Access to Nanostructured Hydrogel Networks through Photocured Body-Centered Cubic Block Copolymer Melts

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• 作者：Vincent F. Scalfani ; Travis S. Bailey
• 刊名：Macromolecules
• 出版年：2011
• 出版时间：August 23, 2011
• 年：2011
• 卷：44
• 期：16
• 页码：6557-6567
• 全文大小：1104K
• 年卷期：v.44,no.16(August 23, 2011)
• ISSN：1520-5835

文摘

Direct access to nanostructured hydrogel networks through high fidelity photocuring of sphere-forming block copolymer melts is demonstrated. Hydrophobic junction points within the hydrogel network are based on an underlying lattice of body-centered cubic spheres (S_BCC), produced via melt-state self-assembly of blended AB diblock and ABA triblock copolymer amphiphiles. Integrated thermally stable photocuring chemistry allows for in situ trapping of these spherical domains, independent from the required melt processing necessary to achieve the highly ordered BCC lattice. Swelling of the photocured solids in aqueous (and organic) media afforded highly elastic gels exhibiting excellent mechanical properties (G鈥? 10³ Pa) and complete preservation of the cured solid shape. The hydrogels fabricated in this study were produced from partially epoxidized (19.6%, relative to diene repeat units) blends of polybutadiene-b-poly(ethylene oxide) diblock (PB鈥揚EO, f_PB = 0.13, M_n = 29鈥?00 g mol^鈥?, 88.5 mol %) and PB鈥揚EO鈥揚B triblock (f_PB = 0.13, M_n = 59鈥?00 g mol^鈥?, 11.5 mol %) copolymers synthesized via anionic polymerization. Addition of UV-activated cationic photoinitiator (4-iodophenyl)diphenylsulfonium triflate (0.5 mol %) produced composite samples exhibiting a highly ordered S_BCC morphology after annealing at moderate temperatures (4 h at 80 掳C or 60 s at 140 掳C) above the PEO melting transition. Composite films (0.33 mm thickness) were then photocured directly from the melt state, postanneal. Cured samples retained the S_BCC structure with extremely high fidelity, effectively prestructuring the network of junction points prior to swelling. The photopatterning potential of these uniquely designed hydrogels is also demonstrated.