Amphiphilic Graft Copolymers Research Articles

Permeability of Novel Chitosan-g-Poly(Methyl Methacrylate) Amphiphilic Nanoparticles in a Model of Small Intestine In Vitro.

Engineering of drug nanocarriers combining fine-tuned mucoadhesive/mucopenetrating properties is currently being investigated to ensure more efficient mucosal drug delivery. Aiming to improve the transmucosal delivery of hydrophobic drugs, we designed a novel nanogel produced by the self-assembly of amphiphilic chitosan graft copolymers ionotropically crosslinked with sodium tripolyphosphate. In this work, we synthesized, for the first time, chitosan-g-poly(methyl methacrylate) nanoparticles thiolated by the conjugation of N-acetyl cysteine. First, we confirmed that both non-crosslinked and crosslinked nanoparticles in the 0.05–0.1% w/v concentration range display very good cell compatibility in two cell lines that are relevant to oral delivery, Caco-2 cells that mimic the intestinal epithelium and HT29-MTX cells that are a model of mucin-producing goblet cells. Then, we evaluated the effect of crosslinking, nanoparticle concentration, and thiolation on the permeability in vitro utilizing monolayers of (i) Caco-2 and (ii) Caco-2:HT29-MTX cells (9:1 cell number ratio). Results confirmed that the ability of the nanoparticles to cross Caco-2 monolayer was affected by the crosslinking. In addition, thiolated nanoparticles interact more strongly with mucin, resulting in a decrease of the apparent permeability coefficient (Papp) compared to the pristine nanoparticles. Moreover, for all the nanoparticles, higher concentration resulted in lower Papp, suggesting that the transport pathways can undergo saturation.

Self-Assembly of Block and Graft Copolymers in Organic Solvents: An Overview of Recent Advances.

This review is an attempt to update the recent advances in the self-assembly of amphiphilic block and graft copolymers. Their micellization behavior is highlighted for linear AB, ABC triblock terpolymers, and graft structures in non-aqueous selective polar and non-polar solvents, including solvent mixtures and ionic liquids. The micellar characteristics, such as particle size, aggregation number, and morphology, are examined as a function of the copolymers’ architecture and molecular characteristics.

Adsorption of amphiphilic graft copolymers in solvents selective for the grafts on a lyophobic surface: a coarse-grained simulation study.

The sorption of graft copolymers on surfaces attractive only for the backbone and its effect on the conformational behavior of adsorbed/desorbed chains in solvents good for the grafts and poor for the backbone was studied by coarse-grained computer simulations. It was found that the sorption and conformational behavior are very complex and are results of an intricate interplay of solvent quality (polymer-solvent interactions) and solvent strength (polymer-surface vs. solvent-surface interactions). Increasing grafting density and length of grafts protect the backbone against adsorption, but the behavior is non-trivial. A decrease in solvent quality promotes the adsorption, because it lowers the overall solubility, but the backbone collapses and the probability of backbone-surface contacts decreases, which simultaneously hinders the adsorption. The results of simulations are presented in the form of phase diagrams depicting the decisive features of the conformational and sorption behavior.

Chemoenzymatic synthesis of dual-responsive graft copolymers for drug delivery: long-term stability, high loading and cell selectivity.

A series of amphiphilic graft copolymers, poly(N-propargyldiethanolamine 4,4'-dithiodibutyionate)-graft-monomethoxy poly(ethylene glycol) (PPD-g-mPEG), were designed via a chemoenzymatic method for pH and reduced glutathione (GSH) dual-responsive drug delivery. The effects of percent grafting and molecular weights of mPEG on critical micelle concentration (CMC) values, size of micelles, drug loading and dual-response were tested. The graft copolymers could easily form homogeneous spherical micelles with appropriate sizes and zeta-potentials. The micelles of PPD-g-mPEG copolymers loaded doxorubicin (DOX) in high efficiency, and showed excellent stability under physiological conditions and synergetic dual-response to weakly acidic pH and GSH. In vitro experiments confirmed that the DOX-loaded micelles could be internalized into cancer cells efficiently and release DOX over time. Furthermore, cell cytotoxicity assays indicated that the graft copolymers were non-cytotoxic to both cancerous and normal cells while the DOX-loaded micelles greatly improved the selectivity ratios between HeLa cells and HL-7702 cells. DOX-loaded micelles also avoided hemolysis of red blood cells (RBCs) effectively compared with commercialized doxorubicin hydrochloride. All these demonstrated the potential of PPD-g-mPEG as a model to create more functional dual-responsive nanocarriers for controlled drug delivery.

