51
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Dittrich J, Kather M, Holzberger A, Pich A, Gohlke H. Cumulative Submillisecond All-Atom Simulations of the Temperature-Induced Coil-to-Globule Transition of Poly(N-vinylcaprolactam) in Aqueous Solution. Macromolecules 2020. [DOI: 10.1021/acs.macromol.0c01896] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Affiliation(s)
- Jonas Dittrich
- Institute for Pharmaceutical and Medicinal Chemistry, Heinrich Heine University Düsseldorf, 40225 Düsseldorf, Germany
- Bioeconomy Science Center (BioSC), Forschungszentrum Jülich, 52425 Jülich, Germany
| | - Michael Kather
- DWI-Leibniz-Institute for Interactive Materials, RWTH Aachen University, 52056 Aachen, Germany
- Institute of Technical and Macromolecular Chemistry, RWTH Aachen University, 52074 Aachen, Germany
| | - Anna Holzberger
- DWI-Leibniz-Institute for Interactive Materials, RWTH Aachen University, 52056 Aachen, Germany
- Institute of Technical and Macromolecular Chemistry, RWTH Aachen University, 52074 Aachen, Germany
| | - Andrij Pich
- Bioeconomy Science Center (BioSC), Forschungszentrum Jülich, 52425 Jülich, Germany
- DWI-Leibniz-Institute for Interactive Materials, RWTH Aachen University, 52056 Aachen, Germany
- Institute of Technical and Macromolecular Chemistry, RWTH Aachen University, 52074 Aachen, Germany
| | - Holger Gohlke
- Institute for Pharmaceutical and Medicinal Chemistry, Heinrich Heine University Düsseldorf, 40225 Düsseldorf, Germany
- Bioeconomy Science Center (BioSC), Forschungszentrum Jülich, 52425 Jülich, Germany
- John von Neumann Institute for Computing (NIC), Jülich Supercomputing Centre (JSC), Institute of Biological Information Processing (IBI-7: Structural Biochemistry), Forschungszentrum Jülich GmbH, 52425 Jülich, Germany
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52
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Comparison based on statistical thermodynamics between globule-to-coil transition of poly(N-isopropylacrylamide) and cold denaturation of a protein. J Mol Liq 2020. [DOI: 10.1016/j.molliq.2020.114129] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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53
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Entropy Rules: Molecular Dynamics Simulations of Model Oligomers for Thermoresponsive Polymers. ENTROPY 2020; 22:e22101187. [PMID: 33286955 PMCID: PMC7597358 DOI: 10.3390/e22101187] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/20/2020] [Revised: 10/02/2020] [Accepted: 10/09/2020] [Indexed: 11/17/2022]
Abstract
We attempted to attain atomic-scale insights into the mechanism of the heat-induced phase transition of two thermoresponsive polymers containing amide groups, poly(N-isopropylacrylamide) (PNIPAM) and poly(2-isopropyl-2-oxazoline) (PIPOZ), and we succeeded in reproducing the existence of lower critical solution temperature (LCST). The simulation data are in accord with experimental findings. We found out that the entropy has an important contribution to the thermodynamics of the phase separation transition. Moreover, after decomposing further the entropy change to contributions from the solutes and from the solvent, it appeared out that the entropy of the solvent has the decisive share for the lowering of the free energy of the system when increasing the temperature above the LCST. Our conclusion is that the thermoresponsive behavior is driven by the entropy of the solvent. The water molecules structured around the functional groups of the polymer that are exposed to contact with the solvent in the extended conformation lower the enthalpy of the system, but at certain temperature the extended conformation of the polymer collapses as a result of dominating entropy gain from “released” water molecules. We stress also on the importance of using more than one reference molecule in the simulation box at the setup of the simulation.
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54
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Quoika PK, Podewitz M, Wang Y, Kamenik AS, Loeffler JR, Liedl KR. Thermosensitive Hydration of Four Acrylamide-Based Polymers in Coil and Globule Conformations. J Phys Chem B 2020; 124:9745-9756. [PMID: 33054215 PMCID: PMC7604866 DOI: 10.1021/acs.jpcb.0c07232] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
![]()
To
characterize the thermosensitive coil–globule transition in
atomistic detail, the conformational dynamics of linear polymer chains
of acrylamide-based polymers have been investigated at multiple temperatures.
Therefore, molecular dynamic simulations of 30mers of polyacrylamide
(AAm), poly-N-methylacrylamide (NMAAm), poly-N-ethylacrylamide (NEAAm), and poly-N-isopropylacrylamide
(NIPAAm) have been performed at temperatures ranging from 250 to 360
K for 2 μs. While two of the polymers are known to exhibit thermosensitivity
(NEAAm, NIPAAm), no thermosensitivity is observed for AAm and NMAAm
in aqueous solution. Our computer simulations consistently reproduce
these properties. To understand the thermosensitivity of the respective
polymers, the conformational ensembles at different temperatures have
been separated according to the coil–globule transition. The
coil and globule conformational ensembles were exhaustively analyzed
in terms of hydrogen bonding with the solvent, the change of the solvent
accessible surface, and enthalpic contributions. Surprisingly, independent
of different thermosensitive properties of the four polymers, the
surface affinity to water of coil conformations is higher than for
globule conformations. Therefore, polymer–solvent interactions
stabilize coil conformations at all temperatures. Nevertheless, the
enthalpic contributions alone cannot explain the differences in thermosensitivity.
This clearly implies that entropy is the distinctive factor for thermosensitivity.
With increasing side chain length, the lifetime of the hydrogen bonds
between the polymer surface and water is extended. Thus, we surmise
that a longer side chain induces a larger entropic penalty due to
immobilization of water molecules.
