Solvent induced amplification of the photoresponsive properties of α,ω-di-[4-cyanophenyl-4′-(6-hexyloxy)-azobenzene]-poly(N-isopropylacrylamide) in aqueous media

Ishii, Norihito; Mamiya, Jun‐ichi; Ikeda, Tomiki; Winnik, Françoise M.

doi:10.1039/c0cc04009f

Cited by 41 publications

(23 citation statements)

References 23 publications

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“…Aqueous solutions of poly( N ‐isopropylacrylamide) (PNIPAM) have been the subject of major scientific interest for over 50 years and have been studied using a variety of techniques including viscometry, turbidimetry, light scattering, fluorescence, and neutron scattering . The origin of this interest resides in the fact that PNIPAM possesses a lower critical solution temperature in water.…”

Section: Introductionmentioning

confidence: 99%

Temperature response of aqueous solutions of pyrene end‐labeled poly(N‐isopropylacrylamide)s probed by steady‐state and time‐resolved fluorescence

Fowler

Duhamel

Qiu

et al. 2017

J Polym Sci B Polym Phys

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Aqueous solutions of a series of monodisperse poly(N‐isopropylacrylamide)s end‐labeled with n‐butyl‐1‐pyrene at one or both chain ends (Pyn‐PNIPAMs with n = 1 or 2) were studied by turbidimetry, light scattering, and fluorescence. For a given polymer concentration and heating rate, the cloud point (Tc) of an aqueous Pyn‐PNIPAM solution, determined by turbidimetry, was found to increase with the number‐average molecular weight (Mn) of the polymer. The steady‐state fluorescence spectra and time‐resolved fluorescence decays of Pyn‐PNIPAM aqueous solutions were analyzed and all parameters retrieved from these analyses were found to be affected as the solution temperature passed through Tc, the solution cloud point, and Tm, the temperature where dehydration of PNIPAM occurred. The trends obtained by fluorescence to characterize the aqueous Pyn‐PNIPAM solutions as a function of temperature were found to be consistent with the model proposed for telechelic PNIPAM by Koga et al. in 2006. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018, 56, 308–318

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Section: Introductionmentioning

confidence: 99%

Temperature response of aqueous solutions of pyrene end‐labeled poly(N‐isopropylacrylamide)s probed by steady‐state and time‐resolved fluorescence

Fowler

Duhamel

Qiu

et al. 2017

J Polym Sci B Polym Phys

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“…18,27,[33][34][35][36][37][38][39] Moreover, the critical azobenzene content, that is the optimized azobenzene content in the polymer for the largest shi of the CPT, is difficult to determine, especially considering the diverse chemical structures of azobenzenes and polymers. 41 These studies motivated and inspired us to undertake the present work aiming to understand why and how solvents can bring large photoinduced CPT shis. 40 The CPT of P(BNMA-co-MAzo) can reversibly shi by as much as 22 C between the trans and cis forms of azobenzene.…”

Section: Introductionmentioning

confidence: 99%

How can photoisomerization of azobenzene induce a large cloud point temperature shift of PNIPAM?

Tremblay

Lacelle

et al. 2014

Polym. Chem.

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We present a comprehensive study of the photo-induced phase transition of azobenzene-containing poly(N-isopropylacrylamide) (PNIPAM) in block copolymers (BCPs) upon the isomerization of azobenzene in the mixed solvent of water and dioxane. The BCP is composed of a poly-[2-(dimethylamino)ethyl methacrylate] (PDMAEMA) block and a PNIPAM block decorated with $2 mol% of azobenzene groups (P(NIPAM-co-MAzo)). In the mixed solvent of water and dioxane, the cloud point temperature (CPT) for the phase transition of the PNIPAM block displays a large shift >10 C induced by the photoisomerization of azobenzene under UV or visible light. The CPT shift of PNIPAM is highly dependent on the solvent composition and the large shift only occurs at high dioxane concentration (>30%). The mechanism of the photo-induced large CPT shift by the isomerization of azobenzene was investigated by means of 1 H NMR spin relaxation studies. With the addition of dioxane, the exchange of hydrogen bonding from PNIPAM-water to PNIPAM-dioxane was detected in the neighborhood of the CPT, thereby demonstrating the better solvation of the BCP chains and the azobenzene moieties by dioxane. We further demonstrate that the spin relaxation of azobenzene in the trans-cis isomerization only displayed a notable change at higher dioxane concentrations where the large shift of the CPT was observed. An improved understanding of the mechanism of photoinduced phase transition offers new insights into the rational design, synthesis and application of photoresponsive polymer materials.

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“…PNIPAM homopolymers with only one azobenzene unit at the chain end have been studied for photoresponsive behaviour where photoisomerization of azobenzene is shown to affect the LCST as well as micellar assembly. 51,58,59 The polymers synthesized here have a single azobenzene unit in the main chain that is attached to a dendron and PNIPAM on either side and hence even though photoisomerization may be restricted it may have an effect on the microenvironment of the micelles. Aqueous solution of P1 and P2 (0.05 wt%) was exposed to UV light (365 nm, intensity of 21 mW cm −2 ) with different irradiation times and UV-visible spectra were recorded.…”

Section: Resultsmentioning

confidence: 99%

Synthesis and tunable thermoresponsive solution morphologies of 2,2‐bis‐methylolpropionic acid dendron–azobenzene–poly(N‐isopropyl acrylamide) copolymers

Kalva

Ambade

2017

Polymer International

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Amphiphilic temperature‐ and photoresponsive linear–dendritic block copolymers comprising second‐generation acetonide‐2,2‐bis‐methylolpropionic acid‐based polyester dendron and linear poly(N‐isopropyl acrylamide) (PNIPAM) linked by an azobenzene unit were synthesized using atom transfer radical polymerization (ATRP) followed by click chemistry. Linear PNIPAM precursor was prepared from an azide‐functionalized azobenzene containing ATRP initiator. Two polymers obtained by varying the chain length of the PNIPAM block showed different morphologies and lower critical solution temperature (LCST) values in aqueous solution. Complete change in morphology of the two polymers into large spherical aggregates and nanotubes, respectively, was observed upon heating the micellar solution above LCST. The azobenzene unit was found to undergo trans–cis photoisomerization in the assemblies and caused a change in the microenvironment of an encapsulated hydrophobic dye without any release. Acetonide groups on the dendron were deprotected to afford hydroxylated polymer that showed well‐defined morphologies above the LCST and after heating–cooling cycle while significant dye encapsulation was seen only above the LCST. © 2017 Society of Chemical Industry

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Solvent induced amplification of the photoresponsive properties of α,ω-di-[4-cyanophenyl-4′-(6-hexyloxy)-azobenzene]-poly(N-isopropylacrylamide) in aqueous media

Cited by 41 publications

References 23 publications

Temperature response of aqueous solutions of pyrene end‐labeled poly(N‐isopropylacrylamide)s probed by steady‐state and time‐resolved fluorescence

Temperature response of aqueous solutions of pyrene end‐labeled poly(N‐isopropylacrylamide)s probed by steady‐state and time‐resolved fluorescence

How can photoisomerization of azobenzene induce a large cloud point temperature shift of PNIPAM?

Synthesis and tunable thermoresponsive solution morphologies of 2,2‐bis‐methylolpropionic acid dendron–azobenzene–poly(N‐isopropyl acrylamide) copolymers

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