PREPARATION OF HIGH DENSITY POLYETHYLENE/POLYETHYLENE-ΒLOCK- POLY(ETHYLENE GLYCOL) COPOLYMER BLEND POROUS MEMBRANES VIA THERMALLY INDUCED PHASE SEPARATION PROCESS AND THEIR PROPERTIES

High density polyethylene (HDPE)/polyethylene-Wock-poly(ethylene glycol) (PE-b-PEG) blend porous membranes were prepared via thermally induced phase separation (TIPS) process using diphenyl ether (DPE) as diluent. The phase diagrams of HDPE/PE-b-PEG/DPE systems were determined by optical microscopy and differential scanning calorimetry (DSC). By varying the content of PE-b-PEG, the effects of PE-b-PEG copolymer on morphology and crystalline structure of membranes were studied by scanning electron microscopy (SEM) and wide angle X-ray diffraction (WAXD). The chemical compositions of whole membranes and surface layers were characterized by elementary analysis, Fourier transform infrared spectroscopy-attenuated total reflection (FTIR-ATR) and X-ray photoelectron spectroscopy (XPS). Water contact angle, static protein adsorption and water flux experiments were used to evaluate the hydrophilicity, antifouling and water permeation properties of the membranes. It was found that the addition of PE-b-PEG increased the pore size of the obtained blend membranes. In the investigated range of PE-b-PEG content, the PEG blocks could not aggregate into obviously separated domains in membrane matrix. More importantly, PE-b-PEG could not only be retained stably in the membrane matrix during membrane formation, but also enrich at the membrane surface layer. Such stability and surface enrichment of PE-b-PEG endowed the blend membranes with improved hydrophilicity, protein absorption resistance and water permeation properties, which would be substantially beneficial to HDPE membranes for water treatment application.     

Preparation of PVDF/PEO-PPO-PEO blend microporous membranes for lithium ion batteries via thermally induced phase separation process

Microporous poly(vinylidene fluoride)/polyethylene oxide-co-polypropylene oxide-co-polyethylene oxide (PVDF/PEO-PPO-PEO, or PVDF/F127) blend membranes were prepared via thermally induced phase separation (TIPS) process using sulfolane as the diluent. Then they were soaked in a liquid electrolyte to form polymer electrolytes. The effects of F127 weight fraction on the morphology, crystallinity and porosity of the blend membranes were studied. It was found that both electrolyte uptake of blend membranes and ionic conductivity of corresponding polymer electrolytes increased with the increase of F127 weight fraction. The maximum ionic conductivity was found to reach 2.94 ± 0.02 × 10⁻³ S/cm at 20 °C. Electrochemical stability window was stable up to 4.7 V (vs. Li⁺/Li). The testing results indicated that the PVDF/F127 blend membranes prepared via TIPS process can be used as the polymer microporous matrices of polymer electrolytes for lithium ion batteries.     

Effect of TiO2 nanoparticles on structure and properties of high density polyethylene membranes prepared by thermally induced phase separation method

Polyethylene/TiO₂ membranes were fabricated via thermally induced phase separation (TIPS) method. A set of characterization tests including FE‐SEM, EDX, XRD, DSC, TGA, DMA, mechanical test and relative pure water flux for characterization of membranes were carried out to investigate the effect of TiO₂ nanoparticles on membrane properties. The results of EDX, XRD and TGA analyses confirmed the presence of TiO₂ nanoparticles in the polymer matrix. The results of DSC analysis revealed that the melting point as well as the crystallinity of the membranes increased slightly with increasing TiO₂ content. However, the glass transition temperature of the membranes was not affected by the presence of particles. Addition of nanoparticles also increased storage modulus, loss modulus and tensile strength at break of the membranes due to the stiffness improvement effect of inorganic TiO₂. Finally, it was observed that incorporation of the nanoparticles improved pure water flux of the membranes. Copyright © 2015 John Wiley & Sons, Ltd.     

