Effects of poly(ethylene glycol)-grafted graphene on the electrical properties of poly(lactic acid) nanocomposites

Maleic anhydride was reacted with the armchair edges of graphene nanosheets (GN) via Diels–Alder reaction. Then, polyethylene glycol (PEG) was grafted onto the GN in the presence of anhydride groups through an esterification reaction. The PEG-grafted GN (PEG-g-GN) was characterised via FTIR analysis, thermogravimetric analysis, scanning electron microscopy, Raman spectroscopy and contact angle measurements, proving that PEG was successfully grafted onto the GN surface. The results indicated that PEG-g-GN possessed high electrical conductivity and was dispersed in polylactic acid (PLA). The composites were fabricated by using PEG-g-GN and GN as the conductive agent in the PLA matrix. Owing to the function of PEG molecular chains, PEG-g-GN can be uniformly dispersed in the PLA matrix and improve the tensile strength of composites to 59.46 MPa and conductivity to 9.69 × 10⁻⁴ S cm⁻¹ at a PEG-g-GN content of 1 wt%.

PEG-grafted GN has been synthesized and the effects of modification on the PLA composite conductivity, mechanical properties are investigated.     

Novel sulfonated poly(ether ether ketone)/triphenylamine hybrid membrane for vanadium redox flow battery applications

A novel sulfonated poly(ether ether ketone)/triphenylamine hybrid membrane with various triphenylamine loadings (1%, 2% and 5%) has been successfully fabricated. Optimum triphenylamine loading was confirmed by exploring the physicochemical properties and morphology of different membranes. The hybrid membrane exhibited lower vanadium permeability than pristine SPEEK membranes due to the acid–base interaction between amine groups and sulfonated groups. Introduction of triphenylamine also improved the proton conductivity because the nitrogen atom of triphenylamine can be protonated and contribute to the proton transfer. As the result, the hybrid membrane demonstrated higher ion selectivity compared with SPEEK and Nafion115 membranes. The VRFB single cell with SPEEK/TPAM-1% membrane showed better performance compared to a Nafion115 membrane at the current density of 60 mA cm⁻². The SPEEK/TPAM hybrid membrane has great potential for VRFB application.

The novel TPAM hybrid membrane exhibited both lower vanadium permeability and higher proton conductivity than pristine SPEEK membrane.     

Controlled degradation of low-fouling poly(oligo(ethylene glycol)methyl ether methacrylate) hydrogels

Degradable low-fouling hydrogels are ideal vehicles for drug and cell delivery. For each application, hydrogel degradation rate must be re-optimized for maximum therapeutic benefit. We developed a method to rapidly and predictably tune degradation rates of low-fouling poly(oligo(ethylene glycol)methyl ether methacrylate) (P(EG)_xMA) hydrogels by modifying two interdependent variables: (1) base-catalysed crosslink degradation kinetics, dependent on crosslinker electronics (electron withdrawing groups (EWGs)); and, (2) polymer hydration, dependent on the molecular weight (M_W) of poly(ethylene glycol) (PEG) pendant groups. By controlling PEG M_W and EWG strength, P(EG)_xMA hydrogels were tuned to degrade over 6 to 52 d. A 6-member P(EG)_xMA copolymer library yielded slow and fast degrading low-fouling hydrogels suitable for short- and long-term delivery applications. The degradation mechanism was also applied to RGD-functionalized poly(carboxybetaine methacrylamide) (PCBMAA) hydrogels to achieve slow (∼50 d) and fast (∼13 d) degrading low-fouling, bioactive hydrogels.

To tune degradation rates of low-fouling hydrogels, a 6-member P(EG)_xMA copolymer library with different electronics and hydration levels was developed.     

Folate-conjugated methoxy poly(ethylene glycol)/poly(epsilon-caprolactone) amphiphilic block copolymeric micelles for tumor-targeted drug delivery.

