Gel Permeation Chromatography Measurements Research Articles

Utilizing environmentally friendly hyperbranched polyglycerol polymers to separate gasoline from deionized water

AbstractHyperbranched polyglycerol polymers (HPG) were synthesized, characterized, and used to separate gasoline from deionized water. The study indicates HPG as potentially effective materials for the recovery of oil from oil/water emulsion. High and low molecular weight HPG were synthesized using the cationic ring‐opening polymerization method and characterized by various methods including, NMR, Fourier transform infrared‐spectroscopy, DXR Raman microscope, carbon hydrogen and nitrogen analysis, gel permeation chromatography measurements, biodegradability, and toxicity testing. The prepared polymers are environmentally friendly, biodegradable, and are able to recover up to 90.30% of oil from oil/water emulsion under an optimized dose of 500 mg L−1 in 1 h. A higher rate of removal can be achieved by increasing the polymer dose up to 200 mg L−1, with a reaction time up to 3 h, and a maximum operating temperature of 60°C. The results of this study offer a simple and effective technology that can be applied for the removal of valuable products, increase the profitability for the oil and gas industry, and protect the environment. © 2020 Society of Chemical Industry and John Wiley & Sons, Ltd.

Amino Acid-Linked Low Molecular Weight Polyethylenimine for Improved Gene Delivery and Biocompatibility.

The construction of efficient and low toxic non-viral gene delivery vectors is of great significance for gene therapy. Herein, two novel polycations were constructed via Michael addition from low molecular weight polyethylenimine (PEI) 600 Da and amino acid-containing linkages. Lysine and histidine were introduced for the purpose of improved DNA binding and pH buffering capacity, respectively. The ester bonds afforded the polymer biodegradability, which was confirmed by the gel permeation chromatography (GPC) measurement. The polymers could well condense DNA into nanoparticles and protect DNA from degradation by nuclease. Compared with PEI 25 kDa, these polymers showed higher transfection efficiency, lower toxicity, and better serum tolerance. Study of this mechanism revealed that the polyplexes enter the cells mainly through caveolae-mediated endocytosis pathway; this, together with their biodegradability, facilitates the internalization of polyplexes and the release of DNA. The results reveal that the amino acid-linked low molecular weight PEI polymers could serve as promising candidates for non-viral gene delivery.

Synthesis, Structural Characterization, Enzymatic and Oxidative Polymerization of 2,6-Diaminopyridine.

Enzymatic polymerization of 2,6-diaminopyridine (DAP) compound in the presence of HRP (Horse radish peroxidase) and H2O2 (hydrogen peroxide) with Poly(DAP-en) with the structures of two different types of polymers obtained by the oxidative polymerization of Poly(DAP-ox) using H2O2 in an aqueous basic environment was illuminated by 1H-NMR, 13C-NMR, FT-IR, UV-Vis spectral methods. GPC (gel permeation chromatography), TGA (thermal gravimetric analysis), DSC (differential scanning calorimetry), CV (cyclic voltammetry), fluorescence analysis and conductivity measurements to characterize the compounds and their electronic structure were examined. SEM analyzes were performed for the morphological properties of the compounds. As a result of the analysis, it was observed that the polymer obtained by enzymatic polymerization was better than the polymer obtained by oxidative method. It was observed that the results of the fluorescence measurements were better than Poly(DAP-en) in Poly(DAP-ox) emitting blue and green light. According to TGA analysis, the first decay temperatures for Poly (DAP-en) and Poly (DAP-ox) were calculated as 342°C and 181°C, respectively. The higher value of glass transition temperature for poly (DAP-en) confirms that the average molar mass is higher than 8650Da for Poly (DAP-en) according to GPC analysis.