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Affiliation(s)
- Patrick K Quoika
- Institute of General, Inorganic and Theoretical Chemistry, and Centre of Molecular Biosciences University of Innsbruck, Innsbruck, A-6020 Austria
| | - Maren Podewitz
- Institute of General, Inorganic and Theoretical Chemistry, and Centre of Molecular Biosciences University of Innsbruck, Innsbruck, A-6020 Austria
| | - Yin Wang
- Institute of General, Inorganic and Theoretical Chemistry, and Centre of Molecular Biosciences University of Innsbruck, Innsbruck, A-6020 Austria
| | - Anna S Kamenik
- Institute of General, Inorganic and Theoretical Chemistry, and Centre of Molecular Biosciences University of Innsbruck, Innsbruck, A-6020 Austria
| | - Johannes R Loeffler
- Institute of General, Inorganic and Theoretical Chemistry, and Centre of Molecular Biosciences University of Innsbruck, Innsbruck, A-6020 Austria
| | - Klaus R Liedl
- Institute of General, Inorganic and Theoretical Chemistry, and Centre of Molecular Biosciences University of Innsbruck, Innsbruck, A-6020 Austria
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55
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A molecular brush with thermoresponsive poly(2-ethyl-2-oxazoline) side chains: a structural investigation. Colloid Polym Sci 2020. [DOI: 10.1007/s00396-020-04704-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
AbstractThe thermoresponsive behavior of a poly(2-oxazoline)-based molecular brush is investigated in aqueous solution. The molecular brush under study, PiPOx100-g-PEtOx17, has a poly(2-isopropenyl-2-oxazoline) (PiPOx) backbone grafted with thermoresponsive poly(2-ethyl-2-oxazoline) (PEtOx) side chains. Since the backbone degree of polymerization is only a factor of ~ 6 higher than the ones of the side chains, it features an architecture between a star-like polymer and a comb-like polymer. Its aqueous solution exhibits lower critical solution temperature (LCST) behavior with a cloud point temperature Tcp = 40.5 °C at 30 g L−1. The temperature-dependent structural evolution is disclosed using dynamic light scattering (DLS) and small-angle neutron scattering (SANS). An increase of the molecular brush size is found upon heating from room temperature to Tcp, which is attributed to the extension of the backbone resulting from the dehydration and collapse of the side chains. Above Tcp, the size decreases again, which indicates the collapse of the whole molecular brush. Large aggregates are found to be present in the solution in the temperature range 25–50 °C. These become more compact, as the temperature is increased across Tcp.
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56
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Mu Q, Zhang Q, Yu W, Su M, Cai Z, Cui K, Ye Y, Liu X, Deng L, Chen B, Yang N, Chen L, Tao L, Wei Y. Robust Multiscale-Oriented Thermoresponsive Fibrous Hydrogels with Rapid Self-Recovery and Ultrafast Response Underwater. ACS APPLIED MATERIALS & INTERFACES 2020; 12:33152-33162. [PMID: 32584536 DOI: 10.1021/acsami.0c06164] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Hydrogels with ultrafast response to environmental stimuli, possessing robust structural integrity and rapid self-recovery, have been considered as promising platforms for numerous applications, for example, in biomimetic materials and nanomedicine. Inspired by the bundled fibrous structure of actin, we developed a robust and ultrafast thermoresponsive fibrous hydrogel (TFH) by fully utilizing the weak noncovalent bonds and strong covalently cross-linked semiflexible electrospun fibrous nets. The TFH exhibits an ultrafast response (within 10 s), rapid self-recovery rate (74% within 10 s), tunable tensile strength (3-380 kPa), and high toughness (∼1560 J/m2) toward temperature. A multiscale orientation is considered to play a key role in the excellent mechanical properties at the fibrous mesh, fiber, and molecular scales. Furthermore, to take advantage of this TFH adequately, a novel kind of noodle-like hydrogel for thermo-controlled protein sorption based on the TFH is prepared, which exhibits high stability and ultrafast sorption properties. The bioinspired platforms hold promise as artificial skins and "smart" sorption membrane carriers, which provide a unique bioactive environment for tissue engineering and nanomedicine.
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Affiliation(s)
- Qifeng Mu
- State Key Laboratory of Separation Membranes and Membrane Processes, School of Materials Science and Engineering, Tiangong University, Tianjin 300387, China
- Graduate School of Life Science, Hokkaido University, Sapporo 001-0021, Japan
| | - Qingsong Zhang
- State Key Laboratory of Separation Membranes and Membrane Processes, School of Materials Science and Engineering, Tiangong University, Tianjin 300387, China
- State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, Research Center for Analysis and Measurement, Donghua University, Shanghai 201620, China
| | - Wen Yu
- State Key Laboratory of Separation Membranes and Membrane Processes, School of Materials Science and Engineering, Tiangong University, Tianjin 300387, China
| | - Mengling Su
- State Key Laboratory of Separation Membranes and Membrane Processes, School of Materials Science and Engineering, Tiangong University, Tianjin 300387, China
| | - Zhongyu Cai
- Research Institute for Frontier Science, Beijing Advanced Innovation Center for Biomedical Engineering, Beihang University, Beijing 100191, China
| | - Kunpeng Cui
- Graduate School of Life Science, Hokkaido University, Sapporo 001-0021, Japan
| | - Yanan Ye
- Graduate School of Life Science, Hokkaido University, Sapporo 001-0021, Japan
| | - Xiaoyun Liu
- State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, Research Center for Analysis and Measurement, Donghua University, Shanghai 201620, China
| | - Lingli Deng
- State Key Laboratory of Separation Membranes and Membrane Processes, School of Materials Science and Engineering, Tiangong University, Tianjin 300387, China
| | - Bingjie Chen
- State Key Laboratory of Separation Membranes and Membrane Processes, School of Materials Science and Engineering, Tiangong University, Tianjin 300387, China
| | - Ning Yang
- State Key Laboratory of Separation Membranes and Membrane Processes, School of Materials Science and Engineering, Tiangong University, Tianjin 300387, China
| | - Li Chen
- State Key Laboratory of Separation Membranes and Membrane Processes, School of Materials Science and Engineering, Tiangong University, Tianjin 300387, China
| | - Lei Tao
- Department of Chemistry, Tsinghua University, Beijing 100084, China
| | - Yen Wei
- Department of Chemistry, Tsinghua University, Beijing 100084, China
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57
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Zanatta M, Tavagnacco L, Buratti E, Chiessi E, Natali F, Bertoldo M, Orecchini A, Zaccarelli E. Atomic scale investigation of the volume phase transition in concentrated PNIPAM microgels. J Chem Phys 2020; 152:204904. [PMID: 32486676 DOI: 10.1063/5.0007112] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Combining elastic incoherent neutron scattering and differential scanning calorimetry, we investigate the occurrence of the volume phase transition (VPT) in very concentrated poly-(N-isopropyl-acrylamide) (PNIPAM) microgel suspensions, from a polymer weight fraction of 30 wt. % up to dry conditions. Although samples are arrested at the macroscopic scale, atomic degrees of freedom are equilibrated and can be probed in a reproducible way. A clear signature of the VPT is present as a sharp drop in the mean square displacement of PNIPAM hydrogen atoms obtained by neutron scattering. As a function of concentration, the VPT gets smoother as dry conditions are approached, whereas the VPT temperature shows a minimum at about 43 wt. %. This behavior is qualitatively confirmed by calorimetry measurements. Molecular dynamics simulations are employed to complement experimental results and gain further insights into the nature of the VPT, confirming that it involves the formation of an attractive gel state between the microgels. Overall, these results provide evidence that the VPT in PNIPAM-based systems can be detected at different time- and length-scales as well as under overcrowded conditions.
