Ethylene Oxide Block Copolymer Research Articles

Hybrid Single Crystals of Poly(ε‐caprolactone) Homopolymers and Poly(ε‐caprolactone)‐b‐Poly(ethylene oxide) Block Copolymers

AbstractHybrid single crystals (HSCs) of different poly(ε‐caprolactone) (PCL) homopolymers with a poly(ε‐caprolactone)‐b‐poly(ethylene oxide) (PCL‐b‐PEO) block copolymer (BCP) were prepared. The effects of PCL length, PCL/PCL‐b‐PEO molar ratio, crystallization temperature (Tc) and solvent on crystal morphology were investigated. The optimal Tc for the formation of more perfect HSCs is between those for homo‐crystals of individual PCL and PCL‐b‐PEO and roughly increases with the length of PCL and PCL/PCL‐b‐PEO molar ratio. The chain folding in the HSCs was studied by comparing the experimentally measured heights obtained by atomic force microscopy (AFM) and theoretically calculated ones based on a sandwich structure model. Under most situations, the PCL homopolymers adopt a larger chain folding number in the HSCs than that in their homo‐crystals, while the chain folding of BCP remains unaltered. However, when both PCL homopolymer and PCL‐b‐PEO BCP crystallize slowly and the overcrowding of the PEO is effectively alleviated, thicker HSCs can be formed, in which the PCL homopolymer preserves the chain folding in its homo‐crystals but the BCP adopts a reduced chain folding number as compared with that in its homo‐crystals. The relative crystallization rate of PCL homopolymer versus BCP also affects the real composition and overall height of the HSCs.This article is protected by copyright. All rights reserved

Effects of Ionic Liquids on the Cylindrical Self-Assemblies Formed by Poly(ethylene oxide)-Poly(propylene oxide)-Poly(ethylene oxide) Block Copolymers in Water.

Aiming at the fundamental understanding of solvent effects in amphiphilic polymer systems, we considered poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) block copolymers in water mixed with an ionic liquid-ethylammonium nitrate (EAN), 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6), or 1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF4)-and we investigated the hexagonal lyotropic liquid crystal structures by means of small-angle X-ray scattering (SAXS). At 50% polymer, the hexagonal structure (cylinders of self-assembled block copolymer) was maintained across the solvent mixing ratio. The effects of the ionic liquids were reflected in the characteristic length scales of the hexagonal structure and were interpreted in terms of the location of the ionic liquid in the self-assembled block copolymer domains. The protic ionic liquid EAN was evenly distributed within the aqueous domains and showed no affinity for the interface, whereas BMIMPF6 preferred to swell PEO and was located at the interface so as to reduce contact with water. BMIMBF4 was also interfacially active, but to a lesser extent.

Dynamics of High Molecular Weight Cylindrical and Lamellar Block Copolymers with X‐ray Photon Correlation Spectroscopy

AbstractThe structure and dynamics of polystyrene (PS)‐b‐poly(ethylene oxide) block copolymers (BCPs) are studied. The BCPs exhibit microphase‐separated cylindrical and lamellar morphologies. Structural dynamics are measured with X‐ray photon correlation spectroscopy in the small‐angle regime. Morphologies and domain sizes are evaluated using small‐angle X‐ray scattering (SAXS), scanning electron microscopy, and atomic force microscopy. Different solvent processing conditions are investigated. Grain sizes evaluated using SAXS are found to depend on processing only for the rubbery majority BCP. The structural relaxation times are examined as a function of PS volume fraction, temperature, morphology, and structural sizes. Well above the glass transition temperature (Tg) of PS, all samples exhibit stretched autocorrelation decays and diffusive dynamics. Near Tg of PS, the dynamics of all samples are anomalous with compressed autocorrelation decays and hyperdiffusive dynamics. This transition occurs at 153 °C or 1.13 Tg of PS. In the diffusive regime (at high temperature), structural relaxation times are dependent on the processing method. Near PS Tg (at low temperature), structural relaxation times scale with the PS volume fraction. Structural relaxation times do not correlate with grain size, indicating that the out‐of‐equilibrium state of PS dominates the structural dynamics of these strongly phase‐segregated BCPs.

