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Since temperature is one of the most significant physiological parameters that dictate the cellular status of living organisms, accurate intracellular temperature measurement is crucial and a valuable biomarker for the diagnosis and treatment of diseases. Herein, we introduce the foremost example of a non-conjugated polymer as a next generation fluorescent thermometer which is capable of addressing the key shortcomings including toxicity and thermal-induced fluorescence quenching associated with π–π conjugated system-based thermometers developed so far. We revealed, for the first time, the unique photophysical and aggregation-induced emission (AIE) characteristics of well-known thermoresponsive poly(N-vinylcaprolactam) (PNVCL) devoid of any classical fluorophore entity. PNVCL underwent a coil to globular conformational transition in an aqueous medium and appeared to be fluorescent above its lower critical solution temperature (LCST) near body temperature (38 °C). Eventually, this intriguing aspect enabled higher cellular uptake of PNVCL at the LCST boundary. By virtue of the AIE effect, the thermo-induced aggregation phenomenon has been ingeniously utilized to apply PNVCL as a novel fluorescent thermometer for intracellular temperature determination.

Unprecedented photoluminescence, AIE and heat-induced emission characteristics of non-conjugated thermoresponsive PNVCL were unveiled for the very first time which eventually empowered PNVCL to act as an intracellular thermometer., Since temperature is one of the most significant physiological parameters that dictate the cellular status of living organisms, accurate intracellular temperature measurement is crucial and a valuable biomarker for the diagnosis and treatment of diseases. Herein, we introduce the foremost example of a non-conjugated polymer as a next generation fluorescent thermometer which is capable of addressing the key shortcomings including toxicity and thermal-induced fluorescence quenching associated with π–π conjugated system-based thermometers developed so far. We revealed, for the first time, the unique photophysical and aggregation-induced emission (AIE) characteristics of well-known thermoresponsive poly(N-vinylcaprolactam) (PNVCL) devoid of any classical fluorophore entity. PNVCL underwent a coil to globular conformational transition in an aqueous medium and appeared to be fluorescent above its lower critical solution temperature (LCST) near body temperature (38 °C). Eventually, this intriguing aspect enabled higher cellular uptake of PNVCL at the LCST boundary. By virtue of the AIE effect, the thermo-induced aggregation phenomenon has been ingeniously utilized to apply PNVCL as a novel fluorescent thermometer for intracellular temperature determination.

Main chain chiral poly(methacrylate)s have been synthesized by controlled reversible addition–fragmentation chain transfer (RAFT) copolymerization of chiral monomer Boc- l -alanine methacryloyloxyethyl ester (Boc- l -Ala-HEMA, A) with Boc- d -alanine methacryloyloxyethyl ester (Boc- d -Ala-HEMA, B) and achiral monomer Boc-2-methylalanine-methacryloyloxyethyl ester (Boc-Aib-HEMA, C), and B with C by changing comonomer feed compositions. We systematically examined the role of l -alanine, d -alanine and 2-aminoisobutyric acid (Aib) as folding nuclei in our designed hybrid polymer-amino acid conjugates. Specific optical rotation and circular dichroism (CD) spectroscopy studies reveal that poly(Boc- l -Ala-HEMA) and poly(Boc- d -Ala-HEMA) formed entirely opposite handed helical structure stabilized by intramolecular hydrogen bonding among the pendant chromophores of the chiral monomers. Poly(Boc-Aib-HEMA) formed random coil structures conformation (unstructured conformation), whereas the resultant copolymers of C with A and B showed an unusual linear relationship of optical activity against comonomer composition, in sharp contrast with Green’s “majority” and “sergeant-and-soldier” rule. After Boc-group expulsion in acidic environment from the polymer side-chains, backbone retained its helicity. Variable temperature chiroptical properties investigation was also performed to examine the thermal stability of the homo and copolymer’s helical conformations. Additionally, pH induced conformational transformation was observed for the homo and copolymers.

Poly{(N,N-(dimethylamino)ethyl methacrylate]-co-(methyl methacrylate)} copolymers of various compositions were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization at 70 degrees C in N,N-dimethylformamide. The polymer molecular weights and molecular weight distributions were obtained from size exclusion chromatography, and they indicated the controlled nature of the RAFT polymerizations; the polydispersity indices are in the range 1.11.3. The reactivity ratios of N,N-(dimethylamino)ethyl methacrylate (DMAEMA) and methyl methacrylate (MMA) (rDMAEMA = 0.925 and rMMA = 0.854) were computed by the extended KelenTudos method at high conversions, using compositions obtained from 1H NMR. The pH- and temperature-sensitive behaviour were studied in aqueous solution to confirm dual responsiveness of these copolymers. The thermal properties of the copolymers with various compositions were investigated by differential scanning calorimetry and thermogravimetric analysis. The kinetics of thermal degradation were determined by Friedmann and Chang techniques to evaluate various parameters such as the activation energy, the order and the frequency factor. (c) 2012 Society of Chemical Industry

Reversible addition-fragmentation chain transfer polymerization at 70 °C in N,N-dimethylformamide was used to prepare poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide) copolymers in various compositions to afford well-defined polymers with pre-determined molecular weight, narrow molecular weight distribution, and precise chain end structure. The copolymer compositions were determined by 1H NMR spectroscopy. The reactivity ratios of N-isopropylacrylamide (NIPAM) and N,N-dimethylacrylamide (DMA) were calculated as r NIPAM = 0.838 and r DMA = 1.105, respectively, by the extended Kelen–Tudos method at high conversions. The lower critical solution temperature of PNIPAM can be altered by changing the DMA content in the copolymer chain. Differential scanning calorimetry and thermogravimetric analysis at different heating rates were carried out on these copolymers to understand the nature of thermal degradation and to determine its kinetics. Different kinetic models were applied to estimate various parameters like the activation energy, the order, and the frequency factor. These studies are important to understand the solid state polymer degradation of N-alkyl substituted polymers, which show great potential in the preparation of miscible polymer blends due to their ability to interact through hydrogen bonding.