High density polyethylene-grafted-maleic anhydride low-k porous films prepared via thermally induced phase separation

Low dielectric constant (low-k) porous films of high density polyethylene-grafted-maleic anhydride were prepared via thermally induced phase separation (TIPS) using di-n-octyl phthalate as the solvent and methanol as the extractant. The results show that, for the process of TIPS, cellular structures of spherical pores were obtained. Lower polymer concentration and lower cooling rate induced larger pores and higher porosity. For the dielectric constant, the introduction of pores considerably reduced the dielectric constant from 2.60 to 1.56 at most. Pore size showed little effect on dielectric constant in our experiment, but porosity was found to be the key influential factor. The relationship between dielectric constant and porosity was found to be best fit to Rayleigh model.     

Structure and performance of polyamide-6 membranes prepared by thermally induced phase separation

<正>The asymmetric polyamide-6(PA6) membranes were prepared by thermally induced phase separation.From the scanning electron microscopy(SEM) images,it is observed that with the increase of silicon dioxide(SiO_2) content the structure of obtained membranes gradually varied from cellular structure to large ball-shaped cluster aggregates. Subsequently,with the addition of SiO_2,pure water flux increased first and then decreased,while rejection showed the opposite trend.Besides,raising the coagulation bath temperature was favorable to increase pure water flux.Consequently, different membrane morphologies and performance were obtained by changing SiO_2 content and coagulation bath temperature.     

Preparation of thermo- and redox-responsive branched polymers composed of three-armed oligo(ethylene glycol)

We herein report the preparation of thermo- and redox-responsive branched polymers by the condensation reaction of three-armed oligo(ethylene glycol) (trisOEG) and cystamine (CA). The prepared branched polymers exhibited a soluble–insoluble transition at a lower critical solution temperature (LCST) and formed coacervate droplets through a liquid–liquid phase separation process. We then demonstrated control of the LCSTs of the branched polymers by varying the feed ratio of CA and the surrounding salt concentration close to body temperature. In addition, the trisOEG-cys _x polymer formed coacervate droplets above the LCST, in which hydrophobic molecules were condensed. The redox response of the branched polymers was also investigated. Interestingly, the branched polymers degraded to low-molecular-weight materials (i.e., trisOEG) in the presence of dithiothereitol as a reducing agent through cleavage of the disulfide bond of CA. This facile preparation of branched polymers is expected to be valuable in the context of functional biomedical materials and modifiers for materials surfaces, such as the bases for drug delivery carriers and separation materials. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 2623–2629     

Effect of annealing on the morphology and properties of poly(lactic acid)/polyhedral oligomeric silsesquioxane asymmetric porous membranes prepared through non-solvent induced phase separation and its application

Non-solvent induced phase separation (NIPS) method was employed to fabricate biodegradable poly(lactic acid) (PLA) nanocomposite membranes. Morphological studies using scanning electron microscopy revealed that all the membranes prepared display asymmetric structures comprising finger-like macropores. The incorporation of modified polyhedral oligomeric silsesquioxane (POSS) particles into the PLA matrix resulted in enhanced crystallinity, mechanical, and thermal properties. Annealing of the membranes was performed to explore the influence of temperature on the morphology and properties. After annealing, membranes become more thin and compact, and drastic enhancement in crystallinity is also observed. Consequently, Young's modulus experiences a significant improvement. The reduction in oil absorption capacity after annealing can be attributed to the higher level of crystallinity, reduced porosity, and smaller pore diameter observed in the annealed membranes. Additionally, the unannealed PLA nanocomposite membranes demonstrated exceptional oil absorption capacity, reaching approximately 88%. It is foreseeable that these PLA/POSS nanocomposite membranes possess the potential to be utilized as effective tools for oil–water separation, offering the advantage of mitigating secondary pollution.     

