矽氣凝膠以其多樣的孔徑分佈和獨特的表面特性，為研究聚合物在受限環境下的結晶行為提供了一個獨特的平台。本論文旨在揭示聚乙二醇（PEG）在疏水性和親水性矽氣凝膠孔隙中的複雜結晶行為。PEG的引入方法包括將氣凝膠粉末分散在PEG水溶液中，然後通過控制乾燥和隨後的熔融滲透進行處理。
結果表明，PEG在溶液狀態下容易滲透到親水性氣凝膠的孔隙中，但熔融滲透並未顯著增強其滲透能力。相反，疏水性氣凝膠由於其疏水性質，阻礙了水溶液的流動，使得只有少量PEG進入大孔隙，大部分PEG留在疏水性氣凝膠的表面。然而，這些附著在表面的PEG分子最終通過熔融滲透進入內孔隙。
通過差示掃描量熱法（DSC）探測的非等溫結晶結果表明，當PEG被引入親水性氣凝膠中時，會發生分級結晶，並且結晶速率適度減緩。另一方面，疏水性氣凝膠對PEG結晶施加了強烈的限制效應，導致結晶速率顯著降低並伴隨著分級結晶。對於分子量為2000 g/mol的PEG，觀察到一種受均相成核控制的結晶現象。然而，這種成核機制的劇變歸因於氣凝膠顆粒催化引發的熱降解現象，PEG的分子量下降。極短的PEG分子進一步滲透到氣凝膠的微孔中，由於缺乏足夠的異相成核位點，其結晶只能通過均相成核進行。
本研究突出了氣凝膠表面特性和滲透方法對PEG結晶行為的顯著影響，提供了關於矽氣凝膠所提供的聚合物結晶複雜受限效應的寶貴見解。所得知識可應用於先進材料的設計，並增強我們對聚合物在受限空間中結晶行為的理解。

Silica aerogels, characterized by varying pore size distributions and distinct surface properties, provide a unique platform for investigating the confinement-mediated crystallization of polymers. This thesis aims to unveil the intricate crystallization behavior of poly(ethylene glycol) (PEG) within the pores of both hydrophobic and hydrophilic silica aerogels. The incorporation of PEG into the aerogels involves dispersing aerogel powders into PEG aqueous solutions, followed by controlled drying and subsequent melt infiltration.
Our experimental results show that PEG easily permeates the pores of hydrophilic aerogels when in solution, but melt infiltration does not significantly enhance PEG penetration into these voids. Conversely, the hydrophobic nature of the aerogel resists the flow of the aqueous solution, allowing only a small fraction of PEG to enter the macropores, with the majority of PEG remaining on the surface of the hydrophobic aerogel. However, these surface-bound PEG molecules eventually infiltrate the inner pores through melt infiltration.
The nonisothermal crystallization probed by differential scanning calorimetry (DSC) reveals that fractionated crystallization of PEG occurs with moderately retarded crystallization rate when incorporating into the hydrophilic aerogels. On the other hand, the hydrophobic aerogel imposes a strong confinement on PEG crystallization, leading to significant reduction of crystallization rate associated with the fractionated crystallization. A homogeneous nucleation-controlled crystallization is observed for the PEG with 2000 g/mol molecular weight. Such a drastic change of nucleation mechanism is however attributed to the occurrence of thermal degradation catalyzed by the aerogel particles, which significantly reduces the chain lengths of PEG. The very short PEG molecules further infiltrates into the micropores of the aerogels, such that their crystallization has to proceed through homogeneous nucleation due to the lack of sufficient heterogeneous nuclei.
This study highlights the significant impact of aerogel surface properties and infiltration methods on PEG crystallization behavior, providing valuable insights into the complex confinement effect on polymer crystallization offered by the silica aerogels. The knowledge gained can be applied to the design of advanced materials and enhances our understanding of polymer crystallization behavior in confined spaces.

1. Feng, J., et al., Printed aerogels: chemistry, processing, and applications. Chemical Society Reviews, 2021. 50(6): p. 3842-3888.
2. Kistler, S.S., Coherent Expanded Aerogels and Jellies. Nature, 1931. 127(3211): p. 741-741.
3. Pekala, R.W., Organic aerogels from the polycondensation of resorcinol with formaldehyde. Journal of Materials Science, 1989. 24(9): p. 3221-3227.
4. Yu, C. and Y.S. Song Phase Change Material (PCM) Composite Supported by 3D Cross-Linked Porous Graphene Aerogel. Materials, 2022. 15, DOI: 10.3390/ma15134541.
5. Azum, N., et al., Chapter 19 - Aerogel applications and future aspects, in Advances in Aerogel Composites for Environmental Remediation, A.A.P. Khan, et al., Editors. 2021, Elsevier. p. 357-367.
6. Maleki, H., L. Durães, and A. Portugal, An overview on silica aerogels synthesis and different mechanical reinforcing strategies. Journal of Non-Crystalline Solids, 2014. 385: p. 55-74.
