Reversible halochromic PLA film for naked-eye detection at the extreme base condition

ABSTRACT

Exposure to extreme base conditions in indoor environments may lead to adverse health effects on living beings. Proper ventilation and real-time detection are very important upon exposure. A simple and highly sensitive reversible base sensor is successfully prepared for real-time detection of the extreme base condition of aqueous base analytes. Halochromic poly lactid acid (PLA) pH film sensor containing thymolphthalein (THY) dye and polyethylene glycol (PEG) was developed by solution casting method. To increase the effectiveness of PLA pH film capabilities as a base sensor, the impact of altering the concentration of THY and PEG substrate was explored. The interactions between PLA, THY, and PEG were observed by Fourier transform infrared (FTIR), and the intensity of color changes was measured using UV-VIS spectroscopy. It was found that the PLA pH film has a clear color response from colorless to blue at pH 11–13 with a rapid response time within a minute. The results also revealed that varying PEG content showed a significant effect on response time compared to varying the THY content. Real-time visual color changes of the PLA pH film with different THY content and PEG content on total color difference, (∆E) values over pH and time were observed. Color changes after immersion in buffer solutions with different pH values were evaluated spectrophotometrically using CIELAB color space. The results indicated that varying the PEG content in the film leads to a faster and more distinct reversible color change. This outcome can be attributed to PEG ability to augment the free volume within the PLA material and enabling PEG and the dye and become trapped between PLA chain. The addition of PEG and THY has improved the flexibility of PLA film, which enables great potential in many applications such as medical, textile, and packaging in base environments.

KEYWORDS:

• PLA film
• Halochromic materials
• reversible base sensor
• smart polymer
• smart sensor

Acknowledgments

The authors would like to thank the Emerging Polymer Group of the School of Materials and Minerals Resources Engineering, (USM) for technical support throughout this research with facilities and laboratory equipment. A huge thanks also go to financial support from Research University Incentive Grant, Universiti Sains Malaysia (101/PBAHAN/8014040)

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Notes on contributors

Siti Amirah Alias

Siti Amirah binti Alias is a PhD candidate in Polymer Engineering at Universiti Sains Malaysia (USM). Specialize in formulation and processing of polymers/biodegradable polymers and her current project involves developing halochromic polymeric pH sensors. Recently, she completed a six-month research training program at MIT-WPU, India, (Nov2022-April2023) sponsored by DST India, which exposed her to the latest developments in polymer chemistry.

Nur Syahirah Ishak

Nur Syahirah Ishak is currently working as Material Engineer in Product Industrilization at Continental Tyre AS Malaysia Sdn. Bhd. She received Master’s degree in Biopolymer from School of Material & Mineral Resources Engineering Universiti Sains Malaysia.

Nuraina Hanim Mohd Nizam

Nuraina Hanim Mohd Nizam, B.Tech (Hons), currently postgraduate, MSc student in polymer engineering in School of Materials and Mineral Resources Engineering, Universiti Sains Malaysia. She is working on self-healing material based rubber and latex.

Syazana Ahmad Zubir

Syazana Ahmad Zubir received her Materials Engineering degree from International Islamic University of Malaysia, Kuala Lumpur, Malaysia and PhD degree from Universiti Kebangsaan Malaysia, Selangor, Malaysia. She joined Universiti Sains Malaysia in 2014 as lecturer in School of Materials and Mineral Resources Engineering. She is in Editorial Board of Scientific Research Journal. She is also a member of Malaysia Board of Technologist and Board of Engineers Malaysia. Her current research interests include shape memory polymer, self-healing polymer for coatings and 3D printing of polymer scaffold.

Hayati Samsudin

Hayati Samsudin is an assistant professor in the Food Technology Division of the School of Industrial Technology at Universiti Sains Malaysia. She received her M.S. and Ph.D. in Packaging from the School of Packaging at Michigan State University. Her research interests include food/packaging interaction, mass transfer in polymers, biodegradable polymers, and starch modification for packaging applications. Since 2007, she has worked on various testing/research contracts and consulting projects involving the interaction between food and packaging, the performance of packaged foods, and their shelf life. She has provided training and advisory services to numerous academic and non-academic organizations and industries. She teaches courses on food packaging and food safety using technological tools such as Kahoot!, Quizziz, Socrative, and genial.ly. She recently completed a sabbatical training program at Purdue University in the area of thermally processed and packaged food products, and was certified for Better Process Control School's thermal processing systems, acidification, and container closure evaluation programs for low-acid and acidified foods in closed containers.

K.I Ku Marsilla

Ku Marsilla Ku Ishak received her PhD (Material & Processing) from University of Waikato, New Zealand. She is now working as a lecturer at School of Materials & Mineral Resources Engineering, Universiti Sains Malaysia. She hasbeen working on formulation and processing of smart polymer/biodegradable polymer for more than 7 years. She has involved in both industry and research projects to develop and process functional polymer materials.