Kinetics of Phase Separation in Poly(ɛ-caprolactone)/Poly(ethylene glycol) Blends

The poly(ɛ-caprolactone)/poly(ethylene glycol) (PCL/PEG) blends reveal a miscibility window of upper critical solution temperature (UCST) character. The kinetics of liquid–liquid phase separation (LLPS) for the blends of PCL/PEG is investigated by time-resolved small angle light scattering (TRSALS). The time evolution of scattering profile is analyzed by linear Cahn–Hilliard theory for early stage of spinodal decomposition (SD). The evolution of the maximum intensity I_m(t) and the corresponding wavenumber q_m(t) obey the power-law scheme (I_m(t)∼t^β and q_m(t)∼t^−α). A relation of β=3α in late stage is obtained almost the same scaling exponents with β≅1 and α≅1/3 for various quenching depths. The α≅1/3 implied that a coarsening mechanism at the late stage of phase separation may proceed with Ostwald ripening or Brownian coalescence process. Besides, the intermediate and late stages of SD can be scaled into a universal from represented well by Furukawa’s structure factor. The percolation to cluster transition is accompanied with α∼0.13→1/3 from intermediate to late stage of SD for the off-critical mixture of PCL/PEG (4/6) blend. In this study, the experimental result demonstrates that the crystallization is a viable mechanism to lock phase-separated structure of the blends. The competition between phase separation and crystallization has been suggested to determine the final morphology.     

Study on the Crystallization,Miscibility, Morphology,Properties of Poly(lactic acid)/Poly(ε-caprolactone) Blends

A series of blends of poly(lactic acid) (PLA) and poly(ε-caprolactone) (PCL) with different mass ratio were prepared by means of the melt blending method to study their crystallization, miscibility, morphology, and thermal and mechanical properties. The result of DSC tests showed that the melting temperatures of PLA and PCL shifted toward each other, and that the largest shift appeared at the PLA₇₀PCL₃₀ blend. This result reveals that the PLA₇₀PCL₃₀ blend gives the strongest interaction intensity among the blends. Combined the result of dynamic mechanical analysis and SEM morphologies, it was found that PLA and PCL form a partial miscible blend, in which an amount of amorphous PCL (amorphous PLA) is dissolved in the PLA-rich phase (PCL-rich phase), leading to a depression of the T_g. value. The polarized optical micrographs showed that PCL can serve as a nucleating agent to promote PLA crystallization in the PLA/PCL blend. Moreover, the PLA₇₀PCL₃₀ blend gave the largest growth rate of PLA spherulite. Finally, the mechanical property of PLA/PCL blends indicated that PLA can easily be tuned from rigid to ductile by the addition of PCL.     

Interfacial Interaction Analysis of Blends of Poly(vinylidene fluoride) and Poly(ethylene–butylacrylate–glycidyl methacrylate) Compatibilized by Poly(butylene succinate): Morphologies,Rheological Behavior,and Mechanical Properties

Poly(vinylidene fluoride) (PVDF) and poly(ethylene–butylacrylate–glycidyl methacrylate) (PTW) are polymers with weak interfacial adhesion. Blends based on PVDF and PTW (50/50?w/w) with poly(butylene succinate) (PBS) (0, 1, 3, 5, 7?wt%) are obtained by compression molding. The estimation of interfacial interaction among PVDF, PTW, and PBS and the properties of PVDF/PTW blends are investigated. The optimal content of PBS to form a co-continuous morphology in PVDF/PTW blends is proposed, indicating that the beneficial effect of PBS (7?wt%) on interfacial adhesion is observed. Overall, estimating interfacial adhesion is a critical issue for designing PVDF/PTW blend with excellent performance, which has a prospect in coating.     

