Polyamide microcapsules containing jojoba oil prepared by inter-facial polymerization

Synthesis of Polyamide-Based Microcapsules via Interfacial Polymerization: Effect of Key Process Parameters

Polyamide microcapsules have gathered significant research interest during the past years due to their good barrier properties; however, the potential of their application is limited due to the fragility of the polymeric membrane. Fully aliphatic polyamide microcapsules (PA MCs) were herein prepared from ethylene diamine and sebacoyl chloride via interfacial polymerization, and the effect of key encapsulation parameters, i.e., monomers ratio, core solvent, stirring rate and time during the polymerization step, were examined concerning attainable process yield and microcapsule properties (shell molecular weight and thermal properties, MC size and morphology). The process yield was found to be mainly influenced by the nature of the organic solvent, which was correlated to the diffusion potential of the diamine from the aqueous phase to the organic core through the polyamide membrane. Thus, spherical microcapsules with a size between 14 and 90 μm and a yield of 33% were prepared by using toluene as core solvent. Milder stirring during the polymerization step led to an improved microcapsule morphology; yet, the substantial improvement of mechanical properties remains a challenge.

Low-Ceiling-Temperature Polymer Microcapsules with Hydrophobic Payloads via Rapid Emulsion-Solvent Evaporation

We report a microencapsulation procedure based on rapid solvent evaporation to prepare microcapsules with hydrophobic core materials and low-ceiling-temperature polymer shell wall of cyclic poly(phthalaldehyde) (cPPA). We use and compare microfluidic and bulk emulsions. In both methods, rapid solvent evaporation following emulsification resulted in kinetically trapped core-shell microcapsules, whereas slow evaporation resulted in acorn morphology. Through the systematic variation of encapsulation parameters, we found that polymer-to-core weight ratios higher than 1 and polymer concentrations higher than 4.5 wt % in the oil phase were required to obtain a core-shell structure. This microencapsulation procedure enabled the fabrication of microcapsules with high core loading, controlled size, morphology, and stability. This procedure is versatile, allowing for the encapsulation of other hydrophobic core materials, i.e., mineral oil and organotin catalyst, or using an alternative low-ceiling-temperature polymer shell wall, poly(vinyl tert-butyl carbonate sulfone).

Formaldehyde-free melamine microcapsules as core/shell delivery systems for encapsulation of volatile active ingredients

The release of volatile bioactive molecules, such as fragrances, can be controlled by microencapsulation in core–shell polymeric delivery systems.

Polyamide capsules via soft templating with oil drops-1. Morphological studies of the capsule wall

Poly(terephthalamide) microcapsules can be reproducibly and easily prepared by interfacial polycondensation around emulsion droplets in water. Oil drops of cyclohexane/chloroform mixture stabilized with poly(vinyl alcohol) containing terephthaloylchloride serve as soft template. The interfacial polycondensation starts immediately after addition of an amine mixture (hexamethylenediamine/diethylenetriamine). Light and scanning electron microscopy prove the formation of capsules with size distribution in the range from a few up to 100 µm depending on particular composition of the reaction mixture. The morphology of the capsule wall is characterized by precipitated particles. If instead of pure organic solvents a reactive oil phase is used as template, the capsules can serve in subsequent reactions as templates for the synthesis of composite particles. In this way, styrene can be radically polymerized inside the capsule leading to composite capsules. The capsule morphology is determined by the partition of all components between all phases.

Antibody-conjugated soybean oil-filled calcium phosphate nanoshells for targetted delivery of hydrophobic molecules

Hollow calcium phosphate nanoparticles capable of encapsulating poorly water-soluble molecules were produced by self-assembly. Previously reported were solid calcium phosphate nanoparticles and water-filled calcium phosphate nanocapsules suited for encapsulating mostly hydrophilic, but not hydrophobic compounds. Here, calcium phosphate was deposited around 100 nm diameter, 1,2-dioleoyl-sn-glycero-3-phosphate stabilized soybean oil nanoemulsions using either calcium chloride or NaOH titrations to achieve shell thickness between 20-70 nm. The surface was functionalized with carboxylic acid via the addition of carboxyethylphosphonic acid to attach Molecular Probes AB-594C antibody using sulpho-n-hydroxysuccinimide and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride with an efficiency of approximately 70%, while retaining near complete antibody function. Hydrophobic pyrene was encapsulated with an efficiency of 95%, at concentrations much higher than its water solubility limit, and exhibited spectral features characteristic of a hydrophobic environment. These materials can be used in the targeted delivery of many useful, yet poorly water-soluble pharmaceutical and nutraceutical compounds.