Characterization and analytical development for amphiphilic poly(γ-glutamic acid) as raw material of nanoparticle adjuvants

Amphiphilic graft copolymer consisting of poly(γ-glutamic acid) (γ-PGA) as the hydrophilic backbone and L-phenylalanine ethyl ester (Phe) as the hydrophobic side chain is an important biodegradable polymer with great potential in medical applications. In this research, we established analytical methods for the characterization and quality control of γ-PGA-graft-Phe (γ-PGA-Phe), which forms nanoparticles in aqueous solution, as a deployment platform in practical applications for vaccine adjuvants. The SEC-RI/MALS system, which uses size exclusion chromatography (SEC) coupled with a multi_angle light scattering (MALS) detector and refractive index (RI) detector, was developed to evaluate the characteristics of various types of polymers. By this method, it was indicated that absolute molecular weight (MW) should be used to measure the branch polymer. A gradient reversed phase HPLC (RP-HPLC) method was developed for the content of γ-PGA-Phe and the impurity levels to control product quality and safety. This quantitative approach could become key elements for identifying and characterizing γ-PGA-Phe. In addition, the degradation mechanism of γ-PGA-Phe was also identified as cleavage of main-chain of γ-PGA-Phe based on the stability study of γ-PGA-Phe in buffer solution with various pH values. The analytical developments described above will be important for use in both characterization and formulation design of biopolymers. Nanoparticles (NPs) composed of well-characterized biodegradable γ-PGA-Phe are expected to have a variety of potential clinical applications such as their use as drug and vaccine carriers.

Ultrafiltration membranes based on hybrids of an amphiphilic graft copolymer and titanium isopropoxide

ABSTRACTGraft copolymer poly(vinyl chloride)‐g‐poly(oxyethylene methacrylate) (PVC‐g‐POEM) is combined with titanium isopropoxide (TTIP) to form hybrids that undergo phase separation in a water bath. The water permeance of the PVC‐g‐POEM membrane increases by hybridization with TTIP owing to an increase in the surface pore size and porosity. Upon heating to 80 °C, the water permeances of PVC‐g‐POEM and PVC‐g‐POEM/TTIP decrease owing to the increased thickness of the top layer. However, the bovine serum albumin (BSA) rejection of PVC‐g‐POEM increases, while that of PVC‐g‐POEM/TTIP decreases. This is attributed to accelerated dissolution of TTIP at 80 °C, resulting in a large number of surface pores. The antifouling performance is significantly improved by TTIP addition and heating owing to increased hydrophilicity, as confirmed by contact angle, O/C atomic ratio, and water content measurements. The PVC‐g‐POEM/TTIP membrane prepared at 25 °C shows the best performance [338 L m−2 h−1 bar−1 (LMH) water permeance, 89.4% BSA rejection, and 91.9% flux ratio recovery]. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45932.

Direct Organization of Morphology-Controllable Mesoporous SnO2 Using Amphiphilic Graft Copolymer for Gas-Sensing Applications.

A simple and flexible strategy for controlled synthesis of mesoporous metal oxide films using an amphiphilic graft copolymer as sacrificial template is presented and the effectiveness of this approach for gas-sensing applications is reported. The amphiphilic graft copolymer poly(vinyl chloride)-g-poly(oxyethylene methacrylate) (PVC-g-POEM) is used as a sacrificial template for the direct synthesis of mesoporous SnO2. The graft copolymer self-assembly is shown to enable good control over the morphology of the resulting SnO2 layer. Using this approach, mesoporous SnO2 based sensors with varied porosity are fabricated in situ on a microheater platform. This method reduces the interfacial contact resistance between the chemically sensitive materials and the microheater, while a simple fabrication process is provided. The sensors show significantly different gas-sensing performances depending on the SnO2 porosity, with the highly mesoporous SnO2 sensor exhibiting high sensitivity, low detection limit, and fast response and recovery toward hydrogen gas. This printable solution-based method can be used reproducibly to fabricate a variety of mesoporous metal oxide layers with tunable morphologies on various substrates for high-performance applications.