An Environment-Friendly Palm Fatty Acid-Based Polymeric Surfactants for Coating Applications: Physicochemical, Surface Tension and Low-Foaming Properties

In this work, two environmental-friendly low-foaming surfactants, anionic oleic acid surfactant (AOAS), and non-ionic oleic acid surfactant (NOAS) were synthesized by copolymerization of palm fatty acids with fully bio-sourced and renewable starting materials using polyesterification method. The chemical structures of both surfactants were confirmed by nuclear magnetic resonance (NMR) and Fourier-transform infrared (FTIR) studies. Acid value determination showed that NOAS achieved a higher conversion rate of 97% than that of AOAS with only 78%. Differential scanning calorimetry (DSC) experiment demonstrated that both surfactants had low Tg, around − 94 °C to − 68 °C. Thermogravimetric analysis (TGA) exhibited polymer decomposition occurred above 150 °C. Gel permeation chromatography (GPC) measurement revealed that both surfactants were polydisperse, with NOAS had higher molecular weight than AOAS. Critical micelle concentration (CMC) of AOAS and NOAS were recorded as 0.0670 mM/L and 0.0999 mM/L respectively. The surface tensions of both AOAS and NOAS were 33.27 mN/m and 41.13 mN/m, respectively. The contact angle measurement indicated that NOAS had a better wettability than AOAS. Cloud point of NOAS surfactant was determined to be 89 °C. These surfactants had better solubility in a non-polar solvent like hexane compared to polar solvents like ethanol and water. The foaming test concluded that both surfactants presented low foaming behavior, with immediate foam height less than 1.5 mm. The physicochemical and surface tension properties confirmed the surface active properties of both AOAS and NOAS. The foaming test results recommended consideration of both AOAS and NOAS for low-foaming applications, particularly to reduce foam formation in coatings.

Application a novel thermo-sensitive copolymer as a potential rheological modifier for deepwater water-based drilling fluids

In deepwater drilling, rheological properties of water-base drilling fluids (WBDF) varied remarkably within the wide temperatures range, causing problems including equivalent circulating densities control, lost circulation, etc. To solve these problems, the key was how to reduce the temperature dependence of rheological properties. In this study, the combination of thermo-sensitive polymer and clay particles was used to solve this problem due to the distinct thermo-rheological properties of these two components. In detail, a novel thermo-sensitive copolymer (PANA) of acrylamide (AM), sodium 2-acrylamido-2-methylpropane sulfonate (NaAMPS) and N-vinylcaprolactam (NVCL) was synthesized by free radical polymerization under optimal conditions. And the structure of PANA was characterized by FTIR, elemental analysis, and gel permeation chromatographic measurements. The thermo-rheological properties of PANA in solution and slurry were investigated through viscometer. Results from rheological tests illustrated that PANA showed certain thermo-thickening phenomenon in the temperature range of 4–95 °C due to the thermo-associative behavior of thermo-responsive caprolactam (CL) moieties. And the temperature dependence of rheology of PANA based drilling fluids was further studied over the temperature range of 4–75 °C according to the American Petroleum Institute (API) standard. Results illustrated that the rheology of PANA based fluids were found to be more stable than those of typical WBDF. The change rate of main rheological parameters of PANA fluids, such as, apparent viscosity (AV), yield value (YP), and low shear rate viscosity (LSRV), was less than 15%, while parameters of typical WBDFs varied dramatically (near or over 30%). Therefore, the relatively stable rheological properties of fluids with temperature changes could be achieved through the synergistic effect between the novel thermo-sensitive copolymer and bentonite particles. In addition, the rheological control mechanism of PANA was further investigated through transmittance tests, Environmental Scanning Electron Microscope (ESEM), zeta potential experiments, and particle size distribution measurements.

Effect of structure on the properties of ambient-cured coating films prepared via a Michael addition reaction based on an acetoacetate-modified castor oil prepared by thiol-ene coupling

The Michael addition reaction was used to create ambient curable film materials based on an acetoacetate-modified castor oil, and a multifunctional alamine was prepared. The thiol-ene coupling reaction could change the proportion of hydroxyl groups in the castor oil, thereby improving the crosslinking density and mechanical properties of the coating films. The acetoacetate-modified castor oil was achieved in two steps. First, the CC bonds of castor oil were coupled using a thiol-ene coupling reaction, which has a high conversion rate and few by-products. Second, acetoacetate-modified castor oil was prepared by a transesterification reaction between tert-butyl acetoacetate and modified castor oil. The acetoacetate-modified castor oil was characterized by Nuclear magnetic resonance (NMR), Fourier Transform infrared spectroscopy (FTIR), Gel Permeation Chromatography (GPC) and viscosity measurements. Finally, coating films were prepared from the acetoacetate-modified castor oil and 4,4-diaminecyclohexylmethane via a Michael addition reaction at room temperature (25 °C). The mechanical properties were noticeably improved compared to those of the unmodified castor oil film. The tensile properties increased from 0.68 MPa to 1.76 MPa, and the glass transition temperature (Tg) increased by approximately 30 °C.

