Hyperbranched poly (amine‐ester)‐poly (lactide‐co‐glycolide) copolymer and their nanoparticles as paclitaxel delivery system

A new hyperbranched poly (amine‐ester)‐poly (lactide‐co‐glycolide) copolymer (HPAE‐co‐PLGA) was synthesized by ring‐opening polymerization of D , L ‐lactide (DLLA) glycolid and branched poly (amine‐ester) (HPAE‐OHs) with Sn(Oct)₂ as catalyst. The chemical structures of copolymers were determined by FT‐IR, ¹H‐NMR(¹³C NMR), TGA and their molecular weights were determined by gel permeation chromatography (GPC). Paclitaxel‐loaded copolymer nanoparticles were prepared by the nanoprecipitation method. Their physicochemical characteristics, e.g. morphology and nanoparticles size distribution were then evaluated by means of fluorescence spectroscopy, environmental scanning electron microscopy (ESEM), and dynamic light scattering (DLS). Paclitaxel‐loaded nanoparticles assumed a spherical shape and have unimodal size distribution. It was found that the chemical composition of the nanoparticles was a key factor in controlling nanoparticles size, drug‐loading content, and drug release behavior. As the molar ratio of DL ‐lactide/glycolide to HPAE increased, the nanoparticles size and drug‐loading content increased, and the drug release rate decreased. The antitumor activity of the paclitaxel‐loaded HPAE‐co‐PLGA nanoparticles against human liver cancer H7402 cells was evaluated by 3‐(4, 5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyl tetrazolium bromide (MTT) method. The paclitaxel‐loaded HPAE‐co‐PLGA nanoparticles showed comparable anticancer efficacy with the free drug. Copyright © 2010 John Wiley & Sons, Ltd.     

Structure and pH‐sensitive properties of poly (vinylidene fluoride) membrane changed by blending poly (acrylic acid) microgels

pH‐sensitive poly (vinylidene fluoride) (PVDF)/poly (acrylic acid) (PAA) microgels membranes are prepared by phase inversion of the N, N‐dimethylformamide solution containing PAA microgels and PVDF in aqueous solution. The composition and structure of the blend membrane are investigated by Fourier transform infrared spectra, X‐ray photoelectron spectroscopy measurements, thermo gravimetric analysis, field‐emission scanning electron microscope and atomic force microscope. The results indicate the surface and cross section of the blend membranes have a porous structure with PAA microgels immobilized inside the pore and on the membrane surface. The blend PVDF membranes exhibit pH‐sensitive water flux, with the most drastic change in permeability observed between pH 3.7 and 6.3. The blend membranes are fouled by bovine serum albumin, and their antifouling property is enhanced by increasing PAA microgels, mainly derived from the improved hydrophilic property. Copyright © 2013 John Wiley & Sons, Ltd.     

聚偏氟乙烯微孔膜的亲水化改性及功能化研究进展

聚偏氟乙烯(PVDF)微孔膜的亲水化改性方法有物理共混、化学共聚、表面涂覆、表面化学处理、表面接枝等几种。其中物理共混和表面涂覆法比较成熟且已获得应用，而PVDF微孔膜的表面化学处理、等离子体或光引发改性技术以及环境敏感性等将成为PVDF微孔膜的改性和功能化研究的主要方向。     

Novel Cross‐Linked Films Prepared from Hyperbranched Poly(amine‐ester)

Summary: Novel hyperbranched poly(amine‐ester) (HPAE) cross‐linked films were prepared by cross‐linking the terminal hydroxyl groups of HPAE using glutaraldehyde (GA). Atom force microscope and scanning electron microscope revealed their smooth surfaces, dense and homogenous matrices. Property characterizations indicated that these cross‐linked films had good hydrophilicity, relative low protein adsorption, and high tensile strength. Also, their swelling behavior varied with the solvent.

Structure of the hyperbranched poly(amine‐ester).     

