Upper Critical Solution Temperature Research Articles

Effect of heterocyclic substituents on the thermo/pH/CO2-responsiveness of multistimuli-responsive homopolymers

A series of novel thermo/pH/CO2-triple responsive homopolymers were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization. These homopolymers contain ethoxy groups, and the end substituents are pyrrolidine, piperidine, N-methylpiperazine, morpholine and thiomorpholine, respectively. The effects of different heterocyclic substituents on the responsiveness of temperature, pH and CO2 were studied. For temperature-response, it was found that the lower critical solution temperature (LCST)-type cloud point (CP) temperature decreased as the number of carbon atoms increases, while the solubility of the polymers changed greatly with the introduction of oxygen, nitrogen and sulfur atoms. And the CP of the polymers can be adjusted by molecular weight, concentration and salt. Furthermore, some of these polymers present upper critical solution temperature (UCST) behavior in alcohols. For pH-response, the initial pH of the polymer solution is different, their critical pH changed accordingly, and is affected by temperature; in addition, changing the pH of solution can also affect the CP. For CO2-response, all of the polymers were completely soluble after pumping with CO2, and their LCST behavior recovered after N2 was pumped in, but there was a gap with the initial CP. The study of these properties reveals the influence of different heterocyclic substituents on the responsiveness of polymers, which is of great significance for understanding the stimulation response properties of polymers and provides ideas for the design of new stimuli-responsive polymers.

Simple Coacervation of Guanidinium-Containing Polymers Induced by Monovalent Salt

Liquid–liquid phase separation (LLPS) of macromolecules, called coacervation, is induced by non-covalent intermolecular associations in aqueous solutions, which is frequently observed in biological processes including cellular compartmentation, signaling, and regulation. Recently, associative interactions between π-conjugated residues have emerged to induce LLPS, along with electrostatic interaction. An arginine residue having a positively charged guanidinium group plays a pivotal role in protein phase behavior because the orientational amphiphilicity of guanidinium groups allows face-to-face π–π stacking despite Coulombic repulsion. In this study, we investigate the simple coacervates of guanidinium-functionalized polyelectrolytes (i.e., poly-arginine) in aqueous media as a function of salt concentration, salt type, and temperature to understand the exclusive role of π-conjugated moieties. Contrary to ammonium-functionalized polyelectrolyte (i.e., poly-lysine) solutions, guanidinium-functionalized polyelectrolyte solutions become turbid by adding monovalent salts and exhibit the upper critical solution temperature (UCST) behavior; the critical temperature is harnessed by salt concentration and salt type. Although a π–π stacked guanidinium pair can exist at a lower salt concentration, LLPS occurs when the number of intermolecular guanidinium pairs goes beyond a critical value to produce the network structure. Furthermore, the enthalpically favored π–π interaction directly affects the bulk rheological behavior and the interfacial property of the coacervates. Our findings provide insights into the underlying interactions of protein phase separation and shed new light on the critical role of π–π stacking in the biological process and material design.

Random ionic polymers: Salt-triggered reversible vesicular self-assembly in water

NaCl salt as an external stimulus triggers the self-assembly of ionic polymers and offers a convenient route to structuring vesicular reversible polymeric nanoparticles. In this contribution, amphiphilic random imidazolium ionic polymers are synthesized by roping the partial anion exchange and the choice of N-substituent. These polymers are evaluated for their self-assembly behavior in water, and it is strengthened by dye encapsulation application in water through self-assembly. The effects of salt and pH study demonstrated the reversibility of self-assembly. The self-assembled nano-aggregates are thermoresponsive at the upper critical solution temperature (UCST) (Cp 47 °C). The synergic balance between hydrogen bonding and ionic self-assembly is attributed to the constituents in the macromolecular structure, making these polyionic liquids (PILs) a “smart” responsive system in water upon the addition of external stimuli, such as NaCl and KPF6. This self-assembly is acquired with partial anion exchange and salt balance in the water. The unusual interfacial activity of polymer to form a regular shape eventually to surfaces organic dye molecule serving as a type of stabilizer or scavenger evidenced by nano-size and vesicular morphology analysis.

