Surface Morphology and Properties of Poly(γ-benzyl L-glutamate)/Poly(butyl acrylate-co-methyl Methacrylate) Blend Film

Poly(γ-benzyl L-glutamate)/poly(butyl acrylate-co-methyl methacrylate) (PBLG/Poly(BA-co-MMA)) blend films were prepared by casting the polymer blend solution in dichloroethane. Surface morphology of the polymer blend film was investigated by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Thermal and mechanical properties of the polymer blend film were studied using differential scanning calorimeter (DSC) and tensile tests. It was revealed that the introduction of Poly(BA-co-MMA) into PBLG could exert marked effects on the surface morphology and the properties of the PBLG film.     

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.     

Surface Morphology and Properties of Rigid Poly(γ-benzyl L-glutamate) Membrane Modified by Flexible Poly(Vinyl Chloride)

Rigid poly(γ-benzyl L-glutamate)/flexible poly(vinyl chloride) (PBLG/PVC) blend membranes were prepared by casting the polymer blend solution in dichloroethane. Structure and morphologies of the PBLG/PVC blend membranes were investigated by Fourier transform infrared spectroscopy (FT-IR), atomic force microscopy (AFM), and scanning electron microscopy (SEM). Thermal, mechanical, and chemical properties of PBLG/PVC blend membranes were studied by differential scanning calorimetry (DSC), tensile tests, and other physical methods. It was found that the introduction of PVC could exert marked effects on the morphology and the properties of PBLG membrane.     

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.     

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.     

Factors Influencing the Surface Morphology of Poly(γ-benzyl L-glutamate)-Block-(Random Coil Polymer) Aggregates Deposited from the Dilute Solution

Poly(γ-benzyl L-glutamate)-block-poly(ethylene glycol) (PBLG-block-PEG, PEG as random coil polymer) was synthesized by a standard N-carboxyl-γ-benzyl-L-glutamate anhydride method. The surface morphology of PBLG-block-PEG copolymer aggregates from the dilute solution was studied by scanning electron microscopy (SEM). The effects of precipitation temperature, precipitation time, various solvent systems, and copolymer solution concentration on the surface morphologies of the polypeptide block copolymer aggregates from the dilute solution were investigated.     

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.     

Application of Poly(acetic Acid)–Based Graft Copolymer as a Compatibilizer for Poly(L-lactic Acid)/Poly(butylenesuccinate) Blend System

Poly(L-lactic acid) (PLLA) was blended with poly(butylenesuccinate) (PBS) using a single-screw extruder to modify the poor characteristics of these polymers. Furthermore, when both polymers were blended, the graft copolymer that was synthesized by partially saponified poly(vinyl alcohol) (PSPVA) and ?-caprolactone (?-CL) was used as a novel compatibilizer. The structure of the synthesized compatibilizer was determined by ¹H or ¹³C NMR. From this result, the ring-opening polymerization of the ?-CL occurred at the hydroxyl group of PSPVA. The structures of the PLLA/PBS solvent-cast blended films could be observed via an optical microscope. From the optical microscopic observation, the structures of the solvent-cast blended films with the synthesized compatibilizer were more homogeneous than those of the solvent-cast blended films without the compatibilizer. The mechanical properties of the PLLA/PBS extruded blended films were determined by a tensile test. The result showed the tensile strength of the blended films with the synthesized compatibilizer was greater than that of the blended films without the compatibilizer.     

Effects of Poly(ϵ-caprolactone) on Structure and Properties of Poly(lactic acid)/Poly(ϵ-caprolactone) Meltblown Nonwoven

To obtain flexile poly(lactic acid)-based melt-blown nonwoven filtration material, poly(lactic acid)/poly(?-caprolactone) melt-blown nonwoven with various components were melt-spun by melt-blown processing in the Melt-blown Experiment Line. The 3 wt.% tributyl citrate to poly(?-caprolactone) was added in the composites as compatibilizer. The effect of poly(?-caprolactone) on the structure, morphology, mechanical and filtration properties of poly(lactic acid)/poly(?-caprolactone) melt-blown nonwoven was reported. Scanning electron microscopy micrographs revealed good dispersion of the additive in the fiber webs. The crystallinity of melt-blown webs with poly(?-caprolactone) was more than that of poly(lactic acid) alone. The tensile strength, ductility and air permeability of poly(lactic acid) melt-blown nonwovens were enhanced significantly. The input of poly(?-caprolactone) increased the diameter of fibers and decreased the filtration efficiency of poly(lactic acid)/poly(?-caprolactone) melt-blown nonwoven.     

