Phase Transition Of Poly Research Articles

Revealing Phase Transitions in Poly(Ethylene Oxide)‐Based Electrolyte for Room‐Temperature Solid‐State Batteries (Adv. Energy Mater. 40/2024)

Revealing Phase Transitions in Poly(Ethylene Oxide)‐Based Electrolyte for Room‐Temperature Solid‐State Batteries (Adv. Energy Mater. 40/2024)

Revealing Phase Transitions in Poly(Ethylene Oxide)‐Based Electrolyte for Room‐Temperature Solid‐State Batteries

AbstractSolid‐state electrolytes (SSEs) offer enhanced safety, extended cycle life, and increased energy density when replacing flammable liquid electrolytes in lithium‐ion batteries. Poly(ethylene oxide) (PEO)‐based SSE is the only candidate that has been commercially implemented in electric vehicles. However, the equipped battery needs to operate at temperatures above 50 °C, and its phase transitions at room temperature are still unclear. Herein, the solidification of the PEO‐lithium bis(trifluoromethanesulfonyl)imide (PEOn‐LiTFSI) system is revisited. Contrary to the prevailing view of forming PEO(6)‐LiTFSI spherulites, the presence of crystalline PEO(8)‐LiTFSI complexes is quantitatively confirmed. The nucleation and growth processes of crystalline PEO and PEO(8)‐LiTFSI spherulites are also visually elucidated, and phase transitions with the impedance change are correlated. In addition, it is demonstrated that the crystalline PEO shell surrounding the PEO(8)‐LiTFSI spherulites hinders the kinetics of crystal growth, thereby enabling the highest ionic conductivity at n = 10. Importantly, it is pointed out that instead of the poor ionic conductivity of the electrolyte layer, the heterogeneous nucleation of PEO(8)‐LiTFSI within the electrodes is the limiting factor in constructing room‐temperature all‐solid‐state batteries.

Greasy Cations Bind to Neutral Macromolecules in Aqueous Solution.

Ions influence the solution properties of macromolecules. Although much is known about anions, cationic effects are considered mostly in terms of weak interactions or exclusion from neutral interfaces. Herein, we have systematically studied the effect of quaternary tetraalkylammonium cations (NH4+, NMe4+, NEt4+, NPr4+, NBu4+) on the phase transition of poly(N-isopropylacrylamide) (PNIPAM) in aqueous solution. Solubility measurements were coupled to 1H NMR and ATR-FTIR spectroscopic measurements. The solubility and NMR measurements revealed a direct binding between the greasiest cations and the isopropyl group of the macromolecule, evidenced from the nonlinear, Langmuir-type chemical shift response only at the isopropyl NMR signals with increasing salt concentrations. The ATR-FTIR measurements focusing on the amide oxygen showed that it is not the main direct-binding site. Additionally, the salting-out effects of the greasier cations correlate with their hydration entropies. These results demonstrate that the most weakly hydrated cations can bind to macromolecules as strongly as the weakly hydrated Hofmeister anions.

An improved methodology to quantify the temperature-induced phase transition in poly(dimethylsiloxane) elastomer

Revealing the molecular chain dynamics and determining the absolute degree of crystallinity during the phase transition have been a challenge in the field of polymer crystallization. In this work, a special low-temperature testing chamber was designed and utilized in combination with a laboratory X-ray diffraction apparatus, in order to perform temperature-dependent time-resolved WAXD measurements of highly flexible poly (dimethylsiloxane) (PDMS) elastomer. From the changes of diffraction patterns and the 2D correlation analysis of WAXD profiles, we can clearly observe the crystallization and melting behaviors of PDMS during cooling and heating. Meanwhile, an improved multi-Gaussian fitting method was developed and applied to quantitatively analysis the structural evolution. Moreover, the constrained amorphous interchain segments show a narrow fitted Gaussian peak like crystalline planes, which can only be discovered when the crystallinity of PDMS exceeds a certain threshold of about 10 %. These results have evidenced that this improved method enables not only an accurate determination of crystallinity, but also a reliable quantification of structural evolution of PDMS elastomeric materials, which might be beneficial for understanding the mechanism of phase transition.

