Vapor-Stripping and Encapsulating to Construct Particles with Time-Controlled Asymmetry and Anisotropy

Abstract

An innovative chemical vapor sublimation and deposition (CVSD) process was shown to produce nanoscale anisotropic hybrid materials. Taking advantage of controlled thermodynamic properties and the mass transfer of molecules, this process allowed for water vapor sublimation from an iced template/substrate and stagewise vapor deposition of poly-p-xylylene onto the sublimating ice substrate. In this study, the use of sensitive soybean agglutinin (SBA) protein tubes was demonstrated as an example to prepare the anisotropic hybrid material based on the CVSD process. The rationale of a timing parameter, Δt, was controlled to program the sublimation of the SBA-ice templates and the deposition of poly-p-xylylene during the CVSD process. As a result of this control, a stripping stage occurred, during which SBA tubes were exposed on the particle surface, and a subsequent encapsulation stage enabled the transformation of the ice templates into a nanometer-sized anisotropic hybrid material of poly-p-xylylene as the matrix with encapsulated SBA tubes. The timing parameter Δt and the controlled stripping and encapsulating stages during CVSD represent a straightforward and intriguing mechanism stemming from physical chemistry fundamentals for the fabrication of hybrid materials from sensitive molecules and with predetermined sizes and asymmetrical shapes. A simulation analysis showed consistency with the experimental results and controllability of the timing mechanism with predictable particle sizes.