Double stimuli responsive mixed aggregates from poly(acrylic acid)-block-poly(ε-caprolactone)-block-poly(acrylic acid) and poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) triblock copolymers

Well defined ABA triblock copolymer comprising a biodegradable poly(ε-caprolactone) (PCL) middle block and two pH responsive poly(acrylic acid) (PAA) outer blocks was synthesized by atom transfer radical polymerization of tert-butyl acrylate, initiated by PCL-based macroinitiator, followed by selective hydrolysis of the poly(tert-butyl acrylate) blocks. The cooperative self-assembly of the synthesized poly(acrylic acid)-block-poly(ε-caprolactone)-block-poly(acrylic acid) (PAA₂₂PCL₂₆PAA₂₂) copolymer with a temperature-responsive poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (PEO₂₆PPO₄₀PEO₂₆, Pluronic P85) triblock copolymer at different compositions in aqueous media was investigated. Based on experimental data, copolymer properties and composition, formation of nano-sized aggregates comprising a mixed PCL/PPO core and a mixed PEO/PAA corona is suggested. The binary mixture of PAA₂₂PCL₂₆PAA₂₂:PEO₂₆PPO₄₀PEO₂₆ copolymers at molar ratio 3:1 favors the formation of mixed aggregates only, while at higher PEO₂₆PPO₄₀PEO₂₆ content the aggregates coexist with pure PEO₂₆PPO₄₀PEO₂₆ micelles.     

Synthesis and micellization of an amphiphilic biodegradable β-cyclodextrin/poly(γ-benzyl L-glutamate) copolymer

β-Cyclodextrin/poly(γ-benzyl L-glutamate) (β-CD-PBLG) copolymers were synthesized by ring-opening polymerization of N-carboxy-γ-benzyl L-glutamate anhydride (BLG-NCA) in N,N-dimethylformamide(DMF) initiated by mono-6-amino-β-cyclodextrin(H₂N-β-CD). The structures of the copolymers were determined by IR, ¹H NMR and GPC. The fluorescence technique was used to determine the critical micelle concentration (CMC) of copolymer micelle solution. The diameter and the distribution of micelles were characterized by dynamic light scattering(DLS) and its shape was observed by transmission electron microscopy(TEM). The results showed that BLG-NCA could be initiated by H₂N-β-CD to produce copolymer. These copolymers showed an amphiphilic nature and could self-assemble into nano-micelles in water. The CMC of copolymer solution and the size of micelle reduced with the increasing of the proportion of hydrophobic parts. TEM images demonstrated the micelles are all spherical. Such copolymers could be expected to find applications in drug delivery systems and other biomedical domains.     

Morphology and Thermal Properties of Poly[bis(β-phenoxyethoxy)phosphazene]

The structure and thermal properties of poly[bis(-phenoxyethoxy)phosphazene)] (PBPEP) newly synthesized by us were investigated. The crystallization from the melt, the volumetric relaxation in the amorphous phase in the upper vicinity of the glass transition temperature (T _g) and the enthalpy of relaxation of the glass in the lower vicinity of the T _g were shown to be very slow. These slow rates may be related to the low chain mobility due to the bulky side chain. Two kinds of crystal forms, called and forms were found in the melt-crystallized sample. These forms were clearly seen as individual types of spherulites by optical microscopy. The melting temperature of these crystals were analyzed by the Hoffmann–Weeks plot. The so-called T(1) transition that had often been detected in many crystalline polyphosphazenes as the transition from the crystal phase to the mesophase was not observed by x-ray diffraction at elevated temperatures.     

