Abstract
Polymer crystallization affects structural and mechanical properties of polymer thin films. In this study, we focused on the thermal annealing-induced crystallization in semi-crystalline poly(l-lactic acid) (PLLA) ultrathin films (referred as nanosheets) was investigated in terms of interfacial interaction of PLLA with air and substrate. The surface structure of the PLLA nanosheets observed by atomic force microscopy showed that roughness of the air-side surface increased due to crystallization of PLLA under thermal annealing, whereas that of the substrate-side surface changed little. The elastic moduli and the physical adhesiveness of the nanosheets also changed only on the surface of the air side from crystallization, in contrast to the substrate side. The X-ray diffraction studies of the PLLA nanosheets with different thickness showed that the crystalline contents steeply increased below ca. 200 nm. These results indicated that the crystallization was enhanced near the surface of the air side and restricted near that of the substrate side due to the different interfacial association of the polymer chains in the nanosheet.
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References
Keddie, J. L., Jones, R. & Cory, R. A. Size-dependent depression of the glass transition temperature in polymer films. Europhys. Lett. 27, 59 (1994).
Forrest, J., Dalnoki-Veress, K., Stevens, J. & Dutcher, J. Effect of free surfaces on the glass transition temperature of thin polymer films. Phys. Rev. Lett. 77, 2002–2005 (1996).
Forrest, J., Dalnoki-Veress, K. & Dutcher, J. Interface and chain confinement effects on the glass transition temperature of thin polymer films. Phys. Rev. E 56, 5705–5716 (1997).
Kawana, S. & Jones, R. Character of the glass transition in thin supported polymer films. Phys. Rev. E 63, 021501 (2001).
Fukao, K. & Miyamoto, Y. Glass transitions and dynamics in thin polymer films: dielectric relaxation of thin films of polystyrene. Phys. Rev. E Stat. Phys. 61, 1743–1754 (2000).
Ellison, C. J. & Torkelson, J. M. The distribution of glass-transition temperatures in nanoscopically confined glass formers. Nat. Mater. 2, 695–700 (2003).
Ellison, C., Ruszkowski, R., Fredin, N. & Torkelson, J. Dramatic reduction of the effect of nanoconfinement on the glass transition of polymer films via addition of small-molecule diluent. Phys. Rev. Lett. 92, 095702 (2004).
Tsui, O. K. C., Russell, T. P. & Hawker, C. J. effect of interfacial interactions on the glass transition of polymer thin films. Macromolecules 34, 5535–5539 (2001).
Kanaya, T., Miyazaki, T., Watanabe, H., Nishida, K., Yamano, H., Tasaki, S. & Bucknall, D. B. Annealing effects on thickness of polystyrene thin films as studied by neutron reflectivity. Polymer 44, 3769–3773 (2003).
Kanaya, T., Inoue, R., Kawashima, K., Miyazaki, T., Tsukushi, I., Shibata, K., Matsuba, G., Nishida, K. & Hino, M. Glassy dynamics and heterogeneity of polymer thin films. J. Phys. Soc. Jpn. 78, 041004 (2009).
Inoue, R., Kanaya, T., Nishida, K., Tsukushi, I. & Shibata, K. Inelastic neutron scattering study of low energy excitations in polymer thin films. Phys. Rev. Lett. 95, 056102 (2005).
Inoue, R., Kanaya, T., Nishida, K., Tsukushi, I., Telling, M., Gabrys, B., Tyagi, M., Soles, C. & Wu, W. L. Glass transition and molecular mobility in polymer thin films. Phys. Rev. E Stat. Nonlin. Soft Matter Phys. 80, 031802 (2009).
Tisato, K., Keiji, T. & Atsushi, T. Study of the surface glass transition behaviour of amorphous polymer film by scanning-force microscopy and surface spectroscopy. Polymer 39, 4665–4673 (1998).
Satomi, N., Takahara, A. & Kajiyama, T. Determination of surface glass transition temperature of monodisperse polystyrene based on temperature-dependent scanning viscoelasticity microscopy. Macromolecules 32, 4474–4476 (1999).
Keddie, J. L., Richard, A. L. & Cory, R. A. Interface and surface effects on the glass-transition temperature in thin polymer films. Farad. Discuss. 98, 219–230 (1994).
