Formation of Polymeric Toroidal-Spiral Particles

• Published in: Langmuir 2012-01, Vol.28 (1), p.729-735
• Main Authors: Sharma, Vishal, Szymusiak, Magdalena, Shen, Hao, Nitsche, Ludwig C, Liu, Ying
• Format: Article
• Language: English
• Subjects: Biocompatible Materials - chemistry; Chemistry; Colloidal state and disperse state; Exact sciences and technology; General and physical chemistry; Kinetics; Materials: Nano-and Mesostructured Materials, Polymers, Gels, Liquid Crystals, Composites; Physical and chemical studies. Granulometry. Electrokinetic phenomena; Polymers - chemistry
• ISSN: 0743-7463; 1520-5827
• DOI: 10.1021/la203338v

Compared to spherical matrices, particles with well-defined internal structure provide large surface to volume ratio and predictable release kinetics for the encapsulated payloads. We describe self-assembly of polymeric particles, whereby competitive kinetics of viscous sedimentation, diffusion, and cross-linking yield a controllable toroidal-spiral (T-S) structure. Precursor polymeric droplets are splashed through the surface of a less dense, miscible solution, after which viscous forces entrain the surrounding bulk solution into the sedimenting polymer drop to form T-S channels. The intricate structure forms because low interfacial tension between the two miscible solutions is dominated by viscous forces. The biocompatible polymer, poly(ethylene glycol) diacrylate (PEG-DA), is used to demonstrate the solidification of the T-S shapes at various configurational stages by UV-triggered cross-linking. The dimensions of the channels are controlled by Weber number during impact on the surface, and Reynolds number and viscosity ratio during subsequent sedimentation. We anticipate applications of the T-S particle in drug delivery, wherein diffusion through these T-S channels and the polymer matrix would offer parallel release pathways for molecules of different sizes. Polyphosphate, as a model macromolecule, is entrained in T-S particles during their formation. The in vitro release kinetics of polyphosphate from the T-S particles with various channel length and width is reported. In addition, self-assembly of T-S particles occurs in a single step under benign conditions for delicate macromolecules, and appears conducive to scaleup.