An electrochemically mediated ATRP synthesis of lignin-g-PDMAPS UCST-thermoresponsive polymer

It is a promising idea to graft zwitterionic polymers onto lignin and prepare lignin-grafted-poly [2-(methacryloyloxy) ethyl] dimethyl-(3-sulfopropyl) ammonium hydroxide (Lignin-g-PDMAPS) thermosensitive polymer with the upper critical solution temperature (UCST). In this paper, an electrochemically mediated atom transfer radical polymerization (eATRP) method was used to prepare Lignin-g-PDMAPS. The structure and property of the Lignin-g-PDMAPS polymer were characterized by the fourier transform infrared spectrum (FT-IR), nuclear magnetic resonance (NMR), X-ray electron spectroscopy (XPS), dynamic light scattering (DLS), differential scanning calorimeter (DSC). Furthermore, the effect of catalyst structure, applied potential, amount of Lignin-Br, Lignin-g-PDMAPS concentration, NaCl concentration on UCST of Lignin-g-PDMAPS were investigated. It was worth noting that polymerization was well controlled when the ligand was tris (2-aminoethyl) amine (Me6TREN), applied potential was −0.38 V and the amount of Lignin-Br was 100 mg. And the UCST of the Lignin-g-PDMAPS aqueous solution (1 mg/ml) was 51.47 °C, the molecular weight was 8987 g/mol, and the particle size was 318 nm. It was also found that the UCST increased and the particle size decreased with the Lignin-g-PDMAPS polymer concentration increased, and the UCST decreased and the particle size increased with the NaCl concentration increases. This work investigated UCST-thermoresponsive polymer which possessed lignin main chain combining the zwitterionic side chain, and provided a new way for development of lignin based UCST-thermoresponsive materials and medical carrier materials, in addition to expand the scope of eATRP.

A thermoresponsive hydrogel with a wide‐range tunable phase transition temperature triggered by small molecules

AbstractThermoresponsive polymer hydrogels have great potential in the fields of smart window and information encryption due to the drastic changes in transmittance caused by the phase transition at specific temperatures. The synthesis of thermoresponsive hydrogels with a wide range and sensitive temperature response is current research goal. Here, we demonstrate a polymethacrylamide (PMAAm) hydrogel with the upper critical solution temperature (UCST) ranging from 62 to −1°C by simply polymerizing the monomer in different concentrations of acetic acid (Ac) solutions. The hydrogel exhibits sensitive temperature response with a temperature hysteresis within 2°C and can maintain stable transmittance changes after 200 cycles of testing. The phase transition mechanism is revealed by combining ultraviolet visible spectra, differential scanning calorimetry, Fourier transform infrared spectra, dynamic light scattering and scanning electron microscope measurements. This thermoresponsive hydrogel can be applied in smart window and information encryption. The smart window prepared with the hydrogel had a very high ΔTlum (The luminous transmittance modulation, 94.4%), ensuring daytime illumination and privacy protection at night. Meanwhile, the smart window exhibits an excellent thermal insulation capability for energy‐saving buildings. The hydrogels with different UCST are flexibly combined to display designed patterns at different temperatures, demonstrating the ability of the hydrogels to be used for information encryption.

Phase behavior for the poly(2-ethyl-2-oxazoline) + supercritical DME + alcohol and carbon dioxide + 2-ethyl-2-oxazoline mixtures at high pressure

