Resilient collapse of thermal sensitive polymer on the surface of the optical fiber taper

• Published in: Journal of polymer science. Part B, Polymer physics Vol. 56; no. 10; pp. 778 - 785
• Main Authors: Zhuang, Yiwei, Cui, Minxin, Huang, Zichao, Zou, Gang, Zhang, Qijin
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc 15.05.2018
• Subjects: Acrylamide; Collapse; fibers; Fluorescence; Nonlinear response; optical fiber sensor; pNIPAM; Refractivity; Rhodamine; sensors; Signal processing; Springback; stimuli‐sensitive polymers
• ISSN: 0887-6266; 1099-0488
• DOI: 10.1002/polb.24590

ABSTRACT In this work, collapse of poly(N‐isopropyl‐acrylamide) (pNIPAM) grafted on the surface of the optical fiber taper is probed by measuring fluorescence of rhodamine B solution at various temperatures. It is observed that the fluorescence intensity through the taper shows a nonlinear response to temperature. According to the optical model for the special designed taper, it is realized that the nonlinear response results from changing in effective refractive index of interfacial layer between taper and solution. Analysis on relationship between signal change and collapse process reveals a springback process during the collapse of pNIPAM chains. Such a novel phenomenon is further investigated on method for fluorescence measurement and molecular weight of the polymer. These results have not only revealed details of the collapse, but also establish a novel technique for study the collapse of thermal sensitive polymers on the surface. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018, 56, 778–785 An unexpected signal is found in relationship between temperature and fluorescent intensity measured by a glass fiber taper when the surface of the taper is grafted by PNIPAM. Analysis through differential method shows the collapse of PNIPAM is responsible for the signal. Detailed work on this phenomenon reveals that the signal is caused by the resilient collapse of thermal sensitive PNIPAM chains on the surface of the taper.