Giant Vesicles Encapsulating Aqueous Two-Phase Systems: From Phase Diagrams to Membrane Shape Transformations.

In this review, we summarize recent studies on giant unilamellar vesicles enclosing aqueous polymer solutions of dextran and poly(ethylene glycol) (PEG), highlighting recent results from our groups. Phase separation occurs for these polymer solutions with concentration above a critical value at room temperature. We introduce approaches used for constructing the phase diagram of such aqueous two-phase system by titration, density and gel permeation chromatography measurements of the coexisting phases. The ultralow interfacial tension of the resulting water-water interface is investigated over a broad concentration range close to the critical point. The scaling exponent of the interfacial tension further away from the critical point agrees well with mean field theory, but close to this point, the behavior disagrees with the Ising value of 1.26. The latter discrepancy arises from the molar mass fractionation of dextran between coexisting phases. Upon encapsulation of the PEG–dextran system into giant vesicles followed by osmotic deflation, the vesicle membrane becomes completely or partially wetted by the aqueous phases, which is controlled by the phase behavior of the polymer mixture and the lipid composition. Deflation leads to a reduction of the vesicle volume and generates excess area of the membrane, which can induce interesting transformations of the vesicle morphology such as vesicle budding. More dramatically, the spontaneous formation of many membrane nanotubes protruding into the interior vesicle compartment reveals a substantial asymmetry and spontaneous curvature of the membrane segments in contact with the PEG-rich phase, arising from the asymmetric adsorption of polymer molecules onto the two leaflets of the bilayers. These membrane nanotubes explore the whole PEG-rich phase for the completely wetted membrane but adhere to the liquid-liquid interface as the membrane becomes partially wetted. Quantitative estimates of the spontaneous curvature are obtained by analyzing different aspects of the tubulated vesicles, which reflect the interplay between aqueous phase separation and spontaneous curvature. The underlying mechanism for the curvature generation is provided by the weak adsorption of PEG onto the lipid bilayers, with a small binding affinity of about 1.6 kBT per PEG chain. Our study builds a bridge between nanoscopic membrane shapes and membrane-polymer interactions.

Tailor‐made controlled rheology polypropylenes from metallocene and Ziegler–Natta resins

Production of controlled rheology polypropylenes (CRPPs) is practiced industrially by modifying existing commodity Ziegler–Natta resins through peroxide‐induced β‐scission reactions, resulting in materials with controlled rheological properties and accompanying narrower molecular weight distributions (MWDs). In this work, this methodology was studied using both metallocene‐based polypropylenes (mPPs) and Ziegler–Natta‐based polypropylenes (ZN‐PPs). Numerical simulations based on a previously proposed kinetic model indicated that the nature of the starting resin has a significant effect on the control of MWD polydispersity index (PDI) and weight‐average molecular weight () of the resulting CRPP. Based on these observations, experiments were carried out to demonstrate the feasibility of producing CRPP with targeted molecular and rheological characteristics. Commercial mPP and ZN‐PP resins were selected to produce CRPP with similar or melt flow rates (MFRs) but varying PDIs. The rheological properties and MWDs of these materials were evaluated through oscillatory shear and gel permeation chromatography (GPC) measurements and their extrusion behavior was briefly studied and assessed with respect to these properties. POLYM. ENG. SCI., 59:1114–1121 2019. © 2019 Society of Plastics Engineers

CoFe2O4 Nano-particles for Radical Oxidative Degradation of High Molecular Weight Polybutadiene

Polymer waste production increased dramatically in the last decades, and has reached to 380 million tons (Mt.) in 2015. Due to their long-term stability, these materials impose a serious environmental challenge. Currently, recycling of polymer waste focuses on re-use of actual products, mechanical processing, chemical recycling, and bio-degradation into environmentally friendly materials. In our previous work, we proposed a new approach for radical-initiated oxidative degradation of polymers using cobalt ferrite (CoFe2O4) nanoparticles. In our current work, we focus on the use of CoFe2O4 nanoparticles as catalysts for radical degradation of high molecular weight polybutadiene. Cobalt ferrite nanoparticles were embedded into the polybutadiene polymeric matrix, with the aim of studying degradation in polymeric products that can be manufactured with catalytic nanoparticles. The polymer degradation process was characterized using gel permeation and size exclusion chromatography measurements, thermogravimetric analysis, FTIR, NMR, and mass spectroscopy. Based on the results from these diverse measurements, we propose a mechanism for the degradation process. Overall, our results show that the radical processes within the polybutadiene polymer lead to two parallel processes: polymer crosslinking and polymer scission. Moreover, we show that the ratio between crosslinking and degradation can be controlled by the reaction duration and catalyst concentration.

