Constrained thermoresponsive polymers – new insights into fundamentals and applications

In the last decades, numerous stimuli-responsive polymers have been developed and investigated regarding their switching properties. In particular, thermoresponsive polymers, which form a miscibility gap with the ambient solvent with a lower or upper critical demixing point depending on the temperature, have been intensively studied in solution. For the application of such polymers in novel sensors, drug delivery systems or as multifunctional coatings, they typically have to be transferred into specific arrangements, such as micelles, polymer films or grafted nanoparticles. However, it turns out that the thermodynamic concept for the phase transition of free polymer chains fails, when thermoresponsive polymers are assembled into such sterically confined architectures. Whereas many published studies focus on synthetic aspects as well as individual applications of thermoresponsive polymers, the underlying structure–property relationships governing the thermoresponse of sterically constrained assemblies, are still poorly understood. Furthermore, the clear majority of publications deals with polymers that exhibit a lower critical solution temperature (LCST) behavior, with PNIPAAM as their main representative. In contrast, for polymer arrangements with an upper critical solution temperature (UCST), there is only limited knowledge about preparation, application and precise physical understanding of the phase transition. This review article provides an overview about the current knowledge of thermoresponsive polymers with limited mobility focusing on UCST behavior and the possibilities for influencing their thermoresponsive switching characteristics. It comprises star polymers, micelles as well as polymer chains grafted to flat substrates and particulate inorganic surfaces. The elaboration of the physicochemical interplay between the architecture of the polymer assembly and the resulting thermoresponsive switching behavior will be in the foreground of this consideration.

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Adamantane Functionalized Poly(2-oxazoline)s with Broadly Tunable LCST-Behavior by Molecular Recognition

Polymers ◽

10.3390/polym13030374 ◽

2021 ◽

Vol 13 (3) ◽

pp. 374

Author(s):

Joachim F. R. Van Guyse ◽

Debaditya Bera ◽

Richard Hoogenboom

Keyword(s):

Phase Transition ◽

Molecular Recognition ◽

High Specificity ◽

Polymer Chains ◽

Solution Temperature ◽

Side Chains ◽

Stimuli Responsive ◽

Thermal Transitions ◽

Stimuli Responsive Polymers ◽

Interactive Behavior

Smart or adaptive materials often utilize stimuli-responsive polymers, which undergo a phase transition in response to a given stimulus. So far, various stimuli have been used to enable the modulation of drug release profiles, cell-interactive behavior, and optical and mechanical properties. In this respect, molecular recognition is a powerful tool to fine-tune the stimuli-responsive behavior due to its high specificity. Within this contribution, a poly(2-oxazoline) copolymer bearing adamantane side chains was synthesized via triazabicyclodecene-catalyzed amidation of the ester side chains of a poly(2-ethyl-2-oxazoline-stat-2-methoxycarbonylpropyl-2-oxazoline) statistical copolymer. Subsequent complexation of the pendant adamantane groups with sub-stoichiometric amounts (0–1 equivalents) of hydroxypropyl β-cyclodextrin or β-cyclodextrin enabled accurate tuning of its lower critical solution temperature (LCST) over an exceptionally wide temperature range, spanning from 30 °C to 56 °C. Furthermore, the sharp thermal transitions display minimal hysteresis, suggesting a reversible phase transition of the complexed polymer chains (i.e., the β-cyclodextrin host collapses together with the polymers) and a minimal influence by the temperature on the supramolecular association. Analysis of the association constant of the polymer with hydroxypropyl β-cyclodextrin via 1H NMR spectroscopy suggests that the selection of the macrocyclic host and rational polymer design can have a profound influence on the observed thermal transitions.

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Thermo- and Photoresponsive Behaviors of Dual-Stimuli-Responsive Organogels Consisting of Homopolymers of Coumarin-Containing Methacrylate

Polymers ◽

10.3390/polym13030329 ◽

2021 ◽

Vol 13 (3) ◽

pp. 329

Author(s):

Seidai Okada ◽

Eriko Sato

Keyword(s):