Phase Behavior and Structure of Poloxamer Block Copolymers in Protic and Aprotic Ionic Liquids.

Ionic liquids are promising media for self-assembling block copolymers in applications such as energy storage. A robust design of block copolymer formulations in ionic liquids requires fundamental knowledge of their self-organization at the nanoscale. To this end, here, we focus on modeling two-component systems comprising a Poly(ethylene oxide)-poly (propylene oxide)-Poly(ethylene oxide) (PEO-PPO-PEO) block copolymer (Pluronic P105: EO37PO58EO37) and room temperature ionic liquids (RTILs): protic ethylammonium nitrate (EAN), aprotic ionic liquids (1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6), or 1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF4). Rich structural polymorphism was exhibited, including phases of micellar (sphere) cubic, hexagonal (cylinder), bicontinuous cubic, and lamellar (bilayer) lyotropic liquid crystalline (LLC) ordered structures in addition to solution regions. The characteristic scales of the structural lengths were obtained using small-angle X-ray scattering (SAXS) data analysis. On the basis of phase behavior and structure, the effects of the ionic liquid solvent on block copolymer organization were assessed and contrasted to those of molecular solvents, such as water and formamide.

Block Copolymers of Ethylene Oxide and Propylene Oxide: Prospects for Medical and Pharmaceutical Application in Russia

Block copolymers of ethylene oxide and propylene oxide (EO/PO block copolymers) are polymeric non-ionic surfactants with a high hydrophilic–lipophilic balance also referred to as pluronics, poloxamers, or proxanols. These compounds are among the most demanded modern excipients for the production of medicines. EO/PO block copolymers are used both in the production of traditional (liquid, semi-solid, and solid) dosage forms and as part of targeted delivery systems. The extensive application of EO/PO block copolymers is due to the diverse array of their properties, including not only solubilising, emulsifying, gelling, and other effects but also thermoreversibility, which is essential for developing in situ delivery systems and 3D printing technologies.The aim of the study was to evaluate the potential of EO/PO block copolymers for medicinal use and to assess the range of medicinal products approved in the Russian Federation that contain EO/PO block copolymers.This review presents an analysis of the register of poloxamer-containing medicines approved in the Russian Federation, a list of the largest manufacturers of EO/PO block copolymers in the world, and a study of the possibility to use copolymers for medical purposes. Currently, there are more than 10 chemical manufacturers producing EO/PO block copolymers for the pharmaceutical, biotechnology, and other industries around the world. EO/PO block copolymers are included in more than 60 medicinal products present in the Russian pharmaceutical market; this observation indicates the need to phase out the import of poloxamers.

Improved Route to Linear Triblock Copolymers by Coupling with Glycidyl Ether-Activated Poly(ethylene oxide) Chains.

Poly(ethylene oxide) block copolymers (PEOz BCP) have been demonstrated to exhibit remarkably high lithium ion (Li+) conductivity for Li+ batteries applications. For linear poly(isoprene)-b-poly(styrene)-b-poly(ethylene oxide) triblock copolymers (PIxPSyPEOz), a pronounced maximum ion conductivity was reported for short PEOz molecular weights around 2 kg mol-1. To later enable a systematic exploration of the influence of the PIx and PSy block lengths and related morphologies on the ion conductivity, a synthetic method is needed where the short PEOz block length can be kept constant, while the PIx and PSy block lengths could be systematically and independently varied. Here, we introduce a glycidyl ether route that allows covalent attachment of pre-synthesized glycidyl-end functionalized PEOz chains to terminate PIxPSy BCPs. The attachment proceeds to full conversion in a simplified and reproducible one-pot polymerization such that PIxPSyPEOz with narrow chain length distribution and a fixed PEOz block length of z = 1.9 kg mol-1 and a Đ = 1.03 are obtained. The successful quantitative end group modification of the PEOz block was verified by nuclear magnetic resonance (NMR) spectroscopy, gel permeation chromatography (GPC) and differential scanning calorimetry (DSC). We demonstrate further that with a controlled casting process, ordered microphases with macroscopic long-range directional order can be fabricated, as demonstrated by small-angle X-ray scattering (SAXS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It has already been shown in a patent, published by us, that BCPs from the synthesis method presented here exhibit comparable or even higher ionic conductivities than those previously published. Therefore, this PEOz BCP system is ideally suitable to relate BCP morphology, order and orientation to macroscopic Li+ conductivity in Li+ batteries.

