Thermal, crystalline, and pressure-sensitive adhesive properties of paramylon monoesters derived from an euglenoid polysaccharide

The thermal, crystalline, and pressure-sensitive adhesive properties of thermoplastic monoesters made from paramylon, a storage polysaccharide of Euglena gracilis, and a long-chain acyl chloride, were examined. Differential scanning calorimetry revealed that the thermal properties of these paramylon monoesters were dependent on the chain length and the average degree of substitution of the long-chain acyl group (av. DSlca). X-ray diffractometry revealed that the product solids with a myristoyl or palmitoyl group had a less ordered lateral acyl chain structure than those with a stearoyl group. Tackiness testing showed that the introduction of a myristoyl group into paramylon with an av. DSlca of ∼2.6 to ∼2.9 yielded palpable pressure-sensitive adhesion. A slight deviation of the chain length and/or av. DSlca from those of tacky paramylon myristate solids weakened or dispersed the tackiness. These results demonstrate the feasibility of using paramylon myristate solids with the av. DSlca in a specific range as a practical pressure-sensitive adhesive.