The experimental isotherms of 2-ethyl-2-oxazoline in supercritical carbon dioxide SCO2) were reported up to a pressure and temperature of 17.48 MPa and 373.2 K, respectively. The unbroken mixture critical line starting from pure SCO2 to pure 2-ethyl-2-oxazoline with a pressure maximum suggests the type I behavior in the system. The theoretical investigation is conducted with the help of Peng-Robinson equation of state (PR EOS) and satisfactory agreement is observed between predicted and experimental results. The solubility of poly(2-ethyl-2-oxazoline) in supercritical DME (dimethyl ether) is examined experimentally which demonstrates UCST (Upper Critical Solution Temperature) phase behavior for poly(2-ethyl-2-oxazoline) concentration range from 3.9 wt% to 5.0 wt%. Furthermore, the experiments are performed to determine the effect of co-solvents on the phase behavior of poly(2-ethyl-2-oxazoline) + DME + alcohol solutions. The phase shift from UCST to LCST (Lower Critical Solution Temperature) is noted for poly(2-ethyl-2-oxazoline) + DME + alcohol (methanol and ethanol) with rising alcohol concentration. Moreover, for poly(2-ethyl-2-oxazoline) + DME + alcohol (1-propanol., 1-butanol., 1-pentanol, and 1-octanol.), UCST phase behavior is observed for all concentrations of the alcohols. The drastic depression in the cloud point curve in the presence of a medium-chain alcohols (1-propanol to 1-octanol) is probably due to the association of alcohol with the polymer molecules.

LCST-UCST Transition Property of a Novel Retarding Swelling and Thermosensitive Particle Gel

Super absorbent resin particles used as profile control and water plugging agent remains a deficiency that the particles swells with high speed when absorbing water, resulting in low strength and limited depth of migration. To address this issue, we proposed a thermosensitive particle gel possessing the upper critical solution temperature (UCST), which was synthesized from hydrophobically modified poly(vinyl alcohol)s (PVA) with glutaraldehyde (GA) as a cross-linker. The structure of the hydrogel was characterized by Fourier transform infrared spectrophotometer (FTIR) and nuclear magnetic resonance (NMR). The thermosensitive-transparency measurement and swelling experiment show that the hydrophobic-modified PVA solutions and corresponding hydrogels exhibited thermosensitive phase transition behaviors with lower critical solution temperature (LCST) and UCST. The results indicated that the temperature-induced phase transition behavior of CHPVA hydrogels leads to their retarding swelling property and great potential as an efficient water plugging agent with excellent temperature and salt resistance.

Effect of phenolic acids on temperature-sensitive property of self-assembly of ionic pair of poly(ethylene imine)/(phenylthio)acetic acid

The ionic pair self-assembly (IPSAM) composed of poly(ethyleneimine) (PEI) and (phenylthio)acetic acid (PTA) was prepared and the effect of phenolic acids (PAs) (e.g. cinnamic acid (CA), hydroxycinnamic acid (HCA), and dihydroxycinnamic acid (DHCA)) on the upper critical solution temperature (UCST) and the temperature-responsive releasing property of IPSAM were investigated. PEI/PTA ionic pair showed a UCST behavior and the PAs decreased the UCST effectively in the order of DHCA > HCA > CA. The PAs were thought to attach to the PEI chain of PEI/PTA ionic pair as pendants. PEI/PTA(3/7) ionic pair was found to be air/water interface-active. CA had little effect on the interfacial activity of the ionic pair. HCA and DHCA significantly decreased the interfacial activity. IPSAM was found as nanoparticles whose diameter was tens of nanometer and PAs had little effect on the shape and the size of IPSAM. The release degree of cargo loaded in IPSAM increased slowly with time lapse when below UCST. Whereas, the release degree increased rapidly with time lapse when above UCST, possibly because of the thermally-induced disintegration of IPSAM.

Smart "Thrombus": Self-Localizing UCST-Type Microcage.

Embolization is often used to block blood supply for controlling the growth of fibroids and malignant tumors, but limited by embolic agents lacking spontaneous targeting and post-treatment removal. So we first adopted nonionic poly(acrylamide-co-acrylonitrile) with an upper critical solution temperature (UCST) to build up self-localizing microcages by inverse emulsification. The results showed that these UCST-type microcages behaved with the appropriate phase-transition threshold value around 40 °C, and spontaneously underwent an expansion-fusion-fission cycle under the stimulus of mild temperature hyperthermia. Given the simultaneous local release of cargoes, this simple but smart microcage is expected to act as a multifunctional embolic agent for tumorous starving therapy, tumor chemotherapy, and imaging.