Amphiphilic block copolymers composed of methoxy poly(ethylene glycol) (MPEG) and poly(epsilon-caprolactone) (PCL) were synthesized and then conjugated with folic acid to produce a folate-receptor-targeted drug carrier for tumor-specific drug delivery. Folate-conjugated MPEG/PCL micelles containing the anticancer drug paclitaxel were prepared by micelle formation in aqueous medium. The size of the folate-conjugated MPEG/PCL micelles formed was about 50-130 nm, depending on the molecular weight of block copolymers, and was maintained at less than 150 nm even after loading with paclitaxel. The in vitro release profile of the paclitaxel from the MPEG/PCL micelles exhibited no initial burst release and showed sustained release. Paclitaxel-loaded folate-conjugated MPEG/PCL micelles (PFOL50) exhibited much higher cytotoxicity for cancer cells, such as MCF-7 and HeLa cells, than MPEG/PCL micelles without the folate group (PMEP50). Confocal image analysis revealed that fluorescent paclitaxel-loaded PFOL50 micelles were endocytosed into MCF-7 cells through the interaction with overexpressed folate receptors on the surface of the cancer cells.     

对映异构聚乳酸/聚乙二醇空间异构复合水凝胶的药物释放及形貌和细胞毒性

背景:目前生物降解水凝胶已被广泛应用于抗癌药物及生物活性大分子的装载,但为了保护生物活性大分子的活性,需要得到凝胶化条件更温和,凝胶化时间更短的凝胶体系.目的:制备对映异构聚乳酸∕聚乙二醇的空间异构复合水凝胶,使其具有更短的凝胶化时间,实现对模拟药物溶菌酶的装载和控释.方法:以聚乙二醇为引发剂,辛酸亚锡为催化剂,丙交酯与聚乙二醇发生开环聚合反应,得到聚乳酸/聚乙二醇的三嵌段共聚物(PLLA-PEG-PLLA 和 PDLA-PEG-PDLA).用1H NMR,FT-IR 和 XRD表征三嵌段共聚物.10% PLLA20-PEG227-PLLA20的水溶液和10%PDLA21-PEG227-PDLA21的水溶液在室温下混合,12 h后形成凝胶.通过XRD考察凝胶化机制,以溶菌酶为模拟药物,考察凝胶的释药特性,通过扫描电镜考察凝胶的形貌,采用MTT法考察凝胶的细胞毒性.结果与结论:成功得到聚乳酸/聚乙二醇的三嵌段共聚物,在嵌段共聚物中,聚乳酸嵌段和聚乙二醇嵌段都能结晶,但以聚乙二醇嵌段的结晶为主.通过XRD证明凝胶中存在空间异构复合作用,溶菌酶在凝胶中通过凝胶的溶蚀和降解行为,在7 d之内释放完全.通过扫描电镜观察到冻干的水凝胶呈三维贯穿的多孔结构,空隙尺寸在50~100 μm 之间.鼠成纤维细胞与浓度为100%的凝胶浸提液共培养72 h之后,细胞的存活率为99.3%.     

Poly(ethylene glycol)–poly(propylene glycol)–poly(ethylene glycol) and polyvinylidene fluoride blend doped with oxydianiline-based thiourea derivatives as a novel and modest gel electrolyte system for dye-sensitized solar cell applications

Unique symmetrical thiourea derivatives with an oxydianiline core were synthesized using cost-effective and simple methods. A new gel electrolyte system was prepared using these thiourea additives along with a highly conductive PEG–PPG–PEG block copolymer, PVDF, and an iodide/triiodide redox couple. The PEG units present in the electrolyte are well-known for their intense segmental motion of ions, which can degrade the recombination rate and favour the charge transfer. The thiourea additives interacted well with the redox couple to limit iodine sublimation and their adsorption induced a negative potential shift for TiO₂. The highest efficiency attained by utilizing such gel polymer electrolytes was 5.75%, especially with 1,1′-(oxybis(4,1-phenylene))bis(3-(6-methylpyridin-2-yl) thiourea) (OPPT), under an irradiation of 100 mW cm⁻². The electrochemical impedance spectroscopy, UV-vis absorption spectroscopy, differential scanning calorimetry, and FTIR spectroscopy data of such gel polymer electrolytes favoured the PCE order of the additives used in DSSCs. The improvement in the DSSC performance with symmetrical thioureas having electron-rich atoms was practically attributed to the reduction of back electron transfer, dye regeneration, and hole transport.