Influence of self-nucleation on phase transition in poly(1-butene)

The self-nucleation effect is often investigated to focus on kinetics and polymorphism of melt crystallization. In this work, the effect of self-nucleation on solid phase transition from the tetragonal phase into the thermodynamically most stable trigonal phase was studied with differential scanning calorimetry (DSC) for the isotactic poly(1-butene). With respect to the initial completely relaxed melt in Domain I, self-nucleation treatment of Domains II and III show the opposite influences on phase transition kinetics, where the former accelerates phase transition but the latter inhibits phase transition. Employing isothermal crystallization experiments, it is found that at the lowered self-nucleation temperature (Ts), the further accelerated phase transition was caused by the enlarged internal stress, which triggers nucleation of form I within form II. Interestingly, although cooling crystallization can be enhanced as Ts was cooled into Domain III, the corresponding phase transition of obtained crystallites was inhibited, even slower than that of relaxed melt in Domain I. As Ts was further lowered to 115 °C with the increased isothermal time, the initial crystallites not only survive but also thicken during the isothermal process at Ts. More interestingly, the annealed crystallites exhibited the most suppressed phase transition. The accelerated phase transition by Ts of Domain II was related to the increased internal stress, which drives the nucleation of transformed trigonal phase within the original tetragonal phase. Differently, the inhibited phase transition by self-nucleation of Domain III was associated with the reduced links between lamellae and amorphous region, which facilitates the transfer of internal stress.

Enhanced Phase Transition in Poly(ethylene glycol) Grafted Butene-1 Copolymers

Enhanced Phase Transition in Poly(ethylene glycol) Grafted Butene-1 Copolymers

Correction to “Ionic Liquid Assisted α–γ′ Phase Transition of Poly(vinylidene fluoride) Thin Films”

Correction to “Ionic Liquid Assisted α–γ′ Phase Transition of Poly(vinylidene fluoride) Thin Films”

Effect of annealing on thermal and dynamic mechanical properties of poly(lactic acid)

AbstractEffects of annealing temperature (Ta: 80–140°C) and time (ta: 3‐30 h) on the crystalline phase transition in poly(lactic acid) (PLA) were studied by differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). In the DSC curves, the sample annealed at Ta = 80°C with time interval (ta: 10–30 h) demonstrates a peculiarly small exothermal peak (Texo) around 130°C, just prior to the melting point, corresponding to the disorder‐to‐order (α’‐to‐α) phase transition, while the sample annealed at temperature (Ta: 90–110°C) shows a double melting behavior considered as the α’‐α phase transition. Towards low temperatures, the glass modulus Eg reported by DMA thermograms, shows an important increase (~30,000 MPa) at Ta = 80°C for ta = 3 h, due to the extremely high self‐nucleation density in low‐crystallized PLA materials. After a sharp drop to 3600 MPa at Ta = 110°C, a marked improvement of Eg (15,900 MPa) is observed around Ta = 120°C for all samples, regardless of time ta. This interesting effect (improvement of Eg in the range Ta = 100–120°C) can be correlated with the grow of crystallinity in the same domain of Ta, and the α’‐α phase transition Ta (Ta: 90–110°C) determined by the double Tm melting DSC peak, which is confirmed by the increase of Tg for Ta = 90–110°C.

Lower Critical Solution Temperature Tuning and Swelling Behaviours of NVCL-Based Hydrogels for Potential 4D Printing Applications.

The phase transitions of poly (N-vinyl caprolactam) (PNVCL) hydrogels are currently under investigation as possible materials for biomedical applications thanks to their thermosensitive properties. This study aims to use the photopolymerisation process to simulate the 4D printing process. NVCL-based polymers with different thermal properties and swellability were prepared to explore the possibility of synthetic hydrogels being used for 4D printing. In this contribution, the thermal behaviours of novel photopolymerised NVCL-based hydrogels were analysed. The lower critical solution temperature (LCST) of the physically crosslinked gels was detected using differential scanning calorimetry (DSC), ultraviolet (UV) spectroscopy, and cloud point measurement. The chemical structure of the xerogels was characterised by means of Fourier transform infrared spectroscopy (FTIR). Pulsatile swelling studies indicated that the hydrogels had thermo-reversible properties. As a result, the effect of varying the macromolecular monomer concentration was apparent. The phase transition temperature is increased when different concentrations of hydrophilic monomers are incorporated. The transition temperature of the hydrogels may allow for excellent flexibility in tailoring transition for specific applications, while the swelling and deswelling behaviour of the gels is strongly temperature- and monomer feed ratio-dependent.

