Microfluidic fabrication of novel polymeric core-shell microcapsules for storage of CO2 solvents and organic chelating agents

Monodispersed polymeric microcapsules loaded with CO2 solvents or chelating agents were produced by capillary microfluidics by photopolymerisation of three different UV curable materials, 1,6-hexanediol diacrylate (HDDA), Norland Optical Adhesive (NOA) 81, and Semicosil (R) 949 UV A/B (PDMS). Polymerization of HDDA and NOA 81 started after exposure to UVA light for 5 s and was completed within a minute, as confirmed by continuous FT-IR. Corrosive aqueous solutions of tetraethylenepentamine and diisopropyl iminodiacetic acid were encapsulated with 100% efficiency into poly(HDDA) and cured NOA81 shells without any leakage during prolonged storage. Poly(HDDA) shells were mechanically more stable than cured NOA81 and PDMS shells and resistant to drying-induced shell buckling. NOA81 and PDMS capsules underwent morphological changes during freeze drying leading to the formation of dimpled and crescent-moon-shaped particles, respectively. The storage stability in a hypotonic solution and buckling resistance of PDMS shells were significantly improved by embedding carbon-based nanomaterials into PDMS matrix. The incorporation of 0.5 wt% multi-walled carbon nanotubes into PDMS matrix led to an increase in a Shore A hardness from 1.6 to 2.3. A uniform distribution of MWCNTs in the polymer network was confirmed by XRD. All fabricated shells were thermally stable up to the temperature of 300 degrees C.

Automated summary

Monodispersed polymeric microcapsules loaded with CO2 solvents or chelating agents were successfully produced by capillary microfluidics. The poly(HDDA) shell exhibited better mechanical stability and resistance to shell buckling, while the NOA81 and PDMS shells underwent morphological changes during freeze drying. Embedding carbon-based nanomaterials into the PDMS matrix improved the storage stability and buckling resistance of PDMS shells. All fabricated shells showed thermal stability up to 300 degrees C.