Phase Transition Of Polymer Research Articles

Thermal behavior of polymers and copolymers based on plant oils with differing saturated and monounsaturated content

AbstractPlant oil‐based acrylic monomers from hydrogenated sunflower (HFM), palm (PMM) and castor (CSM) oils were polymerized to investigate the effect of chemical composition on polymer phase transitions at temperatures relevant to physiological range. While HFM and PMM possess a highly differing content of saturated palmitic and stearic acids combined with unsaturated fatty acids, CSM contains primarily fragments based on monounsaturated ricinoleic hydroxy acid (up to 90%). Differential scanning calorimetry (DSC) measurements indicate that polymers from PMM and HFM are both semicrystalline (with Tm = −6 and −13 °C, respectively), while poly(CSM) appears to be amorphous (Tg = −49 °C). Considering the similarity in polymers' molar mass (Mn = 16 000–20 000 g mol−1), the observed thermal transitions can be explained by the formation of ordered morphological domains due to the presence of saturated palmitic and stearic acid fractions in poly(PMM) and poly(HFM). For copolymers of CSM, PMM and HFM (80 wt% of monomer feed) with styrene, DSC data show two transitions corresponding to the mobility of long alkyl fatty acid side fragments and the macromolecular backbone. For copolymers of PMM and HFM, comparable values (−52.8 and −55.5 °C, respectively) were obtained, while the second transition for poly(CSM‐co‐styrene) appears at 35 °C. We attribute this higher value to the presence of hydroxyl groups in ricinoleic acid fragments of CSM serving as additional chain transfer sites and the formation of macromolecular fractions enriched with polystyrene fragments. We expect that the temperature transitions obtained can be relevant to the future use of these polymers for biomedical applications, including the synthesis of polymer brushes. © 2024 Society of Chemical Industry.

Microalgae aggregation induced by thermoresponsive polymers

Algal biomass harvesting is one of key technical hurdles impeding the commercialization of algae-based biorefinery. The goal of this work is to develop an innovative technology for algae cell harvesting. Thermoresponsive polymers (TRPs) such as poly(N-isopropylacrylamide) (PNIPAM) and its derivatives were studied on their properties and potential applications for microalgae harvesting. Various PNIPAM was synthesized, and the effects of charge, molecular weight (MW), amine content, and polymer concentration on the polymer phase transition temperature, the degree of phase separation, and the harvesting of microalgae (Chlorella vulgaris) were investigated. The lower critical solution temperature (LCST) of PNIPAM decreased with the increase of polymer concentration, while the decline rate reduced under high MW. The amine content didn’t significantly affect the LCST of TRPs. Approx. 92 % of algae cells were harvested by PNIPAM-300 kDa. Modified TRPs showed few benefits in enhancing algae harvesting. TRPs are a promising class of polymers for microalgae harvesting.

Role of flexible spacers in achieving photoinduced phase transitions of azobenzene-based liquid-crystalline polymers at room temperature

Role of flexible spacers in achieving photoinduced phase transitions of azobenzene-based liquid-crystalline polymers at room temperature

Effects of hydrogen cycling on the performance of 70 MPa high-pressure hydrogen storage tank liners formed by different processes

Current research on the compatibility between plastic liners utilized in Type IV high-pressure hydrogen storage containers and hydrogen remains insufficiently comprehensive. Therefore, further exploration into how the high-pressure hydrogen storage process influences the crystalline phase transition of polymers is essential to improve the applicability and safety of plastic lining materials. This study primarily investigated the preparation of polyamide 1012 (PA1012) and polyamide 11 (PA11) through rotational molding and injection molding, denoted as Roto-PA1012/Roto-PA11 and In-PA1012/In-PA11, respectively. Considering the operational parameters of the 70 MPa Type IV hydrogen storage tank, we conducted hydrogen cycling experiment using the long carbon chain polyamide (LCPA) liner materials and comprehensively analyzed the morphology, crystal structure, grain size, mechanical properties and hydrogen barrier properties of polyamide materials before and after hydrogen cycling. The results showed that after hydrogen cycling, no significant changes were observed in Roto-PA1012/Roto-PA11, while In-PA1012/In-PA11 demonstrated severe foaming. Rotational molding of LCPA maintained stable mechanical and hydrogen barrier properties throughout the hydrogen cycle, which can be attributed to the favorable thermodynamic stability of the α' form achieved during rotational molding, leading to uniform and stable crystal sizes. In conclusion, this study provides a theoretical foundation for future investigations into the molding process and material selection of high-barrier polymer liners, as well as the actual production and utilization of Type IV hydrogen storage tanks.

