Thermal characterization of polycarbonate/polycaprolactone blends

In this work, we prepared blends of bisphenol A polycarbonate (PC) and poly(ϵ‐caprolactone) (PCL) in a wide composition range by melt mixing and solution mixing. Two different molecular weights of PCL were used (nominally, 10.000 g/mol, PCL10, and 80.000 g/mol, PCL80). The thermal behavior of both systems was studied via differential scanning calorimetry under dynamic and isothermal conditions. The blends were miscible in the entire composition range in the liquid and amorphous states, as indicated by the single glass‐transition temperature (T_g) exhibited by both the PC/PCL10 and PC/PCL80 blends. The compositional variation of the T_g was accurately described by the Fox equation for the PC/PCL80 blends, whereas slight deviations from this equation were exhibited by the PC/PCL10 blends. For blend compositions containing 40% or more PCL, either one or both blend components crystallized. Crystallization occurred during cooling from the melt or during subsequent heating in the form of cold crystallization. Although PCL crystallization was reduced and its crystallization rate decreased with the addition of PC, PCL was a very effective macromolecular plasticizer for PC, to the extent that crystallization during the scan was detected for some blend compositions. Isothermal crystallization experiments allowed the determination of equilibrium melting points (T) by the Hoffman–Weeks extrapolation method. A T depression was found for both PCL and PC components as the content of the other blend component was increased. The Avrami equation was closely obeyed by both blend components during the isothermal overall crystallization kinetics up to crystalline conversion degrees of 60–70% and with values of Avrami indices ranging from 3 to 4, depending on the crystallization temperature employed. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 771–785, 2001     

Poly-Schiff bases. III. Synthesis and characterization of polyesterazomethines

Ten new polyesterazomethines have been synthesized by solution polycondensation of five different diamines with 4,4′-[terephthaloyloxy]bis-3-ethoxybenzaldehyde and 4,4′-[isophthaloyloxy]bis-3-ethoxybenzaldehyde using dimethylacetamide in the presence of anhydrous LiCL. Fibrous polymers were precipitated by pouring the solutions into water. The polymerization proceeds rapidly to give highly viscous solutions. The resulting polymers were characterized by viscosity measurement, IR, x-ray diffraction study, elemental analysis, and DSC study. ¹H-NMR spectra of some of the polymers were also recorded. The thermal stability of the polymers was evaluated by TGA and IGA study. Electronic spectra of the polymers were recorded in H₂SO₄. © 1996 John Wiley & Sons, Inc.     

Preparation and characterization of novel bone scaffolds based on electrospun polycaprolactone fibers filled with nanoparticles

Novel bone-scaffolding materials were successfully fabricated by electrospinning from polycaprolactone (PCL) solutions containing nanoparticles of calcium carbonate (CaCO(3)) or hydroxyapatite (HA). The diameters of the as-spun fibers were found to increase with the addition and increasing amounts of the nanoparticles. The observed increase in the diameters of the as-spun fibers with the addition and increasing amounts of the nanoparticulate fillers was responsible for the observed increase in the tensile strength of the obtained fiber mats. An increase in the concentration of the base PCL solution caused the average diameter of the as-spun PCL/HA composite fibers to increase. Increasing applied electrical potential also resulted in an increase in the diameters of the obtained PCL/HA composite fibers. Lastly, indirect cytotoxicity evaluation of the electrospun mats of PCL, PCL/CaCO(3), and PCL/HA fibers based on human osteoblasts (SaOS2) and mouse fibroblasts (L929) revealed that these as-spun mats posed no threat to the cells, a result that implied their potential for utilization as bone-scaffolding materials.     

