Abstract
Amphiphilic diblock copolymers consisting of a hydrophobic core containing a polymerized ionic liquid and an outer shell composed of poly(N-isoprolylacrylamide) were investigated by capillary electrophoresis and asymmetrical flow-field flow fractionation. The polymerized ionic liquid comprised poly(2-(1-butylimidazolium-3-yl)ethyl methacrylate tetrafluoroborate) with a constant block length (n=24), while the length of the poly(N-isoprolylacrylamide) block varied (n=14; 26; 59; 88). Possible adsorption of the block copolymer on the fused silica capillary, due to alterations in the polymeric conformation upon a change in the temperature (25 and 45°C), was initially studied. For comparison, the effect of temperature on the copolymer conformation/hydrodynamic size was determined with the aid of asymmetrical flow-field flow fractionation and light scattering. To get more information about the hydrophilic/hydrophobic properties of the synthesized block copolymers, they were used as a pseudostationary phase in electrokinetic chromatography for the separation of some model compounds, that is, benzoates and steroids. Of particular interest was to find out whether a change in the length or concentration of the poly(N-isoprolylacrylamide) block would affect the separation of the model compounds. Overall, our results show that capillary electrophoresis and asymmetrical flow-field flow fractionation are suitable methods for characterizing conformational changes of such diblock copolymers.
Highlights
Responsive polymers are defined as macromolecular compounds that can undergo changes in their properties by adjusting the chemical or physical conditions of their surrounding, for example, by changes in pH, pressure, temperature, solvent composition, ionic strength, light, and electric and magnetic fields [1,2]
Thermoresponsive diblock copolymers based on a hydrophobic polymerized ionic liquid (PIL) block and an amphiphilic PNIPAM one with a varying degree of polymerization of the PNIPAM block form micellar structures in aqueous solvents
These polymers were investigated by capillary electrophoresis and AF4
Summary
Responsive polymers are defined as macromolecular compounds that can undergo changes in their properties by adjusting the chemical or physical conditions of their surrounding, for example, by changes in pH, pressure, temperature, solvent composition, ionic strength, light, and electric and magnetic fields [1,2]. Article Related Abbreviations: AF4, asymmetrical flow-field flow fractionation; DLS, dynamic light scattering; IL, ionic liquid; LCST, lower critical solution temperature; PIL, polymerized ionic liquid; PNIPAM, poly(N-isoprolylacrylamide). In water the polymers are capable to build up micelles and they in general have a tendency to aggregate
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