Lower Critical Solution Temperature-type Phase Research Articles

Miscibility of isotactic poly(1-butene)/isotactic polypropylene blends studied by atomic force Microscopy−Infrared

In this work, miscibility behavior of blends of high molecular weight isotactic poly(1-butene) (PB) and isotactic polypropylene (PP) has been investigated by atomic force microscopy-infrared (AFM-IR) technique. A PP with 10 mol% deuterated units (dPP) was mixed with the PB at 50/50 mass ratio and the melt was found to phase separate, and the distinct C-D stretching bands of the dPP were observed in both phases by AFM-IR, indicative of partial miscibility of the two polymers. By using an AFM-IR quantitative analysis method, PB content in each phase in PB/PP blends can be determined. The phase separation kinetics of a PB/PP 50/50 blend was investigated, and the compositions of the two co-existing phases at equilibrium at different temperatures were determined by AFM-IR, from which a phase diagram was constructed. The PB/PP blends were found to exhibit lower critical solution temperature-type phase behavior, with the critical temperature of around 160 °C by estimate.

Effect of branch structure of thermoresponsive oligomers on draw solution performance in forward osmosis process

A series of three types of oligomers—oligo(butylene oxide)n-block-oligo(ethylene oxide)m-block-oligo(butylene oxide)n oligomers (EBs), glycerol-oligo(ethylene oxide)m-block-(butylene oxide)n oligomers (GEBs), and pentaerythritol-oligo(ethylene oxide)m-block-(butylene oxide)n oligomers (PEBs)—having different branch structures were synthesized. EBs, GEBs, and PEBs had linear, three-branch, and four-branch structures, respectively. These oligomers were tested as draw solutes (DSs) for the forward osmosis (FO) process in order to reveal the effect of their branch structures on the FO performance and DS leakage from the FO membrane. The aqueous solutions of EBs, GEBs, and PEBs exhibited a typical lower critical solution temperature-type phase separation. The FO water fluxes in the case of EB, GEB, and PEB were 4.1–4.8 L m−2 h−1 (LMH) at an osmotic pressure of 28 bar, while the reverse solute fluxes (Js) were 0.79–1.83 gMH at DS concentrations corresponding to an osmotic pressure of 28 bar. Js decreased with an increase in the number of branches in the DS molecule, which improved the FO performance index. The results indicate the importance of introducing a branch structure into DS molecules to design useful DSs.

Controlling the Thermally Induced Phase Separation of Polymer/Ionic Liquid Blended Films with Concentrated-Polymer-Brush-Decorated Hybrid Particles.

The development of quasi-solid electrolytes for electrical devices operating at high voltages is important for addressing future energy storage requirements. Here, we report a new method to fabricate quasi-solid electrolytes through the thermally induced phase separation of a polymer/ionic liquid (polymer/IL) blend. In a polymer/IL blend that exhibits lower critical solution temperature-type phase separation, we demonstrate that the addition of silica particles decorated with concentrated polymer brushes (CPB-SiPs) can prevent macroscopic phase separation after heating, resulting in a quasi-solid electrolyte with a continuous IL phase. This is due to the adsorption of CPB-SiPs onto the polymer/IL interface in the phase-separated structure. We also reveal a relationship between the molecular weight of the CPB and the phase-separated structure. Namely, a quasi-solid film with a bicontinuous phase-separated structure is formed only when polymers with an appropriate molecular weight are grafted on the CPB-SiPs. The resulting quasi-solid film exhibits a relatively high ionic conductivity, owing to the existence of a continuous ion-conductive phase solely consisting of IL. In addition, we fabricated a quasi-solid electrolyte with the blended film and successfully applied it to an electric double-layer capacitor operating at a high voltage, owing to the wider potential window of the IL employed herein.

Carbon-carbon main chain polymer with accumulated oligo(ethylene glycol)-substituted cyclotriphosphazenes: Study on the LCST-type phase separation of organic-inorganic poly(substituted methylene)s

The synthesis and characterization of organic-inorganic thermoresponsive poly(substituted methylene)s are described. Diazoacetates with oligo(ethylene glycol)-substituted cyclotriphosphazenes were synthesized, and the obtained products were employed as monomers for Pd-initiated polymerization to produce carbon–carbon main chain polymers bearing an oligo(ethylene glycol)-substituted cyclotriphosphazene on every main chain carbon atom. The resulting polymers with densely accumulated oligo(ethylene glycol) units around the polymer main chain showed lower critical solution temperature-type phase separation in an aqueous medium. Pd-initiated polymerization of diazoacetates containing oligo(ethylene glycol)-substituted cyclotriphosphazenes was conducted to yield carbon-carbon main chain polymers bearing an oligo(ethylene glycol)-substituted cyclotriphosphazene on every main chain carbon atom. The resulting organic–inorganic poly(substituted methylene)s were found to show an LCST-type phase separation in aqueous media, and thus their thermosensitive behavior was evaluated by turbidity measurements.