Fine structure of poly(vinylidene fluoride) membranes prepared by phase inversion from a water/N‐methyl‐2‐pyrollidone/poly(vinylidene fluoride) system

Poly(vinylidene fluoride) (PVDF) membranes were prepared by the isothermal immersion and precipitation of PVDF/N‐methyl‐2‐pyrollidone dope solutions in either harsh or soft nonsolvent baths. Low‐voltage field emission scanning electron microscopy imaging of the formed membranes at high magnifications (e.g., 300,000×) revealed their nanoscale fine structures, particularly dendrites observed on the surfaces of the macrovoids, cellular pores, and the membrane skin, which have never been successfully presented in the literature. Evidence of crystallization was also demonstrated by X‐ray diffraction and differential scanning calorimetry measurements. The phase diagram at 25 °C, including a binodal, tie lines, and a crystallization‐induced gelation line, was determined both experimentally and theoretically. These results were further used in mass‐transfer calculations to obtain diffusion trajectories and concentration profiles for the membrane region, which were useful for elucidating the relationship between the membrane preparation conditions and the obtained membrane morphologies. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 830–842, 2004     

Fine structure and formation mechanism of particulate phase‐inversion poly(vinylidene fluoride) membranes

The structure and formation mechanism of a microporous phase‐inversion poly(vinylidene fluoride) (PVDF) membrane exhibiting a relatively loosely packed agglomerate of semicrystalline globules are explored. The membrane has been prepared by the coagulation of a solution of PVDF in dimethylformamide by the action of 1‐octanol, which is a soft nonsolvent. Experimental observations pertain to the globule surface, which is dominated by a grainy nanostructure; the globular interior, which exhibits a range of fine structures (e.g., twisted sheets and treelike branches); and the globule–globule connections, which exhibit a sheetlike or ropelike structure. On the basis of the observed structural details and phase diagram considerations, it is proposed that the membrane structure is the result of a unique combination of a polymer crystallization and a liquid–liquid phase‐separation process, with end‐result globular structural features of remarkable uniformity. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1578–1588, 2003     

Synthesis of poly(vinylidene fluoride)‐b‐poly(styrene sulfonate) block copolymers by controlled radical polymerizations

Block copolymers based on poly(vinylidene fluoride), PVDF, and a series of poly(aromatic sulfonate) sequences were synthesized from controlled radical polymerizations (CRPs). According to the aromatic monomers, appropriate techniques of CRP were chosen: either iodine transfer polymerization (ITP) or atom transfer radical polymerization (ATRP) from PVDF‐I macromolecular chain transfer agents (CTAs) or PVDF‐CCl₃ macroinitiator, respectively. These precursors were produced either by ITP of VDF with C₆F₁₃I or by radical telomerization of VDF with chloroform, respectively. Poly(vinylidene fluoride)‐b‐poly(sodium styrene sulfonate), PVDF‐b‐PSSS, block copolymers were produced from both techniques via a direct polymerization of sodium styrene sulfonate (SSS) monomer or an indirect way with the use of styrene sulfonate ethyl ester (SSE) as a protected monomer. Although the reaction led to block copolymers, the kinetics of ITP of SSS showed that PVDF‐I macromolecular CTAs were not totally efficient because a limitation of the CTA consumption (56%) was observed. This was probably explained by both the low activity of the CTA (that contained inefficient PVDF‐CF₂CH₂? I) and a fast propagation rate of the monomer. That behavior was also noted in the ITP of SSE. On the other hand, ATRP of SSS initiated by PVDF‐CCl₃ was more controlled up to 50% of conversion leading to PVDF‐b‐PSSS block copolymer with an average number molar mass of 6000 g·mol^?1. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Multistimuli‐responsive hyperbranched poly(ether amine)s