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Affiliation(s)
- M Zanatta
- Department of Physics, University of Trento, I-38123 Trento, Italy
| | - L Tavagnacco
- CNR-ISC and Department of Physics, Sapienza University of Rome, I-00185 Roma, Italy
| | - E Buratti
- CNR-ISC and Department of Physics, Sapienza University of Rome, I-00185 Roma, Italy
| | - E Chiessi
- Department of Chemical Sciences and Technologies, University of Rome Tor Vergata, I-00133 Roma, Italy
| | - F Natali
- CNR-IOM, Operative Group in Grenoble (OGG), c/o Institut Laue Langevin, F-38042 Grenoble, France
| | - M Bertoldo
- Department of Chemical and Pharmaceutical Sciences, University of Ferrara, I-44121 Ferrara, Italy
| | - A Orecchini
- Department of Physics and Geology, University of Perugia, I-06123 Perugia, Italy
| | - E Zaccarelli
- CNR-ISC and Department of Physics, Sapienza University of Rome, I-00185 Roma, Italy
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58
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Bredt AJ, Ben-Amotz D. Influence of crowding on hydrophobic hydration-shell structure. Phys Chem Chem Phys 2020; 22:11724-11730. [PMID: 32409791 DOI: 10.1039/d0cp00702a] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The influence of molecular crowding on water structure, and the associated crossover behavior, is quantified using Raman multivariate curve resolution (Raman-MCR) hydration-shell vibrational spectroscopy of aqueous tert-butyl alcohol, 2-butyl alcohol and 2-butoxyethanol solutions of variable concentration and temperature. Changes in the hydration-shell OH stretch band shape and mean frequency are used to identify the temperature at which the hydration-shell crosses over from a more ordered to less ordered structure, relative to pure water. The influence of crowding on the crossover is found to depend on solute size and shape in a way that is correlated with the corresponding infinitely dilute hydration-shell structure (and the corresponding first hydration-shell spectra are invariably very similar to pure water). Analysis of the results using a Muller-like two-state equilibrium between more ordered and less ordered hydration-shell structures implies that crossover temperature changes are dictated primarily by enthalpic stabilization of the more ordered hydration-shell structures.
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Affiliation(s)
- Aria J Bredt
- Purdue University, Department of Chemistry, West Lafayette, IN 47907, USA.
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59
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Kang JJ, Jung FA, Ko CH, Shehu K, Barnsley LC, Kohler F, Dietz H, Zhao J, Pispas S, Papadakis CM. Thermoresponsive Molecular Brushes with Propylene Oxide/Ethylene Oxide Copolymer Side Chains in Aqueous Solution. Macromolecules 2020. [DOI: 10.1021/acs.macromol.0c00263] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Jia-Jhen Kang
- Fachgebiet Physik weicher Materie, Physik-Department, Technische Universität München, James-Franck-Straße 1, 85748 Garching, Germany
| | - Florian A. Jung
- Fachgebiet Physik weicher Materie, Physik-Department, Technische Universität München, James-Franck-Straße 1, 85748 Garching, Germany
| | - Chia-Hsin Ko
- Fachgebiet Physik weicher Materie, Physik-Department, Technische Universität München, James-Franck-Straße 1, 85748 Garching, Germany
| | - Kaltrina Shehu
- Fachgebiet Physik weicher Materie, Physik-Department, Technische Universität München, James-Franck-Straße 1, 85748 Garching, Germany
| | - Lester C. Barnsley
- Jülich Centre for Neutron Science JCNS at Heinz Maier-Leibnitz Zentrum, Forschungszentrum Jülich GmbH, Lichtenbergstraße 1, 85748 Garching, Germany
| | - Fabian Kohler
- Laboratory for Biomolecular Design, Physik-Department, Technische Universität München, Am Coulombwall 4a, 85748 Garching, Germany
| | - Hendrik Dietz
- Laboratory for Biomolecular Design, Physik-Department, Technische Universität München, Am Coulombwall 4a, 85748 Garching, Germany
| | - Junpeng Zhao
- Hefei National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China, Hefei 230026, Anhui, China
- Faculty of Materials Science and Engineering, South China University of Technology, Guangzhou 510640, China
| | - Stergios Pispas
- Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation, 48 Vassileos Constantinou Avenue, 11635 Athens, Greece
| | - Christine M. Papadakis
- Fachgebiet Physik weicher Materie, Physik-Department, Technische Universität München, James-Franck-Straße 1, 85748 Garching, Germany
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60
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Lee CH, Bae YC. Thermodynamic framework for switching the lower critical solution temperature of thermo-sensitive particle gels in aqueous solvent. POLYMER 2020. [DOI: 10.1016/j.polymer.2020.122428] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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61
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Accurate and rapid calculation of hydration free energy and its physical implication for biomolecular functions. Biophys Rev 2020; 12:469-480. [PMID: 32180122 DOI: 10.1007/s12551-020-00686-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/02/2020] [Indexed: 01/19/2023] Open
Abstract
Here we review a new method for calculating a hydration free energy (HFE) of a solute and discuss its physical implication for biomolecular functions in aqueous environments. The solute hydration is decomposed into processes 1 and 2. A cavity matching the geometric characteristics of the solute at the atomic level is created in process 1. Solute-water van der Waals and electrostatic interaction potentials are incorporated in process 2. The angle-dependent integral equation theory combined with our morphometric approach is applied to process 1, and the three-dimensional reference interaction site model theory is employed for process 2. Molecular models are adopted for water. The new method is characterized by the following. Solutes with various sizes including proteins can be treated in the same manner. It is almost as accurate as the molecular dynamics simulation despite its far smaller computational burden. It enables us to handle a solute possessing a significantly large total charge without difficulty. The HFE can be decomposed into a variety of physically insightful, energetic, and entropic components. It is best suited to the elucidation of mechanisms of protein folding, pressure and cold denaturation of a protein, and different types of molecular recognition.
