Rheological properties of poly(ε-caprolactone) and poly(styrene-co-acrylonitrile) blends

Summary Rheological properties of poly(-caprolactone) (PCL) and Poly (styrene-co-acrylonitrile) (SAN) blends were examined as a function of the acrylonitrile (AN) content in SAN, to systematically understand the correlation between the interaction parameter and the theological properties of miscible polymer blends. When the plateau modulus (G _N ⁰) and zero shear viscosity ( ₀) of the PCL/SAN blends are plotted against the AN content in SAN, a minimum is observed. Qualitatively, the results obtained parallel the variation of the interchain interaction with the AN content. The negative deviation ofG _N ⁰ and ₀ from linearity seems to be attributed to the increase in the entanglement molecular weight between dissimilar chains which results from the chain extension caused by interchain interaction.     

Physical properties and biodegradation of acrylic acid grafted poly(ε-caprolactone)/chitosan blends

We blended films of acrylic acid grafted polycaprolactone (PCLgAA) and citosan (CS) with different compositions from aqueous acetic acid solution. DSC measurements showed that the melting temperatures and enthalpies of the blends decreased with increasing CS content. From FTIR results, we observe that the amino groups of CS form covalent bonds with the carboxylic groups of PCLgAA in addition to hydrogen bonds between the constituents in the blends. Though the crystal structure of the PCLgAA component was not changed, as proved by WAXD results, blending CS suppressed the crystallinity of the blends. Furthermore, the ductility of CS was increased during tensile testing in PCLgAA/CS blends due to enhanced affinity between the two components. However, PCLgAA/CS blends show greater resistance than PCL/CS blends to biodegradation in an enzymatic environment.     

Different real-time degradation scenarios of functionalized poly(ε-caprolactone) for biomedical applications

Anterior cruciate ligament (ACL) ruptures are a much-commented injury as it can end the season or even career of professional athletes. However, the recovery of a patient from the general population is no less painful during the long period required by current treatments. Artificial ligaments could improve this healing, yet, orthopedic surgeons are still cautious about permanent ACL implants. Therefore, combining biodegradation and bioactivity could be a key feature for the popularization of these devices. This study aim at evaluating the real-time degradation of poly(ε-caprolactone) (PCL) grafted with the bioactive polymer sodium polystyrene sulfonate in different scenarios. PCL physical–chemical properties were evaluated before and after degradation. In addition, in vitro experiments were realized to confirm the long term influence of the grafting on cell response. Altogether, we were able to show different degradations scenarios, enabling to study the impact of degradation environment on degradation mode and rate of functionalized PCL.     

Poly(ε-caprolactone)/poly(m-anthranilic acid) and poly(ε-caprolactone)/poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) electrospun nanofibers: Characterization,antioxidant, and electrochemical properties

Conducting polymers are widely used in many biomedical applications, but their non-degradability and non-biocompatibility limit their widespread use in applications. For this reason, many studies have been carried out on the developing degradable, biocompatible, and electrically conductive polymers. In this study, mixtures of conductive polymers (poly(m-antranilic acid) (P3ANA) and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS)) with biocompatible and biodegradable poly(ε-caprolactone) (PCL) were prepared. Their nanofibers were obtained by electrospinning and their antioxidant properties were investigated by 2,2′-azino-bis-3-ethylbenzthiazoline-6-sulfonic acid (ABTS) and copper ion reducing antioxidant capacity (CUPRAC) assays. Electrochemical properties were also investigated by cyclic voltammetry and electrochemical impedance spectroscopy. The highest antioxidant activity was obtained from PCL/P3ANA3 electrospun nanofiber containing 10% (of PCL w/w) P3ANA with 93 and 614 μg TE/mg values for ABTS and CUPRAC assays, respectively. This nanofiber was found to be non-toxic according to 2,5-diphenyl-2H-tetrazolium bromide (MTT) analysis. PCL/PEDOT:PSS electrospun nanofiber has the highest maximum anodic current value of 0.08 mA. The maximum anodic current value of PCL/P3ANA3 nanofiber with the highest amount of P3ANA is also higher than other PCL/P3ANA nanofibers. These nanofibers were characterized by FT-IR, UV–vis., XRD and TGA and their surface morphologies were examined by scanning electron microscopy (SEM).     