Engineering near-infrared laser-activated gold nanorod vesicles with upper critical solution temperature for photothermal therapy and chemotherapy

Multimodal synergistic therapy based on nanomedicine drug delivery systems can achieve accurate cancer treatment. The anisotropy of gold nanorods (AuNRs) allows the adjustment of the longitudinal localized surface plasmon resonance absorption to the near-infrared band, which shows potential application in the field of photothermal therapy of cancer. Here, we report a new type of thermal-sensitive gold nanorod drug-loaded vesicles (UGRV-DOX) via the self-assembly of AuNRs modified with the amphiphilic polymer (PEG45-b-PS150) and upper critical solution temperature (UCST) polymer (P(AAm-co-AN)). The hollow structure of the vesicle can increase the drug loading capacity, and the polymers on its surface are intertwined to reduce drug leakage. As-prepared UGRV-DOX vesicles exhibits excellent photothermal conversion efficiency and can achieve light-controlled drug release. In vivo anti-tumor experiments showed that UGRV-DOX could ablate HepG2 transplanted tumors significantly under 808 nm laser irradiation, and the inhibition rate was as high as 99.3 %. These tumor-specific nanovesicles prefigure great potentials for high-precision cancer treatment.

Poly(N-acryloyl glycinamide-co-N-acryloxysuccinimide) Nanoparticles: Tunable Thermo-Responsiveness and Improved Bio-Interfacial Adhesion for Cell Function Regulation.

Poly(N-acryloyl glycinamide) (PNAGA) can form high-strength hydrogen bonds (H-bonds) through the dual amide motifs in the side chain, allowing the polymer to exhibit gelation behavior and an upper critical solution temperature (UCST) property. These features make PNAGA a candidate platform for biomedical devices. However, most applications focused on PNAGA hydrogels, while few focused on PNAGA nanoparticles. Improving the UCST tunability and bio-interfacial adhesion of the PNAGA nanoparticles may expand their applications in biomedical fields. To address the issues, we established a reactive H-bond-type P(NAGA-co-NAS) copolymer via reversible addition-fragmentation chain transfer polymerization of NAGA and N-acryloxysuccinimide (NAS) monomers. The UCST behaviors and the bio-interfacial adhesion toward the proteins and cells along with the potential application of the copolymer nanoparticles were investigated in detail. Taking advantage of the enhanced H-bonding and reactivity, the copolymer exhibited a tunable UCST in a broad temperature range, showing thermo-reversible transition between nanoparticles (PNPs) and soluble chains; the PNPs efficiently bonded proteins into nano-biohybrids while keeping the secondary structure of the protein, and more importantly, they also exhibited good adhesion ability to the cell membrane and significantly inhibited cell-specific propagation. These features suggest broad prospects for the P(NAGA-co-NAS) nanoparticles in the fields of biosensors, protein delivery, cell surface decoration, and cell-specific function regulation.

Developing an ecofriendly UCST-type enzymatic cascade system for efficient and cost-effective starch solid wastes treatment

Enzymatic utilization of starch solid wastes is promising but hindered by its high cost. Enzymes immobilization is one solution; however, the key challenge remains the low mass transfer rate between the solid immobilization system and the solid wastes. Herein, an enzymatic modification strategy was applied instead of the traditional immobilization method. A novel system composed of poly(methacrylic acid), polyacrylic acid, and gelatin was firstly prepared and then used to modify α-amylase and glucoamylase to endow them with upper critical solution temperature (UCST) characteristic. As a result, we found that the wastes can be hydrolyzed efficiently with the modified co-enzymes above UCST and can be easily recovered and separated below UCST, thus the cost of starch wastes treatment can be largely reduced. Besides, the proposed method exhibited excellent environmental-friendly and bio-safety properties. Therefore, this method laid a solid foundation for efficient and cost-effective enzymatic conversion of starch solid wastes.