Linkage Abundance and Molecular Weight Characteristics of Technical Lignins by Attenuated Total Reflection-FTIR Spectroscopy Combined with Multivariate Analysis.

Lignin is an attractive material for the production of renewable chemicals, materials and energy. However, utilization is hampered by its highly complex and variable chemical structure, which requires an extensive suite of analytical instruments to characterize. Here, we demonstrate that straightforward attenuated total reflection (ATR)‐FTIR analysis combined with principle component analysis (PCA) and partial least squares (PLS) modelling can provide remarkable insight into the structure of technical lignins, giving quantitative results that are comparable to standard gel‐permeation chromatography (GPC) and 2D heteronuclear single quantum coherence (HSQC) NMR methods. First, a calibration set of 54 different technical (fractionated) lignin samples, covering kraft, soda and organosolv processes, were prepared and analyzed using traditional GPC and NMR methods, as well as by readily accessible ATR‐FTIR spectroscopy. PLS models correlating the ATR‐FTIR spectra of the broad set of lignins with GPC and NMR measurements were found to have excellent coefficients of determination (R 2 Cal.>0.85) for molecular weight (M n, M w) and inter‐unit abundances (β‐O‐4, β‐5 and β‐β), with low relative errors (6.2–14 %) as estimated from cross‐validation results. PLS analysis of a second set of 28 samples containing exclusively (fractionated) kraft lignins showed further improved prediction ability, with relative errors of 3.8–13 %, and the resulting model could predict the structural characteristics of an independent validation set of lignins with good accuracy. The results highlight the potential utility of this methodology for streamlining and expediting the often complex and time consuming technical lignin characterization process.

Hydrophobically Modified Polycarboxybetaine: From Living Radical Polymerization to Self-Assembly.

Polybetaines have received widespread attention due to their smart response properties and structures which resemble biological polymers like peptides and DNA. However, few studies have focused on the controlled synthesis and self-assembly of hydrophobically modified polybetaines due to the difficulty of synthesizing these materials. We report the first molecular weight-controlled synthesis of hydrophobically modified polycarboxybetaines (HMPCB). Poly(dodecyl grafted aminocrotonate -methacrylic acid) (P(DACRO-MAA)) was synthesized via the reversible addition-fragmentation chain-transfer (RAFT) polymerization approach. The two different tautomers of the monomer were also successfully identified and separated via thin layer chromatography (TLC) and column chromatography, making it possible to obtain pure polycarboxybetaine via RAFT synthesis. Both the successfully separated enamine form of the monomer and the resulting polycarboxybetaine were confirmed via FTIR and NMR. The polycarboxybetaine was found to have a low polydispersity (PDI) of 1.214, and its molecular weight was determined as 70590 g/mol via gel permeation chromatography (GPC) measurements. Spherical, rodlike, and fractal assembled structures for the P(DACRO-MAA) were observed with pH change using TEM, zeta sizer, and dynamic light scattering (DLS). The unique self-assembled structures of HMPCB synthesized via RAFT provide an opportunity to understand fundamental polymer science and can be engineered for broad applications.

