End-groups, charged

Whitcombe et al. concentrated on the synthesis of hydrophobic surface imprints in particles with a hydrophilic surface layer. To achieve hydrophilicity of the particles surface they chose divinylbenzene as crosslinker and an additional polymerizable surfactant (PS) (Fig. 4) with a charged end group for the shell polymerization. Thereby, imprinted particles of submicrometer scale, with good monodispersity and high surface area could be prepared. A schematic diagram of the design of hydrophobic surface imprints in particles with a hydrophilic surface layer is shown in Fig. 5. 

Possible Effect of Charged End-groups. A possible reason for differences between samples might be the process used for polymerising the original polyvinyl acetate. Emulsion polymerisation is likely to introduce a proportion of ionic (sulphate or carboxyl) end-groups which would not be expected if bulk polymerisation with benzoyl peroxide had been used. An Antweller Microelectrophoresis apparatus was used to measure rates of electrophoresis of polyvinyl alcohols in solution in a pH 7.8 phosphate buffer. No significant difference was observed between... 

The number of charged end groups per particle is therefore given by K = 2N, = BnaWNJiM, and the surface charge density by... 

The factors that enhance the second order NLO activity of the molecules (high axial ratio, planarity, charged end groups) are es-... 

The dependence of colloid stability on the size of the particles formed and its dependence on electrolyte concentration can be discussed simplistically in the following way [71], Assuming, (1) that the particles formed are spherical, (2) each polymer chain has the same molar mass, M, (3) each chain has two charged end-groups and (4) all the end-groups are anchored at the surface of the particle, it follows that the number of polymer chains per particle, Nc is given by... 

It is reasonable to assume relevance of the special molecular configuration of betaine to the physichochemical mechanism of the protection it affords to PS2 particles against high NaCI. Betaine - a zwitterion having two bulky, oppositely charged end groups - is expected to assume a pre-... 

Except for the charged end-groups of the amphiphilic molecules, field gradients may also be produced by the water dipoles. However, for a hydrated ion the effects of the different surrounding water molecules will largely cancel out and it is only the asymmetry in the hydration sheath that produces a net field gradient. This effect has been considered for sodium ions [327] but its relevance for the halide ions is difficult to judge at present. 

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