Synthesis, characterization and crystal structures of the tetrachlorocuprate and tetrabromocadmate salts of the antimalarial mefloquine

Two new compounds, bis (DL-erythro-α-2-piperydylium-2,8-bis(trifluoromethyl)-4-quinolinemethanol) tetrachlorocuprate(II) tetrahydrate [LH⁺]₂[CuCl₄]^2??4H₂O 1 [L = mefloquine] and bis(DL-erythro-α-2-piperydylium-2,8-bis(trifluoromethyl)-4-quinolinemethanol) tetrabromocadmate (II) bis(methanol) [LH⁺]₂[CdBr₄]^2?·2CH₃OH 2, have been synthesized and characterized by elemental analysis, ¹H-NMR and IR spectroscopy. Single-crystal X-ray diffraction analysis of 1 showed the structure to be ionic with formula unit comprising two protonated monocationic mefloquine molecules of opposite chirality, a tetrachlorocuprate (II) anion and a complement of four water molecules, disordered over several sites. The crystals are orthorhombic, space group Pnma, a = 9.6975(1) Å, b = 29.5385(3) Å, c = 15.9423(1) Å, V = 4566.67(7) ų, Z = 4. The formula unit of compound 2 comprises two protonated monocationic mefloquine molecules, a tetrabromocadmate(II) anion and two molecules of methanol. The crystals are orthorhombic, space group Fdd2, a = 17.2185(5) Å, b = 55.456(2) Å, c = 9.5140(3) Å, V = 9084.6(5) ų, Z = 8. The mefloquine molecule is protonated at the piperidinyl N atom and extensive hydrogen bonding occurs in both crystal structures. The conformation of the mefloquine cation in 1 and 2 is very similar to that recently observed in other salts of the drug, confirming its relevance in the context of antimalarial action.     

Synthesis and characterization of conductive polypyrrole grown on the sulfonated surface of polyethylene films

Chemical synthesis of polypyrrole (PPy) was carried out in the presence of FeCl₃ aqueous solution. The grown PPy is fixed on the sulfonated surface of polyethylene (SPE) films, where the sulfonic groups act as counteranions to balance the positive charge of PPy, giving the composite material of PPy–SPE. For reasons of comparison, two types of polyethylene (PE) have been used, low and high densities with different degrees of sulfonation, SD (g/m²), defined as the ratio of weight increase to the area of the two surfaces of the sample. A series of reaction times was used to evaluate the variation of the electrical conductivity, σ (S/cm), of polypyrrole. It was found that σ increases as reaction time increases. To characterize the samples, Fourier transform infrared (FTIR) spectroscopy and conductivity measurements were performed.     

Lignin,a biomass crosslinker,in a shape memory polycaprolactone network

This work reports a new direction of natural lignin valorization, which utilizes lignin to produce crosslinked polycaprolactone (PCL) via a straightforward synthesis. Lignin's hydroxyl groups of its multibranched phenolic structure allow lignin to serve as crosslinkers, whereas the aromatic groups serve as hard segments. The modified natural lignin containing alkene terminals is crosslinked with a thiol‐terminal PCL via Ru‐catalyzed photoredox thiol‐ene reaction. The high rate of gel contents measured for all crosslinked polymers, with the least being 84% of gel content, indicates efficient crosslinking. The prepared flat rectangular shape lignin‐crosslinked PCL sample demonstrates rapid thermal responsive shape memory behavior at 10 °C and 80 °C showing interconversion between a permanent and temporary shape. The melting temperature of the lignin‐crosslinked PCL is tunable by varying the percent weight of lignin. The 11, 21, and 30 wt % lignin demonstrated T_m of 42 °C, 35 °C, and 26 °C, respectively. The role of lignin as a crosslinker presented in this work suggests that lignin can serve as an efficient biomass‐based functional additive to polymers. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 2121–2130     