PHEA-g-PMMA Well-Defined Graft Copolymer: ATRP Synthesis, Self-Assembly, and Synchronous Encapsulation of Both Hydrophobic and Hydrophilic Guest Molecules

A series of well-defined amphiphilic graft copolymer bearing a hydrophilic poly(2-hydroxyethyl acrylate) (PHEA) backbone and hydrophobic poly(methyl methacrylate) (PMMA) side chains was synthesized by successive reversible addition-fragmentation chain transfer (RAFT) polymerization and atom transfer radical polymerization (ATRP) through the grafting-from strategy. A well-defined PHEA-based backbone with Cl-containing ATRP initiating group in every repeated unit (Mw/Mn = 1.08), poly(2-hydroxyethyl 2-((2-chloropropanoyloxy)methyl)acrylate) (PHECPMA), was first prepared by RAFT homopolymerization of 2-hydroxyethyl 2-((2-chloropropanoyloxy)methyl)acrylate (HECPMA), a Cl-containing trifunctional acrylate. ATRP of methyl methacrylate was subsequently initiated by PHECPMA homopolymer to afford the target well-defined poly(2-hydroxyethyl acrylate)-graft-poly(methyl methacrylate) (PHEA-g-PMMA) graft copolymers (Mw/Mn ≤ 1.36) with 34 PMMA side chains and 34 pendant hydroxyls in PHEA backbone using CuCl/dHbpy as catalytic system. The critical micelle concentration (cmc) of the obtained graft copolymer was determined by fluorescence spectroscopy using N-phenyl-1-naphthylamine as probe while micellar morphologies in aqueous media were visualized by transmission electron microscopy. Interestingly, PHEA-g-PMMA graft copolymer could self-assemble into large compound micelles rather than common spherical micelles, which can encapsulate hydrophilic rhodamine 6 G and hydrophobic pyrene separately or simultaneously.

Improvement in the water solubility of drugs with a solid dispersion system by spray drying and hot-melt extrusion with using the amphiphilic polyvinyl caprolactam-polyvinyl acetate-polyethylene glycol graft copolymer and d-mannitol

The aim of this study was to prepare and characterize solid dispersion particles with a novel amphiphilic polyvinyl caprolactam-polyvinyl acetate-polyethylene glycol graft copolymer, as a water-soluble carrier. Solid dispersion particles were prepared by hot-melt extrusion and spray drying. Indomethacin (IMC) was used as a model comprising drugs with low solubility in water and d-mannitol (MAN) was used as an excipient. The physicochemical properties of prepared particles were characterized by scanning electron microscopy, thermal analysis, powder X-ray diffraction (PXRD) analysis, FTIR spectra analysis, and drug release studies. Stability studies were also conducted under stress conditions at 40°C, 75% relative humidity. We found that dissolution behavior of the original drug crystal could be improved by solid dispersion with the polyvinyl caprolactam-polyvinyl acetate-polyethylene glycol graft copolymer. The PXRD pattern and thermal analysis indicated that the solid dispersion prepared with the polyvinyl caprolactam-polyvinyl acetate-polyethylene glycol graft copolymer and IMC was in an amorphous state. FTIR spectra analysis indicated that the interaction manner between the polyvinyl caprolactam-polyvinyl acetate-polyethylene glycol graft copolymer and IMC may differ with the preparation method and formulation of solid dispersions. Stability studies proved that the amorphous state of IMC in solid dispersion particles was preserved under stress conditions for more than two weeks.

