The preparation of polymeric nanoparticles has received significant interest in recent years 1-5. This interest is largely based on the notion that such nanoparticles ranging in size from 10 nm to more than 100 nm may offer enhanced physical, chemical, or biological properties when optimally designed for specific applications. Although the development of discrete nanoparticles with well-defined functionalities and architectures has been a major step toward unlocking the potential application of these organic nanostructures, single chain globules show very distinct characteristics from the normal bulk polymers. Under electron-microscopy single chain globules are the nano-sized particles 5-8 with essentially no entanglement or interpenetration between chains. The existence of such distinguished globules provides great opportunity for understanding the fundamentals of the polymer chains, such as the re-enter of entanglement state. Recent experimental results 9 of the hot-pressed single chain globules reveal that the single chain globules show a strong ability of compression and expansion. We report on an investigation of the fundamentals of single chain globules in the dry state. A theoretical analysis of the compression/expansion of the single chain globules suggests that the expansion can only occur for macromolecules at least with the chain size larger than a critical value. Our work will also help in understanding the basic physics of nano-particles of pauci-polymer chains 10.
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