Preparation of insect sex pheromone simulacrum dodecanol containing microcapsules via complex coacervation method and its release

Dodecanol(C12OH), as an insect sex pheromone simulacrum, was encapsulated via complex coacervation with gelatin (GE) and acacia gum (AG) as the wall materials and the release behavior of C12OH from microcapsules was investigated via varying solution concentration and crosslinking of wall materials. Firstly, the yeild of coacervation at different pH was tested when mass ratio of GE to AG was set at 1:1. It was observed that, for the complex coacervation maximum yield was achieved at pH = 4.0. Then properties of microcapsules and dispersions with different dispersants were detected. The results showed that with Tween 20/Span 80 (mass ratio 1: 1) as dispersants, it improved the encapsulation efficiency of microcapsules and the stability of the dispersion. When the wall material mass fraction was equal to or higher than 3%, the size of the microcapsules was larger than that prepared with 2% wall material mass fraction and their C12OH loading and encapsulation rate were remarkably higher than the latter. In addition, increasing of crosslinker led to the capsules with much higher crosslinking, C12OH loading and encapsulation rates. Microcapsules crosslinked with formaldehyde had a lower crosslinking but a higher C12OH encapsulation rate compared with those crosslinked with glutaraldehyde at equal level. The structure of microcapsules was analyzed through scanning electronic microscopy with the conclusion that it did encapsulate C12OH in microcapsules. Moreover, to investigate C12OH release from the capsules, microcapsules were placed into an incubator with constant temperature (35 T) and relative humidity(50% RH), and taken out for C12OH examination by weighing the samples. It was found that microcapsules prepared with 3% and 4% mass fraction solution of wall materials, crosslinked with 1% glutaraldehyde manifested a controlled C12OH release behavior as well as thoses done with 5% wall materials solution and 1% glutaraldehyde. This work indicates that the release of C12OH can be well controlled by adjusting polymer concentration and crosslinking of microcapsules. This is of great importance for our ongoing study on the controlled release of authentic insect semichemicals.