Effect of amphiphilic graft co-polymer-carrier on physical stability of bosentan nanocomposite: Assessment of solubility, dissolution and bioavailability

Bosentan is a dual endothelin receptor antagonist used in the treatment of pulmonary arterial hypertension (PAH). But the solubility and bioavailability of this drug are poor, which has restricted the design and development of dosage forms for efficient and successful therapy. The present study was carried out to develop nanocomposites using an amphiphilic graft co-polymer (Soluplus®) as a carrier to enhance the solubility and bioavailability of bosentan. The graft co-polymer-based nanocomposite formulation was prepared using the single-emulsion technique. The nanocomposite was characterised in terms of particle size analysis, solubility, percentage entrapment efficiency, drug-loading capacity, surface morphology, drug content, in vitro dissolution, stability and bioavailability. FT-IR study revealed that there was no interaction between the drug and Soluplus®. DSC analysis of the nanocomposite formulation confirmed that the bosentan was completely encapsulated within a Soluplus®. XRD analysis showed that the drug was converted to an amorphous form irreversibly. SEM images showed that the particles were of size 96–129μm and had slightly smooth to rough textured surface. TEM analysis indicated that the diameters of the prepared bosentan nanocomposite after dispersion in distilled water were 13.69–96.78nm. Statistically significant increases in the solubility, dissolution and bioavailability of the drug were observed. It was confirmed that the use of a graft co-polymer carrier-based nanocomposite formulation is a good approach for efficient delivery of bosentan, the solubility and bioavailability being increased manifold.

Robust Stimuli‐Responsive Membranes Prepared from a Blend of Polysulfone and a Graft Copolymer Bearing Binary Side Chains with Thermo‐ and pH‐Responsive Switching Behavior

A stimuli-responsive membrane exhibiting independent pH- and temperature-responsive behavior was fabricated from a blend of commercial polysulfone with a functional amphiphilic binary graft copolymer, namely, polysulfone-graft-(poly(isopropylacrylamide-co-acrylic acid)-random-poly(methyl acrylate)), denoted PSf-g-(P(NIPAAm-co-AA)-r-PMMA). Two graft copolymers with different lengths of P(NIPAAm-co-AA) side chains were designed and enriched on the membrane surface to serve as thermo- and pH-responsive on/off switches. The differences between the dual-responsive behaviors of the two kinds of polymer-blend membranes were studied by water-flux and contact-angle measurements. The PMMA side chains served to securely anchor the graft copolymers to the membrane substrate, and the blended membrane prepared from binary graft copolymer was more stable and exhibited more robust stimuli-responsive behavior than that prepared from mono-graft copolymer PSf-g-P(NIPAAm-co-AA).

Folate targeted coated SPIONs as efficient tool for MRI

The development of more sensitive diagnostic tools allowing an early-stage and highly efficient medical imaging of tumors remains a challenge. Magnetic nanoparticles seem to be the contrast agents with the highest potential, if properly constructed. Therefore, in this study, hybrid magnetic nanoarchitectures were developed using a new amphiphilic inulin-based graft copolymer (INU-LAPEG-FA) as coating material for 10-nm spinel iron oxide (magnetite, Fe3O4) superparamagnetic nanoparticles (SPION). Folic acid (FA) covalently linked to the coating copolymer in order to be exposed onto the nanoparticle surface was chosen as the targeting agent because folate receptors are upregulated in many cancer types. Physicochemical characterization and in vitro biocompatibility study was then performed on the prepared magnetic nanoparticles. The improved targeting and imaging properties of the prepared FA-SPIONs were further evaluated in nude mice using 7-Tesla magnetic resonance imaging (MRI). FA-SPIONs exhibited the ability to act as efficient contrast agents in conventional MRI, providing a potential nanoplatform not only for tumor diagnosis but also for cancer treatment, through the delivery of anticancer drug or locoregional magnetic hyperthermia.