Design of thermoresponsive poly(ionic liquid) gels containing proline units to catalyse aldol reaction in water

Ionic liquid monomers and a proline-containing monomer were copolymerised in the presence of cross-linker to form ionic liquid polymer gels that show lower critical solution temperature-type phase change in water. The obtained gels were utilised as catalysts for aldol reaction in water. Since proline-catalysed aldol reaction is composed of three equilibrium steps including dehydration condensation reaction and hydrolysis reaction, yield of product was affected by the water content around the proline unit in the gel. Since thus prepared ionic liquid polymer gels showed the thermo-responsive change in water content, the product yield was found to be affected by the temperature around the phase transition temperature.

LCST-Type Phase Behavior of Aqueous Biphasic Systems Composed of Phosphonium-Based Ionic Liquids and Potassium Phosphate

Although aqueous biphasic systems (ABS) composed of phosphonium-based ionic liquids (ILs) have demonstrated superior performance as viable media for biocompatible extraction processes, the formation of ABS with tetrabutylphosphonium trifluoroacetate ([P4444]CF3COO) and tributyloctylphosphonium bromide ([P4448]Br) were seldom investigated. To evaluate the hydrophilicity of [P4444]CF3COO and [P4448]Br, the solubility curves for the mixture of the ILs and water were determined. The influence of temperature on the phase behavior for the [P4448]Br + K3PO4 + H2O and [P4444] CF3COO + K3PO4 + H2O systems were also obtained. Results show that both [P4448]Br + H2O and [P4444]CF3COO + H2O binary systems undergo lower critical solution temperature-type phase transition, and the ABS composed of [P4444]CF3COO and [P4448]Br can be formed with K3PO4 at a wide range of temperatures. Moreover, the ABS are highly temperature dependent, and biphasic region expands with an increase in temperature. On the other hand, the capab...

Rheopectic Gel Formation of Stimuli-Responsive Ionic Liquid/Water Mixtures

A new class of hydrophobic and polar ionic liquids was prepared by coupling hydrophobic tetraoctylphosphonium cation and polar phosphonate-derived anions. Mixtures of these ionic liquids and water showed lower critical solution temperature-type phase behaviour. Furthermore, these mixtures displayed thermoreversible, however, non-linear viscosity change despite their large content of water. The abrupt increase in the viscosity was explained by the occurrence of rheopectic gelation of the ionic liquid/water mixtures by external stimuli such as shear stress.

Multimode Self-Folding Polymers via Reversible and Thermoresponsive Self-Assembly of Amphiphilic/Fluorous Random Copolymers

Multimode self-folding polymers were created via the reversible and thermoresponsive self-assembly of amphiphilic/fluorous random copolymers bearing poly(ethylene glycol) (PEG) and perfluoroalkyl pendants in water, N,N-dimethylformamide (DMF), and 2H,3H-perfluoropentane (2HPFP). The random copolymers with precision primary structure were synthesized by ruthenium-catalyzed living radical copolymerization of PEG methyl ether methacrylates and perfluoroalkyl methacrylates. Owing to three distinct properties of the hydrophobic backbone, hydrophilic PEG chains, and fluorous perfluorinated pendants, the random copolymers allowed various self-assembly modes for different folded structures by changing solvents. Namely, they form self-folding polymers of fluorous and/or hydrophobic cores in water or DMF, while they in turn provide reverse self-folding polymers of hydrophilic PEG cores in 2HPFP. The reverse folding in 2HPFP was further promoted by lower critical solution temperature-type phase separation of the PEG...

A thermoresponsive poly(ionic liquid) membrane enables concentration of proteins from aqueous media.

A new type of poly(ionic liquid) membrane, which shows switchable hydrated states via lower critical solution temperature-type phase behaviour, enables concentration of some water-soluble proteins from aqueous media.