Synthesis and properties of poly(ethylene oxide)‐grafted polyethylene copolymer and terpolymer

A series of graft copolymers were synthesized based on ethylene‐co‐m,p‐methylstyrene (EMS) (backbone copolymer), ethylene‐1‐hexene‐m,p‐methylstyrene (EHMS) (backbone terpolymer), and polyethylene glycol monomethyl ethers (PEGM) (grafts) in this study. The PEGMs with molecular weights of 750 and 2000 were used. The chemical composition of the graft copolymers was analyzed by NMR and DSC measurements. The graft copolymers exhibited a phase‐separated morphology with the backbone and the methoxy polyethylene glycol (MPEG) grafts forming separate crystalline phases. The MPEG phase had a melting temperature lower than the corresponding MPEG homopolymer, as determined by DSC. The melting point of the crystalline phase formed by the EMS and EHMS main chains was lower than that of pure polymer backbone. Copyright © 2009 John Wiley & Sons, Ltd.     

热致相分离法偏二氯乙烯-氯乙烯共聚物多孔膜的制备及性能

以偏二氯乙烯-氯乙烯共聚物[P(VDC-co-VC)]为成膜聚合物, 邻苯二甲酸二甲酯(DMP)为稀释剂, 采用热致相分离(TIPS)法制备了具有多孔结构的P(VDC-co-VC)膜. 通过聚合物-稀释剂二元体系相图、 场发射扫描电镜(FESEM)、 差示扫描量热仪(DSC)、 X射线衍射(XRD)、 原子力显微镜(AFM)、 纯水通量、 接触角、 孔径及其分布、 截留率及力学性能等研究了聚合物含量对P(VDC-co-VC)多孔膜结构和性能的影响. 结果表明, P(VDC-co-VC)-DMP二元体系成膜过程以液-液(L-L)分相为主, 随着聚合物含量增加, 膜的横截面由类花瓣状结构向胞腔状结构转变, 膜的孔连通性降低, 结构变得较为致密, 同时膜上表面孔隙率降低, 粗糙度增大. L-L分相时间和聚合物含量的变化, 导致膜结晶度先降低后增大. 聚合物含量的增加使膜上表面接触角、 断裂强度及蛋白截留率增加, 但膜的平均孔径、 孔隙率及纯水通量先增加后减小. 当聚合物质量分数为30%时, 所得膜通透性较优, 断裂强度可达7.5 MPa.     

Improving the properties of HDPE based separators for lithium ion batteries by blending block with copolymer PE-b-PEG

To improve the performances of HDPE-based separators, polyether chains were incorporated into HDPE membranes by blending with poly(ethylene-block-ethylene glycol) (PE-b-PEG) via thermally induced phase separation (TIPS) process. By measuring the composition, morphology, crystallinity, ion conductivity, etc, the influence of PE-b-PEG on structures and properties of the blend separator were investigated. It was found that the incorporated PEG chains yielded higher surface energy for HDPE separator and improved affinity to liquid electrolyte. Thus, the stability of liquid electrolyte trapped in separator was increased while the interfacial resistance between separator and electrode was reduced effectively. The ionic conductivity of liquid electrolyte soaked separator could reach 1.28 × 10-3 S.cm-1 at 25℃, and the electrochemical stability window was up to 4.5 V (versus Li + /Li). These results revealed that blending PE-b-PEG into porous HDPE membranes could efficiently improve the performances of PE separators for lithium batteries.     

Viscosity reduction and disentanglement in ultrahigh molecular weight polyethylene melt: Effect of blending with polypropylene and poly(ethylene glycol)

A significant reduction in melt viscosity of ultrahigh molecular weight polyethylene (UHMWPE) was obtained by blending with polypropylene (PP) and poly(ethylene glycol) (PEG). The mechanism of viscosity reduction was investigated from the view of disentanglement effect. Dynamic mechanical analysis indicated that the pseudoequilibrium modulus (E′) of UHMWPE/PP(80/20) blend in the rubbery plateau was much lower than that of UHMWPE. Accordingly, the calculated entanglement density (ν_e) of UHMWPE/PP (80/20) blend was smaller than that of UHMWPE. Further reduction in E′ and ν_e of the blend was obtained by the incorporation of 1 phr PEG. Slow DSC analysis showed that the high temperature endotherm and exotherm for UHMWPE at slow temperature ramp diminished and increased, respectively when 5 phr PEG was added. It also revealed that the entanglement level of UHMWPE decreased with the addition of a small amount of PEG.     