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62
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Ortiz de Solorzano I, Bejagam KK, An Y, Singh SK, Deshmukh SA. Solvation dynamics of N-substituted acrylamide polymers and the importance for phase transition behavior. SOFT MATTER 2020; 16:1582-1593. [PMID: 31951239 DOI: 10.1039/c9sm01798d] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Functional groups present in thermo-responsive polymers are known to play an important role in aqueous solutions by manifesting their coil-to-globule conformational transition in a specific temperature range. Understanding the role of these functional groups and their interactions with water is of great interest as it may allow us to control both the nature and temperature of this coil-to-globule transition. In this work, polyacrylamide (PAAm), poly(N-isopropylacrylamide) (PNIPAm), and poly(N-isopropylmethacrylamide) (PNIPMAm) solvated in water are studied with the goal of discovering the structure of the solvent and its interaction with these polymers in determining the polymer conformations. Specifically, all-atom molecular dynamics (MD) simulations were performed on polymer chains with 30 monomer units (30-mers) at 295 K, 310 K and 320 K, which is below and above the lower critical solution temperature (LCST) of PNIPAm (LCST = 305 K) and PNIPMAm (LCST = 315 K), respectively. The MD simulation trajectories suggest that changes in the functional groups in the backbone and side-chains alter the water solvation shell around the polymer. This results in a change in the residence time probability and hydrogen bond characteristics of water at simulated temperatures. Specifically, water molecules reside for longer times near PAAm (no LCST) and PNIPMAm (LCST = 315 K) chains as compared to PNIPAm. This might be one of the possible causes for the higher LCST of PNIPMAm as compared to that of PNIPAm. These results can guide experimentalists and theoreticians to design new polymer structures with tailor-made LCST transitions while controlling the water solvation shell around the functional group.
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Affiliation(s)
- Isabel Ortiz de Solorzano
- Department of Chemical Engineering, Aragon Institute of Nanoscience (INA), University of Zaragoza, Campus Río Ebro-Edificio I+D, C/Poeta Mariano Esquillor S/N, 50018-Zaragoza, Spain
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63
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Thermodynamic insight into the thermoresponsive behavior of chitosan in aqueous solutions: A differential scanning calorimetry study. Carbohydr Polym 2020; 229:115558. [DOI: 10.1016/j.carbpol.2019.115558] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2019] [Revised: 10/29/2019] [Accepted: 10/29/2019] [Indexed: 11/23/2022]
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64
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Mochizuki K. Reduction of water-mediated repulsion drives poly(N-vinylcaprolactam) collapse upon heating. Phys Chem Chem Phys 2020; 22:1053-1060. [PMID: 31867584 DOI: 10.1039/c9cp05491j] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Thermo-sensitive aqueous polymers undergo a coil-to-globule transition on heating, with drastic chemical and structural changes. We performed molecular dynamics simulations for PVCL in water to study the driving forces for the polymer's collapse.
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Affiliation(s)
- Kenji Mochizuki
- Department of Chemistry and Materials
- Faculty of Textile Science and Technology
- Shinshu University
- Nagano 386-8567
- Japan
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65
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Molecular description of the coil-to-globule transition of Poly(N-isopropylacrylamide) in water/ethanol mixture at low alcohol concentration. J Mol Liq 2020. [DOI: 10.1016/j.molliq.2019.111928] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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66
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Stratigaki M, Baumann C, van Breemen LCA, Heuts JPA, Sijbesma RP, Göstl R. Fractography of poly(N-isopropylacrylamide) hydrogel networks crosslinked with mechanofluorophores using confocal laser scanning microscopy. Polym Chem 2020. [DOI: 10.1039/c9py00819e] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Employing mechanofluorophores in polymer fractography to obtain new information on force-induced events when analyzed by confocal laser scanning microscopy.
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Affiliation(s)
- Maria Stratigaki
- DWI – Leibniz Institute for Interactive Materials
- 52056 Aachen
- Germany
| | - Christoph Baumann
- DWI – Leibniz Institute for Interactive Materials
- 52056 Aachen
- Germany
| | - Lambert C. A. van Breemen
- Department of Mechanical Engineering
- Polymer Technology
- Eindhoven University of Technology
- 5600 MB Eindhoven
- The Netherlands
| | - Johan P. A. Heuts
- Laboratory of Supramolecular Polymer Chemistry
- Institute for Complex Molecular Systems
- Eindhoven University of Technology
- 5600 MB Eindhoven
- The Netherlands
| | - Rint P. Sijbesma
- Laboratory of Supramolecular Polymer Chemistry
- Institute for Complex Molecular Systems
- Eindhoven University of Technology
- 5600 MB Eindhoven
- The Netherlands
| | - Robert Göstl
- DWI – Leibniz Institute for Interactive Materials
- 52056 Aachen
- Germany
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67
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Pérez-Ramírez HA, Odriozola G. A coil-to-globule transition capable coarse-grained model for poly(N-isopropylacrylamide). Phys Chem Chem Phys 2020; 22:17913-17921. [PMID: 32744283 DOI: 10.1039/d0cp03101a] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
We present a model for mesoscopic molecular dynamics simulations of poly(N-isopropyl-acrylamide) (pNIPAM).
