Corona, reverse

Block copolymers in a selective solvent, ie., a good solvent for one block but a precipitant for the other, behave like typical amphiphiles. The copolymer molecules aggregate reversibly to form micelles in a manner analogous to the aggregation of classical surfactants. Our block copolymers are very amphiphilic in the sense described above and form well-defined micelles in a wide range of selective solvents. In solvents for polystyrene, the polystyrene block is located in the micelle corona, while the modified block is hidden in the micelle core. 

As far as micelles in organic media are concerned, two types of block copolymers can be considered—those with two hydrophobic blocks and those with one hydrophilic and one hydrophobic block. The latter form the so-called reverse micelles, which contain a hydrophilic core surrounded by a soluble hydrophobic corona. 

Reverse micelles from PMAA and PAA-containing copolymers have been extensively studied by Eisenberg and coworkers [104,105]. These authors considered the micellization of the so-called "block ionomers formed of a major PS block linked to ionized PAA and PMAA segments. Stable spherical micelles were formed by these copolymers in organic solvents such as toluene. Their characteristic size was systematically investigated by a combination of experimental techniques including TEM, SAXS, DLS, and SLS. The micelles were shown to consist of an ionic core and a PS corona. The mobility of the PS segments located near the ionic core was found to be restricted, as discussed in Sect. 2.4. 

A.J. BeU and S.K. Ross, Reverse flow continuous corona discharge ionization. International Journal of Mass Spectrometry 218(2) (2002) LI—L6, also found in part at International Journal for Ion Mobility Spectrometry 5(3) (2002) 95—99. 

This change was found to be reversible if the corona block is not too large and may become of interest for controlled drug delivery applications. It was also shown that these systems can host gold nanoparticles in the P2VP shell [93],... 

Choice of the proper detection scheme is dependent on the properties of the analyte. Different types of detectors are available such as ultraviolet (UV), fluorescence, electrochemical, hght scattering, refractive index (RI), flame ionization detection (FID), evaporative light scattering detection (ELSD), corona aerosol detection (CAD), mass spectrometric (MS), NMR, and others. However, the majority of reversed-phase and normal-phase HPLC method development in the pharmaceutical industry is carried out with UV detection. In this section the practical use of UV detection will be discussed. 

Block copolymers of 23b and alkyl methacrylates [158] and diblock copolymers of 23b with 2-(diethylamino)ethyl methacrylate (23b-DEAEM), 2-(diisopropylamino)ethyl methacrylate (23b-DIPAEM), or 2-(N-morphoHno) ethyl methacrylate (23b-MEMA) exhibited reversible pH-, salt-, and temperature-induced micellization in aqueous solution under various conditions. The micelle diameters were 10-46 nm [238]. The micelles of these hydropho-bically modified polybetaines consist of coronas from 23b and cores from polyDEAEM, polyDIPAEM, or polyMEMA. In aqueous solution, the 23b-MEMA diblock copolymers form micelles with cores of polyMEMA above an upper critical micelle temperature of about 50 °C, and reversibly betainized-DMAEM core micelles below a lower critical micelle temperature of approximately 20 °C [239]. 

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