Critical parameters controlling the properties of monolithic poly(lactic acid) foams prepared by thermally induced phase separation

Monolithic poly(lactic acid) (PLA) foams were produced by thermally induced phase separation. PLA solutions with concentrations 8–22 wt % were prepared in tetrahydrofuran/methanol (THF/MeOH) solvent/nonsolvent mixtures at 55 °C. Homogenous solutions were quenched at ?20 °C to induce phase separation and gelation. Resulting gels were mechanically stabilized by solvent exchange. Subsequent supercritical CO₂ drying yielded monolithic PLA foams. Crystal structure and degree of crystallinity of the foams were obtained by x‐ray diffractometry and differential scanning calorimetry. Morphologies were determined by scanning electron microscopy. Tuning the PLA concentration and THF/MeOH ratio enabled preparation of monolithic PLA foams. Depending on the experimental conditions various morphologies, such as: interconnected networks, thin platelets, lamellar stacks, axialites, and spherulites were formed. Monoliths obtained were highly crystalline. By changing the PLA concentration monoliths with controlled average pore sizes (170–1440 nm) and porosities (80–90%) were produced. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 98–108     

Poly (caprolactone)/poly (ethylene glycol) pervaporation blend membranes: Synthesis,characterization, and performance

Poly (caprolactone) membranes with addition of different poly (ethylene glycol) concentrations were prepared for separation of water/isopropanol azeotropic mixture by pervaporation process. Different characterization tests including Fourier transform infrared, scanning electron microscopy, water contact angle, and thermogravimetric analysis were carried out on the prepared membranes. In addition, the effect of poly (ethylene glycol) PEG content on the swelling degree and the performance of the prepared membranes in pervaporation process were investigated. According to the obtained results, all the membranes were water selective and the blend membrane containing 3 wt% PEG exhibited the best pervaporation performance with a water flux of 0.517 kg/m² hour and separation factor of 1642 at the ambient temperature. Hydrophilicity improvement of the blend membranes was confirmed by constant decrease in water contact angle of the membranes as PEG content increased in the casting solution. Scanning electron microscopy cross‐sectional images indicated that the blend membranes containing PEG had a closed cellular structure. Furthermore, mechanical and thermal properties of the membranes decreased by adding PEG.     

Using two-dimensional time resolved light scattering to study the cure reaction induced phase separation process of epoxy-amine-polyethersulfone blend with secondary phase separation

<正>The generalized two-dimensional correlation analysis based on time-resolved light scattering patterns(2D TRLS) has been employed to study the phase separation process of an epoxy-amine-polyethersulfone blend in which the secondary phase separation takes place.The results of the 2D TRLS provided more detailed information that was not readily observed in the 1D TRLS patterns.(i) During the first process of phase separation,the sequential order of coarsening in size of the domains among the larger and smaller ones has been reversed between the diffusion regime and the hydrodynamic regime. (ii) The change of the larger domains in size,due to the hydrodynamic flow in the late stage of the first phase separation process,keeps on taking place earlier than that of the new domains appeared in the secondary phase separation process. (iii) During the secondary phase separation process the size growth of the smaller domains takes place earlier than that of the larger ones,probably due to the assumption that the coarsening mode could decrease the interface tension more quickly.     

Morphologies and crystalline forms of polyvinylidene fluoride membranes prepared in different diluents by thermally induced phase separation