Micellization, aggregation, and gelation of polystyrene-block-poly(ethylene oxide) in cosolvents added with hydrochloric acid

The micellization, aggregation, and gelation of the polystyrene-block-poly(ethylene oxide) block copolymer in solutions were quantitatively analyzed by small-angle X-ray scattering. The content and concentration of added hydrochloric acid influence the micellization, aggregation, and gelation of a polystyrene-block-poly(ethylene oxide) block copolymer in tetrahydrofuran/water and dimethylformamide/water cosolvents added with hydrochloric acid. The polystyrene-block-poly(ethylene oxide) block copolymer forms spherical micelles with screened Coulomb repulsions when dispersed in tetrahydrofuran/water cosolvents added with hydrochloric acid. The screened Coulomb repulsion arises from the poly(ethylene oxide) shells bound with protonated water and surrounded by unbalanced negative charges. If excessive water is introduced from hydrochloric acid, the non-solvent quality of tetrahydrofuran/water cosolvent predominantly causes aggregation of spherical micelles. Such screened Coulomb repulsions do not form for core-shell cylinders dispersed in dimethylformamide/water added with hydrochloric acid. Hydrochloric acid tends to form complexes with dimethylformamide. The length of core-shell cylinders can increase with the increased content of hydrochloric acid. Long core-shell cylinders favorably form three-dimensional networks through inter-cylinder entanglement. Furthermore, the absence of screened Coulomb repulsions makes entangled cylinders more compact to strongly trap the liquid phase. Thus, gels occurred in dimethylformamide/water cosolvents with added hydrochloric acid. Nevertheless, the content of added hydrochloric acid should be finely controlled. Adding a large amount of hydrochloric acid prohibits network formation and instead favors kinetically trapped rigid cylinders. This study has demonstrated that finely controlling solvent quality by additives provides a physical design strategy for fabricating cylindrical micelles with tunable properties in solutions. This should offer the fundamental understanding of self-assembly for potential applications of block copolymer micelles.

Temperature-sensitive mussel-inspired citrate-based tissue adhesives with low-swelling

ABSTRACT Mussel-inspired tissue adhesives have been widely studied in recent years because of their excellent underwater adhesion. Our recent study has synthesized a series of tissue adhesives with citric acid, dopamine, 1,8-octanediol and poly(ethylene oxide) (PEO), and found that amphiphilic adhesives showed an efficient underwater adhesion mechanism. Poly(propylene oxide)-poly(ethylene oxide) block copolymer (PEO-PPO-PEO) is a thermosensitive amphiphilic material, widely used in medical field. Herein, we replaced PEO with PEO-PPO-PEO to introduce temperature-sensitivity into adhesives, and utilized the hydrophilic-to-hydrophobic transition of PEO-PPO-PEO to reduce the swelling at human temperature. Fortunately, we got positive results that all the synthetized adhesives showed obvious temperature-sensitivity. The transition from low temperature to room temperature of the high concentrated uncured adhesive dispersion made it potentially injectable. After crosslinking, the swelling ratio of cured adhesives showed a significant decrease from 4°C to 37°C. And all the swelling ratios under 37°C were low, ranging from 8.4% to 22.5%. Additionally, the lap-shear adhesion strength on wet porcine skin was in the range of 29.2–67.1 kPa, which was higher than that of commercial fibrin glue (9–15 kPa). By selecting different (PEO)y(PPO)x(PEO)y, we could obtain adhesives with wide mechanical properties and broaden the scope of use of the adhesives.

