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Temperature-Responsive Polymers

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A special issue of Materials (ISSN 1996-1944).

Deadline for manuscript submissions: closed (30 July 2018) | Viewed by 32117

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Prof. Dr. Annabelle Bertin

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1. Federal Institute for Materials Research and Testing (BAM), Department 6.0 Materials Protection and Surface Technologies, Research Group “PolyNanotechBiomed”, Unter den Eichen 87, 12205 Berlin, Germany
2. Freie Universität Berlin, Department of Biology, Chemistry, Pharmacy, Institute of Chemistry and Biochemistry, Takustrasse 3, 14195 Berlin, Germany
Interests: Upper Critical Solution Temperature (UCST)-type polymers

Special Issue Information

Dear Colleagues,

The physical properties of smart polymeric materials change according to environmental factors, such as temperature, pH, light, electric or magnetic fields. Among this group of smart polymeric materials, thermoresponsive polymers’ ability to change their physical properties, in response to changes to the surrounding temperature, render them one of the most interesting materials, as temperature is an easily accessible and controllable parameter, and is also of great relevance in biomedical applications. This is especially the case in areas such as temperature-triggered drug delivery, diagnostics, tissue engineering, bio-separation, sensory applications, and thermally switchable optical devices.

Thermoresponsive polymers can exhibit a lower critical solution temperature (LCST) and/or an upper critical solution temperature (UCST): They phase separate from solution upon heating (LCST) or cooling (UCST), respectively. Depending on the targeted application, one or the other type of phase transition behavior may be preferred. The types of solvents in which this phase transition can take place range from pure water to water/alcohol mixtures or even organic solvents. In mixtures of solvents, co-solvency or co-non solvency effects can come into play. Moreover, thermoresponsive polymers are not limited to their simplest macromolecular architectures as linear homopolymers in solution, and can also be used as three-dimensional networks in the form of gels at various scales (nano, micro, macro), as copolymers to build self-assembled architectures or grafted on macroscopic surfaces, and also on nanomaterials.

Prof. Dr. Annabelle Bertin
Guest Editor

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Keywords

Thermoresponsive polymers, gels, nanomaterials and surfaces
LCST polymers
UCST polymers
Co-solvency, co-nonsolvency
Temperature-triggered biomedical and materials science applications

Published Papers (7 papers)

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Research

21 pages, 2744 KiB

Open AccessArticle

Thermoresponsive Core-Shell Nanoparticles: Does Core Size Matter?

by Martina Schroffenegger and Erik Reimhult

Materials 2018, 11(9), 1654; https://doi.org/10.3390/ma11091654 - 07 Sep 2018

Cited by 14 | Viewed by 4295

Abstract

Nanoparticles grafted with a dense brush of hydrophilic polymers exhibit high colloidal stability. However, reversible aggregation can be triggered by an increase in temperature if the polymer is thermoresponsive, as the polymer shell partly loses its hydration. We investigate the role of nanoparticle curvature on the critical solution temperature (CST) of grafted poly(2-isopropyl-2-oxazoline) (PiPOx) and critical flocculation temperature (CFT) of the core-shell nanoparticle dispersion. Cores with diameters ranging from 5 to 21 nm were studied by temperature-cycled dynamic light scattering and differential scanning calorimetry over a large range of concentrations. We show that core size and curvature only have a minor influence on particle aggregation (CFT and cluster size), while they have major influence on the CST of the polymer shell. The densely grafted shells exhibit three distinct solvation transitions, the relative contributions of each is controlled by the core curvature. We link these transitions to different polymer density regimes within the spherical brush and demonstrate that the CST of the innermost part of the brush coincides with the CFT of the particle dispersion. Full article

(This article belongs to the Special Issue Temperature-Responsive Polymers)

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11 pages, 1806 KiB

Open AccessFeature PaperCommunication

Cononsolvency Transition of Polymer Brushes: A Combined Experimental and Theoretical Study

by Huaisong Yong, Sebastian Rauch, Klaus-Jochen Eichhorn, Petra Uhlmann, Andreas Fery and Jens-Uwe Sommer

Materials 2018, 11(6), 991; https://doi.org/10.3390/ma11060991 - 11 Jun 2018

Cited by 18 | Viewed by 4654

Abstract

In this study, the cononsolvency transition of poly(N-isopropylacrylamide) (PNiPAAm) brushes in aqueous ethanol mixtures was studied by using Vis-spectroscopic ellipsometry (SE) discussed in conjunction with the adsorption-attraction model. We proved that the cononsolvency transition of PNiPAAm brushes showed features of a volume phase transition, such as a sharp collapse, reaching a maximum decrease in thickness for a very narrow ethanol volume composition range of 15% to 17%. These observations are in agreement with the recently published preferential adsorption model of the cononsolvency effect. Full article

