functional molecules may struggle to distinguish between noise vs real sample behavior in small heat events that are not associated with a mass change. How can you confirm whether something is noise from environmental variations vs a real event?
The Innovation of Sample Observation Video
A recent innovation in calorimetry is using sample observation video in DSC and STA testing. This technology, available on instruments like Rigaku’s DSC Vesta and STA8122, allows for accurately assigning heat events with visual confirmation.
The Benefits of Visual Confirmation
The ability to visually observe changes in shape, phase and color during testing is invaluable. It helps researchers differentiate between endothermic heat events, such as a melt versus a decomposition, or exothermic heat events, such as a crystal-crystal phase change versus a decomposition. The following case studies give real-world examples where sample observation is necessary for a thermal event to be dismissed or overlooked, or misassigned.
Case Study 1: Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH)
Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH) is a biopolymer created to have similar mechanical and physical properties to commodity plastics. PHBH offers better processability, higher ductility, and better impact resistance than earlier biopolymers.[i] PHBH was created to solve several problems: The slow degradation of petroleum-based plastics, the poor processability, ductility and impact resistance of biopolymers that existed at the time it was developed, and the slow biodegradation of existing biopolymers at the time it was developed.
In the video above, you can see the STA of PHBH. A very small thermal event is seen during the heating process, which might be disregarded as an artifact of the sample shifting in the pan. However, sample observation makes it apparent that the small baseline kind is the polymer’s melt! Without sample observation, the sample may have been incorrectly characterized, leading to difficulties in processing.
Case Study 2: p-Azoxyanisole
p-Azoxyanisole is an aromatic compound which was used in the development of early liquid crystal displays, and it is still active today in LCD technologies. Careful understanding of its phase behavior is necessary to allow good performance of it – and related molecules – in modern technologies.
The video above shows the phase behavior of p-Azoxyanisole with sample observation. As seen in the video, sample observation allows the correct assignment of the transition to a liquid crystal phase on heating and the transitions to two different crystal phases on cooling. With the ability to observe the sample during the heating and cooling, the two exotherms on cooling, in particular, are much easier to assign correctly.
Case Study 3: Matchstick
Matches are used as portable, single-use fire starters for campers, hikers, and smokers worldwide. They consist of two or three main components:
- Stick – a light wood of a variety prone to splintering is cut into small sticks and soaked in a fire retardant to prevent it from burning took quickly when the match head ignites.
- Match Head – the match head contains a combination of flammable chemicals (such as paraffin wax), oxidizing chemicals (such as potassium chlorate or sulfur), and often a waterproof coating for protection. Some match heads are designed to be self-igniting with enough friction or heat, while others are designed to use a specific strike surface to ignite.
- Strike surface (Optional) – an abrasive strike surface is used for safety matches, which contains a combination of red phosphorous and abrasive materials like glass to provide enough heat and necessary chemicals for the initiation of the combustion.
Sample observation can be used to pinpoint the onset of sudden and energetic reactions like the ignition of a match stick. In the video above, Rigaku highlights the use of sample observation to pinpoint the ignition temperature with a higher degree of sensitivity than is available on the DSC plot, while still enabling accurate quantification of the heat and mass losses.
Conclusion
In conclusion, the use of sample observation video in DSC and STA testing has greatly enhanced the ability of researchers to accurately determine and visually confirm heat events in the study of functional molecules. This has made it a valuable tool in this field of research.
References
- Front. Bioeng. Biotechnol., 05 December 2022, Sec. Industrial Biotechnology, Volume 10 – 2022 | https://doi.org/10.3389/fbioe.2022.1057067
About the Author
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Sarah Ackermann is the Laboratory Services Manager of the Thermal Analysis Labs division. She has over a decade of experience working in thermal analysis on a diverse range of materials, from pyrophorics to phase change materials and nearly everything in between.
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