Water-Soluble Copolypeptides with Oligo-Ethylene-Glycol and Benzyl Pendants: Synthesis, Characterization, and Thermoresponsive Properties

A series of random copolypeptides, i.e. poly(γ-propyl-l-glutamate)-graft-(oligo-ethylene-glycol)-random-poly(γ-benzyl-l-glutamate)s (PPLG-g-OEG3-ran-PBLG) with similar main chain lengths and various compositions of OEG and benzyl pendants were synthesized in three steps, including ring-opening polymerization of γ-chloropropyl-l-glutamic acid-based N-carboxyanhydride (CPLG-NCA) and γ-benzyl-l-glutamic acid-based N-carboxyanhydride (BLG-NCA), nucleophilic substitution in the presence of NaN3, and copper-mediated alkyne–azide 1,3-dipolar cycloaddition. 1H NMR, Fourier transform infrared spectroscopy, and gel permeation chromatography results confirmed the molecular structures of the resulting copolypeptides and characterized their molar masses, molar mass distributions, and the OEG/benzyl compositions. Fourier transform infrared spectroscopy and circular dichroism analysis revealed that PPLG-g-OEG3-ran-PBLG samples adopted α-helical conformations both in aqueous solution and solid state. Variable-temperature UV-visible spectroscopy revealed that PPLG-g-OEG3-ran-PBLG samples with high OEG molar content (x ≥ 0.57) possessed lower critical solution temperature-type phase transitions in water. The cloud point temperature, in the range of 22–53°C, can be readily obtained by controlling the OEG/benzyl composition.

Polystyrene-block-poly (methoxy diethylene glycol acrylate)-block-polystyrene triblock copolymers in aqueous solution—a SANS study of the temperature-induced switching behavior

A concentrated solution of a symmetric triblock copolymer with a thermoresponsive poly(methoxy diethylene glycol acrylate) (PMDEGA) middle block and short hydrophobic, fully deuterated polystyrene end blocks is investigated in D2O where it undergoes a lower critical solution temperature-type phase transition at ca. 36 °C. Small-angle neutron scattering (SANS) in a wide temperature range (15–50 °C) is used to characterize the size and inner structure of the micelles as well as the correlation between the micelles and the formation of aggregates by the micelles above the cloud point (CP). A model featuring spherical core-shell micelles, which are correlated by a hard-sphere potential or a sticky hard-sphere potential together with a Guinier form factor describing aggregates formed by the micelles above the CP, fits the SANS curves well in the entire temperature range. The thickness of the thermoresponsive micellar PMDEGA shell as well as the hard-sphere radius increase slightly already below the cloud point. Whereas the thickness of the thermoresponsive micellar shell hardly shrinks when heating through the CP and up to 50 °C, the hard-sphere radius decreases within 3.5 K at the CP. The volume fraction decreases already significantly below the CP, which may be at the origin of the previously observed gel–sol transition far below the CP (Miasnikova et al., Langmuir 28: 4479–4490, 2012). Above the CP, small, and at higher temperatures, large aggregates are formed by the micelles.

Polymerization of Hydroxy-Containing Diazoacetates: Synthesis of Hydroxy-Containing “Poly(substituted methylene)s” by Palladium-Mediated Polymerization and Poly(ester–ether)s by Polycondensation through O–H Insertion Reaction

Two types of polymerization of hydroxy-containing diazoacetates are described. The polymerization of hydroxy-containing diazoacetates using palladium complexes proceeded successfully under chain-growth mechanism even without a protecting group to give C–C main chain polymers bearing a hydroxy-containing ester substituent on each carbon of the backbone. The resulting polymers had a slightly branched structure due to chain transfer reaction with the hydroxy groups, while the polymers obtained by polymerization of silyl-protected diazoacetates and subsequent deprotection had a completely linear structure. The hydroxy-containing polymers with an appropriate hydrophilic/hydrophobic balance showed a lower critical solution temperature-type phase separation in an aqueous medium. On the other hand, the polymerization of hydroxy-containing diazoacetates using InCl3 as a catalyst proceeded under step-growth mechanism to give oligomers having a distinct repeating unit (ester–ether), where a new ether bond was generated through O–H insertion reaction of diazocarbonyl groups into hydroxy groups.

Cationic Poly(ionic liquid) with Tunable Lower Critical Solution Temperature-Type Phase Transition.

A cationic polyelectrolyte based on the styrenic ionic liquid tributyl-4-vinylbenzylphosphonium pentanesulfonate was found to undergo a lower critical solution temperature (LCST)-type phase transition in aqueous solutions. This phase transition occurs in a wide temperature range in terms of polymer concentration as well as type and concentration of externally added salts. Anion exchange and salting out effects are responsible for the flexible phase transition temperature.

Detection of small differences in the hydrophilicity of ions using the LCST-type phase transition of an ionic liquid–water mixture

The phase separation temperature of the tetrabutylphosphonium trifluoroacetate-water mixture, which undergoes a lower critical solution temperature-type phase transition, is highly sensitive to the hydrophilicity of added salts; this system can be used to compare the hydrophilicity of the added ions.