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Affiliation(s)
- H. A. Pérez-Ramírez
- Área de Física de Procesos Irreversibles
- División de Ciencias Básicas e Ingeniería
- Universidad Autónoma Metropolitana-Azcapotzalco
- 02200 Ciudad de México
- Mexico
| | - G. Odriozola
- Área de Física de Procesos Irreversibles
- División de Ciencias Básicas e Ingeniería
- Universidad Autónoma Metropolitana-Azcapotzalco
- 02200 Ciudad de México
- Mexico
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68
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Podewitz M, Wang Y, Quoika PK, Loeffler JR, Schauperl M, Liedl KR. Coil-Globule Transition Thermodynamics of Poly( N-isopropylacrylamide). J Phys Chem B 2019; 123:8838-8847. [PMID: 31545046 DOI: 10.1021/acs.jpcb.9b06125] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Thermosensitive polymers such as poly(N-isopropylacrylamide) (PNIPAM) undergo a phase transition in aqueous solution from a random-coil structural ensemble to a globule structural ensemble at the lower critical solution temperature (LCST). Above this temperature, PNIPAM agglomerates and becomes insoluble, whereas it is soluble below the temperature. Thus, thermosensitive polymers represent essential targets for several applications, e.g., in drug delivery. Although their ability to change structure in response to a temperature alteration is highly relevant for industrial processes, their thermodynamic properties are mostly qualitatively understood, and the quantitative thermodynamic picture is still elusive. In this study, we used a combined atomistic molecular dynamics and well-tempered metadynamics simulation approach to estimate coil-globule transition thermodynamics. An isotactic 30-mer of PNIPAM was investigated over a broad temperature range between 200 and 360 K. The transition from the globule to the random-coil structure was observed with well-tempered metadynamics. For the first time, the free energy surface of PNIPAM was estimated and it is shown that the simulation results are in line with the experimentally observed thermosensitive behavior. Below the LCST, the random-coil ensemble represents the global energy minimum and is thermodynamically favored by 21 ± 9 kJ/mol compared to the globule ensemble; both are separated by a barrier of 49 ± 14 kJ/mol. In contrast, above the LCST, the globule ensemble is thermodynamically favored by 21 ± 8 kJ/mol over the random-coil ensemble. The barrier from random-coil to globule is 17 ± 10 kJ/mol.
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Affiliation(s)
- Maren Podewitz
- Institute of General, Inorganic and Theoretical Chemistry, and Center for Molecular Biosciences Innsbruck (CMBI) , University of Innsbruck , Innrain 80-82 , A-6020 Innsbruck , Austria
| | - Yin Wang
- Institute of General, Inorganic and Theoretical Chemistry, and Center for Molecular Biosciences Innsbruck (CMBI) , University of Innsbruck , Innrain 80-82 , A-6020 Innsbruck , Austria
| | - Patrick K Quoika
- Institute of General, Inorganic and Theoretical Chemistry, and Center for Molecular Biosciences Innsbruck (CMBI) , University of Innsbruck , Innrain 80-82 , A-6020 Innsbruck , Austria
| | - Johannes R Loeffler
- Institute of General, Inorganic and Theoretical Chemistry, and Center for Molecular Biosciences Innsbruck (CMBI) , University of Innsbruck , Innrain 80-82 , A-6020 Innsbruck , Austria
| | - Michael Schauperl
- Institute of General, Inorganic and Theoretical Chemistry, and Center for Molecular Biosciences Innsbruck (CMBI) , University of Innsbruck , Innrain 80-82 , A-6020 Innsbruck , Austria
| | - Klaus R Liedl
- Institute of General, Inorganic and Theoretical Chemistry, and Center for Molecular Biosciences Innsbruck (CMBI) , University of Innsbruck , Innrain 80-82 , A-6020 Innsbruck , Austria
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69
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Inoue M, Hayashi T, Hikiri S, Ikeguchi M, Kinoshita M. Mechanism of globule-to-coil transition of poly(N-isopropylacrylamide) in water: Relevance to cold denaturation of a protein. J Mol Liq 2019. [DOI: 10.1016/j.molliq.2019.111374] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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70
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Camara M, Liao H, Xu J, Zhang J, Swai R. Molecular dynamics study of the intercalation and conformational transition of poly (N-vinyl caprolactam), a thermosensitive polymer in hydrated Na-montmorillonite. POLYMER 2019. [DOI: 10.1016/j.polymer.2019.121718] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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71
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Albright V, Palanisamy A, Zhou Q, Selin V, Sukhishvili SA. Functional Surfaces through Controlled Assemblies of Upper Critical Solution Temperature Block and Star Copolymers. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:10677-10688. [PMID: 30346775 DOI: 10.1021/acs.langmuir.8b02535] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Endowing surfaces with multiple advanced functionalities, such as temperature-controlled swelling or the triggered release of functional small molecules, is attractive for a large variety of applications ranging from smart textiles to advanced biomedical applications. This Invited Feature Article summarizes recent advances in the development of upper critical solution temperature (UCST) behavior of copolymers in aqueous solutions and compares the fundamental differences between lower critical solution temperature (LCST) and UCST transitions. The effect of polymer chemistry and architecture on UCST transitions is discussed for block copolymer micelles (BCMs) and star polymers in solution and assembled at surfaces. The inclusion of such nanocontainers (i.e., BCMs and star polymers) in layer-by-layer (LbL) coatings and how to control their responsive behavior through deposition conditions and binding partners is explored. Finally, the inclusion and temperature-triggered release of functional small molecules is explored for nanocontainers in LbL coatings. Taken together, UCST nanocontainers containing LbL films are promising building blocks for the development of new generations of practical, functional surface coatings.
