Structure, Properties, and Release Kinetics of the Polymer/Insect Repellent System Poly (l-Lactic Acid)/Ethyl Butylacetylaminopropionate (PLLA/IR3535)

Abstract

The insect repellent ethyl butylacetylaminopropionate (IR3535) was used as a functional additive for poly (l-lactic acid) (PLLA) to modify its structure and mechanical properties and achieve insect repellency. PLLA/IR3535 mixtures at various compositions were prepared via melt extrusion. In the analyzed composition range of 0 to 23 m% IR3535, PLLA and IR3535 were miscible at the length scale represented by the glass transition temperature. Addition of IR3535 resulted in a significant decrease in the glass transition temperature of PLLA, as well as in the elastic modulus, indicating its efficiency as a plasticizer. All mixtures were amorphous after extrusion, though PLLA/IR3535 extrudates with an IR3535 content between 18 and 23 m% crystallized during long-term storage at ambient temperature, due to their low glass transition temperature. Quantification of the release of IR3535 into the environment by thermogravimetric analysis at different temperatures between 50 and 100 °C allowed the estimation of the evaporation rate at lower temperatures, suggesting an extremely low release rate with a time constant of the order of magnitude of 1–2 years at body temperature.

Sustainable Electrospun Poly(l-lactic acid) Fibers for Controlled Release of the Mosquito-Repellent Ethyl Butylacetylaminopropionate (IR3535)

“…Incorporating the repellent IR3535 into bio-sourced and biodegradable PLLA opens the way to the realization of an environment-friendly repellent-delivery device. After successful testing of melt extrusion , and 3D printing of semi-finished and final products of the PLLA/IR3535 system, in this work, electrospinning of fiber mats as an alternative technology for obtaining such an environment-friendly repellent-delivery system is investigated. By systematic variation of the electrospinning parameters, including voltage, nozzle-to-collector distance, flow rate, and solution composition, uniform fibers with a diameter close to 1 μm and containing a large amount of the repellent, exceeding 40 m%, were obtained.…”

“…By systematic variation of the electrospinning parameters, including voltage, nozzle-to-collector distance, flow rate, and solution composition, uniform fibers with a diameter close to 1 μm and containing a large amount of the repellent, exceeding 40 m%, were obtained. Such a high amount of repellent was impossible to incorporate into the polymeric carrier by melt extrusion and 3D printing, ,, where only up to about 25 m% IR3535 was added. Thermal and structural analyses revealed that IR3535 results in a decrease in the glass transition temperature of the polymer component, confirming thermodynamic solubility, as suggested in earlier works, , and causing plasticization of the amorphous PLLA phase.…”

“…Such a high amount of repellent was impossible to incorporate into the polymeric carrier by melt extrusion and 3D printing, ,, where only up to about 25 m% IR3535 was added. Thermal and structural analyses revealed that IR3535 results in a decrease in the glass transition temperature of the polymer component, confirming thermodynamic solubility, as suggested in earlier works, , and causing plasticization of the amorphous PLLA phase. In addition, the presence of IR3535 enhances crystallization of PLLA, with the crystals presumably contributing to the mechanical properties of the fibers, as proven for bulk PLLA .…”

“…It is a transparent liquid at room temperature and has a glass transition temperature of approximately −90 °C. 20,28 The boiling point at atmospheric pressure is slightly below 300 °C and about 110 °C at 0.02 kPa, and its vapor pressure at 20 °C is reported being around 0.15 Pa. 13,29 Chloroform (CHCl 3 ) and dimethylformamide (DMF) with a purity ≥99.8%, both used as solvents for the electrospinning process, were obtained from Sigma-Aldrich (Burlington, USA) and used as received without further purification. PLLA solutions were prepared by dissolving PLLA in CHCl 3 or a CHCl 3 /DMF 90/10% v/v solution at room temperature.…”

“…As such, in-depth analysis of the glass transition temperature by employing fast scanning chip calorimetry combined with in situ evaporation of the liquid to achieve controlled change of the system composition has revealed that PDLLA and IR3535 are thermodynamically miscible in the entire composition range . Regarding the polymer-rich part of the PLLA/IR3535 system, IR3535 acts as a functional plasticizer of PLLA, , offering additional advantages from the point of view of reducing the inherent brittleness of PLLA. , Recently, PLLA-parts/products accommodating up to 25 m% of IR3535 were manufactured by classical melt extrusion , and 3D printing, emphasizing their potential for controlled long-term release of IR3535. Since in the case of electrospun fibers, the carrier geometry/shape is qualitatively different compared to scaffold-like bulk structures and products with a rather low surface-to-volume ratio, it is expected that the IR3535-release characteristics are different, and that personal-protection devices based on fibers can be generated.…”