Fabrication of Dimensional and Structural Controlled Open Pore, Mesoporous Silica Topographies on a Substrate.

Open pore mesoporous silica (MPS) thin films and channels were prepared on a substrate surface. The pore dimension, thickness and ordering of the MPS thin films were controlled by using different concentrations of the precursor and molecular weight of the pluronics. Spectroscopic and microscopic techniques were utilized to determine the alignment and ordering of the pores. Further, MPS channels on a substrate surface were fabricated using commercial available lithographic etch masks followed by an inductively coupled plasma (ICP) etch. Attempts were made to shrink the channel dimension by using a block copolymer (BCP) hard mask methodology. In this regard, polystyrene-b-poly(ethylene oxide) (PS-b-PEO) block copolymer (BCP) thin film forming perpendicularly oriented PEO cylinders in a PS matrix after microphase separation through solvent annealing was used as a structural template. An insitu hard mask methodology was applied which selectively incorporate the metal ions into the PEO microdomains followed by UV/Ozone treatment to generate the iron oxide hard mask nanopatterns. The aspect ratio of the MPS nanochannels can be varied by altering etching time without altering their shape. The MPS nanochannels exhibited good coverage across the entire substrate and allowed direct access to the pore structures.

Nanostructured dimethacrylate-based photopolymerizable systems by modification with diblock copolymers

We report the full characterization of a photocurable dimethacrylate-based formulation modified with small amounts (1 and 3 wt%) of a polystyrene-block-poly(ethylene oxide) (PS-b-PEO) block copolymer (BCP). The UV curable formulation is a mixture of bisphenol A bis(2-hydroxy-3-methacryloxypropyl)ether (Bis-GMA) and triethylene glycol dimethacrylate (TEGDMA) and contains phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (Irgacure819) as photoinitiator. We demonstrate that the addition of a small amount of BCP in the uncured formulation is able to induce a phase separation at the nanometer scale. The nanoscale structure formed in the pre-cure stage is retained after the UV curing, so obtaining nanostructured solid cross-linked materials. The studied materials can be used in the manufacturing process of stereolithography and, therefore, in modern 3D printers. The ability to induce and control the formation of nanostructures in the material by adding BCPs in the formulations could open new opportunities to tailor and improve the properties of the 3D printed objects.

Structure and composition of mixed micelles formed by nonionic block copolymers and ionic surfactants in water determined by small-angle neutron scattering with contrast variation

HypothesisComplex fluids comprising polymers and surfactants exhibit interesting properties which depend on the overall composition and solvent quality. The ultimate determinants of the macroscopic properties are the nano-scale association domains. Hence it is important to ascertain the structure and composition of the domains, and how they respond to the overall composition. ExperimentsThe structure and composition of mixed micelles formed in aqueous solution between poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) block copolymers (Pluronics or Poloxamers) and the ionic surfactant sodium dodecylsulfate (SDS) are determined from an analysis of small-angle neutron scattering (SANS) intensity data obtained at different contrasts. Different polymers and concentrations have been probed. FindingsThe SDS + Pluronic mixed micelles include polymer and some water in the micelle core that is formed primarily by alkyl chains. This is different than what was previously reported, but is consistent with a variety of experimental observations. This is the first report on the structure of SDS + Pluronic P123 (EO19PO69EO19) assemblies. The effects on the mixed micelle structure and composition of the surfactant concentration and the polymer hydrophobicity are discussed here in the context of interactions between the different components.