Performance of Composite Membranes of Poly(ether–block–amide) for Dehydration of Ethylene Glycol and Ethanol

Poly(ether–block–amide) (Pebax 2533) membrane was synthesized on a poly(vinylidene fluoride) (PVDF) ultraporous substrate to study the separation of synthetic ethylene glycol/water and ethanol/water mixtures by pervaporation. The membrane was characterized by FTIR spectroscopy, DSC, SEM, and XRD to assess intermolecular interactions, thermal stability, surface morphology, and crystallinity, respectively. Equilibrium sorption studies were carried out in pure liquids and binary alcohol-water mixtures of different compositions to assess polymer-liquid interactions. Pebax 2533 membrane exhibited the requisite potential for dehydration of the alcohols by showing a selectivity of 1254 and water flux of 0.05 kg m^?2 h^?1 for the ethanol azeotrope, whereas the corresponding selectivity for 95% ethylene glycol feed was 978 with a similar flux. The effect of operating parameters such as feed composition and permeate pressure on membrane performance was evaluated. The membrane exhibited considerable feasibility for scale-up with significant potential for alcohol dehydration.     

Study on the Improvement of Crystallization in HDPE Induced by High–Molecular-Weight Polyethylene Through Dynamic Packing Injection Molding

The effect of high–molecular-weight polyethylene (HMWPE) on crystal morphology was investigated for high-density polyethylene (HDPE) through dynamic packing injection molding (DPIM). With the aid of differential scanning calorimetry (DSC), wide-angle x-ray diffraction (WAXD), and scanning electron microscopy (SEM) measurements, a typical web-like shish kebab morphology, which markedly increases stiffness and toughness, was found in HMWPE-induced samples through DPIM. The SEM results show that the much better web-like shish kebab structure, in which most of the lamellae connect different columns, compared with conventional shish kebab, was formed in HDPE blends with 4% HMWPE content (B4) through DPIM. The WAXD studies indicate that orientation degrees of crystallographic planes (110) and (200) in the B4 samples were much higher than those of samples molded by static packing injection molding and B0 samples molded by DPIM. A combination of the higher degree of crystal orientation and the formation of web-like shish kebab led to simultaneous great increments of stiffness and toughness, which overcomes the traditional limitation that stiffness and toughness cannot be greatly enhanced simultaneously. All these results show that HWMPE favored for great improvement of crystal structures in HDPE when its content is appropriate through DPIM.     

Structure and Performance of Poly(vinyl alcohol)/Poly(γ-benzyl L-glutamate) Blend Membranes

Poly(vinyl alcohol) (PVA)/poly(γ-benzyl L-glutamate) (PBLG) blend membranes with different PBLG wt contents were prepared by pervaporation. Structure and surface morphologies of PVA/PBLG blend membranes were investigated by Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). Thermal, mechanical, and chemical properties of PVA/PBLG blend membrane were studied by differential scanning calorimeter (DSC), tensile strength tests, and other physical methods. It was revealed that the introduction of PBLG homopolymer into PVA could exert an outstanding effect on the properties of PVA membrane.     

Synergistic Effect of Copper Sulfate and Tetramethylthiuram Monosulfide Induced Metal-Coordination Cross-Linking in Nitrile–Butadiene Rubber

The cross-linking microstructure formed by the metal-coordination bonds provides excellent properties for rubber materials. Copper sulfate (CuSO₄) and tetramethylthiuram monosulfide (TMTM) are successfully compounded with nitrile–butadiene rubber (NBR) to fabricate vulcanizates by the coordination cross-linking. The curing characteristics, mobility of macromolecular segment, mechanical properties, morphology analysis, swelling properties, and dynamic features under cyclic compression of the vulcanizates are investigated systematically. The results indicate that the microstructure of 3D cross-linking is held together by the metal-coordination bonds between Cu²⁺ and  CN. The torque during static vulcanization, tensile strength, and cross-linking density of the obtained NBR/CuSO₄/TMTM vulcanizates are better than that of NBR/CuSO₄ vulcanizates, which is attributed to the synergistic effect between the radicals formed by the splitting of TMTM under thermal activation and the Cu²⁺; moreover, the highly reactive [Cu(S_nCNMe₂)]^•2+ complexes are formed by the synergistic effect and promote the coordination stability of NBR and CuSO₄ effectively. The excellent tensile properties of the prepared NBR/CuSO₄/TMTM vulcanizates via synergistic effect made the metal-coordination cross-linking attractive in the field of industrial application.     

