Multiple Micellization and Dissociation Transitions of Thermo- and Light-Sensitive Poly(ethylene oxide)-b-poly(ethoxytri(ethylene glycol) acrylate-co-o-nitrobenzyl acrylate) in Water

Abstract

This article reports on the synthesis of thermo- and light-sensitive hydrophilic block copolymers, poly(ethylene oxide)-b-poly(ethoxytri(ethylene glycol) acrylate-co-o-nitrobenzyl acrylate), and the study of their micellization/dissociation transitions in water in response to temperature changes and UV irradiation. The block copolymers with controlled molecular weights and narrow polydispersities were synthesized by atom transfer radical polymerization of a mixture of ethoxytri(ethylene glycol) acrylate and o-nitrobenzyl acrylate with a molar ratio of 100:10 from a PEO macroinitiator. Dynamic light scattering and fluorescence spectroscopy studies showed that these copolymers were molecularly dissolved in water at lower temperatures and self-assembled into micelles with the thermosensitive block associating into the core and the PEO block forming the corona when the temperature was above the lower critical solution temperature (LCST) of the thermosensitive block. Upon UV irradiation, the o-nitrobenzyl group was cleaved and the LCST of the thermosensitive block was increased, causing the dissociation of micelles into unimers and the release of encapsulated fluorescent dye Nile Red into water. Further increasing the temperature induced the formation of micelles again and the re-encapsulation of Nile Red. The thermo-induced formation and dissociation of micelles were reversible.

Micropatterning of polymethacrylates by single‐ or two‐photon irradiation using π‐conjugated o‐nitrobenzyl ester phototrigger as side chains

“…3,[5][6][7] Besides its application as an orthogonal protecting group in organic synthesis, 8 it has been extensively used in the side chains of polymer as a photochemically labile group and also exhibited utility in photoresist [9][10][11][12][13] and photocontrolled release in light-dissociable block copolymer micelles. 14 In addition, a lot of caged biological active compounds have been prepared by using ONB phototrigger groups. [15][16][17][18][19][20] However, most of the known ONB-caged chromophore showed UV absorption, which is the major drawback and limitation for the practical application, as the presence of UV light provides poor penetration due to light scattering and absorbance by intrinsic polymer chromophores.…”

What can isothermal titration microcalorimetry experiments tell us about the self‐organization of surfactants into micelles?

“…The self-organization of surfactants into micelles is a widely studied phenomenon and many techniques have been used to explore this process, including surface tension measurements (Zhang et al, 2008), Fourier transformed infrared spectroscopy (Su et al, 2002), 1 H-NMR relaxation studies (Cau and Lacelle, 1996;Ma et al, 2007), dynamic light scattering, fluorescence spectroscopy (Jiang et al, 2008), and differential scanning calorimetry experiments in which the enthalpy change related to the micellization process can be calculated from the integration of the heat capacity versus temperature (Alexandridis and Hatton, 1995a;Artzner et al, 2007).…”

New insights into copper-mediated polymerization and polymer topologies

“…The individual polymers were fit such that half the height and half the width of the w(M) distribution gave an excellent fit with the log-normal distribution model, and the M n and Đ values used in the fit were given in Table 3.2. Using the log-normal distribution model above, we simulated the bimodal distribution in Figure 3.1A for the mixture PSTY 175 (1) and Pt-BA 43 (3). Each w(M) vs M was simulated using the M n and Đ values (in Table 3.…”

“…The simulated fit to the experimental data was excellent. The same approach was used for the mixture of PSTY 175 (1) and PEG 52 (4, dn/dc PEG = 0.078) at a w p,A = 0.5 (Figure 3.1B).…”

“…For the mixture of PSTY 175 (1) and PNIPAM 37 (2) at a w p,A = 0.5, we had to use the dn/dc PNIPAM = 0.09 to obtain an excellent fit to the experimental SEC w(M) distribution (Figure 3.1C), since the literature value of 0.107 did not give a satisfactory fit due to different measurement conditions. The value of 0.09 was used in subsequent simulations, and all fits were found to be excellent (vide infra).…”