Deformable Joule heating electrode based on hybrid layers of silver nanowires and carbon nanotubes and its application in a refreshable multi-cell Braille display.

Stretchable electrodes are an essential component in soft actuator systems. In particular, Joule heating electrodes (JHEs) are required for thermal actuation systems. A highly stretchable, patternable, and low-voltage operating JHE based on hybrid layers of silver nanowires (AgNWs) and carbon nanotubes (CNTs) is reported. The conductive layers were applied on a locally pre-strained bistable electroactive polymer (BSEP) membrane to form a wrinkled conductive surface with a low resistance of 300 Ω/sq, and subsequently patterned to a serpentine trace by laser engraving. The resistance of the resulting electrode remains nearly unchanged up to ~80-90% area strain. By applying a voltage of 7 - 9 V to the electrode, the temperature of the BSEP membrane increased to more than 60 °C, well above the polymer's phase transition temperature of 46 °C, thereby lowering its modulus by a factor of 103. An electronic Braille device based on the JHEs on a BSEP membrane was assembled with a diaphragm chamber. The electrode was patterned into 3 × 2 individually addressable pixels according to the standard U.S. Braille cell format. Through Joule heating of the pixels and local expansion of the BSEP membrane using a small pneumatic pressure, the pixels deformed out of the plane by over 0.5 mm to display specific Braille letters. The Braille content can be refreshed for 20,000 cycles at the same operating voltage.

Low-k nano-dielectrics facilitate electric-field induced phase transition in high-k ferroelectric polymers for sustainable electrocaloric refrigeration

Ferroelectric polymer-based electrocaloric effect may lead to sustainable heat pumps and refrigeration owing to the large electrocaloric-induced entropy changes, flexible, lightweight and zero-global warming potential. Herein, low-k nanodiamonds are served as extrinsic dielectric fillers to fabricate polymeric nanocomposites for electrocaloric refrigeration. As low-k nanofillers are naturally polar-inactive, hence they have been widely applied for consolidate electrical stability in dielectrics. Interestingly, we observe that the nanodiamonds markedly enhances the electrocaloric effect in relaxor ferroelectrics. Compared with their high-k counterparts that have been extensively studied in the field of electrocaloric nanocomposites, the nanodiamonds introduces the highest volumetric electrocaloric enhancement (~23%/vol%). The resulting polymeric nanocomposite exhibits concurrently improved electrocaloric effect (160%), thermal conductivity (175%) and electrical stability (125%), which allow a fluid-solid coupling-based electrocaloric refrigerator to exhibit an improved coefficient of performance from 0.8 to 5.3 (660%) while maintaining high cooling power (over 240 W) at a temperature span of 10 K.

Compensation behaviors and phase transitions of a 3D fullerene-like polymer

Compensation behaviors and phase transitions of a 3D fullerene-like polymer

Nanoencapsulation of carotenoid extract via the temperature-induced phase transition of triblock polymer in supercritical carbon dioxide

Abstract Objectives Carotenoids are increasingly explored as nutraceuticals, but their low bioavailability due to poor aqueous solubility limits their applications. This study discusses the development of a novel and organic solvent-free method to develop carotenoid-containing polymeric nanoparticles via temperature-induced phase transition (TIPT) of pluronic F-68 to obtain formulations with the improved dissolution of carotenoids. Methods The nanoencapsulation of carotenoids in pluronic F-68 was performed in supercritical carbon dioxide (scCO2) to avoid oxidative or temperature/solvent-induced degradation. The nanoencapsulates were prepared in scCO2 at 40°C or 60°C and 10 MPa without the aid of any organic solvent. The formulations thereafter were characterised for particle size via dynamic light scattering, particle morphology via scanning electron microscopy and carotenoid content/release via high-performance liquid chromatography (HPLC). Key findings HPLC results showed carotenoid degradation to be negligible in freshly prepared formulations when prepared in scCO2 at 60°C and 10 MPa. The developed particles were spheroidal with sizes ranging between 150 and 250 nm depending on carotenoid content in the preparation. An improvement in the aqueous solubility and storage stability (5°C) of carotenoids was also observed for the formulations prepared in scCO2. Conclusions These results suggest that TIPT under scCO2 can be applied to formulate nanoparticulates with improved dissolution rate and stability of thermosensitive molecules such as carotenoids without causing any degradation during the processing.