Synthesis and Characterization of Poly(ester amide)s Consisting of Poly(L-lactic acid) and Poly(butylene succinate) Segments with 2,2′-Bis(2-oxazoline) Chain Extending

An aliphatic polyester based poly(ester amide)s (PEA) consisting of poly (L-lactic acid) and poly(butylene succinate) was successfully prepared via chain extension reaction of poly(L-lactic acid)-dicarboxylic acid (PLLA-COOH) and poly(butylene succinate)-dicarboxylic acid (PBS-COOH) using 2,2′-bis(2-oxazoline) as a chain extender. PLLA-COOH was obtained by direct polycondensation of L-lactic acid in the presence of 1, 4-succinic acid. PBS-COOH was synthesized by condensation polymerization of 1,4-butylene glycol with excessive succinic acid. The structures of PLLA-COOH, PBS-COOH, and PEAs were characterized by fourier transform infrared (FTIR) and 1H nuclear magnetic resonance (1H NMR). The molar masses were determined by gel permeation chromatography (GPC). The thermal properties of PLLA-COOH, PBS-COOH, and PEAs were characterized by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The lattice parameters of PLLA-COOH, PBS-COOH, and PEAs were investigated by X-ray diffraction (XRD). Furthermore, The mechanical properties were characterized by tensile testing and notch Izod impact testing. The FTIR and 1H NMR results demonstrated the formation of PLLA-COOH, PBS-COOH, and PEAs. The GPC measurements showed that the molar masses of copolymer PEAs decreased with increasing PBS-COOH content. The TGA analysis confirmed that the introduction of PBS improved the thermal properties. DSC data indicated that the melting temperatures of the PEAs were lower than that of the prepolymers. The results of XRD suggested that the PLLA crystal structures was destroyed by the PBS units, and the crystallization of the PEAs mainly attributed to the PBS chain segments.The introduction of PBS units into the polymer structure improved the toughness of PLLA, which was detected in mechanical properties.

Synthesis, Characterization, and Optical, Electrical and Thermal Stabilities of Poly(phenoxy-imine)s Containing Methyl and Hydroxyl Groups

The four different Schiff base compounds were synthesized from condensation reaction of benzaldehyde, 2-hydroxybenzaldehyde, 3-hydroxybenzaldehyde and 2-hydroxy-1-napthaldehyde with 4-amino-3-methylphenol. Then, the Schiff bases were converted into poly(phenoxy-imine)s by oxidative polycondensation in aqueous alkaline medium using NaOCl as oxidant. The structures of synthesized monomers and polymers were determined by Fourier transform infrared, proton-carbon-13 nuclear magnetic resonance (1H-13C-NMR) and ultraviolet–visible (UV–Vis) spectroscopies. The surface morphology of poly(phenoxy-imine)s was determined by scanning electron microscopy images. The molecular weight distributions of poly(phenoxy-imine)s were studied with gel permeation chromatography measurements. The optical properties of compounds were determined from UV–Vis spectroscopy and fluorescence spectroscopy measurements. Electrochemical properties of the compounds were determined by cyclic voltammetry analysis. The solubility tests of the synthesized compounds were performed in various organic solvents. Thermal properties of the compounds were determined by thermogravimetric and differential thermal analysis and differential scanning calorimetry. The electrical conductivity of undoped and iodine-doped poly(phenoxy-imine)s was measured by four-point probe technique at room temperature. The synthesized poly(phenoxy-imine)s show good electrical conductivity with iodine doping and the conductivity increases with the increase in iodine vapor contact time.

A robust strategy for the synthesis of miktoarm star copolymers by combination of ROP and photoinitiated free radical polymerization

A novel approach for the synthesis of miktoarm star copolymers by the combination of ring opening polymerization (ROP) and Type II photopolymerization is described. The method pertains to the use of a multifunctional initiator, bearing primary hydroxyl and tertiary amine functionalities, for the sequential or simultaneous polymerization of vinyl and lactone monomers under mild conditions. In the first step, phosphazene base (P2-t-Bu) catalyzed ROP of ε-caprolactone is accomplished. Subsequently, thus obtained poly(ε-caprolactone) with amine end groups was used as co-initiator for the polymerization of methyl methacrylate by utilizing conventional Type II photoinitiators. The structures, molecular weight characteristics and thermal properties of the polymers are analyzed by NMR, gel permeation chromatography (GPC) and differential scanning calorimetry (DSC) measurements, respectively.