Mechanical and Physical properties of chitosan and whey blended with poly(ε-caprolactone)

Properties important for packaging were studied on blends of 0-15 wt% poly( l caprolactone) and chitosan and a whey-protein-isolate. The blends were obtained by solution mixing, and films were produced by solvent casting. Transparency was measured by UV/VIS spectroscopy and the printability was qualitatively estimted by using a red ethanol dye. Mechanical properties of solid films and seals were assessed by tensile tests. Stiffness and folding endurence were also measured. The blend morphology was characterized by scanning electron microscopy. It was found that all the blends were transparent. The whey-protein-isolate had the best printability properties and printability remained in the poly( l -caprolactone)-blends. Film stiffness decreased and strain at break increased strongly when the pure chitosan and the pure whey-protein-isolate were wetted. The addition of poly( l -caprolactone) to chitosan and whey-protein-isolate had only a moderate effect on the toughness properties but a strong effect on the modulus which could be predicted by the Halpin-Tsai model. The modulus of the whey-protein-isolate increased and the modulus of the chitosan decreased with the addiion of poly( l -caprolactone). It was found that it was impossible to seal chitosan with a standard heat-pulse sealing technique. The whey-protein-isolate was sealable but the strength of the seals was lower than the intrinsic strength of the pure whey-protein-isolate. The folding endurance properties of chitosan and its blends were far better than those of the whey-protein-isolate and its blends.     

Effect of poly(ε-caprolactone) and titanium (IV) dioxide content on the UV and hydrolytic degradation of poly(lactic acid)/poly(ε-caprolactone) blends

The effect of accelerated weathering degradation on the properties of poly(lactic acid) (PLA)/poly(ε-caprolactone) (PCL) blends and PLA/PCL/titanium (IV) dioxide (TiO₂) nanocomposites are presented in this paper. The results show that both polymers are susceptible to weathering degradation, but their degradation rates are different and are also influenced by the presence of TiO₂ in the samples. Visual, microscopic and atomic force microsocpy observations of the surface after accelerated weathering tests confirmed that degradation occurred faster in the PLA/PCL blends than in the PLA/PCL/TiO₂ nanocomposites. The X-ray diffraction results showed the degradation of PCL in the disappearance of its characteristic peaks over weathering time, and also confirmed that PLA lost its amorphous character and developed crystals from the shorter chains formed as a result of degradative chain scission. It was further observed that the presence of TiO₂ retarded the degradation of both PLA and PCL. These results were supported by the differential scanning calorimetry results. The thermogravimetric analysis results confirmed that that PLA and PCL respectively influenced each other's thermal degradation, and that TiO₂ played a role in the thermal degradation of both PLA and PCL. The tensile properties of both PLA/PCL and PLA/PCL/TiO₂ were significantly reduced through weathering exposure and the incorporation of TiO₂.     

Tetracycline hydrochloride-containing poly (ε-caprolactone)/poly lactic acid scaffold for bone tissue engineering application: in vitro and in vivo study

In the current study, tetracycline hydrochloride (TCH), an antibiotic against most of the medically relevant bacteria, was incorporated into poly (ε-caprolactone)/poly lactic acid solution in order to develop a composite scaffold with both antibacterial and osteoinductive properties for the repair of infected bone defects. The composite scaffolds were produced from poly (ε-caprolactone) (PCL) and poly lactic acid (PLA) solution (1:1 (w/w)) incorporated with 3, 5, and 10% (w/w) of TCH by thermally induced phase separation technique. The scaffolds were evaluated regarding their morphology, wettability, porosity, degradation, mechanical properties, and cellular response. The scaffold containing 10% of TCH (PCL/PLA/TCH10%) was chosen as the optimum scaffold for further investigation in a rat femoral defect model. The study showed that after eight weeks, the bone formation was relatively higher in PCL/PLA/TCH10%-treated group with completely filled defect when compared with control (PCL/PLA scaffold without TCH). Histopathological evaluation showed that the defect in PCL/PLA/TCH10%-treated group was fully replaced by new bone and connective tissue. Our results provide evidence supporting the possible applicability of TCH-containing scaffolds for successful bone regeneration.     

