Preparation and dielectric properties of cellulose derivatives with high‐polarity substituents

An attempt was made to prepare highly dielectric polymers from O‐(2,3‐dihydroxypropyl)‐cellulose (DHPC) The structure of O‐(2,3‐dihydroxypropyl)cellulose (Fig. 1) is different from other cellulose derivatives such as methylcellulose or cellulose acetate, since the substituents can be oligo(dihydroxypropyl)s with different chain lengths (n ≥ 1). The chemical structure of DHPC is defined by the number of hydroxyl groups substituted per anhydroglucose unit, i. e., degree of substitution (DS), and the number of combined glycidol groups per anhydroglucose unit, i. e., molar substitution (MS). by cyanoethylation, nitrobenzoylation, cyanobenzoylation, and trifluoroacetylation. To accomplish this, DHPC samples with different molar substitution (MS) were prepared by homogeneous dihyroxypropylation of cellulose with glycidol in a 10 wt.‐% LiCl/DMA solvent system. Among the sample derivatives, all of which are soluble in various organic solvents, the cyanoethylated derivatives with high MS values have dielectric constants higher than 30 at room temperature and 1 kHz. These derivatives also form cholesteric liquid‐crystalline (LC) phases in a wide temperature range, but the dielectric constant is independent of the phase structure. The results are discussed in terms of the structural difference among the sample polymers.