We have studied the morphologies and crystalline forms of polyvinylidene fluoride (PVDF) membranes separately prepared in four different diluents bearing >C?O groups, namely 1,2‐propylene glycol carbonate (PGC), dimethyl phthalate (DMP), diphenyl ketone (DPK), and dibutyl phthalate (DBP), by the thermally induced phase separation (TIPS) method. The permittivities of the diluents and PVDF were measured to compare the different PVDF–diluent systems. The results showed the permittivity of PGC to be much greater than that of PVDF, and those of DMP and DBP to be lower than that of PVDF. The permittivity difference between DPK and PVDF was not apparent above 120 °C. On cooling mixtures with a PVDF concentration of 10 wt %, PVDF crystallization was observed in the PVDF–DMP, PVDF–DBP, and PVDF–PGC systems, while liquid–liquid phase separation occurred in the PVDF–DPK system. A cross‐section of the PVDF–PGC membrane presented smooth PVDF particles in the β‐phase crystalline form. Those of the PVDF–DMP and PVDF–DBP membranes presented PVDF particles consisting of a fibrillar network in the α‐phase. The PVDF–DPK membrane preferentially adopted an α‐phase bicontinuous channel structure. When the concentration of PVDF was 60 wt %, the cross‐sections of the above four membranes revealed PVDF polyhedra, among which the PVDF–DMP, PVDF–DBP, and PVDF–DPK membranes retained the α‐phase crystalline form, and the diffraction peak of the α‐phase became visible in the X‐ray diffraction (XRD) spectrum of the PVDF–PGC membrane. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2010     

Facile fabrication of a novel high performance CO2 separation membrane: Immobilization of poly(amidoamine) dendrimers in poly(ethylene glycol) networks

Poly(amidoamine) (PAMAM) dendrimers showed high CO₂ separation properties and were successfully immobilized in a poly(ethylene glycol) (PEG) network upon photopolymerization of PEG dimethacrylate. The PAMAM dendrimer incorporation ratio was readily controlled, and a stable self-standing membrane containing up to 75 wt.% PAMAM dendrimer was obtained. The CO₂ separation properties over smaller H₂ were investigated by changing the PAMAM dendrimer content or generation and CO₂ partial pressure (ΔPCO₂$\mathrm{\Delta }{P}_{\text{C}{\text{O}}_2}$) under atmospheric conditions. Especially, a polymeric membrane containing 50 wt.% PAMAM dendrimer (0th generation) exhibited an excellent CO₂/H₂ selectivity of 500 with CO₂ permeability of 2.74 × 10⁻¹⁴ m³(STP)m/(m² s Pa) or 3.65 × 10³ barrer (1 barrer = 7.5 × 10⁻¹⁸ m³(STP)m/(m² s Pa)) when a mixture gas (CO₂/H₂: 5/95 by vol.) was fed at 25 °C and 100 kPa with 80% relative humidity. This polymeric materials are promising for a novel CO₂ separation membrane.     

Preparation and Characterization of Chitosan Composite Membranes Crosslinked by Carboxyl-capped Poly（ethylene glycol）

In this study a series of chemically crosslinked chitosan/poly（ethylene glycol） （CS/PEG） composite membranes were prepared with PEG as a crosslinking reagent other than an additional blend. First, carboxyl-eapped poly（ethylene glycol） （HOOC-PEG-COOH） was synthesized. Dense CS/PEG composite membranes were then prepared by casting/evaporation of CS and HOOC-PEG-COOH mixture in acetic acid solution. Chitosan was chemically crosslinked due to the amidation between the carboxyl in HOOC-PEG-COOH and the amino in chitosan under heating, as confirmed by FTIR analysis. The hydrophilicity, water-resistance and mechanical properties of pure and crosslinked chitosan membranes were characterized, respectively. The results of water contact angle and water absorption showed that the hydrophilicity of chitosan membranes could be significantly improved, while no significant difference of weight loss between pure chitosan membranes and crosslinked ones was detected, indicating that composite membranes with amidation crosslinking possess excellent water resistanance ability. Moreover, the tensile strength of chitosan membranes could be significantly enhanced with the addition of certain amount of HOOC-PEG-COOH crosslinker, while the elongation at break didn＇t degrade at the same time. Additionally, the results of swelling behaviors in water at different pH suggested that the composite membranes were pH sensitive.     