In vitro degradation of poly(l-lactide)/poly(ε-caprolactone) blend reinforced with MWCNTs

The physical and mechanical properties of poly(l-lactide)/poly(??-caprolactone) (PLLA/PCL) blends reinforced with multiwalled carbon nanotubes (MWCNTs) before and after in vitro degradation were investigated. Because of brittleness, PLLA needs to be plasticized by PCL as a soft polymer. The MWCNTs are used to balance the stiffness and the flexibility of PLLA/PCL blends. The results showed that with incremental increase in concentration of MWCNTs in composites, the agglomerate points of MWCNTs were increased. The physical and mechanical properties of prepared PLLA/PCL blends and MWCNT/PLLA/PCL nanocomposites were characterized. The X-ray diffraction analysis of the prepared blends and composites showed that MWCNTs, as heterogeneous nucleation points, increased the lamella size and therefore the crystallinity of PLLA/PCL. The mechanical strength of blends was decreased with incremental increase in PCL weight ratio. The mechanical behavior of composites showed large strain after yielding and high elastic strain characteristics. The tensile tests results showed that the tensile modulus and tensile strength are significantly increased with increasing the concentration of MWCNTs in composites, while, the elongation-at-break was decreased. The in vitro degradation rate of polymer blends in phosphate buffer solution (PBS) increased with higher weight ratio of PCL in the blend. The in vitro degradation rate of nanocomposites in PBS increased about 65% when the concentration of MWCNTs increased up to 3% (by weight). The results showed that the degradation kinetics of nanocomposites for scaffolds can be engineered by varying the contents of MWCNTs.     

DSC studies of poly(vinyl chloride)/poly(ε-caprolactone)/poly(ε-caprolactone)-b-poly(dimethylsiloxane) blends

Poly(vinyl chloride)/poly(ε-caprolactone)/poly(ε-caprolactone)-b-poly(dimethylsiloxane) [PVC/PCL/(PCL-b-PDMS)] blends were prepared by solvent casting from tetrahydrofuran. The content of PVC was kept constant (60 wt%); the PCL and PCL-b-PDMS contents were varied by replacing different amounts of PCL [0–20 wt% from the PVC/PCL (60/40) blend] with PCL-b-PDMS copolymer having different molecular weights of the PCL blocks. The thermal properties of prepared blends were investigated by differential scanning calorimetry in order to analyse miscibility (through glass transition temperature) and crystallinity. Differential scanning calorimetry analyses show that the PVC/PCL/PCL-b-PDMS blends are multi-phase materials which contain a PVC plasticized with PCL phase, a block copolymer PCL-b-PDMS phase (with crystalline and amorphous PCL and PDMS domains) and a PCL phase (preponderantly crystalline).     

Improvement in poly(ε-caprolactone) bio-activity. Structural characterization and in vitro assessment

Abstract

Model PCL homopolymers (anionic polymerization) were synthetized and chemically functionalized with anhydrides to improve their bio-activity. Modified polyesters were used to fabricate highly porous PCL membranes by leaching technique, reaching porosities values up to 86.1%. Microstructural characterization revealed that chemical modification did not affect thermal properties and mechanical stabilities of PCL membranes. In vitro assays were carried out by soaking samples in simulated body fluid (SBF) solution. By SEM-EDX and TGA analyses, it was observed that modified polyesters exhibited a hydroxyapatite layer over polymeric surfaces, with calcium/phosphorous ratio of 1.58, close to the value reported by literature for hard tissue.     