(This article belongs to the Special Issue Temperature-Responsive Polymers)

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11 pages, 2141 KiB

Open AccessArticle

Polysulfobetaines in Aqueous Solution and in Thin Film Geometry

by Bart-Jan Niebuur, Jonas Puchmayr, Christian Herold, Lucas P. Kreuzer, Viet Hildebrand, Peter Müller-Buschbaum, André Laschewsky and Christine M. Papadakis

Materials 2018, 11(5), 850; https://doi.org/10.3390/ma11050850 - 21 May 2018

Cited by 12 | Viewed by 3395

Abstract

Polysulfobetaines in aqueous solution show upper critical solution temperature (UCST) behavior. We investigate here the representative of this class of materials, poly (N,N-dimethyl-N-(3-methacrylamidopropyl) ammonio propane sulfonate) (PSPP), with respect to: (i) the dynamics in aqueous solution above the cloud point as function of NaBr concentration; and (ii) the swelling behavior of thin films in water vapor as function of the initial film thickness. For PSPP solutions with a concentration of 5 wt.%, the temperature dependence of the intensity autocorrelation functions is measured with dynamic light scattering as function of molar mass and NaBr concentration (0–8 mM). We found a scaling of behavior for the scattered intensity and dynamic correlation length. The resulting spinodal temperatures showed a maximum at a certain (small) NaBr concentration, which is similar to the behavior of the cloud points measured previously by turbidimetry. The critical exponent of susceptibility depends on NaBr concentration, with a minimum value where the spinodal temperature is maximum and a trend towards the mean-field value of unity with increasing NaBr concentration. In contrast, the critical exponent of the correlation length does not depend on NaBr concentration and is lower than the value of 0.5 predicted by mean-field theory. For PSPP thin films, the swelling behavior was found to depend on film thickness. A film thickness of about 100 nm turns out to be the optimum thickness needed to obtain fast hydration with H₂O. Full article

(This article belongs to the Special Issue Temperature-Responsive Polymers)

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13 pages, 2509 KiB

Open AccessArticle

PMMA-g-OEtOx Graft Copolymers: Influence of Grafting Degree and Side Chain Length on the Conformation in Aqueous Solution

by Irina Muljajew, Christine Weber, Ivo Nischang and Ulrich S. Schubert

Materials 2018, 11(4), 528; https://doi.org/10.3390/ma11040528 - 30 Mar 2018

Cited by 15 | Viewed by 4860

Abstract

Depending on the degree of grafting (DG) and the side chain degree of polymerization (DP), graft copolymers may feature properties similar to statistical copolymers or to block copolymers. This issue is approached by studying aqueous solutions of PMMA-g-OEtOx graft copolymers comprising a hydrophobic poly(methyl methacrylate) (PMMA) backbone and hydrophilic oligo(2-ethyl-2-oxazoline) (OEtOx) side chains. The graft copolymers were synthesized via reversible addition-fragmentation chain transfer (RAFT) copolymerization of methyl methacrylate (MMA) and OEtOx-methacrylate macromonomers of varying DP. All aqueous solutions of PMMA-g-OEtOx (9% ≤ DG ≤ 34%; 5 ≤ side chain DP ≤ 24) revealed lower critical solution temperature behavior. The graft copolymer architecture significantly influenced the aggregation behavior, the conformation in aqueous solution and the coil to globule transition, as verified by means of turbidimetry, dynamic light scattering, nuclear magnetic resonance spectroscopy, and analytical ultracentrifugation. The aggregation behavior of graft copolymers with a side chain DP of 5 was significantly affected by small variations of the DG, occasionally forming mesoglobules above the cloud point temperature (T_cp), which was around human body temperature. On the other hand, PMMA-g-OEtOx with elongated side chains assembled into well-defined structures below the T_cp (apparent aggregation number (N_agg = 10)) that were able to solubilize Disperse Orange 3. The thermoresponsive behavior of aqueous solutions thus resembled that of micelles comprising a poly(2-ethyl-2-oxazoline) (PEtOx) shell (T_cp > 60 °C). Full article

(This article belongs to the Special Issue Temperature-Responsive Polymers)