Toughening and Compatibilization of Acrylonitrile–Butadiene–Styrene/Poly (Ethylene Terephthalate) Blends Using an Oxazoline-Functionalized Impact Modifier

An oxazoline-functionalized core–shell impact modifier was synthesized between aminoethanol and acrylonitrile/butadiene/styrene high rubber powder. According to the Fourier transform infrared spectroscopy test, the nitrile groups were partially converted into oxazoline groups successfully. The oxazoline-functionalized acrylonitrile/butadiene/styrene high rubber powder was used as an impact modifier for acrylonitrile–butadiene–styrene/poly(ethylene terephthalate) blends. The differential scanning calorimeter and rheological tests demonstrated that poly(ethylene terephthalate) was partially miscible with acrylonitrile–butadiene–styrene, because the oxazoline groups of oxazoline-functionalized acrylonitrile/butadiene/styrene high rubber powder reacted with the end groups of poly(ethylene terephthalate). The results of scanning electron microscopy indicated that the morphology of acrylonitrile–butadiene–styrene/poly(ethylene terephthalate) blends with proper oxazoline-functionalized acrylonitrile/butadiene/styrene high rubber powder content was improved significantly. The best mechanical properties were achieved, When 6 wt% oxazoline-functionalized acrylonitrile/butadiene/styrene high rubber powder was added into acrylonitrile–butadiene–styrene/poly(ethylene terephthalate) blends.     

Development and Assessment of Electrospun Poly(ε-caprolactone)–Poly(vinylalcohol) Blend Nanofibers for Pest Control in Stored Products

l-Carvone is a constituent of essential oil consisting of monoterpene ketone that possesses various medicinal properties. In this context, the present study focuses on the fabrication and assessment of electrospun poly(ε-caprolactone)–poly(vinylalcohol blend nanofibers imbibed with l-Carvone (5%, w/v) that served as a suitable polymeric carrier to preserve the antimicrobial and antioxidant activities of l-Carvone for a longer period of time. The fumigant potential of l-Carvone and C-PP fibers were assessed toward saw-toothed beetle, a major pest found in stored products. The prepared fragrant C-PP fibers displayed a promising potential formulation for the control of stored product pest such as saw-toothed beetle.     

Synthesis and Characterizations of Poly(aniline)–Natural Clay Nanocomposites

Aniline (ANI) was polymerized under inert atmosphere in the presence and absence of natural clay initiated by peroxydisulphate (PDS) in an aqueous acidic medium. While increasing the amount of clay the rate of polymerization (R_p) was decreased and showed first order dependence with respect to amount of clay. The % yield was also decreased while increasing the amount of clay due to the confinement of monomer radical cation by the clay. The FTIR spectrum confirmed the presence of benzenoid and quinoid units in the polyaniline (PANI) structure. DSC inferred the absence of T_m due to cross-linking reaction of PANI because of de-doping process. AFM showed the distorted spherical morphology of uniformly dispersed clay platelets in the PANI. The % weight residue remain above 700°C is increased with the increase of amount of clay, which was confirmed by TGA method. Due to confinement effect the intrinsic viscosity value of PANI—nanocomposites were decreased with the increase of amount of clay in the system. PANI-nanocomposites showed improved d.c. conductivity value than the pristine PANI. Suitable mechanism was proposed to explain the experimental results obtained.     