Bidirectionally Modulating the Dissipative Phase Transition of UCST Polymers in a Programmable Manner Using Visible Light

AbstractDynamic phase transitions are important in living organisms for sustaining their adaptive structures and functions. The design of artificial dynamic systems using light as a noninvasive input fuel has gained significant interest to mimic such adaptive features. Here the development of light‐fueled dissipative phase transitions of upper critical solution temperature polymers by introducing pendant spiropyrans as photoactive units, is reported. The reversible open‐close photoisomerization of spiropyrans is designed to undergo either an enhancement or a decline of their net charge, which is subsequently used to regulate the electrostatic interactions between polymer chains, and ultimately shift their phase transition temperatures to either a lower or a higher direction. The degree and speed of such bidirectional shifting are flexibly modulated by manipulating the external illumination parameters or varying the compositions/concentrations of the polymers. The diametrically opposite transmittance changes driven by light are utilized to produce a series of complementary patterns and shapes for application in transient information storage and encryption with improved accuracy and security. This work offers a bidirectional spatiotemporal modulation of dissipative phase transitions of polymers using visible light that allows highly tunable and adaptable features shared with their natural counterparts.

Reprogrammable magnetization pattern and shape morphing of phase-change magnetic soft composites

Magnetic soft composites with programmable magnetization patterns are highly desirable for diverse applications due to their multimodal magnetic response and locomotion. Despite substantial progress achieved in magnetic programming approaches, reprogrammable magnetization using low magnetic fields is still in development and challenging. Here, we report a one-step multi-direction magnetic reorientation strategy capable of reprogramming magnetization patterns in soft composites consisting of an elastomer matrix and magnetized ferromagnetic microparticles encapsulated by a phase-change polymer. Our approach is first based on the overall heating of these soft composites to achieve polymer phase transition, and then use magnet arrays to locally regulate the magnetic field distribution to achieve magnetic reorientation and programmable magnetization. Importantly, this approach allows us to reconstruct the desired magnetization patterns by reheating and redesigning the applied magnetic field. Using this approach, we numerically and experimentally demonstrate that multimodal magnetization and deformation patterns of millimeter-level strip-shaped and multi-arm phase-change soft composites can be achieved without changing the composite structure and the externally applied magnetic field. Furthermore, we demonstrate its functional applications in developing a multistate circuit switching, as well as a flexible magnetic recording that can present a variety of information such as numbers, letters, and face-based patterns.

Thermally Switchable Nanogate Based on Polymer Phase Transition.

Mimicking and extending the gating properties of biological pores is of paramount interest for the fabrication of membranes that could be used in filtration or drug processing. Here, we build a selective and switchable nanopore for macromolecular cargo transport. Our approach exploits polymer graftings within artificial nanopores to control the translocation of biomolecules. To measure transport at the scale of individual biomolecules, we use fluorescence microscopy with a zero-mode waveguide set up. We show that grafting polymers that exhibit a lower critical solution temperature creates a toggle switch between an open and closed state of the nanopore depending on the temperature. We demonstrate tight control over the transport of DNA and viral capsids with a sharp transition (∼1 °C) and present a simple physical model that predicts key features of this transition. Our approach provides the potential for controllable and responsive nanopores in a range of applications.

Experimental investigations of coupled polymer and membrane phase transitions.

Polymers can separate into polymer dense and polymer dilute liquid phases in solution while multicomponent lipid membranes can separate into distinct phases within the two-dimensional plane of the membrane. Recent theoretical and simulation work predicts the presence of a polymer rich surface phase when these two-phase transitions are coupled by including polymer conjugated lipids in membranes, and that the location of this phase boundary is tuned by both polymer and lipid interactions1. Here, we experimentally observe the predicted domains of polymer rich surface phase when a small subset of polymers are conjugated to membranes. These surface phases appear at concentrations where polymers do not condense in the bulk, and the concentration needed to form surface phase depends on membrane composition. Experiments have been conducted both with a simple polyelectrolyte and with FUS proteins in separate measurements, demonstrating the robustness of this effect. 1. Rouches, M., Veatch, S. & Machta, B. Surface Densities Prewet a Near-Critical Membrane. bioRxiv2021.02.17.431700 (2021).

Electrochemical Cloud Point Temperature from Thermoamperometry: Real-Time Analysis for Phase Transition of Thermoresponsive Polymers.