Advance application of Raman spectroscopy for quantitative analysis of noncrystalline components in thin films of poly(ε-caprolactone)/poly(butadiene) blends

A quantitative analysis method for the distribution of noncrystalline poly(butadiene) component in poly(ε-caprolactone)/poly(butadiene) (PCL/PB) binary blends have been analyzed by advance application of Raman spectroscopy, optical microscopy, and differential scanning calorimetry (DSC) techniques. Thin films of different compositions of PCL/PB binary blends were prepared from solution and isothermally crystallized at a certain temperature. After calibration with real data, quantitative analyses by Raman spectroscopy revealed the amorphous PB are trapped inside the PCL crystals. Polarized optical microscopy and real time atomic force microscopy were used to collect data for the crystal morphology and crystal growth rate. For pure PCL crystals, a morphology of truncated lozenge shape was observed, independent of crystallization temperature and regardless of the blends compositions. For the pure PCL and their blends, almost unique crystal growth rate was found. The miscibility behaviors using DSC were drawn through melting point depression method. The Hoffman-Weeks extrapolations of the blends were found to be linear and identical with those of the neat PCL. The interaction parameter for the blends indicating that the PCL and PB blends have no intermolecular interaction, confirming the blends are immiscible. Despite the immiscibility of the blend, the PCL crystals do not bend during the growth process and do not reduce the growth rate as they do for miscible blend systems.     

Compatibilizing capability of poly(β-hydroxybutyrate-,co-ε-caprolactone) in the blend of poly(β-hydroxybutyrate) and poly(ε-caprolactone)

In order to increase the miscibility in the blend of poly(β-hydroxybutyrate) [PHB] and poly(ε-caprolactone) [PCL], PHB/PCL copolyesters were used as compatibilizers. These PHB/PCL copolyesters were synthesized by transesterification in solution phase. The melting point [T_m] depression, which was not observed in PHB/PCL blend without compatibilizer, was observed when PHB/PCL copolyesters as compatibilizers were added to the PHB/PCL blend system. As the amount of compatibilizer added to the blend increased, the crystallization temperature [T_c] of PCL in the blend increased and T_c of PHB in the blend decreased. The difference in T_c between PHB and PCL was gradually reduced. When the sequence length of PHB block and PCL block in the PHB/PCL copolyester increased, the miscibility of the blend increased. This is evidenced by the depression in the T_m of PHB and PCL in the blend and by the decrease in the difference of T_c between PHB and PCL. From the polarizing optical micrographs, the phase separation in PHB/PCL blend was observed. However, in the presence of PHB/PCL copolyester, the spherulite of PHB grows in equilibrium with one phase melt. Received: 27 July 1998/Revised version: 12 October 1998/Accepted: 4 November 1998     

Electrospun fibers from functional polyglycidol/poly(ε-caprolactone) blends with defined surface properties

Highly hydrophilic but water insoluble fibers from star-shaped poly(ethoxyethyl glycidyl ether) and poly(ε-caprolactone) polymer blends in the submicron range were prepared using the electrospinning technique. The fibers were achieved in a smooth and homogeneous manner and do show tremendous decreased protein adsorption. Additionally, using alkyne- or vinyl sulfonate end capped polymer, fibers with the correspondent surface reactivity have been prepared. All fibers showed high biocompatibility and were highly hydrophilic but water stable. Furthermore, nonwovens based on functionalized poly(ethoxyethyl glycidyl ether) were equipped with small biofunctional molecules, e.g., the peptide sequence glycine-arginine-glycine-aspartate-serine (GRGDS). These fibers showed increased cell attachment compared with nonfunctionalized nonwovens. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Production, mechanical properties and in vitro biocompatibility of highly aligned porous poly(ε-caprolactone) (PCL)/hydroxyapatite (HA) scaffolds

We produced highly aligned porous poly(ε-caprolactone) (PCL)/hydroxyapatite (HA) scaffolds by unidirectionally freezing PCL/HA solutions with various HA contents (0, 5, 10 and 20 wt% in relation to the PCL polymer) and evaluated their mechanical properties and in vitro biocompatibility to examine their potential applications in bone tissue engineering. All the prepared scaffolds had a highly aligned porous structure, in which the HA particles were uniformly dispersed in the PCL walls. The elastic modulus of the PCL/HA scaffolds significantly increased from 0.12 ± 0.02 to 2.65 ± 0.05 MPa with increasing initial HA content from 0 to 20 wt%, whereas the pore size decreased from 9.2 ± 0.7 to 4.2 ± 0.8 μm. In addition, the PCL/HA scaffolds showed considerably enhanced in vitro cellular responses that were assessed in terms of cell attachment, proliferation and osteoblastic differentiation.     

