High-Contrast Visualization and Differentiation of Microphase Separation in Polymer Blends by Fluorescent AIE Probes

Abstract

The visualization of microphase separation in immiscible polymer blends is of great academic and industrial significance as the phase-separated structures are directly associated with the properties and performances of the blend materials and ultimately influence the corresponding product quality. However, conventional techniques for detecting microphase separation are generally expensive and time-consuming with troublesome and even destructive sample preparation procedures. Complicated and highly material-dependent chemical reactions or interactions are often involved in some characterization approaches. In this work, we demonstrated a simple, fast, and powerful method for high-contrast visualization and differentiation of micrometer-sized phase separation in polymer blends using luminogens with aggregation-induced emission characteristics (AIEgens) as fluorescent probes. This method relies on the sensitive fluorescence response of AIEgens to the change of environmental rigidity and polarity and operates based on the mechanisms of "restriction of intramolecular motions" and "twisted intramolecular charge transfer". The working principle indicates that this visualization strategy is applicable to a wide scope of polymer blends comprised of components with different rigidities and/or polarities.

Aggregation‐Induced Emission for Visualization in Materials Science

“…The molecular motions and the electron transfer abilities are altered, resulting in the varied emission wavelength and intensity. The direct differentiation of microphase separation in polymer composites was then achieved . For example, AIE molecules in a rigid polymer matrix showed stronger emission than in the soft polymer matrix, as a result of the greater constraint by the lower free volume (Scheme A).…”

“… Schematic representation of the proposed working mechanism for the visualization of phase‐separated morphologies in polymer blends by using fluorescent AIE probes for polymers with different (A) rigidities and (B) polarities …”

“…Firstly, the sample preparation always involves dehydration, which will disturb the structure of the material and disable dynamic evaluation processes . Secondly, some samples may be damaged through the preparation and scanning process . Thirdly, the working window in these techniques is only suitable for evaluation on the nanometer scale, limiting the application for macroscale materials .…”

Cross‐linking induced thermoresponsive hydrogel with light emitting and self‐healing property

“…On the other side, the aggregation‐induced emission (AIE) property of the fluorescent substances could be an alternative based on enhanced emission at aggregation state . The AIE property of TPE was proposed by Professor Tang in 2001 and drew great attentions as bioimaging probes in recent years . At the same time, the researchers began to study the TPE containing hydrogels in recent years, the salt‐responsive luminescent hydrogel and light‐emitting hydrogels containing chitosan were reported by Liang group and Tang group .…”

In Situ Monitoring of RAFT Polymerization by Tetraphenylethylene‐Containing Agents with Aggregation‐Induced Emission Characteristics

“…[10b] On the other hand, commonly used dyes,such as pyrene, rhodamines,a nd coumarins often emit intensely as isolated molecules but experience partial or complete emission quenching when aggregated or clustered. [12] Such mechanism makes the fluorescence of AIEgens highly sensitive to the environmental change to allow them to serve as probes to sense the viscosity change during the polymerization process.AIEgen-based probes have been developed for the direct visualization of gelation process, [13] crystallization process, [14] defects, [15] microphase separation, [16] the glass-transition temperature (T g ), [17] interfacial dynamic self-assembly, [18] and so on. [11] AIE luminogens (AIEgens) often emit weakly in solution but show strong emission in the aggregated state owing to the restriction of intramolecular motion (RIM).…”