Multistimuli‐responsive hyperbranched poly(ether amine)s (hPEAs) were successfully synthesized through nucleophilic addition/ring‐opening reaction of commercial diglycidyl ether and amine via one‐pot synthesis. In aqueous solution, these hPEAs exhibited very sharp response to temperature, pH, and ionic strength, with well‐tunable cloud point (CP). Through changing the poly(ethylene oxide) (PEO) chain content of hPEAs, pH, and ionic strength, the CP could be adjustable from 35 to 100 °C, and increased with the increasing of PEO content, the decreasing of pH and ionic strength. The CP of hPEAs aqueous solution presents a linear relationship to the PEO content in pH range from 6.6 to 8.0. Dynamic light scattering (DLS) investigation indicated that these hPEAs dispersed in aqueous solution to form the stable nanomicelles, whose aggregation can be controlled by temperature, pH, and ionic strength. Moreover, the obtained hPEAs contain reactive amino groups in periphery and hydroxyl groups inside, which can be further functionalized. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4252–4261, 2010     

Comparative studies on miscibility and phase behavior of linear and star poly(2‐methyl‐2‐oxazoline) blends with poly(vinylidene fluoride)

The comparative studies on the miscibility and phase behavior between the blends of linear and star‐shaped poly(2‐methyl‐2‐oxazoline) with poly(vinylidene fluoride) (PVDF) were carried out in this work. The linear poly(2‐methyl‐2‐oxazoline) was synthesized by the ring opening polymerization of 2‐methyl‐2‐oxazoline in the presence of methyl p‐toluenesulfonate (MeOTs) whereas the star‐shaped poly(2‐methyl‐2‐oxazoline) was synthesized with octa(3‐iodopropyl) polyhedral oligomeric silsesquioxane [(IC₃H₆)₈Si₈O₁₂, OipPOSS] as an octafunctional initiator. The polymers with different topological structures were characterized by means of Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy. It is found that the star‐shaped poly(2‐methyl‐2‐oxazoline) was miscible with poly(vinylidene fluoride) (PVDF), which was evidenced by single glass‐transition temperature behavior and the equilibrium melting‐point depression. Nonetheless, the blends of linear poly(2‐methyl‐2‐oxazoline) with PVDF were phase‐separated. The difference in miscibility was ascribed to the topological effect of PMOx macromolecules on the miscibility. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 942–952, 2006     

Thermoreversible gelation of blend of poly(vinylidene fluoride) and poly(vinylidene fluoride-trifluoroethylene) in γ-butyrolactone solution

Thermoreversible gelation behavior of blend of poly(vinylidene fluoride) and poly(vinylidene fluoride-trifluoroethylene) in γ-butyrolactone solution was studied. Sol-gel transition temperature increased with the increase of polymer concentration, but was independent of the blend ratio of two polymers. An equation for gelation rate was derived, assuming that the gelation is a first-order reaction and that the gelation rate obeys an Arrhenius type. According to the equation, the growth index of gelation and supercooling temperature had a dominant effect on gelation rate. The growth index of gelation, which was calculated from the dependence of activation energy on the supercooling temperature in the isothermal gelation, varied with the blend ratio of two polymers. Growth index of gelation larger than 2 was obtained for the blend gels studied in this experiment. It may suggest that the multidimensional growth of gels occurs in such polymer blend solutions. X-ray diffraction and differential scanning calorimetry measurements showed existence of separate crystals due to each component of polymer in the blend gels. © 1996 John Wiley & Sons, Inc.     

Quantitative confirmation of the crystal-amorphous interphase in semicrystalline poly(vinylidene fluoride) and poly (vinylidene fluoride)/poly (ethyl methacrylate) blends

Dielectric and thermal characterizations were performed for poly (vinylidene fluoride) (PVDF)/poly (ethyl methacrylate) (PEMA) blends of different composition. The characteristics of PVDF β relaxation were shown to be little affected in the semicrystalline blends with PEMA. The relaxation strength, however, depends strongly on the PEMA content and a linear relation was found between the intensity of the β relaxation and the weight fraction of the PVDF crystal-amorphous interphase. Phase structures of the PVDF/PEMA blends are also proposed. © 1994 John Wiley & Sons, Inc.     