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Affiliation(s)
- Victoria Albright
- Department of Materials Science and Engineering , Texas A&M University , 575 Ross Street , College Station , Texas 77843 , United States
| | - Anbazhagan Palanisamy
- Department of Materials Science and Engineering , Texas A&M University , 575 Ross Street , College Station , Texas 77843 , United States
| | - Qing Zhou
- Department of Materials Science and Engineering , Texas A&M University , 575 Ross Street , College Station , Texas 77843 , United States
| | - Victor Selin
- Department of Materials Science and Engineering , Texas A&M University , 575 Ross Street , College Station , Texas 77843 , United States
| | - Svetlana A Sukhishvili
- Department of Materials Science and Engineering , Texas A&M University , 575 Ross Street , College Station , Texas 77843 , United States
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72
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Pérez-Mas L, Martín-Molina A, Jain RK, Quesada-Pérez M. Effect of dispersion forces on the behavior of thermosensitive nanogels: A coarse-grained simulation study. J Mol Liq 2019. [DOI: 10.1016/j.molliq.2019.111101] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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73
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74
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Yaghoubi Z, Parsa JB. Preparation of thermo-responsive PNIPAAm-MWCNT membranes and evaluation of its antifouling properties in dairy wastewater. MATERIALS SCIENCE & ENGINEERING. C, MATERIALS FOR BIOLOGICAL APPLICATIONS 2019; 103:109779. [PMID: 31349494 DOI: 10.1016/j.msec.2019.109779] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2019] [Revised: 05/10/2019] [Accepted: 05/19/2019] [Indexed: 01/08/2023]
Abstract
A novel MWCNT-PNIPAAm nanocomposite membrane was developed with an excellent cleaning efficiency of thermo-responsive surface. The thermo-responsive N-isopropyle acryleamide (NIPAAm) monomer was polymerized on the surface of MWCNT via free radical polymerization. The prepared MWCNT-PNIPAAm nanocomposite was characterized by FTIR, SEM and TGA analyses. Various amounts of the prepared nanocomposite were incorporated into the membrane matrix by the physical blending method. The resultant membranes showed better surface wettability and pure water flux compared to pristine Polyethersulfone (PES) membrane. Furthermore, after filtration, the COD value of dairy wastewater was reduced to around 90% for all membranes. The thermo-responsive cleaning method was employed to investigate the cleaning efficiency of MWCNT-PNIPAAm membrane for dairy wastewater. The 99.9% flux recovery ratio was obtained for MWCNT-PNIPAAm-0.05% membranes. All these results confirmed that the presence of MWCNT-PNIPAAm nanocomposite in the membrane matrix improves the membrane hydrophilicity and antifouling properties.
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Affiliation(s)
- Zeynab Yaghoubi
- Department of Applied Chemistry, Faculty of Chemistry, Bu-Ali Sina University, Hamedan 65174-38683, Iran
| | - Jalal Basiri Parsa
- Department of Applied Chemistry, Faculty of Chemistry, Bu-Ali Sina University, Hamedan 65174-38683, Iran.
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75
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Pica A, Graziano G. Why does urea have a different effect on the collapse temperature of PDEAM and PNIPAM? J Mol Liq 2019. [DOI: 10.1016/j.molliq.2019.04.071] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
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76
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Plant leaves inspired sunlight-driven purifier for high-efficiency clean water production. Nat Commun 2019; 10:1512. [PMID: 30944322 PMCID: PMC6447597 DOI: 10.1038/s41467-019-09535-w] [Citation(s) in RCA: 56] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2019] [Accepted: 03/15/2019] [Indexed: 12/03/2022] Open
Abstract
Natural vascular plants leaves rely on differences in osmotic pressure, transpiration and guttation to produce tons of clean water, powered by sunlight. Inspired by this, we report a sunlight-driven purifier for high-efficiency water purification and production. This sunlight-driven purifier is characterized by a negative temperature response poly(N-isopropylacrylamide) hydrogel (PN) anchored onto a superhydrophilic melamine foam skeleton, and a layer of PNIPAm modified graphene (PG) filter membrane coated outside. Molecular dynamics simulation and experimental results show that the superhydrophilicity of the relatively rigid melamine skeleton significantly accelerates the swelling/deswelling rate of the PNPG-F purifier. Under one sun, this rational engineered structure offers a collection of 4.2 kg m−2 h−1 and an ionic rejection of > 99% for a single PNPG-F from brine feed via the cooperation of transpiration and guttation. We envision that such a high-efficiency sunlight driven system could have great potential applications in diverse water treatments. Natural leaves can purify water under sunlight through a combination of osmotic pressure, transpiration, and guttation effects. Here the authors design a composite material mimicking these combined effects, achieving sunlight-driven pure water production from brine with high collection rate.
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77
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Wang L, Zhu X, Cai W, Shao X. Understanding the role of water in the aggregation of poly(N,N-dimethylaminoethyl methacrylate) in aqueous solution using temperature-dependent near-infrared spectroscopy. Phys Chem Chem Phys 2019; 21:5780-5789. [PMID: 30801574 DOI: 10.1039/c8cp07153e] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
For understanding the role of water in the aggregation of polymers, the variation of water structures with the structural change of polymers in the process of aggregation was studied by temperature-dependent near-infrared (NIR) spectroscopy. The NIR spectra of the aqueous poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA) solutions of different concentrations were measured at different temperatures. The spectral changes of the polymer and water with temperature were analyzed by N-way principal component analysis (NPCA). It was found that, at low concentration, the chains of the polymer tend to form a loose hydrophobic structure below 36 °C and then aggregate into a micelle at a lower critical solution temperature (LCST) of around 39 °C. In the process of the aggregation, the water species with two hydrogen bonds (S2) increases gradually before 36 °C and then a sudden decrease occurs after that temperature. The results clearly indicate that water species S2 plays an important role in the formation of the intermediate, i.e., the loose hydrophobic structure of the polymer chains linked by the two hydrogen bonds of S2 water. When the temperature increases, the dissociation of the hydrogen bonds enables the intermediate to be destroyed to form a micelle structure. For the high concentration solution, however, the spectral information of S2 was not found in the aggregation, suggesting direct formation of the micelle from the dehydrated chains.