Nanocomposites by melt intercalation based on polycaprolactone and organoclay

Nanocomposites based on biodegradable polycaprolactone (PCL) and organically modified layered silicates (organoclay) were prepared by melt mixing. Their structures and properties were characterized by wide‐angle X‐ray diffraction, thermal analysis, and rheological measurements. The exfoliation of the organoclay was achieved via a melt mixing process in an internal mixer and showed a dependence on the type of organic modifier, the organoclay contents, and the processing temperature. The addition of the organoclay to PCL increased the crystallization temperature of PCL, but a high content of the organoclay could show an inverse effect. The PCL/organoclay nanocomposites showed a significant enhancement in their mechanical properties and thermal stability due to the exfoliation of the organoclay. The nanocomposites showed a much higher complex viscosity than the neat PCL and significant shear‐thinning behavior in the low frequency range. The shear storage modulus and loss modulus of the nanocomposites also exhibited less frequency dependence than the pure PCL in the low frequency range, and this was caused by the strong interactions between the organoclay layers and PCL molecules and by the good dispersion of exfoliated organoclay platelets in the PCL. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 670–678, 2003     

Synthesis and characterization of polycaprolactone (B)–poly(lactide‐co‐glycolide) (A) ABA block copolymer

Novel poly(lactide‐co‐glycolide) (PLGA)/polycaprolactone (PCL) ABA block copolymers were synthesized by bulk copolymerization of glycolide and lactide with PCL diols prepolymer using stannous octoate as catalyst. The resulting copolymers were characterized by various analytical techniques including gel permeation chromatography, IR, ¹H nuclear magnetic resonance, differential scanning calorimeter and X‐ray diffractometry. Mechanical properties and hydrophilicity of the copolymers were also studied. Data showed that the copolymers presented a part‐regular structure, containing both PCL crystalline and amorphous PLGA domains. The properties of these copolymers can be adjusted by changing the compositions of the copolymers. Copyright © 2000 John Wiley & Sons, Ltd.     

Synthesis and characterization of polyfunctional crosslinking agents for cyanate resins

An efficient crosslinking monomer for a mixed cyanate/epoxy resin system, bisphenol-A-monocyanate monoglycidyl ether 3 , has been synthesized and characterized. The intermediate compound, the monoglycidyl ether of bisphenol-A 2 , was also isolated and purified by extraction and chromatographic separation using a silica gel column. The cyanate functional group in the crosslinking monomer 3 can be cured easily by heat to form a triazine structure 8 , but the epoxy functional group in the crosslinking monomer 3 can not be cured without affecting the cyanate group because the latter is more reactive both under heat and basic conditions. A practical approach for the application of the crosslinking monomer 3 is discussed and tested. Most interestingly, under heat curing, a very tough and strong resin material was produced from this crosslinking mixed resin mixture. By using a secondary amine, diethylamine, as a curing agent, the cyanate groups in the crosslinking monomer 3 react to form the structures 11 or 12 , depending on the molar ratio of monomer 3 to diethylamine. A bifunctional crosslinking agent for a mixed cyanate (thermoset) and polyolefin (thermoplastic) resin system, 2-allylphenyl cyanate 16 , has also been synthesized and characterized. Like 3 , 2-allylphenyl cyanate 16 easily forms the crosslinking triazine compound 17 upon heating. 17 is a crystalline solid with mp = 110–111°C. As a crosslinking agent, 2-allylphenyl cyanate 16 reacts not only with itself, but also with other cyanates to form heterogeneous triazine rings, exemplified by triazines 18 and 19 . Even though it does not self polymerize through the allyl double bond, it can copolymerize with an other olefinic monomer, such as methyl methacrylate, to form a crosslinked and insoluble polymer. © 1995 John Wiley & Sons, Inc.     