A unique gel polymer electrolyte was prepared using PVDF and PEG–PPG–PEG block copolymer with I⁻/I₃⁻ for DSSC application. This is a cost-effective method used for the synthesis of thiourea additives. The GPE with OPPT thiourea additive achieved a good efficiency of 5.7%.     

Covalent polymer functionalized graphene oxide/poly(ether ether ketone) composites for fused deposition modeling: improved mechanical and tribological performance

This paper presents a novel method using poly(aryl ether ketone) containing pendant carboxyl groups to covalently functionalize graphene oxide. The functionalized graphene oxide (LFG) was used to prepare poly(ether ether ketone) (PEEK) composites through melt blending. It is found that LFG has great interface adhesion to the PEEK matrix, and just a small amount of it can simultaneously improve the strength and toughness of the composites, while unmodified graphene oxide could enhance strength but cause toughness damage. The tensile and impact strength of composite with 0.1 wt% LFG are 5.7% and 20.5% higher than that of neat PEEK, respectively. In addition, 0.5 wt% LFG composite shows great friction and wear performance with friction coefficient and specific wear rate 27.3% and 18.3% lower than that of PEEK. Furthermore, the composites can be used as practical high-performance additive manufacturing materials because LFG is able to improve the mechanical performance of the fused deposition modeling (FDM) composite samples significantly.

A polymer “bridge” was designed to connect graphene oxide and poly(ether ether ketone), making stronger and tougher composites.     

Light weight and flexible poly(ether ether ketone) based composite film with excellent thermal stability and mechanical properties for wide-band electromagnetic interference shielding

This study proposes an efficient method for fabricating a light weight and flexible composite film with excellent thermal stability and mechanical properties for wide-band electromagnetic interference (EMI) shielding, which was prepared by melt blending and subsequent melt extrusion using poly(ether ether ketone) (PEEK) as a matrix, multi-walled carbon nanotube wrapped poly(ether sulfone) (wrapped MWCNTs) as a conductive filler, and GENIOPLAST® PELLET S (GPPS, high-temperature lubricant) as a processing aid. GPPS was firstly used in EMI application, to reduce the melt viscosity of PEEK as well as to improve the dispersion of wrapped MWCNTs, which enables it to fabricate a highly efficient EMI shielding (∼74.6 dB mm⁻¹) PEEK/wrapped MWCNT/GPPS1.0 composite film with a thickness of 180 μm. Furthermore, the lightweight composite film exhibits high thermal stability (i.e. degradation temperature at 5% mass loss of 586 °C) and good mechanical properties (tensile strength of 101 MPa), being superior to other previously reported EMI shielding films. The above mentioned enhanced property demonstrated its potential application as a high performance EMI shield for certain applications such as in the aerospace, weapons, and microelectronics industries, which require materials exhibits EMI shielding as well as superior mechanical properties and thermal stability.

Capitalizing on wrapped MWCNTs and high-temperature lubricants produce a light weight and flexible poly(ether ether ketone) composite film with excellent thermal stability and mechanical property for wide-band electromagnetic interference shielding.     

Development of efficient acid cleavable multifunctional prodrugs derived from dendritic polyglycerol with a poly(ethylene glycol) shell

In an attempt to explore the potential of dendritic systems for the development of effective anticancer drug delivery systems, we explored a simple modular approach of preparing polyglycerol doxorubicin prodrugs, with flexibility for drug loading using an acid-sensitive hydrazone linker and further post-modification with poly(ethylene glycol) shell. The resulting drug polymer conjugates showed optimal properties for in vitro and in vivo applications because of their high water solubility, an appropriate size for passive tumor targeting, a high stability at physiological conditions, pronounced acid-sensitive properties, cellular internalization, and a favorable toxicity profile. Doxorubicin polyglycerol conjugates with a high drug loading ratio showed clearly improved antitumor efficacy over doxorubicin in an ovarian xenograft tumor model (A2780) inducing transient complete remissions thus demonstrating the potential of developing efficient multifunctional dendritic drug delivery using our modular approach.     