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Affiliation(s)
- Li Wang
- Research Center for Analytical Sciences, College of Chemistry, Nankai University, Tianjin 300071, P. R. China.
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78
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Tavagnacco L, Chiessi E, Zanatta M, Orecchini A, Zaccarelli E. Water-Polymer Coupling Induces a Dynamical Transition in Microgels. J Phys Chem Lett 2019; 10:870-876. [PMID: 30735054 PMCID: PMC6416711 DOI: 10.1021/acs.jpclett.9b00190] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2019] [Accepted: 02/08/2019] [Indexed: 06/09/2023]
Abstract
The long debated protein dynamical transition was recently found also in nonbiological macromolecules, such as poly- N-isopropylacrylamide (PNIPAM) microgels. Here, by using atomistic molecular dynamics simulations, we report a description of the molecular origin of the dynamical transition in these systems. We show that PNIPAM and water dynamics below the dynamical transition temperature T d are dominated by methyl group rotations and hydrogen bonding, respectively. By comparing with bulk water, we unambiguously identify PNIPAM-water hydrogen bonding as mainly responsible for the occurrence of the transition. The observed phenomenology thus crucially depends on the water-macromolecule coupling, being relevant to a wide class of hydrated systems, independently from the biological function.
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Affiliation(s)
- Letizia Tavagnacco
- CNR-ISC
and Department of Physics, Sapienza University
of Rome, Piazzale A.
Moro 2, 00185 Rome, Italy
| | - Ester Chiessi
- Department
of Chemical Sciences and Technologies, University
of Rome Tor Vergata, Via della Ricerca Scientica I, 00133 Rome, Italy
| | - Marco Zanatta
- Department
of Computer Science, University of Verona, Strada Le Grazie 15, 37138 Verona, Italy
| | - Andrea Orecchini
- Department
of Physics and Geology, University of Perugia, Via A. Pascoli, 06123 Perugia, Italy
- CNR-IOM
c/o Department of Physics and Geology, University
of Perugia, Via A. Pascoli, 06123 Perugia, Italy
| | - Emanuela Zaccarelli
- CNR-ISC
and Department of Physics, Sapienza University
of Rome, Piazzale A.
Moro 2, 00185 Rome, Italy
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79
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Rovigatti L, Gnan N, Tavagnacco L, Moreno AJ, Zaccarelli E. Numerical modelling of non-ionic microgels: an overview. SOFT MATTER 2019; 15:1108-1119. [PMID: 30543246 PMCID: PMC6371763 DOI: 10.1039/c8sm02089b] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/12/2018] [Accepted: 11/26/2018] [Indexed: 05/03/2023]
Abstract
Microgels are complex macromolecules. These colloid-sized polymer networks possess internal degrees of freedom and, depending on the polymer(s) they are made of, can acquire a responsiveness to variations of the environment (temperature, pH, salt concentration, etc.). Besides being valuable for many practical applications, microgels are also extremely important to tackle fundamental physics problems. As a result, these last years have seen a rapid development of protocols for the synthesis of microgels, and more and more research has been devoted to the investigation of their bulk properties. However, from a numerical standpoint the picture is more fragmented, as the inherently multi-scale nature of microgels, whose bulk behaviour crucially depends on the microscopic details, cannot be handled at a single level of coarse-graining. Here we present an overview of the methods and models that have been proposed to describe non-ionic microgels at different length-scales, from the atomistic to the single-particle level. We especially focus on monomer-resolved models, as these have the right level of details to capture the most important properties of microgels, responsiveness and softness. We suggest that these microscopic descriptions, if realistic enough, can be employed as starting points to develop the more coarse-grained representations required to investigate the behaviour of bulk suspensions.
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Affiliation(s)
- Lorenzo Rovigatti
- Dipartimento di Fisica
, Sapienza Università di Roma
,
Piazzale A. Moro 2
, 00185 Roma
, Italy
.
- CNR-ISC
, Uos Sapienza
,
Piazzale A. Moro 2
, 00185 Roma
, Italy
.
| | - Nicoletta Gnan
- Dipartimento di Fisica
, Sapienza Università di Roma
,
Piazzale A. Moro 2
, 00185 Roma
, Italy
.
- CNR-ISC
, Uos Sapienza
,
Piazzale A. Moro 2
, 00185 Roma
, Italy
.
| | - Letizia Tavagnacco
- Dipartimento di Fisica
, Sapienza Università di Roma
,
Piazzale A. Moro 2
, 00185 Roma
, Italy
.
- CNR-ISC
, Uos Sapienza
,
Piazzale A. Moro 2
, 00185 Roma
, Italy
.
| | - Angel J. Moreno
- Centro de Física de Materiales (CSIC, UPV/EHU) and Materials Physics Center MPC
,
Paseo Manuel de Lardizabal 5
, 20018 San Sebastián
, Spain
- Donostia International Physics Center
,
Paseo Manuel de Lardizabal 4
, 20018 San Sebastian
, Spain
| | - Emanuela Zaccarelli
- Dipartimento di Fisica
, Sapienza Università di Roma
,
Piazzale A. Moro 2
, 00185 Roma
, Italy
.
- CNR-ISC
, Uos Sapienza
,
Piazzale A. Moro 2
, 00185 Roma
, Italy
.
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80
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Pérez-Ramírez HA, Haro-Pérez C, Vázquez-Contreras E, Klapp J, Bautista-Carbajal G, Odriozola G. P-NIPAM in water–acetone mixtures: experiments and simulations. Phys Chem Chem Phys 2019; 21:5106-5116. [DOI: 10.1039/c8cp07549b] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The lower critical solution temperature (LCST) of poly-N-isopropylacrylamide (p-NIPAM) diminishes when a small volume of acetone is added to the aqueous polymer solution, and then increases for further additions, producing a minimum at a certain acetone concentration.