Fabrication of self-assembled vesicle nanoparticles of poly(l-lysine)–arachidic acid conjugates for a vascular endothelial growth factor carrier

Numerous growth factors account for tissue and organ development and therapeutic efficiency. Hence, the delivery of growth factors is crucial in regenerative medical practice. However, the delivery of a single factor to regenerate tissues lacks clinical utility in many current approaches. We reported the delivery of the bioactive vascular endothelial growth factor (VEGF) from novel polymeric vesicles. Polymeric vesicles were prepared from the poly(l-lysine)–g-polylysine(AA) amphiphilic graft copolymer through the conjugation of arachidic acid (AA) with poly(l-lysine) for obtaining a VEGF carrier. The prepared copolymer can form a polymersome and effectively condense with VEGF without affecting its size and surface charges. The Gaussian curve fit (GCF) of amide I band were revealed that VEGF efficiently interact through the α-helix of the amphiphilic graft copolymer rather than β-sheet dominated poly(l-lysine). The polymersome–VEGF complex showed a considerably higher binding affinity, transfection efficiency, and less toxicity because of the peptide-based polymer backbone. Compared with the poly(l-lysine)–VEGF complex, polymersome–VEGF revealed a high secretion of VEGF and low toxicity. These polymersomes can deliver angiogenic factors in a controlled manner in tissue regeneration and biomedical engineering.

Poly(ε-caprolactone)-containing graft copolymers for ratiometric extracellular oxygen sensing

A graft copolymer composed of poly(ε-caprolactone) as a hydrophobic chain and poly(N-(2-hydroxypropyl)methacrylamide) as a hydrophilic segment with an internal reference probe for oxygen sensing was prepared. Highly efficient platinum(II)meso-tetra(pentafluorophenyl)porphine (PtTFPP) was used as a typical oxygen probe. Although PtTFPP was highly efficient, it is hydrophobic, limiting its direct application for oxygen sensing in biological conditions. By using the amphiphilic graft copolymer, PTTFPP was successfully incorporated into the micelles formed by this polymer to not only enable the application of PtTFPP for biosensing in medium but also retain its high efficiency. The quantum efficiency of PtTFPP in the micelle solution under nitrogen can reach as high as 0.20. The PtTFPP-containing micelles were tested for high throughput cell respiration and bacteria detection. The influence of an antibiotic, antimycin as a representative example, on cell respiration was also studied. For achieving high accurate sensing, an internal built-in reference probe with aggregation induced emission properties were also polymerized in the graft copolymer. This study demonstrated that the graft polymer approach is a good way to enable highly efficient and hydrophobic oxygen probes for biosensing.

Dual‐responsive crosslinked micelles of a multifunctional graft copolymer for drug delivery applications

ABSTRACTA novel multifunctional amphiphilic graft copolymer has been synthesized consisting of a biodegradable poly(l‐aspartic acid) backbone that was decorated by water‐soluble poly(ethylene glycol) (PEG) and pH‐responsive poly(N,N‐diethylaminoethyl methacrylate) (PDEAEMA) side‐chains as well as thiol pendant groups. This graft copolymer together with doxorubicin (DOX) formed micelles in water at pH = 10.0 with PDEAEMA and DOX acting as the core and PEG serving as the micellar corona. Upon oxidation, the thiol groups dimerized to form disulfide bonds, thus “locking in” the micellar structure. These crosslinked micelles expanded as the pH was decreased from 7.4 to 5.0 or upon the addition, at pH = 7.4, of glutathione (GSH), a thiol‐containing oligopeptide that is present in cancerous cells and cleaves disulfide bonds. At pH = 5.0, GSH addition triggered the disassembly of the micelles. The expansion and disassembly of the micelles have been determined via in vitro experiments to evaluate their DOX release behavior. More importantly, the graft copolymer micelles could enter cells by means of endocytosis and deliver DOX to the nuclei of ovarian cancer BEL‐7402 cells. Thus, this polymer and its micelles are promising candidates for drug delivery applications. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 1536–1546

Biocompatible Soft Nanoparticles with Multiple Morphologies Obtained from Nanoprecipitation of Amphiphilic Graft Copolymers in a Backbone-Selective Solvent