Enhancing the mechanical performance of poly(ether ether ketone)/zinc oxide nanocomposites to provide promising biomaterials for trauma and orthopedic implants

Poly(ether ether ketone)/zinc oxide (PEEK/ZnO) composites were manufactured by using the injection molding technique. Before blending with the PEEK resin matrix, some ZnO nanoparticles were modified by γ-aminopropyltriethoxylsilane (APTES). The effect of surface modification of ZnO nanoparticles by amino groups and Si–O bonds was investigated. PEEK/ZnO composites were characterized by scanning electron microscopy (SEM), thermogravimetric analysis, and X-ray diffraction. The scanning electron micrographs showed that ZnO nanoparticles were encapsulated in the PEEK phase; within this phase, the nanoparticles were homogeneously dispersed. Mechanical and tribological properties were measured by tensile strength, flexural strength, coefficient of friction, and wear rate. It was shown that the interfacial compatibility between ZnO nanoparticles and PEEK matrix was significantly enhanced due to the amino and Si–O bonds decorated on the ZnO nanoparticles. More importantly, the thermal stability of PEEK improved upon the incorporation of ZnO nanoparticles into this matrix. Cell viability studies with mouse osteoblasts demonstrated that cell growth on PEEK and PEEK/ZnO was significantly enhanced. On the basis of the obtained results, PEEK/ZnO composites are recommended as promising candidates for orthopaedic materials and trauma implants.

Poly(ether ether ketone)/zinc oxide (PEEK/ZnO) composites were manufactured by using the injection molding technique.     

Efficacy and safety of scleral crosslinking using poly(ethylene glycol)ether tetrasuccinimidyl glutarate for form-deprivation myopia progression in rabbits

Myopia is becoming increasingly prevalent worldwide at an alarming rate. However, no effective treatment is available for inhibiting myopia progression. Materials chemistry advancements have made it possible to regulate mechanical properties and rate of degradation with good compatibility by developing newly crosslinking systems such as the branched polyethylene glycol (PEG) systems. Herein, we presented a PEG molecule with N-hydroxysuccinimide (NHS) ester functional groups at the chain ends as a macromolecular crosslinking agent for the treatment of myopia. We found that the scleral collagen crosslinked with the four-armed star-shaped PEG molecule with NHS ester functional group (4S-PEG) showed better biomechanical properties, increased thermal stability and higher resistance to degradation. 4S-PEG exhibited relatively low cytotoxicity for human fetal scleral fibroblasts. The retrobulbar injection of 4S-PEG at a relatively low concentration (2.5 mM) showed good effective control of the progression of form-deprivation myopia in rabbits. There were no signs of adverse effect or damage by repeated injections with 4S-PEG in rabbits. The results of this work demonstrate that 4S-PEG can serve as a robust macromolecular crosslinking agent and is expected to have promise for application in the treatment of the progression of myopia.

Poly(ethylene glycol)ether tetrasuccinimidyl glutarate (4S-PEG) can induce type I collagen crosslinking to control the progression of form-deprivation myopia in rabbits.     

Copolymers of amine methacrylate with poly(ethylene glycol) as vectors for gene therapy.

A series of structurally related copolymers of tertiary amine methacrylate with poly(ethylene glycol) (PEG) were investigated for their potential to serve as vectors for gene therapy. The effects of copolymer structure on the complexation and transfection ability were assessed. The ability of the PEG-based copolymers and DMAEMA homopolymer to bind and condense DNA was confirmed by gel electrophoresis, ethidium bromide displacement and transmission electron microscopy. The presence of PEG in the copolymers had a beneficial effect on their ability to bind to DNA. Colloidally stable complexes were obtained for all the PEG-copolymer systems as shown by uniformly discrete spherical images from transmission electron microscopy and approximate diameters of 80-100 nm by dynamic light scattering studies. DMAEMA homopolymer, however, produced agglomerated particles, confirming the important role played by the PEG chains in producing compact stable DNA complexes. Assessment of the effect of ionic strength of the buffer on the complexation and dissociation of the complexes indicated the importance of both electrostatic and non-electrostatic interactions in the polymer-DNA complexation. In vitro transfection experiments showed that DMAEMA homopolymer gave the highest level of transfection comparable to a control poly-L-lysine (PLL) system. The PEG-based copolymers gave reduced levels of transfection, most likely due to the steric stabilization effect of a PEG corona.     