Preparation of Poly(Vinyl Alcohol) Nanocomposite Films Reinforced with Poly(Amide–Imide)/CuO Having N-trimellitylimido-L-valine Linkages for the Improvement of Mechanical and Thermal Properties

In this investigation, nanocomposite films were fabricated by dispersion of poly(amide–imide)/CuO nanocomposites as nanofiller in the poly(vinyl alcohol) matrix via an ultrasonic process. The nanofiller was prepared and mixed with PVA matrix. After dispersion of nanofiller into the poly(vinyl alcohol), the mechanical properties of the nanocomposites were improved. For example, the addition of 6 wt% nanofiller into the poly(vinyl alcohol) matrix enhanced the tensile modulus by 39%. The residual weight at 800°C was 7% for pure poly(vinyl alcohol) while the nanocomposites illustrated 12–19% residue at this temperature.     

Surface Energy and Thermal Stability Studies of Poly(dimethyl siloxane)–Poly(alkyl(meth)acrylate) Copolymers

The correlation between the surface energy and thermal stability of polymers plays an important role in engineering of plastic materials. In this work, microstructural characteristics of copolymers of poly(dimethyl siloxane) with benzyl methacrylate, ethyl methacrylate, and methyl acrylate are correlated with their surface energy and thermal stability. The poly(dimethyl siloxane) segments in the copolymer chains affected the hydrophobic behavior. The surface energy of the synthesized copolymers decreased by increasing segments of alkyl methacrylates. The thermal stability of copolymers suggesting that heat resistance of poly(dimethyl siloxane) copolymers used in this correlation can be improved by adjusting the units of alkyl methacrylates in copolymers.     

Preparation and Catalytic Activity of Gold–Copper Bimetallic Nanoparticles Stabilized by Poly (N-vinyl-2-pyrrolidone) and Immobilized onto Inorganic Supporters

This paper is devoted to preparation of gold–copper bimetallic nanoparticles deposited on inorganic supporters followed by their use in hydrogen peroxide decomposition and oxidation of ethylbenzene. The bimetallic nanoparticles of Au–Cu at molar ratio of 1:1 were synthesized by hydrothermal method in the presence of stabilizing agent—poly (N-vinyl-2-pyrrolidone) and reducing agent—glycine. The bimetallic nanoparticles were characterized by UV–Vis spectroscopy, DLS, and TEM techniques. The catalytic activity of Au–Cu bimetallic nanoparticles was evaluated with respect to decomposition of hydrogen peroxide and oxidation of ethylbenzene.     

Lipase Catalyzed Synthesis and Thermal Properties of Poly(dimethylsiloxane)–Poly(ethylene glycol) Amphiphilic Block Copolymers

Resin immobilized lipase B from Candida antarctica (CALB) was used to catalyze the condensation polymerization of two difuctional siloxane and poly(ethylene glycol) systems. In the first system, 1,3-bis(3-carboxypropyl)tetramethyldisiloxane was reacted with poly(ethylene glycol) (PEG having a number-average molecular weight, M_n = 400, 1000 and 3400 g mol⁻¹, respectively). In the second system, α,ω-(dihydroxy alkyl) terminated poly(dimethylsiloxane) (HAT-PDMS, M_n = 2500 g mol⁻¹) was reacted with α,ω-(diacid) terminated poly(ethylene glycol) (PEG, M_n = 600 g mol⁻¹). All the reactions were carried out in the bulk (without use of solvent) at 80 °C and under reduced pressure (500 mmHg vacuum gauge). The progress of the polyesterification reactions was monitored by analyzing the samples collected at various time intervals using FTIR and GPC. The thermal properties of the copolymers were characterized by DSC and TGA. In particular, the effect of the chain length of the PEG block on the molar mass build up and on the thermal stability of the copolymers was also studied. The thermal stability of the enzymatically synthesized copolymers was found to increase with increased dimethylsiloxane content in the copolymers.     

