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Thermoresponsive polymers have shown great potential in applications such as bioseparation, drug delivery and diagnostic. Only few thermoresponsive polymers that present an upper critical solution temperature (UCST), i.e. phase separate from solution upon cooling, in a relevant temperature range have been reported so far. Moreover, the most studied UCST type polymers namely polybetaines are difficult to use under physiological conditions, which significantly restricts their potential applications. Therefore, UCST polymers with sharp and robust phase transition in physiological conditions (in the presence of salts, ions etc.) are highly needed in order to extend the range of applications of this class of polymers.
Herein, a robust UCST-type copolymer of acrylamide (AAm) and acrylonitrile (AN) (poly(AAm-co-AN)) was prepared by reversible addition fragmentation chain transfer (RAFT) polymerization[4] and its thermo-induced aggregation behavior in aqueous media was studied. At temperature below the UCST, the copolymer chains were aggregated together. The aggregate size was found to be larger with increasing AN contents and became smaller upon dilution of the copolymer solutions. While above the UCST, the copolymer chains were expanded and weekly associated in solution. The association between the copolymer chains formed smaller aggregates with increasing the AN contents or the dilution of the solutions. A model is proposed to explain such aggregation behavior.
Dual orthogonal functionalities in a single material is highly desirable in many fields such as bio-imaging, sensing, coating or diagnostic and therapy. However, a precise and controlled approach to prepare two different functionalities is still a challenging task. Herein, we show the simple preparation method for the synthesis of dual-functional hybrid core/shell/shell nanoparticles consisting of a silica core with a fluorescent and a thermoresponsive polymeric layer. Silica core particles were first coated by a fluorescent layer using surface- nitiated reversible addition-fragmentation chain transfer (RAFT) polymerization. The fluorescent silica nanoparticles were then completely enclosed within a switchable protective coating made of thermoresponsive poly(N-isopropylacrylamide) via RAFT polymerization. Thermoresponsive poly(N-isopropylacrylamide) is known to change its properties according to the surroundings temperature in a reversible and controllable way (LCST behavior). The successful preparation of well-defined dual-functional hybrid core/shell/shell nanoparticles was shown by scanning electron microscopy, thermogravimetric analysis and Fourier transform infrared spectroscopy, while their fluorescence and thermoresponsive properties were confirmed by fluorescence spectroscopy and dynamic light scattering measurements, respectively.
Thermoresponsive polymers have shown great potential in applications such as bioseparation, drug delivery and diagnostic. Only few thermoresponsive polymers that present an upper critical solution temperature (UCST) in a relevant temperature range, i.e. Phase separate from solution upon cooling, have been reported so far. Moreover, the most studied UCST type polymers namely polybetaines are difficult to use under physiological conditions, which significantly restricts their potential applications. Therefore, UCST polymers with sharp and robust phase transition in physiological conditions (in the presence of salts, ions etc.) are highly needed in order to extend the range of applications of this class of polymers.
Herein, a robust UCST-type copolymer of acrylamide (AAm) and acrylonitrile (AN) (poly(AAm-co-AN)) was prepared by reversible addition fragmentation chain Transfer (RAFT) polymerization and its thermo-induced aggregation behavior in aqueous media was studied by turbidity and dynamic light scattering measurements. At temperature below the UCST, the poly(AAm-co-AN) copolymer chains were aggregated together. The aggregate size was found to be larger with increasing AN contents and became smaller upon dilution of the copolymer solutions. While above the UCST, the poly(AAm-co-AN) copolymer chains were expanded and weekly associated in solution. The association between the copolymer chains formed smaller aggregates with increasing the AN Contents or the concentration of the solutions. A model is proposed to explain such aggregationassociation behavior of the poly(AAm-co-AN) copolymer depending on the AN Contents and concentration of the solutions.
Functional polymer based on 2,6-diaminopyridine with tunable UCST behaviour in water/alcohol mixture
(2017)
Thermoresponsive polymers are of great importance in numerous applications such as bioseparation, drug delivery, diagnostic and microfluidic applications.[1-2] Only a few thermoresponsive polymers have been reported that present an Upper Critical Solution Temperature (UCST), i.e. phase separate from solution upon cooling, in a relevant temperature range and “green” solvents such as water or ethanol.[3] Indeed, polymers with UCST behavior below 60°C in alcohol or water/alcohol mixtures are extremely promising for the preparation of “smart” materials for sensing.
In this work, two novel functional polymers of based on a 2,6-diaminopyridine motif were synthesized by free-radical polymerization. Their UCST-type transition temperature is tunable by varying either their concentration in solution or the type of solvent. Insights into this phenomenon are investigated using turbidimetry and temperature dependent dynamic light scattering.
Fluorescent nanoparticles that “light up”/”dim down” by applying external stimuli are of particular interest in the fields of sensing, diagnostics, photonics, protective coatings and microfluidics. The current challenge for these materials is to combine for instance fluorescence and its response to a stimulus such as temperature in a precise manner. Here we present such a system based on a core/shell/shell architecture consisting of a silica core with a fluorescent layer and a thermoresponsive shell.
The silica core nanoparticles were first coated with a fluorescent shell using surface initiated reversible addition-fragmentation chain transfer (RAFT) polymerization. The fluorescent nanoparticles were then completely engulfed by a switchable protective coating made of thermoresponsive poly(N-isopropylacrylamide). The fluorescence of the nanoparticles could be “switched on” at room temperature and “switched off” with increasing environmental temperature because of the presence of the thermoresponsive layer. Insights into this phenomenon will be given based on temperature dependent fluorescence measurements and dynamic light scattering.
Temperature switches “on” and “off” nanoparticle fluorescence in a core/shell/shell architecture
(2017)
Fluorescent nanoparticles that light “on/off” by applying external stimuli are of particular interest in the fields of sensing, diagnostics, photonics, protective coatings and microfluidics. The current challenge for these materials is for instance to combine fluorescence and its response to a stimulus such as temperature in a precise manner. Here we present such a system based on a core/shell/shell architecture consisting of a silica core with a fluorescent layer and a thermoresponsive shell.
In this work the silica core nanoparticles were first coated with a fluorescent shell using surface initiated reversible addition-fragmentation chain transfer (RAFT) polymerization. The fluorescent nanoparticles were then completely engulfed by a switchable protective coating made of thermoresponsive poly(N-isopropylacrylamide). The fluorescence of the nanoparticles could be “switched on” at room temperature and “switched off” with increasing environmental temperature because of the presence of the thermoresponsive layer. Insights into this phenomenon will be given based on temperature dependent fluorescence measurements and dynamic light scattering.