Modification of cellulase with smart-green polymers to promote low-cost and cleaner production of cellulosic ethanol

Cellulosic ethanol produced using the enzymatic method is promising; however, developing an efficient and green cellulase hydrolysis system to cut the cost of cellulosic ethanol and promote cleaner biofuel production remains challenging. Herein, based on the fact that multiple hydrogen bond can be generated between poly (methyl acrylic acid-co-acrylic acid) and gelatin, cellulase was first covalently bonded to the copolymer and then mixed with gelatin, to endow the cellulase with ideal upper critical solution temperature (UCST). As a result, the affinity between cellulase and the substrate did not decrease significantly after the modification (the Km value of modified cellulase (4.62 g/L) was not significantly different from that of free cellulase (4.55 g/L)). The enzymes can be switched on-demand between free state (above 36 °C), enabling high hydrolysis reactivity for insoluble substrates such as paper or corn stalks, and fixed state (at 4 °C), facilitating enzymes separation and reuse (the modified cellulase still has 58.2% of its initial activity for 20 batches). Thus, the cost of cellulosic ethanol production could be significantly reduced in the precondition of high catalytic efficiency. Furthermore, the system presents nontoxic and biodegradable properties. The system can be completely degraded in soil after 7 days and the inhibition rate of the degraded products on luminescent bacteria was only 2%, which can promote cleaner cellulosic biofuel production.

Application of a novel and green temperature-responsive deep eutectic solvent system to simultaneously extract and separate different polar active phytochemicals from Schisandra chinensis (Turcz.) Baill

In the present study, a novel and green temperature-responsive deep eutectic solvent (TRDES) system was developed and applied for the simultaneous extraction and separation of different polar active phytochemicals from Schisandra chinensis (Turcz.) Baill. The TRDES, consisting of amino alcohols and phenolic compounds, was chosen as the switching medium, and an upper critical solution temperature (UCST) type switchable solvent was obtained by adding an inorganic salt solution. The switchable phase diagram was plotted based on the relationship between the phase change temperature, the concentration and the amount of sodium chloride solution. Under optimal parameters, the yields with TRDES for different polar active phytochemicals (lignanoids and polysaccharides) from the dried fruit of Schisandra chinensis (DFSC) were 1.62 ∼ 1.17-fold and 1.39-fold to those with conventional solvents. Also, the TRDES system was still effective on extraction of DFSC lignanoids and polysaccharides after four cycles of extraction. The separated polysaccharides and lignanoids both had strong antioxidant activities with IC50 values of 1.92 mg/ mL and 0.10 mg/ mL against 2,2′-Azinobis(3-ethylbenzothiazoline-6-sulfonic acid)(ABTS), respectively. The extraction mechanism of TRDES was postulated by Density functional theory (DFT) calculations the hydrogen bonding in TRDES was the main factor to the higher extraction yield. This temperature-responsive deep eutectic solvent could be widely used for the efficient extraction and separation of multi-polar components. As a green and recyclable solvents, TRDES has great potential for the lower cost production from plants.

LCST/UCST transition of acrylate copolymer with cosolvency behaviors in alcohol aqueous solutions

Though the mechanism of temperature-induced lower critical solution temperature (LCST) in water is clear for the classic homopolymer poly(N-isopropylacrylamide) (PNIPAM), the LCST of other homopolymer or copolymer remains to be understood. In this work, a novel random copolymer poly(2-hydroxyethyl-co-methyl acrylate) (P(HEA-co-MA)) was prepared. The LCST of the copolymer P(HEA-co-MA) can vary from 11 °C to 65 °C by adjusting flexibly the ratio of the two monomers, showing a broad tunable range. The experimental results showed that the balance of hydrogen bond bridge formed by P(HEA-co-MA) in water and the hydrophobic interaction between polymers can cause the LCST transition of P(HEA-co-MA). An interesting observation is that the sharp phase transition (cosolvency) of P(HEA-co-MA) exists when a rather small amount of alcohol or water is added in polymer solutions at constant temperatures. Moreover, it was found that the increase of LCST is correlated with the increase of alcohol concentration in the water-rich regime, but the decrease of upper critical solution temperature (UCST) is related to the increase of water concentration in the alcohol-rich regime. This work shed light on the understanding of cosolvency by studying the solution behavior of copolymer P(HEA-co-MA) in mixed solvents, which can be of interest for the design of stimuli-responsive polymer materials by variation in solvent composition.