PVDF membrane formation by diffusion‐induced phase separation‐morphology prediction based on phase behavior and mass transfer modeling

The equilibrium phase behavior of water (nonsolvent)‐DMF (solvent)‐PVDF system at 25°C was investigated via both theoretical and experimental approaches. Using binary interaction parameters, χ_ij, obtained previously, the theoretical phase boundaries were computed and were found to match closely the measured binodal and crystallization‐induced gelation data. Membranes were prepared using the isothermal immersion‐precipitation processes in various dope and bath conditions. The formed membranes demonstrated a broad spectrum of morphologies: At one extreme, asymmetric structure was obtained featuring a continuous tight skin and a sublayer composed of parallel macrovoids and cellular pores; at the other limit, skinless microporous membrane was produced with spherical particles packed into a bi‐continuous structure. The crystalline characters of PVDF gels and membranes were examined by small angle light scattering, scanning electron microscopy, and differential scanning calorimetry techniques. In addition, diffusion trajectories and concentration profiles in the membrane solution before precipitation were calculated for the immersion process. These results predicted reasonably the various morphologies observed in the membranes. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2079–2092, 1999     

Thin poly(ionic liquid) and poly(vinylidene fluoride) blend films with ferro‐ and piezo‐electric polar γ‐crystals

Ferro‐ and piezo‐electric poly(vinylidene fluoride) (PVDF) thin film is reported to be obtained by using a poly(ionic liquid) (PIL) [poly(2‐(dimethylamino)ethyl methacrylate) methyl chloride quaternary salt] through solution route. The short range interactions between localized cationic ions of PIL and polar >CF₂ of PVDF are responsible for modified polar γ‐PVDF (T₃GT₃Ḡ) formation. Modification in chain conformation of PVDF is confirmed by FTIR, XRD, and DSC studies suggesting the miscible PVDF–PIL (PPIL) blend. Up to 40 wt % loading of PIL in PVDF matrix enhances relative intensity of γ‐phase up to 50% in the entire crystalline phase. The P‐E hysteresis loop of PVDF‐PIL blends at 25 wt % PIL loading (PPIL‐25) thin film at sweep voltage of ±50 V shows excellent ferroelectric property with nearly saturated high remnant polarization ∼6.0 µC cm⁻² owing to large proportion of γ‐PVDF. However, non‐polar pure PVDF thin film shows unsaturated hysteresis loop with 1.4 µC cm⁻² remnant polarization. The operation voltage decreases effectively because of the polar γ‐phase formation in PPIL blended film. High‐sensitivity piezo‐response force microscopy shows electromechanical switching property at low voltages in PPIL‐25 thin films through local switching measurements, making them potentially suitable as ferroelectric tunnel barriers. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 795–802     

Enhanced electrical properties of highly oriented poly(vinylidene fluoride) films prepared by solid‐state coextrusion

Oriented poly(vinylidene fluoride) (PVDF) films with β‐form crystals have been commonly prepared by cold drawing of a melt‐quenched film consisting of α‐form crystals. In this study, we have successfully produced highly oriented PVDF thin films (20 µm thick) with β‐crystals and a high crystallinity (55–76%), by solid‐state coextrusion of a gel film to eight times the original length at an established optimum extrusion temperature of 160°C, some 10°C below the melting temperature. The resultant drawn films had a highly oriented (orientation function f_c = 0.993) fibrous structure, showing high mechanical properties of an extensional elastic modulus of 8.3 GPa and tensile strength of 0.84 GPa, along the draw direction. Such highly oriented and crystalline films exhibited excellent ferroelectric and piezoelectric properties. The square hysteresis loop was significantly sharper than that of a conventional sample. The sharp switching transient yielded the remnant polarization P_r of 90 mC/m², and the electromechanical coupling factor k_t was 0.24 at room temperature. These values are about 1.5 times greater than those of a conventional β‐PVDF film. Thus, solid‐state coextrusion near the melting point was found to be a useful technique for the preparation of highly oriented and highly crystalline β‐PVDF films with superior mechanical and electrical properties. The morphology of the extrudate relevant to such properties is discussed. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2549–2556, 1999     

Low contents of graphite improving general properties of poly(vinylidene fluoride)