Block Copolymer and Nanosilica-Modified Epoxy Nanocomposites

The effects of nanoscale silica particle additives on the tensile properties of neat and poly(ethylene-alt-propylene)-b-poly(ethylene oxide) block copolymer (BCP)-modified epoxies were evaluated. Nanosilica and BCP modifiers were dispersed both individually and together in epoxy formulations. The nanosilica formed a stable dispersion, and BCP modifiers formed well-dispersed spherical micelle nanostructures in the matrix. When both additives were used, BCP micelles were observed to adsorb on nanosilica surfaces, resulting in limited aggregation of nanosilica particles. Tensile tests on bulk specimens showed that the addition of nanosilica to both neat and BCP-modified epoxy formulations increased the modulus of the composites. Compact tension tests also revealed increases in the critical stress intensity factor, KIc, and critical strain energy release rate, GIc, in both the block copolymer and nanosilica-modified epoxies. Combining both additives in the epoxy enhanced toughness beyond that obtained with the individually modified formulations. Increasing nanosilica loading up to 25 wt % produced a monotonic increase in the modulus and GIc. The nanocomposite with 25 wt % nanosilica reached an optimal level of toughness at low BCP concentrations (ca. 4 wt %). Scanning electron micrographs obtained from fracture surfaces revealed topological features indicative of micelle cavitation and nanosilica debonding, toughening mechanisms that operate in concert.

Evolution of Protrusions on Lithium Metal Anodes Stabilized by a Solid Block Copolymer Electrolyte Studied Using Time-Resolved X-ray Tomography.

Growing demand for rechargeable batteries with higher energy densities has motivated research focused on enabling the lithium metal anode. A prominent failure mechanism in such batteries is short circuiting due to the uncontrolled propagation of lithium protrusions that often have a dendritic morphology. In this paper, the electrodeposition of metallic lithium through a rigid polystyrene-b-poly(ethylene oxide) (PS-b-PEO or SEO) block copolymer electrolyte was studied using hard X-ray microtomography. In this system, protrusions were approximately ellipsoidal globules: we take advantage of this simple geometry to quantify their growth as a function of polarization time and electrolyte salt concentration. The growth of 47 different globules was tracked with time to obtain average velocities of globule growth into the electrolyte. The globule diameter was a linear function of globule height in the electrolyte with a slope of about 6, independent of time and electrolyte salt concentration.

Nanocomposite gels of poloxamine and Laponite for β-Lapachone release in anticancer therapy

Nano-hybrid systems have been shown to be an attractive platform for drug delivery. Laponite® RD (LAP), a biocompatible synthetic clay, has been exploited for its ability to establish of strong secondary interactions with guest compounds and hybridization with polymers or small molecules that improves, for instance, cell adhesion, proliferation, and differentiation or facilitates drug attachment to their surfaces through charge interaction. In this work, LAP was combined with Tetronics, X-shaped amphiphilic PPO-PEO (poly (propylene oxide)–poly (ethylene oxide) block copolymers. β-Lapachone (BLPC) was selected for its anticancer activity and its limited bioavailability due to very low aqueous solubility, with the aim to improve this by using LAP/Tetronic nano-hybrid systems. The nanocarriers were prepared over a range of Tetronic 1304 concentrations (1 to 20% w/w) and LAP (0 to 3% w/w). A combination of physicochemical methods was employed to characterize the hybrid systems, including rheology, particle size and shape (DLS, TEM), thermal analysis (TG and DSC), FTIR, solubility studies and drug release experiments. In vitro cytotoxicity assays were performed with BALB/3T3 and MCF-7 cell lines. In hybrid systems, a sol-gel transition can occur below physiological temperature. BLPC exhibits the most significant increase in solubility in formulations with a high concentration of T1304 (over 10% w/w) and 1.5% w/w LAP, or systems with only LAP (1.5%), with a 50 and 100-fold increase in solubilisation, respectively. TEM images showed spherical micelles of T1304, which elongated into wormlike micelles with concentration (20%) and in the presence of LAP, a finding that has not been reported before. A sustained release of BLPC over 140 hours was achieved in one of the formulations (10% T1304 with 1.5% laponite), which also showed the best selectivity index towards cancer cells (MCF-7) over BALB/3T3 cell lines. In conclusion, BLPC-loaded T1304/LAP nano-hybrid systems proved safe and highly effective and are thus a promising formulation for anticancer therapy.