Chain extension of poly (butylene adipate-co-terephthalate) and its microcellular foaming behaviors

A facile chain extension and solid-phase batch foaming method was proposed to prepare microcellular poly (butylene adipate-co-terephthalate) (PBAT) foams in the presence of supercritical CO2. Branching structure and micro cross-linking structure were generated in modified PBAT with styrene-acrylonitrile-glycidyl methacrylate terpolymer (SAG) as chain extender, which was confirmed by Fourier transform infrared spectra, gel permeation chromatography and gel fraction measurements. The intrinsic viscosity and branching degree of modified PBAT increased as well as their viscoelasticity was improved respectively, with the SAG content increasing. The crystallization temperature and crystallinity of various PBAT samples increased and then decreased slightly due to the heterogeneous nucleation effect of branching points and the generation of cross-linking structure. An interesting complex cellular structure was observed in modified PBAT foams with the SAG content of 1 and 3 wt%, owing to the different rheological properties in branching molecular chain regions and linear molecular chain regions.

Initiator‐free photopolymerization of common acrylate monomers with 254 nm light

AbstractUsing an available light source at a wavelength of 254 nm, common acrylate monomers were polymerized without any photoinitiators, which was confirmed using Fourier transform IR (FTIR) spectroscopy, 1H NMR, gel permeation chromatography and fast atom bombardment mass spectrometric measurements. It was found that phenyl acrylate shows higher conversion than n‐ and t‐butyl acrylates. A trifunctional acrylate was also used for UV curing. The cured films were fabricated successfully on different kinds of substrates by using a batch‐ or conveyor‐type irradiation apparatus. It is indicated from FTIR spectral measurements that ca 40%–50% of acryloyl groups are consumed by the photopolymerization. Oxygen concentration in the sample chamber influences the photopolymerization, indicating that the polymerization proceeds via a radical process. © 2018 Society of Chemical Industry

Room Temperature Synthesis of Self-Assembled AB/B and ABC/BC Blends by Photoinitiated Polymerization-Induced Self-Assembly (Photo-PISA) in Water

A series of self-assembled monomethoxypoly(ethylene glycol)-b-poly(2-hydroxypropyl methacrylate)/poly(2-hydroxypropyl methacrylate) (mPEG113-PHPMA/PHPMA) blends are prepared by aqueous photoinitiated polymerization-induced self-assembly (photo-PISA) of HPMA at room temperature mediated by a binary mixture of mPEG113-CEPA and CEPA (CEPA = 4-cyano-4-(ethylthiocarbonothioylthio)pentanoic acid). High rates of polymerization are observed in all cases, and quantitative monomer conversions can be achieved within 15 min of 405 nm visible light irradiation. Gel permeation chromatography (GPC) measurement confirms good control is maintained under aqueous photo-PISA conditions at different [mPEG113-CEPA]/[CEPA] ratios. A morphological phase diagram is constructed for the first time by changing the degree of polymerization (DP) of PHPMA and [mPEG113-CEPA]/[CEPA] ratio. The introduction of homopolymer promotes the formation of higher order morphologies and larger spherical micelles. The obtained AB/B assemblies can be used as seeds for preparing ABC/BC assemblies by seeded polymerization of hydrophilic or hydrophobic monomers. This method provides a facile platform for in situ preparation of various AB/B and ABC/BC assemblies in water at room temperature.

Cobalt-Catalyzed Oxidation of the β-O-4 Bond in Lignin and Lignin Model Compounds.

In this work we demonstrate the use of Co(acac)3 in combination with N-hydroxyphthalimide as an oxidant for the selective α-oxidation of the representative β-O-4 linkages in lignin model compounds. The oxidation reaction proceeds under mild conditions at 80 °C using 1,4-dioxane as the solvent and an oxygen atmosphere. The prior α-oxidation in the β-O-4 linkage of the lignin polymer is known to result in an easier cleavage of the adjacent C–O and C–C bonds because of a decrease in bond stability. Finally, the conditions were successfully transferred to kraft- and organosolv-lignin samples as proven by 2D-NMR (HSQC) experiments and gel permeation chromatography measurements.