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10 pages, 3571 KiB

Open AccessArticle

Temperature and Recognition Dual Responsive Poly(N-Isopropylacrylamide) and Poly(N,N-Dimethylacrylamide) with Adamantyl Side Group

by Qiujing Dong, Chunhua Luo, Na Li, Jiaxiang Chi and Qingqing Zhang

Materials 2018, 11(4), 473; https://doi.org/10.3390/ma11040473 - 22 Mar 2018

Cited by 6 | Viewed by 4770

Abstract

A series of copolymers with an adamantyl side group (poly(NIPAM-co-AdMA) and poly(DMAM-co-AdMA)) were prepared by radical copolymerization of N-isopropylacrylamide (NIPAM) and N,N-dimethylacrylamide (DMAM) with a 2-methyl-2-adamantylmethacrylate (AdMA) monomer. The structure and composition of the as-synthesized copolymers were characterized by Fourier transform infrared (FT-IR) spectroscopy, proton nuclear magnetic resonance (¹H NMR) spectroscopy, gel permeation chromatography (GPC), thermogravimetric analysis (TGA), and elemental analysis. Temperature and recognition dual responsivity of the copolymers was investigated by cloud point (T_cp) and dynamic light scattering (DLS), respectively. The results show that the as-synthesized copolymers are a kind of temperature-responsive polymer with a lower critical solution temperature (LCST). T_cp was approximately consistent with the critical temperature of intermolecular copolymer association (T_ass) from DLS. For these copolymers, T_cp decreases with increasing content of AdMA unit in the copolymers. After the addition of β-cyclodextrins (β-CD), T_cp increases, and the increment of T_cp values gradually became large with increasing content of AdMA in the copolymers. It is host-guest molecular recognition of β-CD and adamantyl groups that endows the as-synthesized copolymers with recognition-tunable thermosensitivity. Full article

(This article belongs to the Special Issue Temperature-Responsive Polymers)

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12 pages, 1517 KiB

Open AccessArticle

Stepwise Thermo-Responsive Amino Acid-Derived Triblock Vinyl Polymers: ATRP Synthesis of Polymers, Aggregation, and Gelation Properties via Flower-Like Micelle Formation

by Nobuyuki Higashi, Sho Matsubara, Shin-nosuke Nishimura and Tomoyuki Koga

Materials 2018, 11(3), 424; https://doi.org/10.3390/ma11030424 - 15 Mar 2018

Cited by 15 | Viewed by 4360

Abstract

Novel thermo-responsive ABA-type triblock copolymers (poly(NAAMe_n-b-NAGMe₂₄₀-b-NAAMe_n), n = 18–72) composed of naturally occurring amino acid–based vinyl polymer blocks such as poly(N-acryloyl-l-alanine methyl ester (poly(NAAMe)) as the A segment and poly(N-acryloyl-glycine methylester)(poly(NAGMe)) as the B segment have been synthesized by the atom transfer radical polymerization (ATRP). Their thermal behaviors were analyzed in dilute aqueous solutions by turbidimetry. The turbidity curves provided two-step LCST transitions, and a flower-like micelle formation was confirmed at the temperature region between the first and second LCST transitions by dynamic light scattering, AFM and TEM. At higher copolymer concentrations, hydrogels were obtained at temperatures above the first LCST due to network formation induced with the flower-like micelles as cross-linker. The hydrogels were found to be switched to a sol state when cooled below the first LCST. These hydrogels also exhibited self-healable and injectable capabilities, which were evaluated by rheological measurements. Full article

(This article belongs to the Special Issue Temperature-Responsive Polymers)

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17 pages, 3599 KiB

Open AccessArticle

Post-Modified Polypeptides with UCST-Type Behavior for Control of Cell Attachment in Physiological Conditions

by Xuan Xue, Lalitha Thiagarajan, James E. Dixon, Brian R. Saunders, Kevin M. Shakesheff and Cameron Alexander

Materials 2018, 11(1), 95; https://doi.org/10.3390/ma11010095 - 09 Jan 2018

Cited by 9 | Viewed by 4379

Abstract

Upper Critical Solution Temperature (UCST)-type thermally responsive polypeptides (TRPs) with phase transition temperatures around 37 °C in phosphate-buffered saline (PBS) buffer (pH 7.4, 100 mM) were prepared from poly(l-ornithine) hydrobromide and coated on non-tissue culture-treated plastic plates (nTCP). Cell adhesion was observed at temperatures above the phase transition temperature of the coating polymer (39 °C), while cell release was triggered when the culture temperature was switched to 37 °C. Approximately 65% of the attached cells were released from the surface within 6 h after changing the temperature, and more than 96% of the released cells were viable. Water contact angle measurements performed at 39 and 37 °C demonstrated that the surface hydrophobicity of the new TRP coatings changed in response to applied temperature. The cell attachment varied with the presence of serum in the media, suggesting that the TRP coatings mediated cell attachment and release as the underlying polymer surface changed conformation and consequently the display of adsorbed protein. These new TRP coatings provide an additional means to mediate cell attachment for application in cell-based tissue regeneration and therapies. Full article

(This article belongs to the Special Issue Temperature-Responsive Polymers)

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