An expedient in to the phase behaviour and scattering profile in PEO-PPO-PEO block copolymer mixed systems in aqueous solution

The present study aims to develop copolymeric micelles giving an account on the clouding behavior of two series of poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (PEO-PPO-PEO) block copolymers with varying molecular weight of PPO: one with moderate hydrophilicity i.e., 40 % PEO (L64, P84, P104) blended with very hydrophobic copolymers i.e., 10 % PEO (L61, L81, L101, L121). Marked changes in the solution behavior in our mixed copolymeric solution systems depicted the micellization and micelle growth/ transition along with the phase separation (2ϕ) which is well explained from cloud Point (CP) and solution relative viscosity (ηrel) study. The CP analysis showed the lower cloud point (LCP) and the conventional upper cloud point (UCP) i.e., two marvelous CP in the aqueous mixed Pluronics® system which motivated to explore the hypothesis of double cloud point. Such shifting phenomenon from LCP towards UCP demonstrated an increment in dynamic light scattering (DLS) intensity resulting in the obvious increment in the micellar dimensions i.e., hydrodynamic diameter (Dh) for the examined mixed copolymeric system. In addition, the small-angle neutron scattering (SANS) data were fitted to obtain the predictable parameters such as, hard sphere radius (Rhs), aggregation number (Nagg) and micellar morphology. Our findings corroborated the micellar transition from spherical to elongated ellipsoidal micelles with temperature ageing depicting a strong dependence on the amphiphilicity and concentration of the two BCPs in the mixed solution environment.

X-Ray Microtomography Analysis of Li-Sulfur Batteries with a Block Copolymer Electrolyte

Li-ion batteries are the dominant solution for many applications, from small electronic devices up to hybrid and fully electric vehicles.[1] However, this technology is now mature and new chemistries are needed to reach high specific energy while ensuring safety. Despite a relatively low operating voltage, sulfur (S8) is an attractive cathode active material due to its high theoretical specific capacity; a factor of six higher than traditional LiCoO2 cathodes.[2] To realize high energy density systems, the S8 cathode must be paired with a Li metal anode. Many challenges remain to be addressed to effectively couple a Li metal with a S8 cathode such as the low S8 utilization, the strong volume change of active material upon cycling, the insulating nature of S8 and of the final product Li2S, the solubility of polysulfides in the electrolyte.[3] This issues lead to poor capacity retention, limited cycle life, and low Coulombic efficiency. To address the polysulfide dissolution problem one approach consists in confining S8 within mesoporous and nanoporous carbon.[4] However, conventional liquid electrolytes are not stable against Li metal. A solution is then to use a solid polymer electrolytes, such as polystyrene-b-poly(ethylene oxide) (SEO) block copolymer doped with LiTFSI salt, known to stabilize Li metal.[5]The goal of this study is to understand the behavior of Li-S8 batteries comprising a SEO electrolyte. The cathode is a composite made of carbon, SEO electrolyte and sulfur-impregnated carbon nanospheres.[6] The cells were cycled and exhibited significant capacity fade. We thus used hard X-ray microtomography to determine the reason for this capacity fade. Figure 1 represents tomography images prior and after cycling. In addition to polysulfide dissolution, our observations indicate that the battery failure in our system is also due to strong changes at the Li/SEO interface.

Coalescence-Driven Verticality in Mesoporous TiO2 Thin Films with Long-Range Ordering.

Mesoporous semiconducting films with continuous interconnectivity and minimal tortuosity, such as densely ordered arrays of vertical channels, are ideal for ensuring a maximal surface area at the heterojunction to increase the density of charges or photons. While the design of these films with nanostructures below 50 nm using modern lithography is not feasible, continuously perpendicular pores can be obtained throughout a TiO2 film using a traditional soft-templating approach and lyotropic crystal engineering. We demonstrate here that a polystyrene-b-poly(ethylene oxide) block copolymer in a three-solvent system can self-assemble into a body-centered cubic Im3̅m template. The long-range three-dimensional periodicity of the template combined with a high degree of vertical contraction results in coalescence of the pores into orthogonal channels that are strongly interconnected with their nearest neighbors in the (011̅) plane. This work presents evidence of lateral long-range ordering with continuously transverse vertical porosity in a TiO2 material, which will enable functional applications, such as filtration, sensing, catalysis, and optoelectronics. To this end, we demonstrate the ability of the films to template and host methylammonium lead iodide perovskite nanocrystals.

