Spectroscopic Characterization of Unimer Micelles of Hydrophobically Modified Polysulfonates

Abstract

Polysulfonates modified with bulky hydrophobic groups of cyclic structure form unimolecular micelles (unimers) in aqueous solution owing to intramolecular self-organization. This chapter deals with the characterization of the unimers of random copolymers of sodium 2-(acrylamido)-2-methylpropanesulfonate and hydrophobic methacrylamides carrying cyclododecyl, 1-adamantyl, or 1-naphthylmethyl substituent group, by light scattering, small-angle X-ray scattering, fluorescence, NMR, and IR techniques. The absence of intermolecular association is indicated by the absence of non-radiative energy transfer from naphthalene to pyrene which are labeled respectively on the individual polymer molecules. Light scattering studies show that the unimers have extremely large ratios of mass to dimension indicating an extremely compact conformation. Local motions of the hydrophobes in the unimers are highly restricted as indicated by 1 H-NMR relaxation times. FTIR indicates that hydrogen bonding between the spacer amide bonds contributes to the stabilization of the compact unimer structure.Amphiphilic polymers, a class of water-soluble polymers consisting of both hydrophobic and hydrophilic segments in a polymer chain, have a tendency to selforganize in aqueous solution. Water molecules surrounding the hydrophobes in the amphiphilic polymers in aqueous solution form an ice-like structure (7) because the water molecules tend to form the largest possible number of hydrogen bonds on the surface of the hydrophobes. The hydrophobes would associate such that they have the smallest possible area of contact with the aqueous phase by releasing the structured water molecules into free water. The principal driving force for this hydrophobic association is a large increase in entropy which is sufficient to overcome a positive enthalpy change due to the breakup of the hydrogen bonds (2,5). The hydrophobic association is the main cause for the self-organization of amphiphilic polymers in aqueous solution.In amphiphilic polyelectrolytes, the hydrophobic interaction competes with electrostatic repulsion. Therefore, the balance of the contents of the hydrophobes and charged segments in the polymers are a critical factor to determine whether or not the self-organization occurs. For example, amphiphilic polycarboxylic acids, which adopt an extended chain conformation at high pH, would collapse to form compact conformation upon decreasing pH (4-9). This transition from an extended to a compact 0097-6156/95/0598-0490$13.75/0

Fluorescence Study of the Interaction between Hydrophobically Modified Polymers and Charged Particles in Aqueous Media

“…Amphiphilic materials such as semiconductors, display devices, solar cells, and sensors are widely used in the field of electronic devices. , In particular, the amphiphilic polymers play an important role in the formation of conductive lines, thin film transistors, sealants, and moisture barrier layers, which are the key elements of electronic devices. − For instance, poly­(styrene­sulfonate) (PSS) is known to be used with conducting polymer poly­(3,4-ethylene­di­oxy­thio­phene) (PEDOT), and PEDOT/PSS has been used for organic light-emitting diodes, organic solar cells, organic thin film transistors, and sensors. , In addition, from the point of view of environmental issues, water-soluble polymers are one of the most prominent materials in various industrial fields, and thus the market for water-soluble polymer has been growing rapidly in recent years. Thus, amphiphilic polymers such as hydrophobically modified (HM) water-soluble polymers have been widely studied fundamentally and practically for two decades or more. − Therefore, the association behavior of HM-polyanions, several sodium 2-(acryl­amido)-2-methyl­propane­sulfonates (AMPSs) having hydrophobic units and their interactions with liposomes, and surfactant micelles have been fundamentally studied so far. − ,− As the HM-PAMPS polymers, two PAMPS polymers consisting of PAMPS bearing a 5 mol % (1-pyrenyl)­butyl- N - n -octadecyl group (PyBuODA) randomly (PAMPS-PyBuODA) and PAMPS end-modified with a PyBuODA group ( e -PyBuODA-PAMPS) as shown in Figure are focused on in this article. It has already been reported that the random copolymer PAMPS-PyBuODA shows an obvious tendency for intrapolymer self-association owing to the hydrophobic association of the PyBuODA group in aqueous media .…”

Photophysical Behavior of Zinc(II) Tetraphenylporphyrin Covalently Incorporated in a Cholesterol-Bearing Polymethacrylate

“…We previously reported on the spectroscopic and photochemical behavior of zinc(I1) tetraphenylporphyrin (Zn-TPP)$ moieties covalently encapsulated in unimolecular micelles (unimer micelles) formed from hydrophobically modified polyelectrolytes in aqueous solution (15)(16)(17)(18)(19). An example of such ZnTPP-functionalized hydrophobically modified polyelectrolytes is the terpolymer of sodium 2-(acrylamido)-2-methylpropanesulfonic acid (39.9 mol %), Ncyclododecylmethacrylamide (60 mol %), and zinc(I1) 5-(4acrylamidophenyl)-l0,15,20-triphenylporphynate (0.1 mol %).…”