Studies on graphite flakes with a lateral size greater than 50 μm, having a large number of stacked collapse blocks, are neglected and replaced by graphene nanosheets or by powdered graphite, which can be obtained from graphite through chemical or physical exfoliation, as filler in polymer composites. Besides, the production of graphene nanosheets or the purification of powdered graphite uses a high concentration of strong and toxic acids that pollutes the environment. These processes are extremely time-consuming and generate an expensive product. Composites of poly(vinylidene fluoride) (PVDF) were prepared via extrusion with graphite flakes with up to 60 μm thick and 700 μm lateral size, in the range from 0.1 to 5% m/m. The quality of graphite flakes was analyzed by thermogravimetric analysis, x-ray diffraction (XRD), Raman spectroscopy, Fourier-transform infrared spectroscopy, and scanning electron microscopy. The increase in the graphite content in the PVDF matrix improved thermal resistance while showed an increase in the degree of crystallinity up to 25% by XRD and 43% by differential scanning calorimetry, approximately. Although the graphite acted as a nucleating agent, the content of the PVDF beta phase did not change. In the composites with up to 2.0% of graphite, a significant increase in mechanical properties, 13% modulus, and 36% in the storage modulus, evaluated by thermodynamic-mechanical analysis and tensile tests. In the analyses of time-domain nuclear magnetic resonance and oscillatory rheology in parallel plates, it was noticed that the increase of mechanical properties is due to the reinforcing effect along with the lubricant protection of stacked graphene sheets, attenuating the stress and friction between the polymer chains. Therefore, even though graphite flakes are inexpensive, that filler without any treatment at low contents are capable of significantly improving the performance of PVDF. This work suggests that these composites could be employed in applications such as electrical insulator with less energy dissipation, and also in oil pipelines, specifically to replace PVDF-based terpolymers or mixtures thereof, and polyamide-11 in flexible risers as a barrier layer, improving their performance.     

The morphology of poly(vinylidene fluoride) crystallized from blends of poly(vinylidene fluoride) and poly(ethyl acrylate)

A combined optical and electron microscopical study has been carried out of the crystallization habits of poly(vinylidene fluoride) (PVF₂) when it is crystallized from blends with noncrystallizable poly(ethyl acrylate) (PEA). The PVF₂/PEA weight ratios were 0.5/99.5,5/95, and 15/85. Isothermal crystallization upon cooling the blends from the single-phase liquid region was carried out in the range 135–155°C, in which the polymer crystallizes in the α-orthorhombic unit cell form. The 0.5/99.5 blend yielded multilayered and planar lamellar crystals. The lamellae formed at low undercoolings were lozenge shaped and bounded laterally by {110} faces. This habit is prototypical of the dendritic lateral habits exhibited by the crystals grown from the same blend at high undercoolings as well as by the constituent lamellae in the incipient spherulitic aggregates and banded spherulites that formed from the 5/95 and the 15/85 blends, respectively. In contrast with the planar crystals grown from the 0.5/99.5 blend, the formation of the aggregates grown from the 5/95 blend is governed by a conformationally complex motif of dendritic lamellar growth and proliferation. The development of these aggregates is characterized by the twisting of the orientation of lamellae about their preferential b-axis direction of growth, coupled with a fan-like splaying or spreading of lamellae about that axis. The radial growth in the banded spherulites formed from the 15/85 blend is governed by a radially periodic repetition of a similar lamellar twisting/fan-like spreading growth motif whose recurrence corresponds to the extinction band spacing. This motif differs in its fan-like splaying component from banding due to just a helicoidal twisting of lamellae about the radial direction. © 1993 John Wiley & Sons, Inc.     