Drug Delivery System Based on pH-Sensitive Biocompatible Poly(2-vinyl pyridine)-b-poly(ethylene oxide) Nanomicelles Loaded with Curcumin and 5-Fluorouracil.

Smart polymeric micelles (PMs) are of practical interest as nanocarriers for the encapsulation and controlled release of hydrophobic drugs. Two hydrophobic drugs, naturally-based curcumin (Cur) and synthetic 5-fluorouracil (5-FU), were loaded into the PMs formed by a well-defined pH-sensitive poly(2-vinyl pyridine)-b-poly(ethylene oxide) (P2VP90-b-PEO398) block copolymer. The influence of the drug loading on the micellar sizes was investigated by dynamic light scattering (DLS) and it appears that the size of the PMs increases from around 60 to 100 nm when Cur is loaded. On the contrary, the loading of the 5-FU has a smaller effect on the micellar sizes. This difference can be attributed to higher molar mass of Cur with respect to 5-FU but also to higher loading efficiency of Cur, 6.4%, compared to that of 5-FU, 5.8%. In vitro drug release was studied at pH 2, 6.8, and 7.4, and it was observed that the pH controls the release of both drugs. At pH 2, where the P2VP sequences from the “frozen-in” micellar core are protonated, the drug release efficiencies exceed 90%. Moreover, it was demonstrated, by in vitro assays, that these PMs are hemocompatible and biocompatible. Furthermore, the PMs protect the Cur against the photo-degradation, whereas the non-ionic PEO corona limits the adsorption of bovine serum albumin (BSA) protein on the surface. This study demonstrates that these pH-sensitive PMs are suitable for practical utilization as human-safe and smart, injectable drug delivery systems.

Porous Ultra-Thin Films from Photocleavable Block Copolymers: In-Situ Degradation Kinetics Study of Pore Material.

On the basis of the major application for block copolymers to use them as separation membranes, lithographic mask, and as templates, the preparation of highly oriented nanoporous thin films requires the selective removal of the minor phase from the pores. In the scope of this study, thin film of polystyrene-block-poly(ethylene oxide) block copolymer with a photocleavable junction groups based on ortho-nitrobenzylester (ONB) (PS-hν-PEO) was papered via the spin coating technique followed by solvent annealing to obtain highly-ordered cylindrical domains. The polymer blocks are cleaved by means of a mild UV exposure and then the pore material is washed out of the polymer film by ultra-pure water resulting in arrays of nanoporous thin films to remove one block. The removal of the PEO materials from the pores was proven using the grazing-incidence small-angle X-ray scattering (GISAXS) technique. The treatment of the polymer film during the washing process was observed in real time after two different UV exposure time (1 and 4 h) in order to draw conclusions regarding the dynamics of the removal process. In-situ X-ray reflectivity measurements provide statistically significant information about the change in the layer thickness as well as the roughness and electron density of the polymer film during pore formation. 4 H UV exposure was found to be more efficient for PEO cleavage. By in-situ SFM measurements, the structure of the ultra-thin block copolymer films was also analysed and, thus, the kinetics of the washing process was elaborated. The results from both measurements confirmed that the washing procedure induces irreversible change in morphology to the surface of the thin film.

Polyarylate–Poly(ethylene oxide) Block Copolymers for Membrane Separation of Carbon Dioxide from Gas Mixtures

Polyarylate–Poly(ethylene oxide) Block Copolymers for Membrane Separation of Carbon Dioxide from Gas Mixtures