Preparation of robust polyamide microcapsules by interfacial polycondensation ofp-phenylenediamine and sebacoyl chloride and plasticization with oleic acid

Abstract

Microcapsules produced by interfacial polycondensation of p-phenylenediamine (PPD) and sebacoyl chloride (SC) were studied. The products were characterized in terms of morphology, mean diameter and effectiveness of dodecane encapsulation. The use of Tween 20 as dispersion stabilizer, in comparison with polyvinyl alcohol (PVA), reduced considerably the mean diameter of the microcapsules and originated smoother wall surfaces. When compared to ethylenediamine (EDA), microcapsules produced with PPD monomer were more rigid and brittle, prone to fracture during processing and ineffective retention of the core liquid. The use of diethylenetriamine (DETA) cross-linker in combination with PPD did not decrease capsule fragility. On the other hand, addition of a small fraction of oleic acid to the organic phase remarkably improved wall toughness and lead to successful encapsulation of the core-oil. Oleic acid is believed to act as a plasticizer. Its incorporation in the polymeric wall was demonstrated by FTIR and (1)H-NMR.

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

“…Significant research has been carried out on polyamide microcapsules starting from a range of monomers (aliphatic or aromatic, bifunctional or polyfunctional, etc.) [ 24 , 27 , 31 , 33 , 36 , 38 , 39 , 40 , 41 , 42 , 43 , 44 ]. The effect of process variables such as ratio of monomers, type and concentration of the emulsifier, emulsification method, and time on the final ΡA MCs properties, especially the size, shell integrity, permeability along with release profiles and mechanisms, has been investigated.…”

“…However, both the mechanical stability and the release properties through the shell of the MCs, as well as the success of MCs synthesis, depend on the inherent nature of the monomers [ 2 , 6 , 7 , 40 ]. Aliphatic chlorides such as sebacoyl and succinyl chloride [ 6 , 31 , 38 ] have lower reactivity than aromatic ones such as terephthaloyl chloride [ 6 , 28 , 41 , 45 ]; however, the former tend to form more favorable conformations to the reactions with diamine due to their flexible aliphatic chain [ 6 ]. Furthermore, aliphatic chlorides are more susceptible to hydrolysis, but form less porous and smoother polyamide shells [ 27 , 38 , 42 ].…”

“…Aliphatic chlorides such as sebacoyl and succinyl chloride [ 6 , 31 , 38 ] have lower reactivity than aromatic ones such as terephthaloyl chloride [ 6 , 28 , 41 , 45 ]; however, the former tend to form more favorable conformations to the reactions with diamine due to their flexible aliphatic chain [ 6 ]. Furthermore, aliphatic chlorides are more susceptible to hydrolysis, but form less porous and smoother polyamide shells [ 27 , 38 , 42 ]. On the other hand, aliphatic amines, such as ethylene diamine and 1,8 diamino-octane, are preferred due to their reactivity and hydrophilic nature [ 6 , 36 , 38 , 44 ].…”

“…Furthermore, aliphatic chlorides are more susceptible to hydrolysis, but form less porous and smoother polyamide shells [ 27 , 38 , 42 ]. On the other hand, aliphatic amines, such as ethylene diamine and 1,8 diamino-octane, are preferred due to their reactivity and hydrophilic nature [ 6 , 36 , 38 , 44 ]. The tendency of the amine component to diffuse towards the organic phase is the rate-determining step of interfacial polymerization.…”

“…Although aliphatic polyamides have been extensively studied as polymeric materials in the literature, there are very few studies concerning aliphatic polyamide microcapsules [ 31 , 34 , 38 , 46 ]. In this context, the present work aims to examine and improve the synthesis of polyamide 210 microcapsules (ΡA 210 MCs) from sebacoyl chloride (SC) and ethylene diamine (EDA).…”