A pH-sensitive double [60]fullerene-end-capped polymers via ATRP: Synthesis and aggregation behavior

A double [60]fullerene (C-60)-end-capped water-soluble polymer [C-60-DMAEMA(68)-C(CH3)(2)COOCH2](2) was synthesized by cycloaddition of the double azido-terminated [DMAEMA(68)-C(CH3)(2)COOCH2](2) with C-60. The well-defined [Br(Cl)-DMAEMA(68)-C(CH3)2COOCH(2)](2) was first synthesized via ATRP using ethylene bis(2-bromoisobutyrate) as initiator in ethanol. TGA and spectrophotometric analyses confirmed that monoaddition to C-60 had occurred. In aqueous solution, [C-60-DMAEMA(68)-C(CH3)(2)COOCH2](2) self-assembled into flower micelles. The aggregation behaviors in unbuffered distilled water and in acidic solution at pH 3 were studied by laser light scattering (LLS). The micelles formed in distilled water has an aggregation number (N-agg) of similar to 242 which is about three times larger than that at pH 3 solution (N-agg = 81). However, the micellar size is bigger at pH 3, due to the highly stretched corona resulting from the charge repulsion among the protonated amino groups. After calcination, the C-60 core could be seen clearly by AFM. The critical micelle concentration (CMC) Of [C-60-DMAEMA(68)-C(CH3)(2)COOCH2](2)) is lower in unbuffered distilled water (28.6 mg dm(-3)) than in solution at pH 3 (176.8 mg dm(-3)). (c) 2007 Elsevier Ltd. All rights reserved.