Cloud point temperature (Tcp) is a thermal index used to define the phase transition of thermoresponsive polymers. In this study, we used electrochemical techniques to obtain an electrochemical cloud point temperature (Tecp) that exhibits the more accurate phase transition temperature and can replace Tcp. Thermoamperometry on an ultramicroelectrode was conducted with a poly(arylene ether sulfone) (PES10) as a model system to obtain a current-temperature (i-T) curve in real time; the Tecp of the PES10 was determined from the i-T curve. The i-T curve shows an unprecedented current decrease in the PES10 solution despite increasing temperature; on the other hand, the current increased linearly with increasing temperature in the solution without PES10. This phenomenon was analyzed by considering the characteristics of PES10 during phase transition, such as dynamic viscosity, temperature of the solution, and electrode impedance. It was confirmed that the current drops shown in the i-T curves were mainly due to the decrease of real electrode area. The comparison of Tecp and Tcp showed that both depended similarly on the concentrations of the thermoresponsive polymer and the supporting electrolyte. The results reveal that by adjusting the concentration of polymer and electrolyte in an organic solution, Tecp, as a new analytical method, can be used in electric circuit-based energy storage appliances such as Li-ion batteries and supercapacitors.

Computer simulation and machine learning of polymer collapse and critical adsorption phase transitions

Collapse and critical adsorption of polymers are two crucial phase transitions in polymer science, both are accompanied by significant changes in polymer conformation. In this paper, Langevin dynamics and dynamic Monte Carlo methods are used to simulate the collapse and critical adsorption of polymer, respectively, and corresponding phase transition temperatures are estimated. Meanwhile, a large number of polymer conformations at different temperatures are obtained. In the machine learning method, a large number of extended random coil and collapsed spherical, desorption and adsorption conformations are used to train the neural network, so that the neural network can learn the characteristics of different states of the polymer, and it can quickly and accurately analyze the polymer conformations at different temperatures and obtain the corresponding collapse phase transition temperature and critical adsorption temperature. The results demonstrate that machine learning can correctly calculate the phase transition temperature of polymer system, which provides new ideas and methods for machine learning technology in the study of polymer phase transitions.

AC/DC Thermal Nano-Analyzer Compatible with Bulk Liquid Measurements

Nanocalorimetry, or thermal nano-analysis, is a powerful tool for fast thermal processing and thermodynamic analysis of materials at the nanoscale. Despite multiple reports of successful applications in the material sciences to study phase transitions in metals and polymers, thermodynamic analysis of biological systems in their natural microenvironment has not been achieved yet. Simply scaling down traditional calorimetric techniques, although beneficial for material sciences, is not always appropriate for biological objects, which cannot be removed out of their native biological environment or be miniaturized to suit instrument limitations. Thermal analysis at micro- or nano-scale immersed in bulk liquid media has not yet been possible. Here, we report an AC/DC modulated thermal nano-analyzer capable of detecting nanogram quantities of material in bulk liquids. The detection principle used in our custom-build instrument utilizes localized heat waves, which under certain conditions confine the measurement area to the surface layer of the sample in the close vicinity of the sensing element. To illustrate the sensitivity and quantitative capabilities of the instrument we used model materials with detectable phase transitions. Here, we report ca. 106 improvement in the thermal analysis sensitivity over a traditional DSC instrument. Interestingly, fundamental thermal properties of the material can be determined independently from heat flow in DC (direct current) mode, by using the AC (alternating current) component of the modulated heat in AC/DC mode. The thermal high-frequency AC modulation mode might be especially useful for investigating thermal transitions on the surface of material, because of the ability to control the depth of penetration of AC-modulated heat and hence the depth of thermal sensing. The high-frequency AC mode might potentially expand the range of applications to the surface analysis of bulk materials or liquid-solid interfaces.

Processes of Electrospun Polyvinylidene Fluoride-Based Nanofibers, Their Piezoelectric Properties, and Several Fantastic Applications.

Since the third scientific and technological revolution, electronic information technology has developed rapidly, and piezoelectric materials that can convert mechanical energy into electrical energy have become a research hotspot. Among them, piezoelectric polymers are widely used in various fields such as water treatment, biomedicine, and flexible sensors due to their good flexibility and weak toxicity. However, compared with ceramic piezoelectric materials, the piezoelectric properties of polymers are poor, so it is very important to improve the piezoelectric properties of polymers. Electrospinning technology can improve the piezoelectric properties of piezoelectric polymers by adjusting electrospinning parameters to control the piezoelectrically active phase transition of polymers. In addition, the prepared nanofibrous membrane is also a good substrate for supporting piezoelectric functional particles, which can also effectively improve the piezoelectric properties of polymers by doping particles. This paper reviews the piezoelectric properties of various electrospun piezoelectric polymer membranes, especially polyvinylidene fluoride (PVDF)-based electrospun nanofibrous membranes (NFs). Additionally, this paper introduces the various methods for increasing piezoelectric properties from the perspective of structure and species. Finally, the applications of NFs in the fields of biology, energy, and photocatalysis are discussed, and the future research directions and development are prospected.

