ABSTRACT
Bacterial cellulose (BC) was mechanically fractured in vacuum at 77 K; this resulted in the scission of the ß-1,4 glycosidic linkages of BC. The chain-end-type radicals (mechanoradicals) generated from the scissions were assigned by electron spin resonance (ESR) spectral analyses. A diblock copolymer of BC and poly(methyl methacrylate) (BC-block-PMMA) was produced by the mechanical fracture of BC with MMA (methyl methacrylate) in vacuum at 77 K. Radical polymerization of MMA was initiated by the mechanoradicals located on the BC surface. The BC surface was fully covered with the PMMA chains of the BC-block-PMMA. Novel modification of the BC surface with the BC-block-PMMA was confirmed by spectral analyses of ESR, Fourier-transform infrared, (1)H NMR, and gel permeation chromatography.
Subject(s)
Cellulose/chemistry , Gluconacetobacter xylinus/chemistry , Glycosides/chemistry , Polymethyl Methacrylate/chemistry , Electron Spin Resonance Spectroscopy , Free Radicals/chemical synthesis , Free Radicals/chemistry , Polymethyl Methacrylate/isolation & purificationABSTRACT
We have studied the ground state of a fullerene-based magnet, the alpha;{'}-phase tetra-kis-(dimethylamino)-ethylene-C60 (alpha'-TDAE-C(60)), by electron spin resonance and magnetic torque measurements. Below T(N) = 7 K, nonparamagnetic field dependent resonances with a finite excitation gap (1.7 GHz) are observed along the a axis. Strong enhancement in their intensity as temperature is decreased is inconsistent with excitation from a singlet state, which had been proposed for the alpha'-phase ground state. Below T(N), nonquadratic field dependence of the magnetic torque signal is also observed in contrast to quadratic field dependence in the paramagnetic phase. The angle-dependent torque signals below T(N) indicate the existence of an anisotropy of the bulk magnetization. From both experiments, we propose an antiferromagnetic ground state driven by the cooperative orientational ordering of C(60) in the alpha'-TDAE-C(60).