Structural analysis of poly(amidoamine) dendrimer immobilized in crosslinked poly(ethylene glycol)

Polymeric membranes comprised of poly(amidoamine) (PAMAM) dendrimer immobilized in a poly(ethylene glycol) (PEG) network exhibit an excellent CO₂ separation selectivity over H₂. The CO₂ permeability increases with PAMAM dendrimer concentration in the polymeric membrane and becomes 500 times greater than H₂ permeability when the dendrimer content was 50 wt % at ambient conditions (5 kPa of CO₂ partial pressure). However, the detailed morphology of the membrane has not been discussed. The immiscibility of PAMAM dendrimer and PEG matrix results in phase separation, which takes place in a couple of microns scale. Especially, laser scanning confocal microscope captures a 3D morphology of the polymeric blend. The obtained 3D reconstructions demonstrate a bicontinuous structure of PAMAM dendrimer‐rich and PEG‐rich phases, which indicates the presence of PAMAM dendrimer channel penetrating the polymeric membrane, and CO₂ will preferentially pass through the dendrimer channel. In addition, Fourier transform of the 3D reconstructions indicates the presence of a periodic structure. An average size of the dendrimer domain calculated is 2–4 μm in proportion to PAMAM dendrimer concentration. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

Fabrication of Gene Carrier via Self-assembly of Poly[(dimethylamino)ethyl Methacrylate] and Poly(aspartic acid)-grafted-Poly(ethylene glycol)

A biocompatible complex has been prepared as gene carrier via electrostatic interaction, which is composed of a polycation, that is, poly[(dimethylamino)ethyl methacrylate] end-capped with cholesterol moiety (Chol-PDMAEMA₃₀), along with a polyanion named poly(aspartic acid)-grafted-poly(ethylene glycol) (PASP-g-PEG). The complexes have less cytotoxicity compared to the case of alone Chol-PDMAEMA₃₀ or branched polyethylenimine (PEI) system.

In the present study, biocompatible complexes have been prepared as gene carrier via electrostatic interaction, which is composed of a polycation, that is, poly[(dimethylamino)ethyl methacrylate] end-capped with cholesterol moiety (Chol-PDMAEMA₃₀), along with a polyanion named poly(aspartic acid)-grafted-poly(ethylene glycol) (PASP-g-PEG). We first synthesized polysuccinimide (PSI) via condensation polymerization of aspartic acid, and then used PEG-NH₂ to react with the partial pentacyclic rings of PSI to yield a kind of graft copolymer polysuccinimide-grafted-poly(ethylene glycol) (PSI-g-PEG). After hydrolysis of the residual succinimide units, a new biodegradable and biocompatible graft copolymer PASP-g-PEG was prepared successfully. Chol-PDMAEMA₃₀ was synthesized via oxyanion-initiated polymerization, as reported in our previous literature. We investigated the interactions between every pair among calf thymus DNA, Chol-PDMAEMA₃₀, and PASP-g-PEG by agarose gel retardation assay. The results indicate that the prepared complexes could completely bind DNA and may become more stable during systemic circulation. The complexes have less cytotoxicity compared to the case of alone Chol-PDMAEMA₃₀ or branched polyethylenimine (PEI) system. Furthermore, the physicochemical properties of the complexes were also investigated by zeta potential, transmission electron microscopy (TEM) and dynamic light scattering (DLS) measurements. These biodegradable and biocompatible polymeric carriers have potential applications in gene delivery.     

Synthesis and characterization of poly(ϵ-caprolactone)-poly(ethylene glycol) block copolymer

Poly(ϵ-caprolactone)–poly(ethylene glycol)–poly(ϵ-caprolactone) triblock copolymers (PECL) covering a wide range of poly(ethylene glycol) (PEG) lengths were synthesized with alkali metal alkoxide derivatives of poly(ethylene glycol). The effects of various factors, such as amount of the initiator, reaction time and temperature, polarity of solvent, length of PEG segment, and counterion on the polymerization were investigated. The copolymers were characterized by ¹H-NMR, IR, GPC, and DSC. It was found that THF system is superior to toluene system. The conversion of the monomer increased with increase of the initiator concentration. High molecular weight of the copolymer and high conversion of the monomer was obtained at below 30°C within 5 min. The polymerization process was studied by GPC and the coexistence of propagation and transesterification reaction was found, which leaded to relatively broad molecular weight distribution of the copolymers. © 1997 John Wiley & Sons, Inc.