Study on the thermoresponsive two phase transition processes of hydroxypropyl cellulose concentrated aqueous solution: from a microscopic perspective
- 593 Downloads
In this paper, it was discovered that during the heating process from 35 to 63 °C, hydroxypropyl cellulose (HPC) concentrated aqueous solution (20 wt%) would first go through coil-to-globule transition and then sol–gel transition with temperature elevation. The microdynamic mechanisms of the two phase transitions were thoroughly illustrated using mid and near infrared spectroscopy in combination with two-dimensional correlation spectroscopy (2Dcos) and perturbation correlation moving window (PCMW) technique. Mid infrared spectroscopy is an effective way to study the hydrophobic interactions in HPC molecules. And near infrared spectroscopy is a potent method to study hydrogen bonds between HPC molecules and water molecules. Boltzmann fitting and PCMW could help determine the exact transition temperatures of each involving functional groups in the two processes. Moreover, 2Dcos was used to discern the sequential moving orders of the functional groups during the two phase transitions. Depending on the structure of HPC and the thermodynamic conditions, the dominating associative elements in either process might vary. During the coil-to-globule transition, HPC molecules precipitated to form an opaque system with mobility.It was discovered that the driving force of the coil-to-globule transition process in microdynamics could only be the dehydration and hydrophobic interactions of C–H groups. However, in the sol–gel transition, the system crosslinked to form a physical network with no mobility. The driving force of this process in microdynamics was primarily the self-assembly behavior of O–H groups in HPC “active molecules”.
KeywordsHydroxypropyl cellulose Two-dimensional correlation spectroscopy Coil-to-globule transition Sol–gel transition Hydrophobic interactions Hydrogen bonding
- Alexandridis P, Hatton TA (1995) Poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) block-copolymer surfactants in aqueous-solutions and at interfaces–thermodynamics, structure, dynamics, and modeling. Colloid Surf A- Physicochem Eng Asp 96(1–2):1–46. doi:10.1016/0927-7757(94)03028-x CrossRefGoogle Scholar
- Czarnik-Matusewicz B, Pilorz S, Hawranek JP (2005) Temperature-dependent water structural transitions examined by near-IR and mid-IR spectra analyzed by multivariate curve resolution and two-dimensional correlation spectroscopy. Anal Chim Acta 544(1–2):15–25. doi:10.1016/j.aca.2005.04.040 CrossRefGoogle Scholar
- Lozinsky VI, Simenel IA, Kulakova VK, Kurskaya EA, Babushkina TA, Klimova TP, Burova TV, Dubovik AS, Grinberg VY, Galaev IY, Mattiasson B, Khokhlov AR (2003) Synthesis and studies of N-vinylcaprolactam/N-vinylimidazole copolymers that exhibit the “proteinlike” behavior in aqueous media. Macromolecules 36(19):7308–7323. doi:10.1021/ma034456n CrossRefGoogle Scholar
- Wahlund PO, Galaev IY, Kazakov SA, Lozinsky VI, Mattiasson B (2002) “Protein-like” copolymers: effect of polymer architecture on the performance in bioseparation process. Macromol Biosci 2(1):33–42. doi:10.1002/1616-5195(20020101)2:1<33:aid-mabi33>3.3.co;2-1 CrossRefGoogle Scholar