Nematic-to-Isotropic Phase Transition in Poly(L-Lactide) with Addition of Cyclodextrin during Abiotic Degradation Study.

Poly(L-lactide) is capable of self-assembly into a nematic mesophase under the influence of temperature and mechanical stresses. Therefore, subsequent poly(L-lactide) films were obtained and characterized, showing nematic liquid crystal properties both before and after degradation. Herein, we present that, by introducing β-cyclodextrin into the polymer matrix, it is possible to obtain a chiral nematic mesophase during pressing, regardless of temperature and time. The obtained poly(L-lactide) films exhibiting liquid crystal properties were subjected to degradation tests and the influence of degradation on these properties was determined. Thermotropic phase behavior was investigated using polarized optical microscopy, X-ray diffraction, and differential scanning calorimetry. The degradation process demonstrated an influence on the liquid crystal properties of pressed polymer films. The colored planar texture of the chiral nematic mesophase, which was not observed prior to degradation in films without the addition of β-cyclodextrin, appeared after incubation in water as a result of the entrapment of degradation products in the polymer matrix. These unusual tailor-made properties, obtained in liquid crystals in (bio)degradable polymers using a simple method, demonstrate the potential for advanced photonic applications.

Ionic Liquid Assisted α–γ′ Phase Transition of Poly(vinylidene fluoride) Thin Films

Ionic Liquid Assisted α–γ′ Phase Transition of Poly(vinylidene fluoride) Thin Films

Phase Transitions in Poly(vinylidene fluoride)/Polymethylene-Based Diblock Copolymers and Blends.

The crystallization and morphology of two linear diblock copolymers based on polymethylene (PM) and poly(vinylidene fluoride) (PVDF) with compositions PM23-b-PVDF77 and PM38-b-PVDF62 (where the subscripts indicate the relative compositions in wt%) were compared with blends of neat components with identical compositions. The samples were studied by SAXS (Small Angle X-ray Scattering), WAXS (Wide Angle X-ray Scattering), PLOM (Polarized Light Optical Microscopy), TEM (Transmission Electron Microscopy), DSC (Differential Scanning Calorimetry), BDS (broadband dielectric spectroscopy), and FTIR (Fourier Transform Infrared Spectroscopy). The results showed that the blends are immiscible, while the diblock copolymers are miscible in the melt state (or very weakly segregated). The PVDF component crystallization was studied in detail. It was found that the polymorphic structure of PVDF was a strong function of its environment. The number of polymorphs and their amount depended on whether it was on its own as a homopolymer, as a block component in the diblock copolymers or as an immiscible phase in the blends. The cooling rate in non-isothermal crystallization or the crystallization temperature in isothermal tests also induced different polymorphic compositions in the PVDF crystals. As a result, we were able to produce samples with exclusive ferroelectric phases at specific preparation conditions, while others with mixtures of paraelectric and ferroelectric phases.

Facilitated phase transformation of PVDF in its composite with an ionic liquid

The phase transition of poly(vinylidene fluoride) (PVDF) from α-to γ′-phase is hardly accessible, especially for the low-temperature crystallized α-phase, owing to the diminished thermal energy available for transformation. In this study, the phase transition ability of α-PVDF is greatly improved in its composites with a typical imidazole ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]). The enhanced phase transition is achieved by two thermal steps, including the crystallization of α-phase and subsequent annealing at a higher temperature. The transformed lamellar morphology is dependent on the crystallization temperature of α-phase, while the phase transition efficiency mainly rests with the annealing temperature. The phase transition is always accompanied by the thermal degradation with elimination of HF, which is significantly accelerated by [BMIM][PF6]. The introduction of molecular defects and carbon-carbon double bonds probably increase the fraction of planar chain conformation, therefore, enhancing the phase transition efficiency.