Synthesis,Characterization of Fulvic Acid–Poly(Methylmethacrylate) Graft Copolymers Based on Surface-Initiated Atom Transfer Radical Polymerization and its Effect on Performance of Poly(Lactic Acid)

Fulvic acid–poly(methylmethacrylate) graft copolymers were synthesized by surface-initiated atom transfer radical polymerization with fulvic acid. The result demonstrated that the hydrophobicity of fulvic acid–poly(methylmethacrylate) was improved after modification by surface-initiated atom transfer radical polymerization. Furthermore, poly(lactic acid)/fulvic acid–poly(methylmethacrylate) composites were prepared to improve the performances of poly(lactic acid) by blend melting. Compared to poly(lactic acid) with X_c of 5.38%, the X_c of poly(lactic acid)/fulvic acid–poly(methylmethacrylate) composites was 19.94%. Moreover, the impact strength of poly(lactic acid)/fulvic acid–poly(methylmethacrylate) composites was increased by 5.19% compared to poly(lactic acid). In all, this study provided an effective and feasible method for optimizing interface performance and enhancing the thermal stability of poly(lactic acid).     

Slow-Release of Curcumin Induced by Core–Shell Mesoporous Silica Nanoparticles (MSNs) Modified MIL-100(Fe) Composite

As a biocompatible porous material, bio-MOF is a very promising material as a carrier for hydrophobic drugs, including curcumin. However, the stability of bio-MOF against water and humidity still needs to be improved; therefore, surface modifications are required. This study aims to modify the MIL-100(Fe)-based bio-MOF through core–shell architecture by employing mesoporous silica nanoparticles (MSNs or SiO₂) for improving the stability and performance of MIL-100(Fe) to provide a slow-release feature of curcumin. The composites were synthesized via sonochemistry-assisted or mechanochemistry-assisted green protocol to form core–shell structure of MIL-100(Fe)@SiO₂ (Composite-1) or SiO₂@MIL-100(Fe) (Composite-2). Structural, textural, and morphological analyses, including XRD, FTIR, SEM, TEM, and N₂ adsorption–desorption, are discussed in this study to evaluate the composite formation. BET surface area of the MIL-100(Fe) decreased from 1197.45 m²/g to 565.63 and 823.70 m²/g after forming composite-1 and composite-2 with SiO₂. The loading capacity, however, just increased slightly up to 97.89% after the modification. The presence of SiO₂ as shell (composite-1) protects the MIL-100(Fe) from degradation under the acidic condition at pH 5.8 and can maintain the slow-release of curcumin. In contrast, the presence of SiO₂ as core (composite-2) induces the sustained release due to faster degradation of MIL-100(Fe) in acidic condition. Both composites serve as a model for either sustained release or delayed release drug delivery systems.

     

Preparation and Evaluation of Poly(Ethylene Glycol)–Poly(Lactide) Micelles as Nanocarriers for Oral Delivery of Cyclosporine A

A series of monomethoxy poly(ethylene glycol)–poly(lactide) (mPEG–PLA) diblock copolymers were designed according to polymer–drug compatibility and synthesized, and mPEG–PLA micelle was fabricated and used as a nanocarrier for solubilization and oral delivery of Cyclosporine A (CyA). CyA was efficiently encapsulated into the micelles with nanoscaled diameter ranged from 60 to 96 nm with a narrow size distribution. The favorable stabilities of CyA-loaded polymeric micelles were observed in simulated gastric and intestinal fluids. The in vitro drug release investigation demonstrated that drug release was retarded by polymeric micelles. The enhanced intestinal absorption of CyA-loaded polymeric micelles, which was comparable to the commercial formulation of CyA (Sandimmun Neoral®), was found. These suggested that polymeric micelles might be an effective nanocarrier for solubilization of poorly soluble CyA and further improving oral absorption of the drug.     