Effect of maleic anhydride grafted poly(lactic acid) on rheological behaviors and mechanical performance of poly(lactic acid)/poly(ethylene glycol) (PLA/PEG) blends

A series of polylactic acid (PLA)/polyethylene glycol (PEG) blends was prepared by melt blending using PEG as a plasticizer to address the disadvantages of PLA brittleness. PEG can weaken the intermolecular chain interactions of PLA and improve its processing properties. PLA-grafted maleic anhydride (GPLA) was reactively blended with PLA/PEG to obtain a high tenacity PLA/PEG/GPLA blend. GPLA was prepared by melt grafting using diisopropyl peroxide as the initiator and maleic anhydride as the graft. The effects of different PEG molecular weights (1000–10 000 g mol⁻¹) on the properties of PLA/PEG/GPLA blends were investigated. GPLA reacted with PEG1000 (M_w = 1000 g mol⁻¹) to form short PLA branched chains and reacted with {"type":"entrez-protein","attrs":{"text":"PEG10000","term_id":"1256949604","term_text":"PEG10000"}}PEG10000 (M_w = 10 000 g mol⁻¹) to form a small number of PLA branched chains, which was unconducive to increasing the intermolecular chain entanglement. The branched PLA formed by the reaction between PEG6000 (M_w = 6000 g mol⁻¹) and GPLA had a remarkable effect on increasing intermolecular chain entanglement. The complex viscosity, modulus, and melt strength values of PLA/PEG6000/GPLA blends were relatively large. The elongation at break of the blends reached 526.9%, and the tensile strength was 30.91 MPa. It provides an effective way to prepare PLA materials with excellent comprehensive properties.

Preparation of PLA/PEG/GPLA blends with high toughness by reactive blending of PLA grafted maleic anhydride (GPLA).     

High-performance cellulose nanofibers,single-walled carbon nanotubes and ionic liquid actuators with a poly(vinylidene fluoride-co-hexafluoropropylene)/ionic liquid gel electrolyte layer

This study describes new actuators with cellulose nanofibers, single-walled carbon nanotubes and ionic liquids (CNFs/SWCNTs/ILs) and examines the electrochemical and electromechanical properties of CNF/SWCNT/IL gel hybrid actuators. Further, the effects of the CNF species present on the electrode and the electrolyte layer species of poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF(HFP)) or CNF/IL on the electrochemical and electromechanical properties of the low-voltage electroactive polymer actuators are investigated. The CNF/SWCNT/IL structure revealed a network of highly entangled CNFs and SWCNTs. The results indicated that the CNF/SWCNT/IL electrodes and the PVdF(HFP)/IL electrolyte actuators can significantly outperform the CNF/SWCNT/IL electrodes and the CNF/IL electrolyte actuators. PVdF(HFP) was considered to be a better polymer electrolyte than CNF. Further, the frequency dependences of the displacement responses of these CNF/SWCNT/IL electrode actuators were successfully simulated using a double-layered charging kinetic model. The equivalent circuit models exhibited by the PVdF(HFP)/IL electrolyte actuators are different when compared to those exhibited by the CNF/IL electrolyte actuators. Based on the results of this study, the CNF/SWCNT/IL electrodes and the PVdF(HFP)/IL electrolyte actuators are promising for application as electrochemical materials that are useful in real-world applications, including wearable and energy-conversion devices.

This study describes new actuators with cellulose nanofibers, single-walled carbon nanotubes and ionic liquids (CNFs/SWCNTs/ILs) and examines the electrochemical and electromechanical properties of the CNF/SWCNT/IL gel hybrid actuators.     