Understanding the effect of urea on the phase transition of poly(N-isopropylacrylamide) in aqueous solution by temperature-dependent near-infrared spectroscopy

Regulating the folding state by denaturants is essential for the structure and function of proteins. Poly(N-isopropyl acrylamide) (PNIPAM) is usually regarded as a model for protein denaturation. The effects of urea, as a denaturant, on the aggregations of PNIPAM was studied by temperature-dependent near-infrared (NIR) spectroscopy, and particularly the variation of water structures was analyzed. The NIR spectra of the polymer-urea solutions containing different polymer concentrations were measured at different temperatures. N-way principal component analysis (NPCA) was performed to observe the spectral information. Three principal components (PCs) containing the spectral information of CH groups were obtained, showing three kinds of CH in the system. Obvious dehydration of the three CH groups occurs at 27.5 °C in solution, but the temperature turns to 27 °C for two kinds of the CH and 26.5 °C for the third one, respectively, in the urea-add solution. The effect of urea on the formation of the intramolecular hydrogen bonds that promotes polymer folding is suggested. The spectral information of NH in urea molecule indicates that the direct interaction of urea and polymer facilitates the stability of the polymer globule state. Furthermore, the spectral information of OH shows that the release of the water molecules with three hydrogen bonds (S3), which may connect the NH and CO groups in PNIPAM in solution, leads to the phase transition. When urea is added, urea may reduce the content of the S3 water to facilitate the release, making the phase transition at a low temperature.

Energetics and Mechanisms of poly(N-isopropylacrylamide) Phase Transitions in Water–Methanol Solutions

The phase transitions of poly(N-isopropylacrylamide) (PNIPAM) in water–methanol mixed solutions were studied in detail by high-sensitivity differential scanning calorimetry. From this study, the de...

Phase transitions of poly(oligo(ethylene glycol) methyl ether methacrylate)-water systems

The phase diagrams for poly (oligo (ethylene glycol) methyl ether methacrylate) (POEGMA) hydrogels with varying side chain lengths over broad temperature and composition ranges are shown for the first time. It is also shown that the ability of water to crystallize is strictly correlated with the occurrence of a volume phase transition in hydrogels, as both phenomena require the continuous water pathways in the system. A discontinuity in the water phase appears above wp = 0.83 for PMEO2MA and wp = 0.56 for other POEGMAs. In contrast to PMEO2MA, POEGMA hydrogels with longer oligoether chains are characterized by two distinct regimes for the glass transition as a function of polymer content. It was also confirmed that crystallization of the polymer network can be observed for POEGMA networks with suitably long oligoether chain lengths, namely, n ≥ 7. Moreover, the range of the polymer crystalline phase occurrence was found to increase with the length of the oligoether chain.

Dielectric Response Triggered by a Non-ferroelectric Phase Transition in Poly(Vinylidene Fluoride)/Poly(Ethylene Glycol)/Halloysite Composites

Thermoresponsive dielectric materials have attracted the interest of researchers as they exhibit very important application prospects in stimuli-responsive smart devices. In this contribution polyethylene glycol (PEG), impregnated in halloysite nanotubes (HNTs), was incorporated into poly(vinylidene fluoride) (PVDF) for tailoring the thermoresponsive dielectric properties based on a non-ferroelectric phase transition. The PVDF/PEG/HNTs displayed a remarkable rise of dielectric constant between 20 and 30 °C. The mechanism is related to the enhanced orientational polarization effect triggered by the solid–liquid phase transition of the PEG. This make it possible to design stimuli-responsive smart materials through a simple, low-cost and efficient strategy. The present work provides an alternative and innovative routine for tailoring thermal-induced dielectric behaviors via a non-ferroelectric phase transition by introducing PEG into a high-dielectric-constant polymer matrix.

Honeycomb-like porous chitosan films prepared via phase transition of poly(N-isopropylacrylamide) during water evaporation under ambient conditions.

Honeycomb-like porous chitosan (CS) films are attractive tools for developing functional materials for filters, catalyses, adsorbents, biomaterials, etc. A simple method for fabricating honeycomb-like porous CS films without special reagents, facilities, and techniques would make them accessible. Here we introduce an easily available method for fabricating honeycomb-like CS films without a strong acid/base, toxic reagents, or special facilities/techniques. An aqueous solution containing CS and poly(N-isopropylacrylamide) (PNIPAm) was allowed to stand at 25 °C to evaporate water. After 3 days, CS–PNIPAm composite films with homogenously phase-separated PNIPAm particles were obtained. The PNIPAm particles were removed by immersion in methanol, and the resulting films dried under reduced pressure to become honeycomb-like porous CS films. The pore size could be varied in the range of 0.5–3.0 μm by altering the CS concentration and the molecular weight of CS where the pore size was reduced under conditions with stronger interaction between CS molecules. We reveal that the key to success with this system is the decrease of lower critical solution temperature (LCST) of PNIPAm with water evaporation. In addition, we confirmed the removed PNIPAm was recyclable in this system. Furthermore, we found this method was also applicable to alginate. The proposed facile method for fabricating honeycomb-like porous polymeric films could provide various functional porous materials.