Stealth nanocarriers are a promising technology for the treatment of diseases. However, the preparation and characterization of well-defined soft nanoparticulate systems remain challenging. Here we describe a platform of amphiphilic graft copolymers leading to nanoparticles with multiple morphologies and the role of the hydrophilic backbone in their interaction with a model protein. The amphiphilic graft copolymers platform was composed of hydrophilic backbone poly(2-methyl-2-oxazoline-co-2-pentyl-2-oxazoline) (P(MeOx-co-PentOx)), prepared via cationic ring-opening polymerization. Hydrophobic poly(d,l-lactide) (PLA) chains were grafted on the backbone via Huisgen 1,3-dipolar cycloaddition. The "click" copper-catalyzed cycloaddition reactions of azides with alkynes (CuAAC) were successfully carried out, and a series of amphiphilic copolymers were prepared containing a backbone with a number-average molecular weight of 14.2 × 103 g mol-1 and different hydrophobic PLA grafts with various molecular weights (2.8 × 103-12.4 × 103 g mol-1). These original architectures of copolymers, when nanoprecipitated in water, the backbone-selective solvent, allowed us to obtain various structures of nanoparticles with a hydrodynamic diameter in the range of 65-99 nm. More interestingly, a plurality of morphologies going from unilamellar, multilamellar, and large compound vesicles to core-shell nanoparticles and depending on the PLA molecular weights were evidenced by combining cryo-transmission electron microscopy (cryo-TEM) and small-angle neutron scattering (SANS) studies. A first evaluation of their stealthiness by studying the stability and the interaction of these nano-objects with a model protein revealed the role played by the P(MeOx-co-PentOx) in these interactions, demonstrating the utility of this amphiphilic graft copolymers platform with well-defined architectures for the design of nanocarriers in drug delivery applications.

Self-assembling polyether-b-polymethacrylate graft copolymers loaded with indomethacin

ABSTRACTThe amphiphilic graft copolymers containing polyether-b-polymethacrylate side chains are proposed as carriers for a nonsteroidal anti-inflammatory drug, indomethacin (IMC). Two series of copolymers, poly((methyl methacrylate)-co-(poly(ethylene glycol methacrylate)-graft-poly((methacrylic acid)-co-(tert-butyl methacrylate)))) (P(MMA-co-(PEGMA-graft-P(MAA-co-tBMA)))) and poly((methyl methacrylate)-co-(poly(propylene glycol methacrylate)-graft-poly((methacrylic acid)-co-(tert-butyl methacrylate)))) (P(MMA-co-(PPGMA-graft-P(MAA-co-tBMA)))) were applied in the micellization process. The effects of grafting degree (5–15%), length of the graft polymethacrylic segments (29–186 units), composition (PEG vs. PPG), and content of acidic fraction (52–89%) were verified in the design of two different types of micelles (depending on polyether nature) with proper stability and controlled release of the drug. The methacrylic segment with MAA units resulted in negatively charged layer as it was indicated by measurements of zeta potential (from −2 to −44 mV) The sizes of particles were in the range of 160–225 nm. The type of polyether segment influenced on the content of the drug encapsulation (PEG 39% vs. PPG 93% at 48% of hydrophobic fraction). In vitro experiments demonstrated significantly larger IMC releasing at pH 7.4 than in acidic conditions. The lower drug release rates were monitored for copolymers with long side chains containing large content of acidic units, what enhanced particle stabilization and drug-polymer interactions. The drug release profiles were well fitted to the Higuchi model, suggesting diffusion mechanism. The results confirmed that the graft copolymers might be applied as the carriers releasing a various doses of drug with the rate, which can be adjusted by wider sort of structural parameters than is possible in linear amphiphilic copolymers.

Potential of amphiphilic graft copolymer α-tocopherol succinate-g-carboxymethyl chitosan in modulating the permeability and anticancer efficacy of tamoxifen

