Abstract
In this study, we synthesized amphiphilic poly(2,7–(9,9–dioctylfluorene))–block–N,N–(diisopropylamino)ethyl methacrylate (POF–b–PDPMAEMA) rod-coil diblock copolymers by atom transfer radical polymerization (ATRP). The structure and multifunctional sensing properties of these copolymers were also investigated. The POF rod segment length of 10 was fixed and the PDPAEMA coil segment lengths of 90 and 197 were changed, respectively. The micellar aggregates of POF10–b–PDPAEMA90 rod-coil diblock copolymer in water showed a reversible shape transition from cylinder bundles to spheres when the temperature was changed from 20 to 80 °C or the pH was changed from 11 to 2. The atomic force microscopy (AFM) and transmission electron microscopy (TEM) measurements indicated that the temperature had also an obvious influence on the micelle size. In addition, since POF10–b–PDPAEMA90 had a lower critical solution temperature, its photoluminescence (PL) intensity in water is thermoreversible. The PL spectra showed that the POF–b–PDPAEMA copolymer had a reversible on/off profile at elevated temperatures, and thus could be used as an on/off fluorescent indicator for temperature or pH. The fluorescence intensity distribution of pH switched from “off–on” to “on–off” as the temperature increased. These results showed that the POF–b–PDPAEMA copolymer has a potential application for temperature and pH sensing materials.
Highlights
The self-assembly of conjugated rod-coil block copolymers has been studied extensively towards novel structural, functional, and physical properties of supramolecular species [1,2,3].The aggregation and microphase separation of such block copolymers driven by various novel functionalities of p–p interaction through solvent selection or rigid segmentation may result in various nanosized morphologies [4,5,6]
The results show that the surface structure and fluorescence characteristics for the amphiphilic POF–b–PDPAEMA rod-coil diblock copolymers can be manipulated by tuning the mixed solvent composition, temperature, and pH
POF–b–PDPAEMA micelles were prepared in different ratios of solutions
Summary
The self-assembly of conjugated rod-coil block copolymers has been studied extensively towards novel structural, functional, and physical properties of supramolecular species [1,2,3]. Two kinds of amphiphilic POF–b–PDPAEMA rod-coil diblock copolymers with different segment lengths, POF10 –b–PDPAEMA90 and POF10 –b–PDPAEMA197 , were synthesized by atom transfer radical polymerization (ATRP) for systematic investigation in this study. Some important parameters such as solution temperature, acid-base value, and water/tetrahydrofuran ratio were used to study the surface morphology and photophysical properties of copolymers. The results show that the surface structure and fluorescence characteristics for the amphiphilic POF–b–PDPAEMA rod-coil diblock copolymers can be manipulated by tuning the mixed solvent composition, temperature, and pH
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