Complex Thin Film Morphologies of Poly(n-hexyl isocyanate)(5k,10k)鈥揚oly(蔚-caprolactone)1鈥?(10k,17k) Miktoarm Star Polymers

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• 作者：Rarm Phinjaroenphan ; Young Yong Kim ; Brian J. Ree ; Takuya Isono ; Jinseok Lee ; Supagorn Rugmai ; Heesoo Kim ; Santi Maensiri ; Toyoji Kakuchi ; Toshifumi Satoh ; Moonhor Ree
• 刊名：Macromolecules
• 出版年：2015
• 出版时间：August 25, 2015
• 年：2015
• 卷：48
• 期：16
• 页码：5816-5833
• 全文大小：1044K
• ISSN：1520-5835

文摘

Two series of crystalline鈥揷rystalline miktoarm star polymers were prepared and their thin film morphologies were investigated in detail by synchrotron grazing incidence X-ray scattering (GIXS): poly(n-hexyl isocyanate)(5000)鈥損oly(蔚-caprolactone)_1鈥?(17000) (PHIC(5k)鈥揚CL_1鈥?(17k)) and poly(n-hexyl isocyanate)(10000)鈥損oly(蔚-caprolactone)_1鈥?(10000) (PHIC(10k)鈥揚CL_1鈥?(10k)). In addition, their thermal properties were examined. All miktoarm star polymers revealed a two-step thermal degradation behavior where the PHIC arm was degraded first, followed by the PCL arm underwent degradation. Interestingly, all miktoarms were found to show a highly enhanced thermal stability, regardless of their molecular weight over 3k to 17k, which might be attributed to their one-end group capped with the counterpart arm(s) via arm-joint formation. Surprisingly, all miktoarm star polymers always developed only lamellar structure in toluene- and chloroform-annealed films via phase-separation, regardless of the length of PHIC arm as well as the length and number of PCL arm. Despite having highly imbalanced volume fractions, lamellar structure was constructed in the films of miktoarm star polymers through the override of volume fraction rule based on the rigid chain properties, self-assembling characteristics, conformational asymmetry, and compressibilities of PHIC and PCL arms. Furthermore, the orientation of such lamellar structures was controlled by the selection of either toluene or chloroform in the solvent-annealing process. The PHIC arm phases in the lamellar structures favorably formed a mixture of edge-on and face-on structures with fully extended backbone and bristle conformations even under the confined lamellar geometry and arm-joint. The PCL arm phases still crystallized, forming fringed-micelle like structures in which orthorhombic crystals were laterally grown along the in-plane direction of lamellae although their crystallization was somewhat suppressed by the confined lamellar geometry and arm-joint. Overall, crystalline鈥揷rystalline PHIC鈥揚CL_1鈥? miktoarm polymers demonstrated very interesting but unusual, very complex hierarchical structures in the solvent-annealed thin films.