Hollow colloidosomes prepared using accelerated solvent evaporation.

Nur Nabilah Shahidan,Sineenat Thaiboonrod,Kevin M Shakesheff,Cameron Alexander,Brian R Saunders,Ruixue Liu

doi:10.1021/la402788a

Abstract

We demonstrate a new, scalable, simple, and generally applicable two-step method to prepare hollow colloidosomes. First, a high volume fraction oil-in-water emulsion was prepared. The oil phase consisted of CH2Cl2 containing a hydrophobic structural polymer, such as polycaprolactone (PCL) or polystyrene (PS), which was fed into the water phase. The water phase contained poly(vinylalcohol), poly(N-isopropylacrylamide), or a range of cationic graft copolymer surfactants. The emulsion was rotary evaporated to rapidly remove CH2Cl2. This caused precipitation of PCL or PS particles which became kinetically trapped at the periphery of the droplets and formed the shell of the hollow colloidosomes. Interestingly, the PCL colloidosomes were birefringent. The colloidosome yield increased and the polydispersity decreased when the preparation scale was increased. One example colloidosome system consisted of hollow PCL colloidosomes stabilized by PVA. This system should have potential biomaterial applications due to the known biocompatibility of PCL and PVA.

Highlights

Colloidosomes are an important subgroup of microcapsules whose shells consist of coagulated or fused colloid particles.[1]
CH2Cl2 (98%), pyrene (99%), and PS with a weightaverage molecular weight (Mw) of 35 kg/mol were purchased from Aldrich and used as received
The colloidosome shells were proposed to consist of small particles which were separated by polymer surfactant

Summary

■ INTRODUCTION

Colloidosomes are an important subgroup of microcapsules whose shells consist of coagulated or fused colloid particles.[1]. Increased CPol values caused precipitation within the oil droplets at an earlier stage of CH2Cl2 evaporation and this increased Dn. For the small-scale PCL10/M1-PNP90 colloidosome preparations, conditions that gave stable dispersions with a majority of colloidosomes with a size in the range of about 5−100 μm were those for entry 2 in Table 2 (Dn = 12 μm). Drying of the samples for SEM caused contraction of the polymer surfactant phase (due to water evaporation) and a loss of contrast between the two phases This is why the particles that comprise the colloidosome shells were less distinct when examined by SEM compared to optical and fluorescence microscopy. We noticed that the colors of the particles that comprised the colloidosome shells changed with orientation of the colloidosome with respect to the transmitted polarized light direction Article imply a preferred orientation of the semicrystalline regions of the PCL within the shell-particles

■ CONCLUSIONS AND OUTLOOK

■ ACKNOWLEDGMENTS

■ REFERENCES