Physical characterization and rheological behavior of polyurethane/poly(ϵ-caprolactone) blends,prepared by solution blending using dimethylacetamide

Blending effects of thermoplastic polyurethane based on polycaprolactone diol, PU (PCL diol), and poly (ϵ-caprolactone) (PCL) on the rheological properties and morphological behavior of the solvent-cast blends were investigated by parallel plate rheometer. The amount of PCL was varied from 20 to 50% by weight. Fourier transform infrared (FTIR) results showed existence of hydrogen bonding in PU/PCL blends. From FTIR, we also found the increase of PCL composition tends to reduction of intermolecular hydrogen bonding and enhancing of microphase separation in blends. Differential scanning calorimetry (DSC) indicated that these blend systems are partially miscible. Based on rheological characterization, decrease can be seen in the moduli, zero shear viscosity and plateau modulus of blends, as compared with net PU. Using Cole-Cole plots and composition dependencies of η₀ and the other viscoelastic functions expressed variation of morphology of blends due to increase of PCL content. Frequency sweep tests on PU/PCL (80/20) at five temperatures showed validity of time-temperature superposition in this blend. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Enzymatic degradation,electronic, and thermal properties of graphite- and graphene oxide-filled biodegradable polylactide/poly(ε-caprolactone) blend composites

Commodity polymers are the most widely used materials for electronic packaging applications. However, they are nondegradable and causing serious environmental damage. Addressing this challenge, the relative effects of graphite (G) and graphene oxide (GO) dispersion on the enzymatic degradation, electronic properties, thermal degradation, and crystallization behavior of enzyme degradable polylactide/poly(ε-caprolactone) blend composites is investigated. Owing to the oxygenated surface functionalities and excellent thermal conductivity arising from the carbon structure, the randomly dispersed GO particles do not provide electrical pathways and facilitate large enhancements in the electrical resistivity (126%) and thermal conductivity (72%) of the blend composites. However, while the G particles enhanced the thermal conductivity of the composites, they had little effect on enzymatic degradation. Furthermore, they reduced the electrical resistivity, particularly at high concentration (0.25 wt % G), as a result of the conducting delocalized electrons in the G structure and due to network formation. We also find that the energy required to initiate and propagate the thermal degradation process for GO-filled blend composites is relatively lower than that of G-filled blend composite. However, the former composites show higher crystallization rate coefficients value than that of G-filled composites and the neat blend, thereby providing better crystallization ability and miscibility with the matrix. In summary, the GO-filled blend composites are observed to show potential for use in sustainable materials for thermal management applications. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47387.     

Effects of processing conditions on hybrid filler selective localization,rheological, and thermal properties of poly(ε-caprolactone)/poly(lactic acid) blends

In this study, the effects of processing conditions through different mixing sequences were used to analyze the factors, which could influence the hybrid filler selective localization in an immiscible polymer blend and how localization can influence the rheological and thermal properties. Different selective localizations were observed depending on the mixing sequence used when the hybrid filler was added. Notably, nanoparticles can interact with each other, which favor a synergy between them and alters, besides the localization, the dispersion state, or can interact with one polymer phase, and also alter the nanoparticles' selective localization. An improvement in rheological properties was observed in the hybrid nanocomposite in which there was interaction between the nanoparticles, favoring the hexagonal boron nitride exfoliation. On the other hand, for the storage modulus and degree of crystallinity, the sharpest increase occurred in the hybrid nanocomposite in which the nanoparticles could interact preferably with one polymer phase. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 137, 48711.     