(Invited) Reducing-Environment-Responsive Gel Capsules Prepared Via Inverse Miniemulsion Periphery RAFT Polymerization from Water-Soluble Emulsifier Stabilizing W/O Emulsions

Nano and micron-sized capsules having an inner water phase, such as liposomes and polymersomes, have been extensively studied as drug carriers because they can load water-soluble protein drugs. However, they have a few disadvantages of low mechanical strength and low loading efficiency of drugs. Therefore, the preparation of stable capsules having an inner water phase is required for constructing carriers for water-soluble protein drugs. In this study, the gel capsules consisting of an amphiphilic capsule membrane and an inner water phase were strategically prepared via inverse miniemulsion periphery reversible addition fragmentation chain transfer (RAFT) polymerization. This paper also describes the release of encapsulated model drugs from the gel capsules in response to a reducing environment. A water-soluble block copolymer emulsifier composed of PMPC block as a hydrophilic component and an amphiphilic poly[oligo(ethylene glycol) methacrylate] (POEGMA) block as a lipophilic component was synthesized via RAFT polymerization. The 1H NMR and gel permeation chromatography measurements revealed that the synthesized PMPC-b-POEGMA had 22 repeating units of PMPC and 171 repeating units of POEGMA with a narrow molecular weight distribution. The water-in-oil (W/O) emulsions were successfully formed by sonication of the water-chloroform mixture containing the resulting PMPC-b-POEGMA, which acted as a stabilizer of water droplets in a chloroform continuous phase because the PMPC and POEGMA blocks were distributed to the water and chloroform phases, respectively. The concentration of the PMPC-b-POEGMA emulsifier affected the droplet size and colloidal stability of the W/O emulsions, which was a similar attribute of conventional surfactants. The optimization of the PMPC-b-POEGMA concentration revealed that the 10 % (w/v) (relative to dispersed phase) of the PMPC-b-POEGMA emulsifier was suitable for the formation of W/O emulsions when chloroform and water were used as a continuous and a dispersed phase, respectively. Next, the amphiphilic poly[poly(ethylene glycol) methacrylate] (PPEGMA) gel layer, which contained bis(2-methacryloyl)oxyethyl disulfide (BMOD) as a reducing-environment-responsive crosslinker, was prepared by inverse miniemulsion periphery RAFT polymerization from the PMPC-b-POEGMA that stabilized the W/O emulsions. The resulting PPEGMA gel capsules were colloidally stable in not only chloroform but also water without additional hydrophilic surface modification because of the amphiphilicity of their gel capsule layer. The PPEGMA gel capsules were taken up by L929 cells with low cytotoxity. Furthermore, the drug-release behavior from the PPEGMA gel capsules in response to dithiothreitol (DTT), which is a reducing agent, was investigated using fluorescein-conjugated dextran (FITC-Dex) as a model drug. The FITC-Dex release rate from the gel capsules in a phosphate buffer (PB) solution (pH 7.4, 20 mM) with DTT was fast compared to that without DTT. When the BMOD-based crosslinks, which contain disulfide bonds, in the PPEGMA gel capsules layer are cleaved in a PB solution with DTT, a decrease in the crosslinking density of the layer induced an increase in the diffusion coefficient of FITC-Dex within the gel capsule layer. Therefore, the FITC-Dex release from the PPEGMA gel capsules was enhanced under a reducing environment. Although the application of PPEGMA gel capsules as smart drug carriers require further research regarding their structural change in response to reducing environments and controlling the drug release rate, the smart functions of the gel capsules can provide useful platforms for constructing a drug carrier that can deliver water-soluble drugs, such as low-molecular-weight drugs, proteins, and DNAs into the cytosol, which has a reducing environment. Figure 1

Macromolecular modifications of poly(etherketoneketone) (PEKK) copolymer at the melting state

Macromolecular modifications of poly(etherketoneketone) (PEKK) copolymer prepared from diphenyl ether (DPE), terephthalic acid (T) and isophthalic acid (I) with a T/I ratio of 60/40 have been investigated above its melting temperature by gel permeation chromatography (GPC), differential scanning calorimetry (DSC) and rheological measurements to assess the evolution of PEKK matrix during composite consolidation step. We mainly focused in this study on anaerobic conditions, i.e. degradation under nitrogen or in lack of oxygen. During exposure, thermal degradation leads to an increase of weight average molar mass Mw and viscosity which is typical to crosslinking/branching mechanism as already observed for PEEK in the literature. However, thanks to GPC measurements, it appears that a chain scission mechanism occurs in the same time related to a constant number average molar mass Mn. Crosslinking kinetics are identified at several temperatures between 320 and 400 °C with rheological measurements from a kinetic scheme governing the crosslinking mechanism. At last, the influence of the crosslinking process on PEKK crystallization is investigated. The final crystallinity and crystallization kinetics decrease with crosslinking due to branching of macromolecular chains.