CO2 switchable hollow nanospheres

Meng Mu; Xinjie Luo; Wei Wang; Hongyao Yin; Yujun Feng

doi:10.1016/j.jcis.2018.03.020

CO₂ switchable hollow nanospheres

J Colloid Interface Sci. 2018 Jul 15:522:10-19. doi: 10.1016/j.jcis.2018.03.020. Epub 2018 Mar 8.

Authors

Meng Mu¹, Xinjie Luo², Wei Wang¹, Hongyao Yin², Yujun Feng³

Affiliations

¹ Chengdu Institute of Organic Chemistry, Chinese Academy of Sciences, Chengdu 610041, PR China; University of Chinese Academy of Sciences, Beijing 100049, PR China.
² Polymer Research Institute, State Key Laboratory of Polymer Materials Engineering, Sichuan University, Chengdu 610065, PR China.
³ Chengdu Institute of Organic Chemistry, Chinese Academy of Sciences, Chengdu 610041, PR China; Polymer Research Institute, State Key Laboratory of Polymer Materials Engineering, Sichuan University, Chengdu 610065, PR China. Electronic address: yjfeng@scu.edu.cn.

PMID: 29574264
DOI: 10.1016/j.jcis.2018.03.020

Abstract

Hypothesis: Hollow nanospheres, characterized by a cavity inside a solid shell, have potential applications due to their unique structure, but the unchangeable morphology and permeability of the shell restrain their further practical utilization. While several smart hollow nanospheres that can respond to pH, ion strength, and temperature have been developed, they are inclined to suffer from problems associated with high energy consumption or the difficult removal of residual stimulants. Thus, it is desirable to develop a novel and free-of-residual trigger stimulating mode.

Experiments: In this work, CO₂ is used to fabricate smart hollow nanospheres composed of crosslinked poly(diethylamino-ethyl methacrylate) (PDEAEMA) network from polystyrene (PS)/PDEAEMA core-shell nanospheres by a template-removal technique. The morphology evolution of the resultant nanospheres during the fabrication process was characterized by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), thermogravimetry analysis (TGA) and dynamic light scattering (DLS) and was visualized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM).

Findings: Hollow nanospheres can be generated by experiencing a morphology change from a core nanosphere, core-shell, yolk-shell to a final hollow structure. The increase in shell-stiffness can restrain the collapse of hollow spheres. It is demonstrated that CO₂ is easy to introduce and remove (via N₂ input) without stimulation residues in this system. In addition, mild CO₂/N₂ purging can only reversibly change the swelling/collapse of hollow particles; violent CO₂/N₂ bubbling can reversibly regulate both the size and aggregation/re-dispersion state of the hollow nanospheres, which can be intuitively observed by atomic force microscopy (AFM).

Keywords: Aggregation/redispersion transition; CO(2)-switchability; Hollow nanospheres; Protonation–deprotonation; Swelling/deswelling transition.