Dehydration, Micellization, and Phase Separation of Thermosensitive Polyoxazoline Star Block Copolymers in Aqueous Solution

Sezonenko, Tetiana; Qiu, Xing‐Ping; Winnik, Françoise M.; Sato, Takahiro

doi:10.1021/acs.macromol.8b02528

Cited by 23 publications

(25 citation statements)

References 29 publications

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“…The obtained values of ¯ for the CPh6-PEtOx are close to those reported in the literature for linear PEtOx, to reported values from Schubert and Nischang et al [26] of ¯ = 0.84 cm 3 g −1 , from Ye et al [42] of ¯ = 0.85 cm 3 g −1 , and ¯ = 0.87 cm 3 g −1 from Chen et al [43]. In addition, the specific partial volumes for CPh6-PAlOx are in good agreement with the values of ¯ for star-shaped PEtOx and PiPrOx [44][45][46]. MMs calculated by the relation (2) are shown in Table 1, which also gives the values of intrinsic viscosity [].…”

Section: Introductionsupporting

confidence: 70%

Synthesis and Conformational Characteristics of Thermosensitive Star-Shaped Six-Arm Polypeptoids

et al. 2020

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Star-shaped six-arm poly-2-alkyl-2-oxazine and poly-2-alkyl-2-oxazoline with hexaaza [26]orthoparacyclophane derivative core were synthesized successfully using cationic ring-opening polymerization. Conformational behavior of prepared polymer stars were investigated by the methods of molecular hydrodynamics and optics in molecular dispersed solutions. It was shown that conformation characteristics of star-shaped polypeptoids depends on arm length, while the chemical structure weakly affects the behavior of the studied polymers in solutions. This behavior is caused by the close equilibrium rigidity of arms. The star-shaped polypeptoids have relatively high intramolecular density. All synthesized stars exhibit LCST behavior. Phase separation temperature depends on arm structure. It is lower for poly-2-alkyl-2-oxazines, monomer units of which contains one methylene group more than monomers of poly-2-alkyl-2-oxazoline.

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Section: Introductionsupporting

confidence: 70%

Synthesis and Conformational Characteristics of Thermosensitive Star-Shaped Six-Arm Polypeptoids

et al. 2020

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“…T onset were generally lower than the cloud point temperatures at 50% transmittance recorded by turbidimetry, especially for pEFS8-46 solutions at lower concentrations, which presented a wider transition (Figure 3b). As for other thermosensitive polymers [49,50], such a difference might be ascribed to the greater sensitivity of the calorimetric technique in detecting the beginning of the phase transition, when the fraction of multichain aggregates is not yet large enough to be detected by turbidimetry. Table 3.…”

Section: Characterization Of the Phase Transitionmentioning

confidence: 99%

Investigation of the LCST-Thermoresponsive Behavior of Novel Oligo(Ethylene Glycol)-Modified Pentafluorostyrene Homopolymers

et al. 2021

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Amphiphilic tetrafluorostyrene monomers (EFS8) carrying in the para position an oligoethylene glycol chain containing 8 oxyethylenic units on average were synthesized and used for preparation via activator regenerated by electron transfer atom transfer radical polymerization (ARGET-ATRP) of the corresponding amphiphilic homopolymers (pEFS8-x) with different degrees of polymerization (x = 26 and 46). Combining light transmittance and nano-differential scanning calorimetry (n-DSC) measurements revealed that pEFS8-x homopolymers displayed a lower critical solution temperature (LCST) thermoresponsive behavior in water solutions. Moreover, n-DSC measurements revealed the presence in heating scans of a broad endothermic peak ascribable to the dehydration process of the polymer single chains (unimers) and their collapse into aggregates. Consistently, dynamic light scattering (DLS) measurements showed below the LCST the presence of small nanostructures with a hydrodynamic diameter size Dh of 6–7 nm, which collapsed into concentration-dependent larger multichain aggregates (Dh = 300–3000 nm) above LCST. Interestingly, n-DSC data showed that the unimer-aggregate transition was reversible up to a specific temperature (Trev) of each homopolymer, which in any case was higher than Tmax. When heating above Trev the transition was no longer reversible, causing the shift of Tonset and Tmax at lower values, thus suggesting an increase in hydrophobicity of the polymer systems associated with a temperature-dependent dehydration process.

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“…Usually, the studies of the solutions temperature behavior in LCST-type phase transition are conducted utilizing light scattering, cloud point measurement, differential scanning calorimetry, infrared (IR) spectroscopy, NMR spectroscopy, small angle X-ray scattering etc., [ 23 , 24 , 25 , 26 , 27 , 28 ]. Among these methods, NMR spectroscopy stands out, because it can provide quantitative information on the LCST phase separation behavior.…”

Section: Introductionmentioning

confidence: 99%

Temperature Behavior of Aqueous Solutions of Poly(2-Oxazoline) Homopolymer and Block Copolymers Investigated by NMR Spectroscopy and Dynamic Light Scattering

2020

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1H NMR methods in combination with dynamic light scattering were applied to study temperature behavior of poly(2-isopropyl-2-oxazoline) (PIPOx) homopolymer as well as PIPOx-b-poly(2-methyl-2-oxazoline) (PMeOx) and poly(2-ethyl-2-oxazoline) (PEtOx)-b-PMeOx diblock copolymers in aqueous solutions. 1H NMR spectra showed a different way of phase transition for the main and side chains in PIPOx-based solutions. Additionally, the phase transition is irreversible for PIPOx homopolymer and partially reversible for PIPOx-b-PMeOx copolymer. As revealed by NMR, the phase transition in PEtOx-based copolymers solutions exists despite the absence of solution turbidity. It is very broad, virtually independent of the copolymer composition and reversible with some hysteresis. Two types of water molecules were detected in solutions of the diblock copolymers above the phase transition—“free” with long and “bound” with short spin–spin relaxation times T2. NOESY spectra revealed information about conformational changes observed already in the pre-transition region of PIPOx-b-PMeOx copolymer solution.

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Dehydration, Micellization, and Phase Separation of Thermosensitive Polyoxazoline Star Block Copolymers in Aqueous Solution

Cited by 23 publications

References 29 publications

Synthesis and Conformational Characteristics of Thermosensitive Star-Shaped Six-Arm Polypeptoids

Synthesis and Conformational Characteristics of Thermosensitive Star-Shaped Six-Arm Polypeptoids

Investigation of the LCST-Thermoresponsive Behavior of Novel Oligo(Ethylene Glycol)-Modified Pentafluorostyrene Homopolymers

Temperature Behavior of Aqueous Solutions of Poly(2-Oxazoline) Homopolymer and Block Copolymers Investigated by NMR Spectroscopy and Dynamic Light Scattering

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