Biomass-derived carbon helices induced phase transition in poly(N-ispropylacrylamide): A sustainable tailoring of coil-globule transition in thermoresponsive polymer

Functional carbon helices (FCHs) containing various oxygenated functionalities derived directly from lignocellulosic biomass is proved to be a potential eco friendly candidate for biomolecules. No study reports the effect of biomass derived platform molecules on the thermoresponsive behavior of polymers, which have been proved potential candidates in carrying various drug delivery applications, gels, and tissue engineering in this vast area of research. Poly(N-isopropylacrylamide) (PNIPAM) is a thermoresponsive polymer that has been found to be a prevailing tool in carrying various aforesaid applications. This study reports a powerful impact on the thermoresponsive behavior of PNIPAM by a non-hazardous alternative form of a herbecious plant Parthenium hysterophorus. Fluorescence spectroscopy was deployed to study the microenvironment provided by carbon helices around the polymer structure. The results obtained are directly correlating with the increased polarity with higher concentration of FCHs and further confirmed a decrease in fluorescence intensity. Moreover, for better understanding of interactions between PNIPAM and FCHs, Fourier transform infrared spectroscopy (FTIR) was employed. The analysis of hydrodynamic diameter (dH) was carried out by dynamic light scattering (DLS) and the aggregate size of PNIPAM was found to increase in higher concentration of FCHs. A decrease from 34.7 °C to 29.0 °C in the lower critical solution temperature (LCST) of PNIPAM in FCHs was further confirmed by differential scanning calorimetry (DSC). Field emission scanning electron microscopy (FESEM) and Transmission electron microscopy (TEM) were also taken into account to understand the morphological changes of PNIPAM in presence of biomass derived carbon helices. The micrographs of PNIPAM-biomass are representing a perturbed morphology of PNIPAM during interaction with FCHs. In this study, high degree of oxygenated functionalities on the carbon helices has a meaningful impact on the conformational phase behavior of PNIPAM. The tendril like functional carbon helices (TLFCHs) are uniquely causing a decrease in the lower critical solution temperature (LCST) of PNIPAM. Our combined study indicates that biomass derived carbon helices significantly decrease the LCST of PNIPAM by 5 °C. Ultimately, the polymer achieves compact globule conformational and complete aggregated state.

Microscopic insights into the phase transition of poly(N-isopropylacrylamide) in aqueous media: Effects of molecular weight and polymer concentration

We study a temperature (T)-induced phase transition of semi-dilute poly(N-isopropylacrylamide) (pNIPAm) in H2O and D2O, focusing on effects of molecular weight and polymer concentration. We use simultaneous small- and wide-angle x-ray scattering (SWAXS) and dielectric relaxation spectroscopy (DRS). The hydration number Zhyd of pNIPAm is determined by DRS. We observe a gradual decrease of Zhyd with increasing T below TS − 6 K, where TS is the spinodal temperature, and its subsequent steep decrease on approaching TS. This eccentric two-mode dehydration behavior implies strong cooperative nature of hydration/dehydration of the pNIPAm chains. Furthermore, the observed dehydration is coupled to the critical fluctuations manifested by a power-law divergence of the correlation length ξ. The emergence of a low-q interference peak provides evidence that high-density microglobules are formed even far below Ts, where a swollen coil state of polymer chains is generally considered to be predominant. The local number density of the microglobules is almost unchanged below Ts, but then exhibits a step-like increase just above Ts, where most pNIPAm chains are already collapsed. This observation suggests that in addition to the ordinary (macroscopic) density order parameter, the local number density of the microglobules should serve as an additional order parameter monitoring the phase transition of aqueous pNIPAm. The correlation length significantly decreases at higher polymer concentration because of the stronger interpenetration effect between different chains. At higher concentration, ξ converges to similar values independent of molecular weight, which indicates an already congested state of the pNIPAm chains. Lowering averaged molecular weight leads to a stronger tendency of inter-chain aggregation and interface formation especially at high T.