Temperature-Driven and Reversible Assembly of Homopolyelectrolytes Derived from Suitably Designed Ionic Liquids in Water

Polycationic-type homopolymers derived from polymerisable ionic liquids with adequate hydrophobicity were prepared to form spherical nanoparticles in water that changed their diameter as a function of temperature. The diameter change was attributed to a temperature-sensitive and reversible lower critical solution temperature-type phase change of the polymers in water.

Precise synthesis of end-functionalized thermosensitive poly(vinyl ether)s by living cationic polymerization

A series of poly(2-methoxyethyl vinyl ether)s with narrow molecular weight distributions and with perfectly defined end groups of varying hydrophobicities was successfully synthesized by base-assisting living cationic polymerization. The end group was shown to greatly affect the temperature-induced phase separation behavior of aqueous solutions (lower critical solution temperature-type phase separation) or organic solutions (upper critical solution temperature-type phase separation) of the polymers. The cloud points were also influenced largely by the molecular weight and concentration of the polymer. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

Key Factors to Prepare Polyelectrolytes Showing Temperature-Sensitive Lower Critical Solution Temperature-type Phase Transitions in Water

Tetrabutylphosphonium styrenesulfonate and its homopolymer showed a lower critical solution temperature-type phase transition in water. As the hydrophobicity of these monomeric and polymeric salts affects phase behaviour, the phase transition temperature of the polyelectrolyte was changed by the introduction of monomers having different alkyl chain length on the phosphonium cations.

Reversible thermoresponsive behavior of poly(2-chloroethyl vinyl ether-alt-maleic anhydride) in mixed solvent of tetrahydrofuran/hexane

Poly(2-chloroethyl vinyl ether-alt-maleic anhydride) can exhibit lower critical solution temperature-type phase behavior reversibly by tuning the solvent composition in mixed solvent of tetrahydrofuran (THF) and hexane. The effect of solvent composition and polymer concentration on cloud point of polymer solution was investigated. The cloud point temperature for high molecular weight polymer was lower than that for lower molecular weight polymer. High resolution 1H NMR spectra in mixed solvent of THF-d 8 and hexane were also measured for comprehending thermoresponsive behavior of polymer solution in molecular level; however, any discontinuous change in the NMR signals around the cloud point could not be recognized.

Phase behavior of poly(4‐tert‐butylstyrene‐stat‐4‐tert‐ butoxystyrene)/polyisoprene blends with competitive interactions

AbstractThe phase behavior of statistical copolymers composed of (4‐tert‐butylstyrene) (B) and (4‐tert‐butoxystyrene) (O), abbreviated as s‐BO, with polyisoprene (I) was investigated by optical microscopic (OM) observation and small‐angle neutron scattering (SANS) measurements. It has been known that B/I blend shows lower critical solution temperature (LCST) type phase diagram, while O/I blend has upper critical solution temperature (UCST) type one. Several blends of s‐BOs having mol fraction of B, mB, comparable to 0.50, with I showed both UCST and LCST type phase diagram. Furthermore, UCST type phase behavior was observed for blends having small mB, while LCST type one was for that of large mB at all used temperatures. Hence, the phase behavior of s‐BO/I blend can be understood as a result of the competition of two interactions having opposite temperature dependence. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 2272–2280, 2009

Miscibility of DMPC-TMPC copolycarbonate/SMMA copolymer blends and their interaction energies of binary pairs involved in blends

The isothermal miscibility map and phase-separation temperatures caused by lower critical solution temperature-type phase behavior for blends of poly[2,2,-propane-bis{4-(2-methyl phenyl)} carbonate]-poly[2,2,-propane-bis{4-(2,6-dimethyl phenyl)} carbonate] (DMPC-TMPC) with poly[(styrene)-co-(methyl methacrylate)] (SMMA) copolymers have been determined. SMMA copolymers containing equal to or less than 37 wt% MMA formed miscible blends with DMPC-TMPC copolycarbonates containing equal to or more than 60 wt% TMPC. The observed phase-separation temperatures indicate that the miscibility decreases as the DMPC content in DMPC-TMPC increases, while addition of MMA to the styrene initially increases miscibility with DMPC-TMPC but ultimately leads to immiscibility. The binary interaction energies involved in these blends were calculated from the phase boundaries using the lattice-fluid theory combined with the binary interaction model. The spinodal temperatures predicted from the lattice-fluid theory using the calculated interaction energies are similar to the experimental phase-separation temperatures. Copyright © 2004 Society of Chemical Industry