Functional Group ◽

Solution Temperature ◽

Stimuli Responsive ◽

Critical Solution Temperature ◽

Equilibrium Degree ◽

Stimuli Responsive Polymers ◽

Responsive Polymers ◽

Dual Functional ◽

Wide Range ◽

Increasing Temperature

Coumarin-containing vinyl homopolymers, such as poly(7-methacryloyloxycoumarin) (P1a) and poly(7-(2′-methacryloyloxyethoxy)coumarin) (P1b), show a lower critical solution temperature (LCST) in chloroform, which can be controlled by the [2 + 2] photochemical cycloaddition of the coumarin moiety, and they are recognized as monofunctional dual-stimuli-responsive polymers. A single functional group of monofunctional dual-stimuli-responsive polymers responds to dual stimuli and can be introduced more uniformly and densely than those of dual-functional dual-stimuli-responsive polymers. In this study, considering a wide range of applications, organogels consisting of P1a and P1b, i.e., P1a-gel and P1b-gel, respectively, were synthesized, and their thermo- and photoresponsive behaviors in chloroform were investigated in detail. P1a-gel and P1b-gel in a swollen state (transparent) exhibited phase separation (turbid) through a temperature jump and reached a shrunken state (transparent), i.e., an equilibrium state, over time. Moreover, the equilibrium degree of swelling decreased non-linearly with increasing temperature. Furthermore, different thermoresponsive sites were photopatterned on the organogel through the photodimerization of the coumarin unit. The organogels consisting of homopolymers of coumarin-containing methacrylate exhibited unique thermo- and photoresponsivities and behaved as monofunctional dual-stimuli-responsive organogels.

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A polyelectrolyte-containing copolymer with a gas-switchable lower critical solution temperature-type phase transition

Polymer Chemistry ◽

10.1039/c8py01265b ◽

2019 ◽

Vol 10 (2) ◽

pp. 260-266 ◽

Cited By ~ 4

Author(s):

Jin-Jin Li ◽

Yin-Ning Zhou ◽

Zheng-Hong Luo ◽

Shiping Zhu

Keyword(s):

Phase Transition ◽

Cloud Point ◽

Lower Critical Solution Temperature ◽

Solution Temperature ◽

Critical Solution Temperature ◽

Type Phase

A polyelectrolyte-containing copolymer with a CO2/N2-switchable cloud point, resulting from the gas-induced alternation of hydrophilicity, was prepared.

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Unexpected LCST-type phase behaviour of a poly(vinyl thiazolium) polymer in acetone

RSC Advances ◽

10.1039/c6ra09023k ◽

2016 ◽

Vol 6 (62) ◽

pp. 57117-57121 ◽

Cited By ~ 5

Author(s):

Konrad Grygiel ◽

Weiyi Zhang ◽

Christophe Detrembleur ◽

Jiayin Yuan

Keyword(s):

Phase Transition ◽

Lower Critical Solution Temperature ◽

Acetone Solution ◽

Phase Behaviour ◽

Solution Temperature ◽

Critical Solution Temperature ◽

Type Phase

A poly(vinyl thiazolium) polymer in acetone solution exhibited an unexpected lower critical solution temperature (LCST)-type phase transition.

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Effects of the Hydrophilic–Lipophilic Balance of Alternating Peptides on Self-Assembly and Thermo-Responsive Behaviors

International Journal of Molecular Sciences ◽

10.3390/ijms20184604 ◽

2019 ◽

Vol 20 (18) ◽

pp. 4604 ◽

Cited By ~ 6

Author(s):

Ihsan ◽

Nargis ◽

Koyama

Keyword(s):

Aqueous Solutions ◽

Self Assembly ◽

Polymer Chains ◽

Systematic Evaluation ◽

Solution Temperature ◽

Critical Solution Temperature ◽

Hydrophilic Lipophilic Balance ◽

Upper Critical Solution Temperature ◽

Cloud Points ◽

Micellization Behavior

A series of N-substituted poly(Gly–alter–Val) peptides were successfully synthesized for the systematic evaluation of the micellization behavior of alternating peptides. Three-component polymerization employing an aldehyde, a primary ammonium chloride, and potassium isocyanoacetate afforded four alternating peptides in excellent yields. We investigated the dependence of the hydrophilic–lipophilic balance of alternating peptides on the micellization behavior. All the aqueous solutions of alternating peptides exhibited upper critical solution temperature (UCST) behaviors, strongly indicating that the alternating binary pattern would mainly contribute to the UCST behaviors. The cloud points of alternating peptides shifted to higher temperatures as the side chains became more hydrophilic, which is opposite to the trend of typical surfactants. Such unusual micellization behaviors appeared to be dependent on the quasi-stable structure of single polymer chains formed in water.