A non-enzymatic glucose sensor based on electrospun 3-D copper oxide micro-nanofiber network films using carboxylic-functionalized poly(arylene ether ketone)s as templates

Benefitting from the carboxylic functional group, the high performance polymer PCA-PAEK was first used as a template to produce 3-D rope-like CuO micro-nanofiber (CuO-MNF) network films via electrospinning and subsequent calcination. FT-IR proved the ion exchange reaction between the template and Cu²⁺ ions, and demonstrated the final structure of CuO when combined with EDX and XRD spectra. SEM and TGA revealed the small amount of Cu²⁺ immobilized on the template, resulting in small diameter (348 nm), short length and 3-D network structure of the CuO-MNFs. The CuO-MNFs were then investigated in detail for direct electrocatalytic oxidation of glucose, which was evaluated using cyclic voltammetry and chronoamperometry. Results revealed a higher sensitivity, faster response and better anti-interference than CuO-MNFs produced from traditional templates at +0.40 V. The improved performance was ascribed to the high surface-to-volume ratio and the excellent 3-D network structure after immobilization. Therefore, it was concluded that the functional group on PCA-PAEK determined the morphology and performance of the CuO-MNFs.

3-D network films of rope-like CuO-MNFs with high surface-to-volume ratio were prepared. The product is a promising electrode material for fabrication of amperometric enzymeless glucose sensors.     

Micellar carriers based on block copolymers of poly(epsilon-caprolactone) and poly(ethylene glycol) for doxorubicin delivery.

Diblock copolymers of poly(epsilon-caprolactone) (PCL) and monomethoxy poly(ethylene glycol) (MPEG) with various compositions were synthesized. The amphiphilic block copolymers self-assembled into nanoscopic micelles and their hydrophobic cores encapsulated doxorubicin (DOX) in aqueous solutions. The micelle diameter increased from 22.9 to 104.9 nm with the increasing PCL block length (2.5-24.7 kDa) in the copolymer composition. Hemolytic studies showed that free DOX caused 11% hemolysis at 200 microg ml(-1), while no hemolysis was detected with DOX-loaded micelles at the same drug concentration. An in vitro study at 37 degrees C demonstrated that DOX-release from micelles at pH 5.0 was much faster than that at pH 7.4. Confocal laser scanning microscopy (CLSM) demonstrated that DOX-loaded micelles accumulated mostly in cytoplasm instead of cell nuclei, in contrast to free DOX. Consistent with the in vitro release and CLSM results, a cytotoxicity study demonstrated that DOX-loaded micelles exhibited time-delayed cytotoxicity in human MCF-7 breast cancer cells.     

Hyaluronic acid grafted with poly(ethylene glycol) as a novel peptide formulation.

Hyaluronic acids (HA) grafted with poly(ethylene glycol) (PEG) (PEG-g-HA) were synthesized. The materials characterization, enzymatic degradability and peptide (insulin) release from solutions of the copolymers were examined. Distribution of bioactive peptides within the polymer chain is well-known for combinations of PEG and polysaccharides as aqueous polymer two-phase systems. Insulin was preferentially partitioned into the PEG phase in a PEG/HA solution system. Enzymatic degradation of the copolymers was strongly dependent on the PEG content. Thermal analysis revealed that PEG-g-HA exhibited a variation in phase-separated structures depending on the PEG content. The solution of PEG-g-HA enabled insulin to remain in the PEG moieties dispersed in the HA matrix. Leakage of insulin from the copolymers was dependent upon the PEG content. Leakage rate of insulin from copolymer containing between 7 and 39% by weight of PEG were similar. A dramatic increase in leakage rate occurred when the PEG content was increased to greater than 39% by weight. It is considered that the loaded insulin was partitioned into the PEG moieties and became entangled with the PEG chains. The conformational change of insulin was effectively prevented in PEG-g-HA solutions, although insulin was denatured in storage of both phosphate buffered solution and HA solution. Such a heterogeneous-structured polymeric solution may be advantageous as an injectable therapeutic formulation for ophthalmic or arthritis treatment.