梳状聚合物电解质的合成与表征

用1H -NMR方法对苯乙烯 /马来酸酐共聚物多缩乙二醇酯的合成进行了表征 ,说明用1H -NMR的方法进行该类化合物的合成研究是简便准确的。并且通过热失重对该电解质的热稳定性进行了研究。     

Thermal diffusivity of polycaprolactone/poly(bisphenol A carbonate) blends by flash radiometry

This article presents thermal diffusivity (D) measurement by flash radiometry for the polymer blend of polycaprolactone (PCL) and poly(bisphenol A carbonate) (PC) with a lower critical solution temperature (LCST) phase diagram. The dependence of D on temperature is significantly changed by annealing above the cloud point. D is largely increased by the growth of PCL crystallite in the blends. In the miscible state, D is smaller than that predicted by the rule of mixtures, whereas the dependence of D on the weight fraction of PC for the immiscible (phase‐separated) state is well expressed by the rule of mixtures. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 745–749, 1999     

Biomedical applications of electrospun polycaprolactone fiber mats

Polycaprolactone (PCL) is a biodegradable polyester emerging into biomedical applications because of its biodegradability, biocompatibility, chemical stability, thermal stability and good mechanical properties. Electrospinning is a versatile method using electrostatic forces for fabricating continuous ultrafine fibers that offer various advantages such as high surface area and high porosity. Thus, this method has gained interest for use in many fields, especially biomedical fields. This review focuses on researches and studies in electrospinning, PCL, electrospinning of PCL and also biomedical applications of the electrospun PCL fiber mats. Copyright © 2016 John Wiley & Sons, Ltd.     

Syntheses of biodegradable polymer networks based on polycaprolactone and glutamic acid

Biodegradable trifunctional oligomer was synthesized from polycaprolactone and glutamic acid and characterized by Fourier‐transform infrared (FTIR) and proton nuclear magnetic resonance (¹H NMR) spectroscopies. Injectable and in situ crosslinkable polymer networks were fabricated by the copolymerization of oligomer with triethylene glycol dimethacrylate (TEGDMA) and used to evaluate the initial compressive strengths, viscosities, shrinkages, thermal stabilities, and biodegradabilities in the forms of polymer network neat resin and their composites with β‐tricalcium phosphate. The initial compressive strengths (CS) values of neat resins ranged from 9.54 to 187.6 MPa. Both neat resins and composites had polymerization shrinkage ranging from 0% to 11.7%, which increased with increasing of TEGDMA contents in resin. Moreover, in polymer composite resins, shrinkage values decreased with increasing filler level from 0% to 4.6%, and exothermic evolution values decreased from 33.5°C to 29.7°C as increasing filler level. The composite with the formulation of (polycaprolactone)‐glutamate triacrylate (PCLGTA)/TEGDMA (25/75) and powder/liquid (P/L) ratio of 1.0 exhibited the highest exothermal and lowest shrinkage values. The increase of oligomer in the formulation led to an increase in viscosity.     

Synthesis and properties of biodegradable polycaprolactone/polyurethanes using fluoro chain extenders

In this study, biodegradable fluorine‐containing polyurethanes (PU/OFHD) were synthesized using 4,4'‐diphenylmethane diisocyanate, polycaprolactone diol (PCL), and 2,2,3,3,4,4,5,5,‐octafluoro‐1,6‐hexanediol (OFHD). PCL is a biodegradable soft segment, and OFHD is a fluoro chain extender. In addition, other polyurethanes (PU/HD) were synthesized using 4,4'‐diphenylmethane diisocyanate, PCL, and another chain extender [i.e., 1,6‐hexanediol (HD)] for comparison. Gel permeation chromatography analysis indicated that the molecular weight of PU/OFHD is greater than that of PU/HD. ¹⁹F nuclear magnetic resonance analysis revealed that the OFHD chain extender was successfully incorporated into the backbone of PU. According to Fourier transform infrared spectroscopy and X‐ray photoelectron spectroscopy analyses, strong interactions between the C=O and CF₂ groups in PU/OFHD exist. Based on thermal analysis, PU/OFHD exhibited an initial decomposition temperature that was 6.5–7.9°C higher than that of PU/HD. Differential scanning calorimetry and dynamic mechanical analysis analyses indicated that both the glass transition (Tg) and dynamic Tg of PU/OFHD are higher than those of PU/HD. Mechanical property analysis demonstrated that the tensile strength of PU/OFHD is higher than that of PU/HD. Moreover, PU/OFHD exhibited better chemical resistance than PU/HD. The scanning electron microscope images indicated that both PU/HD and PU/OFHD exhibited higher hydrolytic degradation at a higher PCL content. However, PU/OFHD is less degradable than PU/HD. Copyright © 2015 John Wiley & Sons, Ltd.     

