A concise review of dynamical processes in polymorphic environments of a block copolymer: Rotational diffusion and photoisomerization

Abstract

This article describes our ongoing efforts to understand dynamical processes such as rotational diffusion and photoisomerization in polymorphic environments of a block copolymer. The objective is to explore how the typical properties of a block copolymer solution such as critical micelle temperature (CMT) and temperature-induced sol-gel transition influence the rotational diffusion of hydrophobic solute molecules. Rotational diffusion of solute molecules differs significantly below and above the CMT of a block copolymer solution, while there is no influence of sol-gel transition on solute rotation. This is rationalized on the basis of the site of solubilization of the solute molecules which is the palisade layer of the micelles in both phases and unaffected by gelation. A similar result has been obtained in case of photoisomerization studies carried out with a carbocyanine derivative in the sol and gel phases of the block copolymer. The isomerization studies have been extended to the reverse phases (sol and gel phases) of the block copolymer to explore the nature of the water present in the cores of the reverse micelles. Our results provide evidence for the existence of water droplets with properties resembling bulk water. In essence, we show that despite having vastly differing bulk properties, both the solution and gel phases (normal as well as reverse) offer identical microscopic environment.

Utilizing an aggregate forming microenvironment sensitive coumarin–cholesterol conjugate as a sensor of pluronic organization and micro-polarity

“…37 Along with the change in polarity during sol-gel transition of pluronics viscosity of the medium also change appreciably. [1][2][3][4] So, it is necessary to verify the effect of medium viscosity on the uorescence properties. Glycerol and ethylene glycol have been chosen which are known to undergo change in viscosity with change in temperature to verify the viscosity effect on uorescence.…”

“…2 A more pronounced temperature effect on PPO solubility over PEO imparts amphiphilicity to pluronics. 3,4 Thus, these block polymers form micelle followed by gelation both as a function of temperature and concentration, unlike conventional surfactants. Anhydrous hydrophobic core region of the spherical micelle consists of PPO units helps in solubilization of water insoluble drug molecules.…”

Effect of Electrostatic Interaction on the Location of Molecular Probe in Polymer−Surfactant Supramolecular Assembly: A Solvent Relaxation Study

“…Using fluorescence anisotropy measurements, Dutt et al have recently reported on the rotational dynamics of a solubilized probe in different phases of pluronic micelles. [31][32][33][34][35] Grant et al have demonstrated from anisotropy measurements that a suitable molecular probe can be used as a local reporter for the different regions of the copolymer micelles. 36,37 Relaxation of the water molecules in different regions of pluronic micelles have recently been reported by Bhattacharya et al [38][39][40] and Kumbhakar et al [41][42][43] All these studies indicate that the dynamical processes in these micelles largely depend on the EO and PO ratios of the polymer.…”

Monitoring thermo-reversible dehydration of the pluronic microenvironment using 4-chloro-1-naphthol as an ESPT fluorescent molecular probe

“…33 These polymers possess amphiphilicity due to the temperature induced preferential solubility of one unit over another. 34,35 As a result, they form spherical micelles and gels, as a function of both temperature and concentration. 36,37 The highly hydrophobic anhydrous inner core region of these micelles helps in solubilizing water insoluble drug molecules.…”