Non-Solvent- and Temperature-Induced Phase Separations of Polylaurolactam Solutions in Benzyl Alcohol as Methods for Producing Microfiltration Membranes

The possibility of obtaining porous films through solutions of polylaurolactam (PA12) in benzyl alcohol (BA) was considered. The theoretical calculation of the phase diagram showed the presence of the upper critical solution temperature (UCST) for the PA12/BA system at 157 °C. The PA12 completely dissolved in BA at higher temperatures, but the resulting solutions underwent phase separation upon cooling down to 120–140 °C because of the PA12’s crystallization. The viscosity of the 10–40% PA12 solutions increased according to a power law but remained low and did not exceed 5 Pa·s at 160 °C. Regardless of the concentration, PA12 formed a dispersed phase when its solutions were cooled, which did not allow for the obtention of strong films. On the contrary, the phase separation of the 20–30% PA12 solutions under the action of a non-solvent (isopropanol) leads to the formation of flexible microporous films. The measurement of the porosity, wettability, strength, permeability, and rejection of submicron particles showed the best results for a porous film produced from a 30% solution by non-solvent-induced phase separation. This process makes it possible to obtain a membrane material with a 240 nm particle rejection of 99.6% and a permeate flow of 1.5 kg/m2hbar for contaminated water and 69.9 kg/m2hbar for pure water.

Water model determines thermosensitive and physicochemical properties of poly(N-isopropylacrylamide) in molecular simulations

Poly (N-isopropylacrylamide) (PNIPAM) is a famous representative of thermosensitive polymers. Thermosensitive polymers undergo a phase transition with lower critical solution temperature. Commonly, their phase behavior is linked to a conformational collapse above a certain temperature. This thermosensitive conformational transition is called Coil-Globule transition. In contrast, most other polymers usually show inverse temperature behavior, i.e., an upper critical solution temperature, corresponding to a Globule-Coil transition. Besides their numerous possible applications, thermosensitive polymers are of interest for fundamental research, because of similarities to macromolecular conformational transitions, e.g., protein folding. The counter-intuitive behavior of thermosensitive polymers is commonly associated with solvation effects. Thus, an accurate description of the solvent is crucial for the investigation of thermosensitive polymers in molecular simulations. Here, we investigate the influence of the in silico water model on the thermosensitive Coil-Globule transition in molecular dynamics simulations. To this end, we performed extensive atomistic simulations of the syndiotactic PNIPAM 20-mer at multiple temperatures with eight different water models–four of which are 3-point water models (TIP3P-type) and four are 4-point water models (TIP4P-type). We found that the thermosensitive Coil-Globule transition is strongly influenced by the water model in the simulations. Depending on the water model, the conformational ensemble of the polymer is shifted significantly, which leads to dramatically different results: The estimated transition temperature may span between 255 and 350 K. Consequently, depending on the description of the solvent, the physicochemical and mechanical properties of these polymers, e.g., the polymer-solvent affinity and persistence length, vary. These divergent results originate from the strength of interactions between polymer and solvent, but also on the bulk state of the solvent. Both these quantities vary between water models. We found that the Lennard-Jones interaction parameter ϵ of the water model correlates with the transition temperature of the polymer. Indeed, the quadrupole moment of the water model shows an even higher correlation with this quantity. Our results suggest a connection between the phase diagram of the solvent and the thermosensitive transition of the polymer.