Recent studies showed an enhanced oral bioavailability of tamoxifen (TMX) by hydrophobically modified α-tocopherol succinate-g-carboxymethyl chitosan (Cmc-TS) micelles. As a continued effort, here we evaluated TMX-loaded polymeric micelles (TMX-PMs) for its enhanced permeability with increased anticancer efficacy and decreased hepatotoxicity. We employed co-solvent evaporation technique to encapsulate TMX into Cmc-TS. Apparent permeability assay of TMX-PMs was performed on Caco-2 cell line. The absorptive transport of TMX increased significantly about 3.8-fold when incorporated into Cmc-TS PMs. Cytotoxicity of Cmc-TS PMs was studied on MCF-7 cell line by MTT and; confocal microscopy was used for cellular uptake. Confocal microscopy revealed that Cmc-TS PMs could effectively accumulate in the cytosol of MCF-7 cell lines. In vitro data was further validated using N-methyl-N-nitrosourea (MNU)-induced mammary carcinogenesis model in Sprague-Dawley rats. Hepatotoxicity profiles of TMX-PMs at three different doses were also evaluated against the free drug TMX. TMX-PMs were more effective in suppressing breast tumor in MNU-induced mammary carcinoma model than free TMX with better safety profile. In addition, histological data shows that tumors are “benign” in TMX-PMs treated group compared with “malignant” tumors in free TMX treated and control groups. Overall, the results implicate that our Cmc-TS PMs may serve as a promising carrier for the intracellular delivery of anticancer drug molecules via oral route.

Preparation, characterization and performance study of modified PVDF-based membranes containing palladium nanoparticle-modified graphene hierarchical nanostructures: as a new catalytic nanocomposite membrane

A well-defined amphiphilic graft copolymer (PVDF-g-PAm) was synthesized via surface-initiated atom transfer radical polymerization (SI-ATRP) of acrylamide (Am) from C–F bonds of PVDF as a macro-initiator. PVDF-g-PAm-synthesized copolymer was thoroughly characterized using Fourier-transform infrared spectroscopy (FTIR) and 1H-nuclear magnetic resonance spectroscopy (1H NMR). Blend of PVDF and PVDF-g-PAm copolymer was filled with already prepared hierarchical nanostructures of palladium nanoparticles-functionalized graphene oxide (Pd NPs–FGO) to achieve high-performance catalytic nanocomposite membranes. The catalytic activity and reusability of the prepared catalytic membranes for the Suzuki reaction were investigated in a homemade cell. Results revealed that the reactivity and reusability of catalytic membranes containing the hierarchical nanostructures (Pd NPs–FGO) were remarkably improved compared with that of the conventional catalytic membranes containing the unsupported Pd NPs in the membrane matrix. Therefore, the strategy of immobilization of the Pd NPs on the FGO surface is a good approach to minimize the potential Pd NPs loss. The thermal properties, morphology and catalyst content of the prepared catalytic nanocomposite membranes were also studied by means of different techniques such as thermogravimetric analysis (TGA), differential scanning calorimeter (DSC), scanning electron microscopy (SEM) and inductively coupled plasma atomic emission spectroscopy (ICP).

Synthesis and self-assembly behavior of POSS tethered amphiphilic polymer based on poly(caprolactone) (PCL) grafted with poly(acrylic acid) (PAA) via ROP, ATRP, and CuAAC reaction

This investigation reports the preparation and self-assembly behavior of polyhedral oligomeric silsesquioxane (POSS) containing poly(caprolactone)-graft-poly(acrylic acid) (POSS-PCL-graft-PAA) polymer. This article focuses on the self-assembly behavior of POSS tethered amphiphilic graft copolymer. In this investigation, POSS tethered alkyne functionalized polycaprolactone (PCL) was prepared by strategic ring opening polymerization (ROP) of e-caprolactone and α-propargyl-e-caprolactone using hydroxyl-terminated POSS as an initiator. Azide-terminated poly(tert-butyl acrylate) (PtBA) was grafted onto functional PCL via Cu-catalyzed azide-alkyne “click” (CuAAC) reaction. Finally, hydrolysis of the tert-butyl ester group into acid furnished the POSS tethered PCL-graft-PAA polymer. This amphiphilic graft copolymer was characterized by GPC, NMR, and FT-IR analyses and the morphology of the graft copolymer analyzed by HRTEM and FESEM analyses. On changing the graft copolymer concentration (low to high) in water, the morphology of the final graft copolymer changed from micelles to worm-like and core-shell. The structural motif of POSS plays an important role in this morphological transformation. The pH sensitivity was studied using DLS analysis as well as via release profile of rhodamine B as a model compound.