Surface Modification of Nanoporous Poly(ϵ-caprolactone) Membrane with Poly(ethylene glycol) to Prevent Biofouling: Part II. Effects of Graft Density and Chain Length

Biofouling is a common problem in wastewater treatments and medical devices. It is important to find a strategy to prevent biofouling and surface modification. This study presents a novel approach to modifying the surface of nanoporous poly(?-caprolactone) membrane with poly(ethylene glycol) (PEG) to prevent biofouling problems. Oxygen plasma and poly(ethylene glycol)-monoacrylates (PEGMAs) were utilized in the surface modification process. Mouse embryonic fibroblast was used as a model biofoulant. The effects of the density and length of PEG chains on surface properties and cell adhesion were investigated. Contact angle measurements and attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectra illustrated that PEG can be successfully immobilized on the membrane surface. Membranes which were pre-treated with higher PEG concentrations can lead to higher grafting density and greater resistance against cell adhesion. The resistance against cell adhesion cannot be enhanced while the PEG concentration is higher than a certain point, i.e., 0.1 M. For different chain lengths, PEG(400)MA can provide higher resistance to cell adhesion than PEG(200)MA and PEG(1000)MA.     

Surface Modification of Nanoporous Poly(ϵ-caprolactone) Membrane with Poly(ethylene glycol) to Prevent Biofouling: Part I. Effects of Plasma Power and Treatment Time

Biofouling, a result of protein adsorption and cell adhesion on a surface, is detrimental to membrane performance. The objective of this study is to modify the polycaprolactone (PCL) membrane surface with poly(ethylene glycol) (PEG) to prevent fibroblast adhesion. To achieve this goal, oxygen plasma and PEG(400)-monoacrylate were used to graft the PEG onto the membrane surface through covalent bonding. Various plasma treatment conditions were investigated to optimize the PEG-grafting quality and to achieve minimum fibroblast adhesion. After the treatment, the water contact angle decreased significantly. Attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) spectra indicated that PEG was successfully grafted onto the PCL membrane with the appearance of the PEG characteristic peaks. X-ray photoelectron spectroscopy (XPS) revealed that different plasma powers and treatment times changed the surface composition of membranes. To evaluate the applicability of this new strategy for the prevention of biofouling, NIH 3T3 fibroblast was used as a model biofoulant. Cell adhesion and morphology studies indicate that either lower plasma power or shorter treatment time is able to improve resistance to the cell adhesion. This simple and efficient method can be applied to inhibit biofouling on the membrane surface.     

Miscibility of Poly(Ethylene-co-Vinylalcohol)/Poly(δ-Valerolactone) Blend and Tissue Engineering Scaffold Fabrication Using Naphthalene as Porogen

Herein, various poly(ethylene-co-vinylalcohol)/poly(δ-valerolactone) blends were prepared at different ratios by solvent casting for use in tissue engineering. The miscibility of these polymers was studied in detail using differential scanning calorimetry, Fourier-transform infra-red spectroscopy, and X-ray diffraction. The Avrami model have been applied for determining the isothermal crystallization kinetics of poly(ethylene-co-vinyl alcohol), poly(δ-valerolactone) and their blend with equal compositions, in which the Avrami parameters, the maximum crystallization time and the half-time were deducted. Cell adhesion and cell proliferation of the resultant materials were examined by an (3-(4, 5-dimethylthiazolyl-2)-2, 5-diphenyltetrazolium bromide)MTT assay; the blend containing equal amounts of the two polymers showed the best performance. Micropores and their connections were formed by using a new porogen under vacuum at temperatures slightly less than the glass transition temperature. The produced micropores and their interconnections were studied using scanning electron microscopy.     