Preparation of Temperature-Sensitive SiO2–PSBMA for Reducing the Viscosity of Heavy Oil

Viscosity reduction by emulsification is one of the most effective methods for the recovery of heavy oil. Nanoparticles with low toxicity and low cost can stabilize oil-in-water (O/W) Pickering emulsions to reduce the viscosity of heavy oil and thereby have become a new type of emulsifier in recent years. The stimuli-responsive emulsions formed by responsive particles can achieve emulsification and demulsification under external stimuli, providing convenient conditions for heavy oil transportation and recovery, where the temperature response is easier to achieve. In this study, six groups of temperature-sensitive SiO2–PSBMA (PSBMA: polysulfobetaine methacrylate) with different particle sizes were prepared by the reverse atom transfer radical polymerization (RATRP) method. The morphologies of SiO2 particles before and after grafting were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and atomic force microscopy (AFM), and the structure of the product was characterized by Fourier transform infrared (FT-IR) spectroscopy, which showed that PSBMA was successfully grafted to SiO2. The grafting ratios (η) of six groups of SiO2–PSBMA measured by thermogravimetric analysis (TGA) were similar (34.50–42.94%). The temperature sensitivity of SiO2–PSBMA was determined by dynamic light scattering (DLS) and the contact angles at different temperatures, which showed that its upper critical solution temperature (UCST) was about 40–50 °C. SiO2–PSBMA was applied to GD2 heavy oil to reduce the viscosity at 60 °C, which showed that the SiO2–PSBMA had a good emulsification effect. With the increase of particle size, the viscosity reduction rate (VRR) showed a trend of first increase and then decrease. The highest VRR was 96.41%, achieved by 227.61 nm SiO2–PSBMA. All of the emulsions stabilized by SiO2–PSBMA were able to demulsify at room temperature. It can be used as an intelligent temperature-responsive viscosity reducer for heavy oil to control emulsions on demand.

Synthesis of Recyclable UCST-Type Copolymer PPSP and Its Application in Enhancing Lignocellulosic Enzymatic Hydrolysis and Recycling Cellulase

The cost of lignocellulosic enzymatic hydrolysis can be reduced by adding additives with upper critical solution temperature (UCST) response. A recyclable UCST-type copolymer PPSP was synthesized, for enhancing lignocellulosic enzymatic hydrolysis and the cellulase recovery effect of substrate reabsorption. For the hydrolysis system of corncob residue without adding PPSP, only 50% of cellulase amount was saved at a room temperature of 25 °C by adding the fresh corncob residue. The substrate enzymatic digestion efficiency for 72 h was increased by 1.3 times with only adding 0.5 g/L PPSP10-3. After the hydrolysis, 70% of cellulase amount was saved at 25 °C by using the above method. Both lignocellulosic hydrolysis and recovery of cellulase performances were improved by adding PPSP. This may be attributed to the fact that PPSP preferentially adsorbed on lignin to form a hydration membrane to reduce the no-productive adsorption of cellulase and enhanced lignocellulosic enzymatic hydrolysis, while increasing the concentration of free cellulase in the system and strengthening recovery of cellulase. This work will provide one way to reduce the cost of lignocellulosic enzymatic hydrolysis.

Phase behavior investigation of the vinyl toluene and poly (vinyl toluene) + co-solvents in supercritical CO2

This study's purpose is to probe the binary and ternary systems phase behavior including vinyl toluene and poly(vinyl toluene) + co-solvents in supercritical solvent i.e. supercritical CO2 respectively. The vapor + liquid phase behavior of a binary supercritical CO2 + vinyl toluene solution was investigated at five different temperatures from 313.2 K to 393.2 K, up to 20.55 MPa of pressure, and vinyl toluene liquid phase mole fractions ranging from 0.070 to 0.67. Experimental data were compared to computed values using the Peng-Robinson, and Patel-Teja cubic equations of state. At each temperature, the results demonstrated good agreement with experimental readings.The phase separation behavior of poly(vinyl toluene) [P(VT)] + monomers (vinyl toluene, dimethyl ether, toluene, xylene) solutions under supercritical CO2 was presented from 304.55 K to 434.75 K at a pressure range of 14.66–192.59 MPa with different monomer concentration ranges. P(VT) + monomers (vinyl toluene, xylene) + supercritical CO2 ternary mixture phase transition shows phase gradient region from upper critical solution temperature (UCST) to upper-lower critical solution temperature (U-LCST) region in (pressure vs temperature) diagram. Furthermore, P(VT) + monomers (dimethyl ether, toluene) + supercritical CO2 demonstrates UCST to LCST phase separation curves.