Synthesis,photocrosslinking characteristics,and biocompatibility evaluation of N‐vinyl pyrrolidone/polycaprolactone fumarate biomaterials using a new proton scavenger

Photocrosslinkable and biodegradable polymeric networks were formulated based on N‐vinyl pyrrolidone‐poly(ε‐caprolactone fumarate) (NVP/PCLF) compositions for hard tissue engineering applications using a new proton scavenger, propylene oxide (PO). The synthesized macromers were obtained as a white clear paste with no colorization. The obtained macromers were thoroughly characterized using spectroscopic (NMR and FT‐IR) and chromatographic (gel permeation chromatography (GPC)) techniques. Photocrosslinking of the PCLF/NVP compositions was achieved using camphorquinone and dimethyl toluidine (DMT) as a photoinitiator system. The cytocompatibility of the macromers and their corresponding networks were evaluated via MTT assay. Characterization of the networks indicated the importance of NVP content on the network properties. Sol fraction studies indicated that more than 90% of the PCLFs were crosslinked over the studied range of PCLF/NVP compositions; however most of the NVP above a stoichiometric ratio of one NVP to fumerate unit remained unreacted. It was also found that in the concentrations more than 10% NVP, the unreacted NVP monomer neither participated in the crosslinking reaction nor homopolymerized to poly(vinyl pyrrolidone) (PVP). The elastic modulus (G′) and estimated molecular weight between crosslinks also confirmed that at the higher NVP content the PCLF photocrosslinking was hindered. Copyright © 2008 John Wiley & Sons, Ltd.     

Synthesis and characterization of 1,3,4-oxadiazole-containing polyazomethines

Novel 1,3,4-oxadiazole-containing polyazomethines were synthesized by the polycondensation of diamines, 2,5-bis (m-aminophenyl)-1,3,4-oxadiazole (BMAO) and 2,5-bis (p-aminophenyl)-1,3,4-oxadiazole (BPAO), with aromatic dialdehydes, isophthalaldehyde and terephthalaldehyde, in m-cresol at 20°C. These polymers were yellow to orange in color and had reduced viscosities up to 1.13 dL/g and electric conductivity as high as 10^?11?10^?12 S cm^?1. All the polyazomethines were insoluble in common organic solvents but dissolved in concentrated sulfuric acid. Thermogravimetry showed that thermal degradation started at around 400°C in air and nitrogen atmospheres. Doping with iodine markedly increased the conductivity and produced the black-colored semiconductive polyazomethines with a maximum conductivity of the order of 10^?6 S cm^?1. Electronic spectra of the undoped polymers indicated a large bathochromic shift of the absorption maxima due to C?N bonds of the monomer diamines (285 nm for BMAO and 315 nm for BPAO). This suggests that π-electrons of the polymers are extensively delocalized along the main chain.     