Tanaka, K., Tateishi, Y., Okada, Y. & Nagamura, T. Interfacial mobility of polymers on inorganic solids. J. Phys. Chem. B 113, 4571–4577 (2009).
Despotopoulou, M. M., Miller, R. D., Rabolt, J. F. & Frank, C. W. Polymer chain organization and orientation in ultrathin films: a spectroscopic investigation. J. Polym. Sci. B Polym. Phys. 34, 2335–2349 (1998).
Wang, Y., Chan, C.-M., Ng, K.-M. & Li, L. What controls the lamellar orientation at the surface of polymer films during crystallization? Macromolecules 41, 2548–2553 (2008).
Garlotta, D. A literature review of poly (lactic acid). J. Polym. Environ. 9, 63–84 (2001).
Okamura, Y., Kabata, K., Kinoshita, M., Saitoh, D. & Takeoka, S. Free-standing biodegradable poly(lactic acid) nanosheet for sealing operations in surgery. Adv. Mater. 21, 4388–4392 (2009).
Miyazaki, H., Kinoshita, M., Saito, A., Fujie, T., Kabata, K., Hara, E., Ono, S., Takeoka, S. & Saitoh, D. An ultrathin poly(L-lactic acid) nanosheet as a burn wound dressing for protection against bacterial infection. Wound Repair Regen. 20, 573–579 (2012).
Fujie, T., Kawamoto, Y., Haniuda, H., Saito, A., Kabata, K., Honda, Y., Ohmori, E., Asahi, T. & Takeoka, S. Selective molecular permeability induced by glass transition dynamics of semicrystalline polymer ultrathin films. Macromolecules 46, 395–402 (2013).
Zhokhavets, U., Erb, T., Gobsch, G., Al-Ibrahim, M. & Ambacher, O. Relation between absorption and crystallinity of poly(3-hexylthiophene)/fullerene films for plastic solar cells. Chem. Phys. Lett. 418, 347–350 (2006).
Zhang, Q. M., Xu, H., Fang, F., Cheng, Z. Y., Xia, F. & You, H. Critical thickness of crystallization and discontinuous change in ferroelectric behavior with thickness in ferroelectric polymer thin films. J. Appl. Phys. 89, 2613 (2001).
Rats, D., Hajek, V. & Martinu, L. Micro-scratch analysis and mechanical properties of plasma-deposited silicon-based coatings on polymer substrates. Thin Solid Films 340, 33–39 (1999).
Kalb, B. & Pennings, A. J. General crystallization behaviour of poly (L-lactic acid). Polymer 21, 607–612 (1980).
Langford, J. I. A rapid method for analysing the breadths of diffraction and spectral lines using the Voigt function. J. Appl. Crystallogr. 11, 10–14 (1978).
Peng, Z. L. & Chen, S. H. Effects of surface roughness and film thickness on the adhesion of a bioinspired nanofilm. Phys. Rev. E Stat. Nonlin. Soft Matter Phys. 83, 051915 (2011).
Yang, Z., Fujii, Y., Lee, F. K., Lam, C. H. & Tsui, O. K. C. Glass transition dynamics and surface layer mobility in unentangled polystyrene films. Science 328, 1676–1679 (2010).
Paeng, K., Swallen, S. F. & Ediger, M. D. Direct measurement of molecular motion in freestanding polystyrene thin films. J. Am. Chem. Soc. 133, 8444–8447 (2011).
Acknowledgements
We acknowledge funding by the Global COE program for Practical Chemical Wisdom, the project for High-Tech Research Center and the ‘Leading Graduate Program in Science and Engineering, Waseda University’ from MEXT, Japan. And this work was supported in part by JSPS KAKENHI (Grant Number 15H05355 for TF and 25289252 for ST) from MEXT, Japan and Mizuho Foundation for the Promotion of Science for TF.
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Udagawa, A., Fujie, T., Kawamoto, Y. et al. Interfacial effects on the crystallization and surface properties of poly(l-lactic acid) ultrathin films. Polym J 48, 157–161 (2016). https://doi.org/10.1038/pj.2015.95
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DOI: https://doi.org/10.1038/pj.2015.95
