Kinetic analysis of mechanoradical formation during the mechanolysis of dextran and glycogen.

Naoki Doi,Shin-Ichi Kondo,Masayuki Kuzuya,Tetsuo Adachi,Yasushi Sasai,Yukinori Yamauchi

doi:10.3762/bjoc.13.116

Naoki Doi, Shin-Ichi Kondo + Show 4 more

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https://doi.org/10.3762/bjoc.13.116

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Abstract

A detailed electron spin resonance (ESR) analysis of mechanically induced free radicals (mechanoradicals) formation of glucose-based polysaccharides, dextran (Dx) and glycogen (Gly) was performed in comparison with amylose mechanoradicals. The ESR spectra of the samples mechanically fractured at room temperature were multicomponent. The radical concentration of Dx and Gly mechanoradicals gradually decreased during vibratory milling after reaching the maximum value. Although the molecular weight of Dx or the particle diameter of Gly steeply diminished until reaching the each maximum value of radical concentration, after that the molecular weight or the particle diameter slowly decreased. These results suggested that Dx and Gly mechanoradicals might be more unstable than amylose radicals possessing an intramolecular helical structure due to the branched structure.

Highlights

There are many reports on the mechanolysis of synthetic and natural polymers
Because amylose is an α-glucose-based polysaccharide and its detailed analysis of electron spin resonance (ESR) spectra of mechanoradicals has been studied [5], we selected it as a reference sample
In a previous paper [5], we studied the radical formation by plasma-irradiation and mechanolysis of amylose and the β-glucose-based linear polysaccharide, cellulose, in view of the difference of bonding type

Summary

Introduction

There are many reports on the mechanolysis of synthetic and natural polymers. It is well-known that mechanically induced radicals, so-called mechanoradicals, are produced by the mechanolysis of a polymer at a temperature below its glasstransition temperature (Tg) due to the disruption of the polymer main chain [1]. Most pulverization operations for a practical use are carried out at room temperature, electron spin resonance (ESR) spectroscopy analyses of mechanoradical formation have generally been conducted at low temperature (77 K) [2]. In previous papers we discussed the mechanoradical formation through mechanolysis of synthetic polymers [3,4] and polysaccharides such as amylose and cellulose [5] at room tem-.

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