Cytotoxicity and Compatibility of Polymeric Blend: Evaluation of the Cytotoxicity in Fibroblast Bovine Cells and Compatibility of Poly(ɛ-Caprolactone)/Poly(Methyl Methacrylate-co-Butyl Methacrylate) Blend Films

Blends between poly(?-caprolactone) and poly(methyl methacrylate-co-butyl methacrylate) were prepared by solution blending in the presence of dichloromethane as solvent. The compatibility of the blends was studied by Fourier-transform infrared spectroscopy, Raman spectroscopy, micro-Raman imaging, and thermogravimetric analysis. Cytotoxicity assays were also performed to assess the feasibility of using such materials in veterinary devices. Based on results, we conclude that poly(?-caprolactone) and poly(methyl methacrylate-co-butyl methacrylate)-form compatible blends owing to specific interactions between carbonyl groups of poly(methyl methacrylate-co-butyl methacrylate) and hydrogens present in the polymeric chain of poly(?-caprolactone). Furthermore, these materials were not toxic to bovine fibroblasts, which supports their possible use in cattle veterinary devices.     

Effects of N,N′-Ethylenebis(stearamide) on the Properties of Poly(ethylene terephthalate)/Organo-montmorillonite Nanocomposite

Poly(ethylene terephthalate)/organo-montmorillonite (PET/OMMT) nanocomposites were melt-compounded using twin screw extruder followed by injection molding. N,N′-ethylenebis(stearamide) (EBS) was selected as a dispersing agent to improve the dispersibility and exfoliation of OMMT clay in PET matrix. Morphological properties of the PET/OMMT nanocomposites were examined by using X-ray diffraction analysis, transmission electron microscopy and atomic force microscopy. Thermal properties of the nanocomposites were characterized by using dynamic mechanical thermal analysis. It was found that the OMMT are well dispersed and exfoliated in the presence of EBS. Remarkable enhancement in impact strength and storage modulus of PET/OMMT was achieved by the addition of EBS.     

Enhancement of Poly(Vinyl Alcohol)–Poly(Vinyl Pyrrolidone) Blend Properties using Modified Copper (II) Oxide and Ultrasonic Irradiation

Copper (II) oxide nanoparticles supported within poly(vinyl alcohol)/poly(vinyl pyrrolidone) films have been successfully prepared through ultrasonication method. It is discernible that before the preparation of blends, the surface of copper (II) oxide nanoparticles was modified with citric acid and vitamin C as biosafe capping agents. X-ray diffraction scans illustrated the semicrystalline nature of the obtained pure blend and exhibited a good combination between the blend and the modified copper (II) oxide nanoparticles. Also, thermal stability of blends was improved in comparison to the pure polymer blend with increasing modified copper (II) oxide nanoparticles.     

Preparation and characterization of poly(ethylene glycol)-block-poly[ε-(benzyloxycarbonyl)-l-lysine] thin films for biomedical applications

The nanoscale architectures evident in the thin films of self-assembling hybrid block copolymers—which are tailored to inherit the advantageous properties of their constituent synthetic (homo)polymer and polypeptide blocks—have continued to inspire a variety of new applications in different fields, including biomedicine. The thin films of symmetric hybrid block copolymer, α-methoxy-poly(ethylene glycol)-block-poly[ε-(benzyloxycarbonyl)-l-lysine], MPEG₁₁₂-b-PLL(Z)₁₇, were prepared by solvent casting in five different solvents and characterized using Attenuated Total Reflectance-Fourier Transform Infrared spectroscopy, Thermogravimetric analysis, Derivative Thermogravimetric analysis, Differential Scanning Calorimetry, Contact Angle goniometry, Wide-Angle X-ray Diffraction, and Scanning Electron Microscopy. Film thickness was estimated to be 51 ± 23 μm by the “step-height” method, using a thickness gauge. Although no significant change to the block copolymer’s microstructure was observed, its solvent-cast films displayed divergent physical and thermal properties. The resulting cast films proved more thermally stable than the bulk but indicated greater block miscibility. Additionally, the thin films of MPEG₁₁₂-b-PLL(Z)₁₇ preserved the microphase separation exhibited by the bulk copolymer albeit with appreciable loss of crystallinity. The surface properties of the polymer–air interface were diverse as were the effects of the casting solvents. Oriented equilibrium morphologies are also evident in some of the as-cast thin films.