Preparation,properties, and laser processing of poly(ɛ-caprolactone)/poly(lactic acid) blends with addition of natural fibers as a potential for printing plates application

In this research, biodegradable blend of poly(ɛ-caprolactone) (PCL) and poly(lactic acid) (PLA) is proposed as a new material for the production of a printing plate for embossing process. Printing plates for embossing consist of raised printing elements and recessed nonimage elements. In production of printing plates, laser technology was used in order to form a relief printing plate. The embossing process is based on the principle of the pressure of the relief printing plate into the printing substrate, which causes the controlled deformation of the substrate and three-dimensional (3D) effect. Coir fibers (CFs) were added as a natural filler to PCL/PLA blends to improve and adjust the properties of produced blends. Scanning electron microscopy micrographs, dynamic mechanical analysis analysis, roughness, and hardness were measured on prepared materials, and 2D and 3D microscopy was conducted on laser engraved printing plates. Results have shown that the addition of CFs improved the mechanical properties of produced materials. DMA results indicate the semicrystalline structure of all prepared blends, and that the addition of CFs raises the elasticity of the composites. Laser engraving showed that it is possible to engrave the produced biodegradable materials and to use it as a material for production of printing plates.     

Studying the miscibility and thermal behavior of polybenzoxazine/poly(ε-caprolactone) blends using DSC, DMA, and solid state C NMR spectroscopy

Polymer blends of polybenzoxazine (PBZ) and poly(ε-caprolactone) (PCL) were prepared by solution blending of PCL and benzoxazine monomer (B-m), followed by thermal curing of B-m. The miscibility and thermal behavior of these PBZ/PCL blends were investigated by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), Fourier transform infrared spectroscopy (FTIR), and solid state ¹³C nuclear magnetic resonance (NMR) spectroscopy. The FTIR spectra indicated that hydrogen bonding interactions occur between the carbonyl groups of PCL and the hydroxyl groups of PBZ upon curing. The DSC results revealed that this PBZ/PCL blend system has a single glass transition temperature over the entire range of compositions that we investigated. The DMA results indicated that the values of T_g of the PBZ/PCL blends were higher than those of the pure polymers. In addition, at higher PCL concentrations we observed two glass transitions for the PBZ/PCL blends: One, for the PCL component, occurred in the low-temperature region and the other, for the PBZ component, in the high-temperature region; this finding indicates that PCL and PBZ are partially miscible in the amorphous phase. The most pronounced effect of the addition of PCL was to broaden the glass transition region, judging from the E″ peaks and the decrease in the value of the loss tangent (tan δ) in the transition region upon increasing the PCL content. We have also studied the ¹H spin-lattice relaxation times in the laboratory frame, , and in the rotating frame, , as a function of the blend composition. The results are in good agreement with those from the DSC analysis; i.e. the blends are completely homogeneous on the scale of 40-70 nm. The values of indicate that the PCL present in the blends exists in both crystalline and amorphous phases; the mobility difference between these PCL phases is clearly visible from the data. In addition, the amorphous phase of PCL is not miscible with PBZ; i.e. it is larger than 2-4 nm.     

Enhancing the grafting amount of Poly(ε-caprolactone) on MgO nanoparticles by modifying with ethylene glycol for improving mechanical properties of Poly(ε-caprolactone)

A new surface modification method to improve the graft polymerization of ε-caprolactone (CL) on MgO surface was developed. The MgO nanoparticles were first modified with ethylene glycol (EG), and then used for initiating graft polymerization of CL. The modified MgO nanoparticles were attested by fourier transform infrared spectroscopy, thermal gravimetric analysis and dispersion stability test. The results showed that EG was successfully grafted onto the MgO surface, the hydroxyl group of the grafted EG initiated the graft polymerization of CL onto the MgO surface in the presence of stannous octanoate. The PCL grafting amount (11.13%) on MgO modified with EG (MgO-EG) is much higher than that of unmodified MgO (3.95%). MgO-EG-PCL with 11.13 wt% of grafted PCL exhibited the most excellent dispersibility in chloroform. The MgO-EG-PCL/PCL composites exhibited the most significant improvement, tensile strength and the elongation at break of PCL increased from 15.64 to 19.58 MPa and from 272.34% to 420.73%, respectively.