Three-Dimensional Fluorescent Imaging to Identify Multi-Paths in Polymer Aging

Abstract

It is of great significance to disclose the diverse aging pathways for polymers under multiple factors, so as to predict and control the potential aging evolution. However, the current methods fail to distinguish multiple pathways (multi-paths) of polymer aging due to the lack of spatiotemporal resolution. In this work, using polyimide as a model polymer, the hydroxyl, carboxyl, and amino groups from the polyimide aging process were labeled using specific fluorescent probes through boron-oxygen, imine, and thiourea linkages, respectively. When the excitation and emission wavelengths of each fluorescent probe were controlled, the multi-paths in polyimide aging can be visualized individually and simultaneously in three-dimensional fluorescent images. The overall aging process under hydrothermal treatment was destructured into the pyrolysis and hydrolysis pathways. Three-dimensional dynamic studies discovered that the increased humidity, along with the decreased oxygen content, could hamper the pyrolysis reaction and accelerate the hydrolysis reaction, leading to severe degradation of the overall polyimide aging. More importantly, the oxygen showed a higher regulation coefficient in accelerating the pyrolysis reaction, than the water vapor in motivating the hydrolysis reactions. Such a multidimensional identification methodology is able to guide the long-term use of polymers and control their aging process to a harmless direction in advance by tuning the contents of oxygen and water vapor.

Real-Time Imaging of Stress in Single Spherulites and Its Relaxation at the Single-Particle Level in Semicrystalline Polymers

“…The fluorescence intensity of CD/SiO 2 particles in the stretched polypropylene film can be quantified as a gray value using Leica Application Suite X software (Figure S11). , As expected, the fluorescence intensity of the CD/SiO 2 particles was also positively correlated with stress. When the stress reached 8.2 MPa, the fluorescence intensity of CD/SiO 2 particles was 5.5 times higher than that in the absence of stress and 1.8 times higher than that of fluorescent CDs (Figure d).…”

Characterization Techniques of Polymer Aging: From Beginning to End

“…Moreover, dynamic studies were further carried out in the surface area ( x – y plane), depth ( z axis), and volume ( x – y – z space) of aging sites. Aging intrusion along the z axis followed a zero-order reaction, while the aggressive enlarged volume conformed to the first-order reaction (Figure D) . As a result, dynamic equations and kinetic rate constants could be estimated: rate constants of the fluorescent volume to generate the hydroxyl, carboxyl, and amino groups were 1.663 × 10 –6 , 1.525 × 10 –6 , and 1.437 × 10 –6 m s –1 , respectively.…”

“…Aging intrusion along the z axis followed a zero-order reaction, while the aggressive enlarged volume conformed to the first-order reaction (Figure 7D). 76 As a result, dynamic equations and kinetic rate constants could be estimated: rate constants of the fluorescent volume to generate the hydroxyl, carboxyl, and amino groups were 1.663 × 10 −6 , 1.525 × 10 −6 , and 1.437 × 10 −6 m s −1 , respectively. Moreover, kinetic rate constants, affected by the contents of oxygen or humidity, could be estimated in multipath aging.…”

“…(C) Multipath distinction and imaging of polyimide for the generated hydroxyl, carboxyl, and amino groups, and (D) dynamic calculations of the aging process for different functional groups. Reproduced with permission from ref . Copyright 2021 American Chemical Society.…”

Fluorescence monitoring of the degradation evolution of aliphatic polyesters

“…S1, ESI †). It has been reported that the carboxyl groups can be activated by N-hydroxysuccinimide (NHS) and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC), [24][25][26] giving a reaction with an amino-functionalized fluorescent probe to form amides (Scheme S1, ESI †). To verify the potential of AF to label the carboxyl groups, carboxyl-rich polymethylacrylic acid (PMAA) was used.…”