Aggregation and Adsorption at the Air–Solution Interface of the Cetyltrimethyl Ammonium Tosylate With Two Poly(oxyethylene)–Poly(oxypropylene)–Poly(oxyethylene) Block Copolymers Aqueous Mixtures

The aqueous mixed systems (EO₇₆PO₃₀EO₇₆) (TBCP8400)—cetyltrimethyl ammonium tosylate (CTAT), and (EO₉₇PO₆₉EO₉₇) (TBCP12600)—CTAT were studied to determine both the bulk aggregation and the adsorbed monolayer at the air/water interface. Results were interpreted with the pseudophase separation model plus the regular solution theory for aggregates and monolayers. The behavior is different for TBCP8400–CTAT and TBCP12600–CTAT mixtures, but it is strongly non-ideal in both cases. In bulk, TBCP8400–CTAT mixtures produce aggregates more close to CTAT micelles having TBCP8400 as a solubilizate than the inverse. At low CTAT content, the interaction is repulsive becoming attractive at high TBCP8400 content. The TBCP12600–CTAT aggregates strongly differ from the structure of both pure component micelles, and the interaction is always repulsive. In both cases, the interaction seems not to be cooperative but gradual. CTAT effect on copolymers aggregates seems to be more similar to that of a zwitterionic surfactant than to that of an ionic one. However, CTAT is not included in the aggregates as an ion pair, as revealed by the ionization degree results. It seems that cetyltrimethyl ammonium and tosylate ions have different effects on aggregates which in part are opposite. The adsorbed monolayers also show different behavior. In TBCP8400–CTAT system, the monolayer is mainly a CTAT one with inclusion of TBCP8400 as a monolayer-soluble impurity. However, the inclusion of the non-ionic surfactant alters the structure of the monolayer, which differs from that of the pure CTAT one. The area per adsorbed molecule (A₀) is systematically higher than the ideal and computed ones. The system TBCP12600–CTAT shows a monolayer composition which is almost the same that the overall surfactant mixture composition, and the monolayer structure differs from both the pure-TBCP12600 and the pure-CTAT monolayers ones. The experimental A₀ values are systematically lower than the ideal and the computed ones. Then, in both cases the A₀ values for the pure components do not remain invariable in the mixed monolayer. The phenomenon is interpreted on the basis of the conformation of the copolymers adsorbed at the air/solution interface.     

Synthesis and Characterization of Some Poly(1,2-Phenylenedithiocarbamate)–Metal Complexes

Poly(1,2-phenylenedithiocarbamate) (PPDTC) was prepared by the reaction of 2-aminothiophenol with carbon disulfide followed by condensation through the removal of H₂S gas. PPDTC was used as a ligand to prepare four poly(1,2-phenylenedithiocarbamate)–metal complexes of iron(II), cobalt(II), copper(II), and lead(II), by refluxing with the metal salts. The polymer and its metal complexes were investigated by elemental analyses, UV–visible and IR spectroscopy, inherent viscosity, and magnetic susceptibility. The DC electrical conductivity variation with the temperature in the range 298–498 K of PPDTC and its polymeric copper complex was measured. Both polymer and polymer metal complexes showed an increase in electrical conductivity with an increase in temperature: typical semiconductor behavior. The proposed structure of the complexes is (MLX₂·mH₂O) _n .     

Crystallization and Porosity Evolution of AlOOH–Fe(NO3)3 Gels

Monolithic planar boehmite gels of thickness 0.15 mm seeded by Fe(NO₃)₃ were examined by quantitative DTA, dilatometry, SEM, surface area and pore size distribution and on-line optical transmittance from RT to 1270°C. Dispersed Fe³⁺ ions resulted in 5wt% Fe₂O₃, seeds in monolithic boehmite gels which affected the crystallization of corundum phase and the associated evolution of porosity (the change of inter-colloidal to inter-grain porosity) during heat treatment. Transformation of to -(Al, Fe)₂O₃ took place within individual grains of 100–120 nm size and was similar to unseeded boehmite gels except the a significantly higher frequency of homogeneous nucleation of corundum phase occurred. Gradual elimination of inter-grain pores during sintering was associated with the increase of light transmittance. Ceramics became transparent after sintering at temperatures over 1270°C.