Thermal and mechanical behavior of amorphous and semi-crystalline poly(vinylidene fluoride)/poly(methyl methacrylate) blends

Various PVDF/PMMA (poly(vinylidene fluoride)/poly(methyl methacrylate)) blends were selected for mechanical testing in compression. At low PVDF content (less than 50/50 w/w), the blends remain amorphous and PVDF and PMMA are fully miscible. In PVDF-richer blends, PVDF crystallizes in part, leading to a PMMA-enriched homogeneous amorphous phase. In this study, the degree of crystallinity was set at equilibrium by appropriate annealing of the samples before testing. Mechanical analysis was focused on the low deformation range, and especially on the yield region. Depending on the test temperature and blend composition, three types of response were identified, depending on whether plastic deformation is influenced: 1) by the PMMA secondary relaxation motions, 2) by the PVDF/PMMA glass transition motions, or 3) by the crystallite-constrained PVDF chains.     

Composition distributions within poly(vinylidene fluoride) spherulites as grown in blends with poly(methyl methacrylate)

Upon crystalline solidification of one component in a homogeneously molten polymer blend, composition profiles develop outside (i.e., in the rest melt) and behind (i.e., within the spherulites) the crystal growth front. The present article is devoted to the detailed verification and the interpretation of these distributions and their temporal development inside growing spherulites. To this end, the energy dispersive X‐ray emission (EDX) of suitable elements has been recorded locally resolved in a scanning electron microscope and evaluated correspondingly. The investigations were performed at the melt homogeneous blend of poly(vinylidene fluoride) (PVDF) as crystallizing and poly(methyl methacrylate) (PMMA) as steadily amorphous component. If the spherulites are not volume filling, the mean PMMA content 〈?_PMMA〉 inside the PVDF spherulites is for all blends about 0.2 below the starting composition. ?_PMMA increases however slightly from the center of a spherulite to its border. That increase reflects the PMMA concentration in front of the spherulite surface, which increases likewise with time, and is clearly above the initial composition. There is at the spherulite surface, consequently, a remarkable jump in composition from the spherulite internal to its amorphous surroundings. It may amount up to 0.5. With volume filling spherulites, a slight variation of the composition from the center of a spherulite to its border is observed, too. This proves that also at these conditions composition profiles develop in the spherulite's surroundings. They remain however so weak that they do not inhibit crystallization even in its later stages. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 338–346, 2006     

Crystallization and morphology of poly(vinylidene fluoride)/poly(3‐hydroxybutyrate) blends. I. Spherulitic morphology and growth by polarized microscopy

The development of the poly(3‐hydroxybutyrate) (PHB) morphology in the presence of already existent poly(vinylidene fluoride) (PVDF) spherulites was studied by two‐stage solidification with two separate crystallization temperatures. PVDF formed irregular dendrites at lower temperatures and regular, banded spherulites at elevated temperatures. The transition temperature of the spherulitic morphology from dendrites to regular, banded spherulites increased with increasing PVDF content. A remarkable amount of PHB was included in the PVDF dendrites, whereas PHB was rejected into the remaining melt from the banded spherulites. When PVDF crystallized as banded spherulites, PHB could consequently crystallize only around them, if at all. In contrast, PHB crystallized with a common growth front, starting from a defined site in the interfibrillar regions of volume‐filling PVDF dendrites. It formed by itself dendritic spherulites that included a large number of PVDF spherulites. For blends with a PHB content of more than 80 wt %, for which the PVDF dendrites were not volume‐filling, PHB first formed regular spherulites. Their growth started from outside the PVDF dendrites but could later interpenetrate them, and this made their own morphology dendritic. These PHB spherulites melted stepwise because the lamellae inside the PVDF dendrites melted at a lower temperature than those from outside. This reflected the regularity of the two fractions of the lamellae because that of those inside the dendrites of PVDF was controlled by the intraspherulitic order of PVDF, whereas that from outside was only controlled by the temperature and the melt composition. The described morphologies developed without mutual nucleating efficiency of the components. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 873–882, 2003     

聚醚砜和溶剂对聚偏氟乙烯膜结晶性能的影响

研究了非相容性聚合物及不同溶剂对聚偏氟乙烯相转化膜结晶性能的影响。采用红外光谱和DSC方法测定了膜的晶型及结晶度。结果显示,与非相容性材料以适当的比例共混和采用溶度参数较低的溶剂可以降低膜β晶型的含量。