Characterization of surface NH3+Cl- groups on poly(styrene-co-Boc-aminostyrene) microspheres obtained by controlled acidic treatment.
Different samples of aminated latex of poly(styrene-co-Boc-aminostyrene) microspheres with mean diameters varying from 0.7 to 1.0 microm were prepared by dispersion copolymerization of styrene (ST) and Boc-aminostyrene (Boc-AMST). The copolymer compositions determined by nuclear magnetic resonance (1H NMR) were Boc-AMST/ST 6.9/93.1 mol/mol % (BOC7 sample) and Boc-AMST/ST 31.3/68.7 mol/mol % (BOC30 sample). The average molecular weights determined by gel permeation chromatography were 126 kDa (BOC7 sample) and 51 kDa (BOC30 sample). The latex containing NH-carbo-tert-butoxy groups (NH-Boc) were treated with 2 M HCl in isopropyl alcohol/water (1:1 vol/vol), at 50 degrees C for 3, 6, 9, 24, and 30 h, in order to control the extent of deprotection reaction of the NH-Boc. The deprotection reaction resulted in the formation of NH3+Cl- groups on the particle surfaces. The kinetic of the deprotection reaction was investigated by 1H NMR analyses and the yield varied from 20 to 40%. The resulting -NH3+Cl- groups on the microsphere surfaces were examined, in particular, by electron spectroscopy imaging (ESI) using an energy-filtered transmission electron microscope (EFTEM) that clearly demonstrated the presence of Cl on the particle surfaces. Scanning electron photomicrographs recorded for the above samples showed that the particle morphology was maintained after the acidic treatment.
Synthesis and characterization of styrene/Boc‐p‐amino styrene copolymers
The preparation and characterization of styrene (ST)/Boc-p-aminostyrene (Boc-AMST) copolymers, obtained by free radical polymerization in solution, are reported. The preparation of Boc-AMST as well as the evaluation of the reactivity ratios of ST and Boc-AMST by Kelen and Tudos method constitute the focal aspects of the present contribution. The evaluation of the reactivity ratios substantiated a higher reactivity of Boc-AMST (rBocAMST = 0.96) with respect to ST (rST = 0.47). ST/Boc-AMST copolymers characterized by a “quasi” random distribution of monomeric units with tendency to alternating placement, were thus obtained. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2910–2918, 2000
The Cosmopolitan Imagination: The Renewal of Critical Social Theory
Gerard Delanty provides a comprehensive assessment of the idea of cosmopolitanism in social and political thought which links cosmopolitan theory with critical social theory. He argues that cosmopolitanism has a critical dimension which offers a solution to one of the weaknesses in the critical theory tradition: failure to respond to the challenges of globalization and intercultural communication. Critical cosmopolitanism, he proposes, is an approach that is not only relevant to social scientific analysis but also normatively grounded in a critical attitude. Delanty's argument for a critical, sociologically oriented cosmopolitanism aims to avoid, on the one hand, purely normative conceptions of cosmopolitanism and, on the other, approaches that reduce cosmopolitanism to the empirical expression of diversity. He attempts to take cosmopolitan theory beyond the largely Western context with which it has generally been associated, claiming that cosmopolitan analysis must now take into account non-Western expressions of cosmopolitanism.