Porous electrospun polycaprolactone fibers: Effect of process parameters

The effect of electrospinning process parameters (solution flow rate, applied voltage, spinning distance) on the size and surface morphology of porous electrospun poly(ε‐caprolactone) was investigated in this study. Response surface methodology was implemented for the design and conduction of electrospinning experiments. The feed solution was a 12.5% w/v poly(ε‐caprolactone) (PCL) solution in a binary solvent mixture of 90%v/v chloroform/dimethyl sulfoxide. Spinning distance of 10–25 cm, applied voltage of 10–25 kV and feed flow rate of 0.5–5 mL/h were the range of limiting values of the independent variables used for the development of a central composite design. Second‐order polynomial equations, correlating electrospinning process parameters to relative pore coverage, and fiber average diameter were developed and validated. An increase in any of the investigated parameters (solution flow rate, applied voltage, spinning distance) resulted in the increase of both, pore formation on electrospun fibers, and produced fiber average diameter. Under the experimental conditions investigated, the relative pore surface coverage was 15.8–31.9% and the average fiber diameter was in the range of 1.6–3.3 μm. Applied voltage was proven to be the parameter with the strongest impact on both, fiber diameter and surface morphology. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 1878–1888     

Electrospun nanofibrous polycaprolactone scaffolds for tissue engineering of annulus fibrosus

The annulus fibrosus comprises concentric lamellae that can be damaged due to intervertebral disc degeneration; to provide permanent repair of these acquired structural defects, one solution is to fabricate scaffolds that are designed to support the growth of annulus fibrosus cells. In this study, electrospun nanofibrous scaffolds of polycaprolactone are fabricated in random, aligned, and round-end configurations. Primary porcine annulus fibrosus cells are grown on the scaffolds and evaluated for attachment, proliferation, and production of extracellular matrix. The scaffold consisting of round-end nanofibers substantially outperforms the random and aligned scaffolds on cell adhesion; additionally, the scaffold with aligned nanofibers strongly affects the orientation of cells.     

Synthesis and characterization of 1,3,4-thiadiazole-containing polyazomethines and copolyazomethines

Novel 1,3,4-thiadiazole-containing polyazomethines and copolyazomethines were synthesized by the solution polycondensation, in m-cresol at 25°C, of aromatic dialdehydes, isophthalaldehyde and terephthalaldehyde, with 2,5-bis (m-aminophenyl)-1,3,4-thiadiazole (BMAT) and with BMAT and aromatic diamines, bis (4-aminophenyl) ether and 1,5-diaminonaphthalene, respectively. These polymers were tan yellow to yellow in color and had reduced viscosities up to 0.32 dL/g in concentrated sulfuric acid and electric conductivity as high as 10^?9?10^?11 S cm^?1 at 25°C. All the polymers were insoluble in common organic solvents but dissolved completely in concentrated sulfuric acid and formic acid. However, they were readily hydrolyzed in concentrated sulfuric acid. X-ray diffraction diagrams showed that the crystallinity of polyazomethines were low, but copolyazomethines were highly crystalline. These azomethine polymers are highly thermally and thermooxidativelly stable and exhibited no appreciable decomposition up to 400°C in both air and nitrogen atmospheres. Doping with iodine dramatically raised the conductivity and produced the dark brown- to completely black-colored semiconductive polymers with a maximum conductivity of the order of 10^?5 S cm^?1. Electronic spectra of the undoped polymers indicated a large bathochromic shift of the π?π^* absorption band (310 nm) due to C?N bonds of BMAT. This result suggests that π-electrons of the polymers are extensively delocalized along the main chain.     

Chitosan‐g‐polycaprolactone copolymer fibrous mesh scaffolds and their related properties

Chitosan‐g‐polycaprolactone copolymers (CPCs) with desired composition proportions were synthesized by carefully controlling the weight ratio of polycaprolactone side chains changing approximately between 45 and 48 wt% so that the obtained CPCs could be further processed via different processing techniques. Aqueous acetic acid solutions and dimethyl sulfoxide were respectively employed as solvents to fabricate CPCs into fibrous mesh scaffolds that had nearly similar parameters characterized by the average porosity and pore‐size of scaffolds as well as the average diameter of filaments under optimal processing conditions. The swelling index, surface group analysis, antibacterial activity and tensile mechanical properties of these mesh scaffolds were investigated in several ways, and the scaffolds showed quite different properties due to the different processing methods employed, although the same type of CPC was used. Copyright © 2008 John Wiley & Sons, Ltd.