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Control of osmotic pressure through CO2-capture and release facilitated by the lower critical solution temperature (LCST) phase transition of acylated branched polyethylenimine

RSC Advances ◽

10.1039/c6ra00371k ◽

2016 ◽

Vol 6 (32) ◽

pp. 26526-26530 ◽

Cited By ~ 2

Author(s):

Jeongseon Park ◽

Minwoo Noh ◽

Min Keun Chey ◽

Yeongbong Mok ◽

Ji-Hun Seo ◽

...

Keyword(s):

Phase Transition ◽

Phase Separation ◽

Osmotic Pressure ◽

Co2 Capture ◽

Low Temperatures ◽

Solution Temperature ◽

Critical Solution Temperature ◽

Low Salt ◽

Branched Polyethylenimine ◽

Capture And Release

A solution of acylated polyethylenimine absorbs CO2 at low temperatures and draws water from high-salt saline due to the high osmotic pressure, while it liberates CO2 after phase separation by mild heating and releases water into low-salt saline.

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Thermoresponsive polymers with lower critical solution temperature: from fundamental aspects and measuring techniques to recommended turbidimetry conditions

Materials Horizons ◽

10.1039/c7mh00016b ◽

2017 ◽

Vol 4 (2) ◽

pp. 109-116 ◽

Cited By ~ 135

Author(s):

Qilu Zhang ◽

Christine Weber ◽

Ulrich S. Schubert ◽

Richard Hoogenboom

Keyword(s):

Lower Critical Solution Temperature ◽

Temperature Behavior ◽

Solution Temperature ◽

Thermoresponsive Polymers ◽

Critical Solution Temperature ◽

Measuring Techniques

This focus article addresses fundamental and practical aspects of investigating polymers with lower critical solution temperature behavior.

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Thermally responsive polymeric hydrogel brushes: synthesis, physical properties and use for the culture of chondrocytes

Journal of The Royal Society Interface ◽

10.1098/rsif.2006.0158 ◽

2006 ◽

Vol 4 (12) ◽

pp. 117-126 ◽

Cited By ~ 38

Author(s):

John Collett ◽

Aileen Crawford ◽

Paul V Hatton ◽

Mark Geoghegan ◽

Stephen Rimmer

Keyword(s):

Crosslink Density ◽

Cell Attachment ◽

Viable Cell ◽

Contact Angles ◽

Polymer Chains ◽

Solution Temperature ◽

Critical Solution Temperature ◽

Thermally Responsive ◽

Isopropyl Acrylamide ◽

Responsive Polymer

Hydrogel brushes are materials composed of a water-swollen network, which contains polymer chains that are grafted with another polymer. Using a thermally responsive polymer, poly( N -isopropyl acrylamide) (polyNIPAM), as the graft component we are able to maintain the critical solution temperature ( T crit ), independent of the overall composition of the material, at approximately 32°C. The change in swelling at T crit is a function of the amount of polyNIPAM in the system. However, there is a much smaller change in the surface contact angles at T crit . PolyNIPAM-based materials have generated considerable interest, as ‘smart’ substrates for the culture of cells and here, we show the utility of hydrogel brushes in cell culture. Chondrocytes attached to the hydrogel brushes and yielded viable cell cultures. Moreover, the chondrocytes could be released from the hydrogel brushes without the use of proteases by reducing the temperature of the cultures to below T crit to induce a change in the conformation of the polyNIPAM chain at T crit . The importance of the crosslink hydrogel component is illustrated by significant changes in cell attachment/cell viability as the crosslink density is changed.

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Phase Separation Behaviors Of Polyimide Blends

MRS Proceedings ◽

10.1557/proc-511-87 ◽

1998 ◽

Vol 511 ◽

Author(s):

C. H. Ryu ◽

Y. C. Bae

Keyword(s):

Phase Transition ◽

Molecular Weight ◽

Glass Transition ◽

Transition Temperature ◽

Critical Temperature ◽

Solution Temperature ◽

Critical Solution Temperature ◽

Phase Transition Temperatures ◽

Phase Behaviors ◽

System Phase

ABSTRACTWe investigated phase behaviors of polyimide blends such as polyethermide(PEI)/polystyrene(PS), PEI/polyamideimide(PAI), PEI/polyethyleneoxide(PEO), and PAI/PEO systems. Our sample systems exhibited lower critical solution temperature(LCST) phase behaviors. In the PEI/PS system, phase transition occurred near or above the glass transition temperature(Tg) of PS and the critical temperature of the system increased with decreasing molecular weight of PS. For PEI/PAI and PEI/PEO systems, the critical temperature of PEI/PAI system is higher than that of PEI/PEO system. Phase transition temperatures of PAI/PEO systems appeared near or below the melting point of PEO.

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