Our previous research [27] has investigated the effects of the monomer composition, crosslinking agent content, blowing agent type, and content on the morphology and blowing agent encapsulation efficiency of the microspheres, and found out the porous and non-core-shell structure microspheres with a low encapsulation efficiency of blowing agent were formed when VDC was copolymerized with individual AN or MMA, whereas microspheres with a core-shell structure and a high encapsulation efficiency of blowing agent were formed when the feeding monomer mass ratios of VDC-AN-MMA were 50/20/30, 60/20/20, and 70/20/10. Addition of 0.2-0.4 wt% divinyl benzene crosslinking agent facilitated the formation of the core-shell structure microspheres with a high encapsulation efficiency of blowing agent. Microspheres with wrinkled surfaces and a pronounced internal topography were formed as the carbon atom number of isopentane, pentane, hexane, and heptane increased from 5 to 7, but it was favorable to improvement of encapsulation efficiency of blowing agent. However, further studies have found that microspheres with a core-shell structure or a high encapsulation efficiency of blowing agent were the necessary conditions for microspheres expansion. But it does not mean that there must be a splendid expansion property. Because the expansion properties of microspheres are determined by \(T_{\rm g}\), viscoelastic properties and internal gas pressure generated by the blowing agent during the expansion process. When they are matched properly, microspheres will have excellent expansion properties. However, the systematic relationship among the polymer properties, blowing agent, and the expansion properties of thermally expandable microspheres has not been established. The encapsulated content of the blowing agent is an important factor in determining the expansion properties of microspheres. The barrier performance of the shell polymer of the microspheres is crucial in preventing it from spreading outward. Otherwise, the escaping of blowing agent will not provide enough internal gas pressure to drive the microspheres expansion. [PERSON] et al. have proposed that the polymer shell layer barrier performance can be characterized by the density of the cohesion [PERSON] et al. (2018). The homopolymers formed by AN or VDC are semi-crystalline polymers with excellent barrier properties. Therefore, VDC and AN are particularly used as the primary monomers for the preparation of low-temperature thermally expandable microspheres [PERSON] et al. (2018); [PERSON] et al. (2018). In this study, VDC, MMA, or/and AN as the monomers were used for obtaining the low-temperature thermally expandable copolymer microspheres having low expansion start. The encapsulated content of blowing agent in microspheres is a key factor in the expansion properties of thermally expandable microspheres. Low boiling point blowing agents, especially in low-temperature thermally expandable microspheres, are easily dissipated during storage and transport by the permeation diffusion or volatilization through micropore of the shell polymer. Therefore, it is of great significance to study the diffusion characteristics of blowing agent in polymer microspheres for selecting suitable storage conditions of thermally expandable microspheres. In this paper, the effects of the composition, \(T_{\rm g}\), crosslinking degree, blowing agent type, and \(E_{\rm r}\) on the expansion properties of vinylidene chloride copolymer thermally expandable microspheres were studied. The diffusion properties of blowing agent in VDC-MMA-AN copolymer microspheres were investigated, and the storage and transport conditions of low-temperature vinylidene chloride copolymer thermally expandable microspheres were explored.