7. Li, C., et al., A review of silicon-based aerogel thermal insulation materials: Performance optimization through composition and microstructure. Journal of Non-Crystalline Solids, 2021. 553: p. 120517.
8. Kim, H., et al., Eco-Friendly Synthesis of Water-Glass-Based Silica Aerogels via Catechol-Based Modifier. Nanomaterials (Basel), 2020. 10(12).
9. Duan, Y., et al., Hydrophobic silica aerogels by silylation. Journal of Non-Crystalline Solids, 2016. 437: p. 26-33.
10. Aghabararpour, M., et al., Mechanical properties of isocyanate crosslinked resorcinol formaldehyde aerogels. Journal of Non-Crystalline Solids, 2018. 481: p. 548-555.
11. Malfait, W.J., et al., Surface Chemistry of Hydrophobic Silica Aerogels. Chemistry of Materials, 2015. 27(19): p. 6737-6745.
12. Khedkar, M.V., et al., Physicochemical properties of ambient pressure dried surface modified silica aerogels: effect of pH variation. SN Applied Sciences, 2020. 2(4): p. 696.
13. Cai, H., et al., Preparation of silica aerogels with high temperature resistance and low thermal conductivity by monodispersed silica sol. Materials & Design, 2020. 191: p. 108640.
14. Sing, K.S.W., Reporting physisorption data for gas/solid systems with special reference to the determination of surface area and porosity (Recommendations 1984). 1985. 57(4): p. 603-619.
15. Yang, K., et al., Structural analysis of embedding polyethylene glycol in silica aerogel. Microporous and Mesoporous Materials, 2021. 310: p. 110636.
16. Güzel Kaya, G. and H. Deveci, MORPHOLOGICAL, TEXTURAL AND THERMAL PROPERTIES OF LOW-COST SILICA AEROGEL COMPOSITES. Konya Journal of Engineering Sciences, 2021. 9(3): p. 787-796.
17. Tang, X., W. Chen, and L. Li, The Tough Journey of Polymer Crystallization: Battling with Chain Flexibility and Connectivity. Macromolecules, 2019. 52(10): p. 3575-3591.
18. Celikbilek Ersundu, M., A.E. Ersundu, and Ş. Aydın, Crystallization Kinetics of Amorphous Materials. 2012. p. 127-162.
19. Zitzenbacher, G., et al., Calculation of the Contact Angle of Polymer Melts on Tool Surfaces from Viscosity Parameters. Polymers (Basel), 2017. 10(1).
20. Atiyah, A., LECTURE 2 HOMOGENEOUS NUCLEATION. 2016.
21. TEC Science. Heterogeneous Nucleation. Retrieved from https://www.tec-science.com/material-science/solidification-of-metals/heterogeneous-nucleation/".
22. Snyder, C.R., H. Marand, and M.L. Mansfield, Lateral Substrate Completion Rate in the Lauritzen−Hoffman Secondary Surface Nucleation Theory:  Nature of the Friction Coefficient. Macromolecules, 1996. 29(23): p. 7508-7513.
23. Cheng, S.Z.D. and B. Lotz, Enthalpic and entropic origins of nucleation barriers during polymer crystallization: the Hoffman–Lauritzen theory and beyond. Polymer, 2005. 46(20): p. 8662-8681.
24. Hoffman, J.D., et al., Relationship between the lateral surface free energy .sigma. and the chain structure of melt-crystallized polymers. Macromolecules, 1992. 25(8): p. 2221-2229.
25. Toda, A., K. Taguchi, and K. Nozaki, Gibbs–Thomson, Thermal Gibbs–Thomson, and Hoffman–Weeks Plots of Polyethylene Crystals Examined by Fast-Scan Calorimetry and Small-Angle X-ray Scattering. Crystal Growth & Design, 2019. 19(4): p. 2493-2502.
26. Toda, A., et al., Crystallization and melting behaviors of poly(vinylidene fluoride) examined by fast-scan calorimetry: Hoffman-Weeks, Gibbs-Thomson and thermal Gibbs-Thomson plots. Polymer, 2019. 169: p. 11-20.
27. Schick, C., R. Androsch, and J.W.P. Schmelzer, Homogeneous crystal nucleation in polymers. Journal of Physics: Condensed Matter, 2017. 29(45): p. 453002.
28. Chatterjee, A.M. Heterogeneous nucleation in the crystallization of high polymers from the melt. 1974.
29. Liu, G., A.J. Müller, and D. Wang, Confined Crystallization of Polymers within Nanopores. Accounts of Chemical Research, 2021. 54(15): p. 3028-3038.
30. Shi, G., et al., Segmental Dynamics Govern the Cold Crystallization of Poly(lactic acid) in Nanoporous Alumina. Macromolecules, 2019. 52

(18): p. 6904-6912.
31. Nandan, B., J.Y. Hsu, and H.L. Chen, Crystallization Behavior of Crystalline‐Amorphous Diblock Copolymers Consisting of a Rubbery Amorphous Block. Journal of Macromolecular Science, Part C, 2006. 46(2): p. 143-172.