Excitonic switching across a Z2 topological phase transition: From Mott-Wannier to Frenkel excitons in organic materials

Controllable topological phase transitions are appealing as they allow for tunable single particle electronic properties. Here, by using state-of-the-art manybody perturbation theory techniques, we show that the topological $Z_2$ phase transition occurring in the single particle spectrum of the recently synthetized ethynylene bridged polyacene polymers is accompanied by a topological excitonic phase transition: the band inversion in the non-trivial phase yields real-space exciton wave functions in which electrons and holes exchange orbital characters with respect to the trivial phase. The topological excitonic phase transition results in a broad tunability of the singlet-triplet splittings, opening appealing perspectives for the occurrence of singlet fission. Finally, the flatness of the single-particle electronic structure in the topological non trivial phase leads to negatively dispersing triplet excitons in a large portion of the Brillouin zone, opening a route for spontaneously coherent energy transport at room temperature.

Cell-Size Space Regulates the Behavior of Confined Polymers: From Nano- and Micromaterials Science to Biology.

Polymer micromaterials in a liquid or gel phase covered with a surfactant membrane are widely used materials in pharmaceuticals, cosmetics, and foods. In particular, cell-sized micromaterials of biopolymer solutions covered with a lipid membrane have been studied as artificial cells to understand cells from a physicochemical perspective. The characteristics and phase transitions of polymers confined to a microscopic space often differ from those in bulk systems. The effect that causes this difference is referred to as the cell-size space effect (CSE), but the specific physicochemical factors remain unclear. This study introduces the analysis of CSE on molecular diffusion, nanostructure transition, and phase separation and presents their main factors, i.e., short- and long-range interactions with the membrane surface and small volume (finite element nature). This serves as a guide for determining the dominant factors of CSE. Furthermore, we also introduce other factors of CSE such as spatial closure and the relationships among space size, the characteristic length of periodicity, the structure size, and many others produced by biomolecular assemblies through the analysis of protein reaction-diffusion systems and biochemical reactions.

Smart Protein Refolding System Based on UCST-Type Ureido Polymers.

We have reported that ureido polymers exhibit upper critical solution temperature (UCST)-type phase behavior in solution, which is the opposite of lower critical solution temperature (LCST)-type behavior. Furthermore, UCST-type ureido polymers undergo liquid-liquid phase separation (LLPS) upon cooling rather than the liquid-solid phase transition of the typical LCST-type polymers. In this study, ureido polymers with hydrophobic groups were prepared to evaluate the effects of cooling-induced LLPS of UCST-type polymers on refolding of proteins. When protein was heated with a ureido polymer functionalized with undecyl groups, aggregation of the protein was prevented. Subsequent cooling incubation resulted in the spontaneous release of the protein from the polymer. The released protein had enzymatic activity, suggesting that the protein refolded properly. Interestingly, efficient refolding was observed when the solution of the UCST-type ureido polymer and protein was incubated at around the phase separation temperature of the polymer, implying that cooling-induced LLPS of the polymer enhanced the release of the protein. Additionally, by centrifugation at 4 °C, the refolded protein was readily separated from the ureido polymers, which precipitated upon cooling.

Dextran-graft-PNIPAM / Au nanoparticles / perylenediimide hybrid system as thermosensitive optical switches and fluorescent labels for potential use in nanophotonics and biomedical applications

A triple thermosensitive polymer Dextran-g-Poly(N-isopropylacrylamide)/Au nanoparticles/Perylenediimide (D-g-PNIPAM/AuNPs/PDI) hybrid nanosystem was formulated in aqueous solution for potential use as thermoresponsive fluorescent optical switch and label. The completely reversible effect of sharp enhancement-quenching of the photoluminescence of D-g-PNIPAM/AuNPs/PDI nanosystem was revealed during the heating-cooling cycle in the narrow temperature range of 25–47 °C, containing the temperature point of the LCST phase transition of the thermosensitive polymer. The sharp change in the intensity of photoluminescence was shown to result from the competing effects of plasmonic enhancement and non-radiative FRET transfer of electronic excitation energy during thermo-induced LCST transition of the D-g-PNIPAM macromolecule. The observed effect allows to carry out the temperature control of the photoluminescence intensity, which appears to be particularly important for potential applications of D-g-PNIPAM/AuNPs/PDI hybrid nanosystem in photonics, biology and medicine, such as thermosensitive fluorescent optical switch and label or intracellular fluorescent thermometer.