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Affiliation(s)
- H. A. Pérez-Ramírez
- Área de Física de Procesos Irreversibles
- División de Ciencias Básicas e Ingeniería
- Universidad Autónoma Metropolitana-Azcapotzalco
- Av. San Pablo 180
- 02200 Ciudad de México
| | - C. Haro-Pérez
- Área de Física de Procesos Irreversibles
- División de Ciencias Básicas e Ingeniería
- Universidad Autónoma Metropolitana-Azcapotzalco
- Av. San Pablo 180
- 02200 Ciudad de México
| | - E. Vázquez-Contreras
- Departamento de Ciencias Naturales
- CNI
- Universidad Autónoma Metropolitana – Cuajimalpa
- Av. Vasco de Quiroga 4871
- 05348 Ciudad de México
| | - J. Klapp
- Instituto Nacional de Investigaciones Nucleares
- ININ
- Km. 36.5, Carretera México – Toluca
- 52750 Ocoyoacac
- Mexico
| | - G. Bautista-Carbajal
- Academia de Matemáticas
- Universidad Autónoma de la Ciudad de México
- 07160 Ciudad de México
- Mexico
| | - G. Odriozola
- Área de Física de Procesos Irreversibles
- División de Ciencias Básicas e Ingeniería
- Universidad Autónoma Metropolitana-Azcapotzalco
- Av. San Pablo 180
- 02200 Ciudad de México
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81
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Consiglio G, Forte G. Molecular dynamics study of coil-to-globule transition in a thermo-responsive oligomer bound to various surfaces: hydrophilic surfaces stabilize the coil form. Phys Chem Chem Phys 2018; 20:29754-29763. [PMID: 30462107 DOI: 10.1039/c8cp05396k] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The structural and dynamical properties of 40-mer of thermo-responsive polymer PNIPAM covalently bound to different surfaces have been studied, at different temperatures, by means of molecular dynamics simulations. Evolution of the radius of gyration, Rg, of the polymer chain and radial distribution functions (RDFs) calculated for the carbon atoms of the PNIPAM backbone with water oxygens and for the hydrogen atom of the amide groups with water oxygens indicate that functionalized surfaces affect the coil-to-globule transition of PNIPAM, by means of electrostatic interactions, increasing the lower critical solution temperature (LCST) of the polymer. Such interactions, mainly represented by a H-bond, hinder the transition in the globular form while hydrophobic groups on the surface, such as -OCH3, contribute to the globular collapse. A significant alteration in the arrangement of water molecules around the polymer is testified by: (i) the absence of the second peak in the RDF between the C atoms of the PNIPAM backbone and the O atoms of water at the same temperature at which the radius of gyration decreases; (ii) the height of both the first and the second peak of the RDF between the H atom of the amide groups and water O atoms decreases when the temperature increases above the LCST. Finally, the H-bond autocorrelation function indicates that: (i) hydrogen bonds between the bound-to-surface PNIPAM acceptor groups (O[double bond, length as m-dash]C[double bond splayed right]) and the H atoms of water molecules are less persistent than H-bonds formed between the free PNIPAM acceptor groups and water; (ii) H-bonds between the PNIPAM acceptor groups and hydroxyl groups on the quartz surface are longer lived than those formed on graphene oxide.
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Affiliation(s)
- Giuseppe Consiglio
- Dipartimento di Scienze Chimiche, Università di Catania, I-95125 Catania, Italy.
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82
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Camerin F, Gnan N, Rovigatti L, Zaccarelli E. Modelling realistic microgels in an explicit solvent. Sci Rep 2018; 8:14426. [PMID: 30258102 PMCID: PMC6158278 DOI: 10.1038/s41598-018-32642-5] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2018] [Accepted: 08/29/2018] [Indexed: 11/30/2022] Open
Abstract
Thermoresponsive microgels are polymeric colloidal networks that can change their size in response to a temperature variation. This peculiar feature is driven by the nature of the solvent-polymer interactions, which triggers the so-called volume phase transition from a swollen to a collapsed state above a characteristic temperature. Recently, an advanced modelling protocol to assemble realistic, disordered microgels has been shown to reproduce experimental swelling behavior and form factors. In the original framework, the solvent was taken into account in an implicit way, condensing solvent-polymer interactions in an effective attraction between monomers. To go one step further, in this work we perform simulations of realistic microgels in an explicit solvent. We identify a suitable model which fully captures the main features of the implicit model and further provides information on the solvent uptake by the interior of the microgel network and on its role in the collapse kinetics. These results pave the way for addressing problems where solvent effects are dominant, such as the case of microgels at liquid-liquid interfaces.
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Affiliation(s)
- F Camerin
- CNR-ISC, Uos Sapienza, Piazzale A. Moro, 2, 00185, Roma, Italy.
- Dipartimento di Scienze di Base e Applicate per l'Ingegneria, Sapienza Università di Roma, via A. Scarpa, 14, 00161, Roma, Italy.
| | - N Gnan
- CNR-ISC, Uos Sapienza, Piazzale A. Moro, 2, 00185, Roma, Italy
- Dipartimento di Fisica, Sapienza Università di Roma, Piazzale A. Moro, 2, 00185, Roma, Italy
| | - L Rovigatti
- CNR-ISC, Uos Sapienza, Piazzale A. Moro, 2, 00185, Roma, Italy
- Dipartimento di Fisica, Sapienza Università di Roma, Piazzale A. Moro, 2, 00185, Roma, Italy
| | - E Zaccarelli
- CNR-ISC, Uos Sapienza, Piazzale A. Moro, 2, 00185, Roma, Italy.
- Dipartimento di Fisica, Sapienza Università di Roma, Piazzale A. Moro, 2, 00185, Roma, Italy.
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