32. Van Horn, R.M., M.R. Steffen, and D. O'Connor, Recent progress in block copolymer crystallization. POLYMER CRYSTALLIZATION, 2018. 1(4): p. e10039.
33. Xu, W., Y. Zheng, and P. Pan, Crystallization-driven self-assembly of semicrystalline block copolymers and end-functionalized polymers: A minireview. Journal of Polymer Science, 2022. 60(15): p. 2136-2152.
34. Nakagawa, S., H. Marubayashi, and S. Nojima, Crystallization of polymer chains confined in nanodomains. European Polymer Journal, 2015. 70: p. 262-275.
35. Badrinarayanan, P., K.B. Dowdy, and M.R. Kessler, A comparison of crystallization behavior for melt and cold crystallized poly (l-Lactide) using rapid scanning rate calorimetry. Polymer, 2010. 51(20): p. 4611-4618.
36. Honda, A., et al., Cold Crystallization and Polymorphism Triggered by the Mobility of the Phenyl Group in Alkyl Azo Dye Molecules. Crystal Growth & Design, 2021. 21(11): p. 6223-6229.
37. Rozwadowski, T., Y. Yamamura, and K. Saito, Interplay between Melt and Cold Crystallization in a Smectic Liquid Crystal, 4-Pentylphenyl 4-(trans-4-Pentylcyclohexyl)benzoate. Crystal Growth & Design, 2021. 21(5): p. 2777-2785.
38. Gu, F., H. Bu, and Z. Zhang, A unique morphology of freeze-dried poly(ethylene oxide) and its transformation. Polymer, 2000. 41(21): p. 7605-7609.
39. Braun, H.-G. and E. Meyer Structure Formation of Ultrathin PEO Films at Solid Interfaces—Complex Pattern Formation by Dewetting and Crystallization. International Journal of Molecular Sciences, 2013. 14, 3254-3264 DOI: 10.3390/ijms14023254.
40. Beech, D.R., et al., Melting of low molecular weight poly(ethylene oxide). Polymer, 1972. 13(2): p. 73-77.
41. Ungar, G. and A. Keller, Time-resolved synchrotron X-ray study of chain-folded crystallization of long paraffins. Polymer, 1986. 27(12): p. 1835-1844.
42. Cheng, S.Z.D., et al., Isothermal thickening and thinning processes in low-molecular-weight poly(ethylene oxide) fractions. 1. From nonintegral-folding to integral-folding chain crystal transitions. Macromolecules, 1991. 24(13): p. 3937-3944.
43. Yuanxin Hea, H.L., Xiang Xiaoc, and Xinyu Zhaod, Polymer Degradation: Category, Mechanism and Development Prospect, in 2021 3rd International Conference on Geoscience and Environmental Chemistry (ICGEC 2021). 2021. p. 7.
44. Afifi-Effat, A.M. and J.N. Hay, The thermal stabilization of polyethylene oxide. European Polymer Journal, 1972. 8(2): p. 289-297.
45. 賴偉淇, 生物可分解高分子PLLA與其摻合物PEG之結構與性質研究, in 材料科學與工程學研究所. 2004, 國立臺灣大學: 台北市. p. 232.
46. Lai, W.-C. and W.-B. Liau, Thermo-oxidative degradation of poly(ethylene glycol)/poly(l-lactic acid) blends. Polymer, 2003. 44(26): p. 8103-8109.
47. Banpean, A., et al., Small- and wide-angle X-ray scattering studies on confined crystallization of Poly(ethylene glycol) in Poly(L-lactic acid) spherulite in a PLLA/PEG blend. Polymer, 2021. 229: p. 123971.
48. Li, M., et al. Interfacial Interactions during Demolding in Nanoimprint Lithography. Micromachines, 2021. 12, DOI: 10.3390/mi12040349.
49. Hongbo, L. and D. Yucheng, Nanoimprint Lithography, in Lithography, W. Michael, Editor. 2010, IntechOpen: Rijeka. p. Ch. 23.
50. Kim, S., G. Kim, and A. Manthiram, A review on infiltration techniques for energy conversion and storage devices: from fundamentals to applications. Sustainable Energy & Fuels, 2021. 5(20): p. 5024-5037.
51. de Jongh, P.E. and T.M. Eggenhuisen, Melt infiltration: an emerging technique for the preparation of novel functional nanostructured materials. Adv Mater, 2013. 25(46): p. 6672-90.
52. Manohar, N., K.J. Stebe, and D. Lee, Effect of Confinement on Solvent-Driven Infiltration of the Polymer into Nanoparticle Packings. Macromolecules, 2020. 53(15): p. 6740-6746.
53. Manohar, N., K.J. Stebe, and D. Lee, Solvent-Driven Infiltration of Polymer (SIP) into Nanoparticle Packings. ACS Macro Letters, 2017. 6(10): p. 1104-1108.
54. Emmerling, A. and J. Fricke, Small angle scattering and the structure of aerogels. Journal of Non-Crystalline Solids, 1992. 145: p. 113-120.