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.     

Biocompatibility of Modified Bionanocellulose and Porous Poly(ϵ-caprolactone) Biomaterials

Biocompatibility of modified bionanocellulose (BC) and porous poly(? caprolactone) (PCL) were compared to UHMWPE. For all the materials lack of cytotoxic effect to mouse fibroblasts was observed in vitro. In vivo study, subcutaneous implantations in Wistar rats, lasted for seven, 14, and 30 days. Subsequently the composition of surrounding tissue and explants surface changes was evaluated. No symptoms of acute inflammation were observed. Surrounding tissue thickness, the number of granulocytes, lymphocytes, macrophages, and blood vessels differed in time and revealed regular healing process. It is concluded that investigated PCL and BC are the materials with superior biocompatibility with high application potential.     

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.     

Effects of storage on thermomechanical properties of poly(ɛ-caprolactone) blends containing poly(vinyl pyrrolidone/iodine)

Abstract

This study reports the effects of: the molecular weight ratio of poly(?-caprolactone) (PCL) in blends containing polymer of high (50 000 g mol^-1 ) and low (4000 g mol^-1 ) molecular weight; the concentration (0, 1, and 5 wt-%) of poly(vinyl pyrrolidone/iodine) (PVP/I); and storage at 30°C and 75% relative humidity; on the thermomechanical properties of films prepared by solvent evaporation from solutions containing both PCL and PVP/I. The tensile properties were found to be statistically dependent on the molecular weight ratio of PCL but not on the concentration of PVP/I. The reductions in tensile strength and elongation at break associated with increasing amounts of low molecular weight PCL were attributed to a reduction in the concentration of chain entanglements. No changes were observed in viscoelastic properties or the glass transition temperature. Following storage there were no changes in the tensile strength, glass transition temperature, or viscoelastic properties of the films; however, significant reductions in elongation at break were observed. It is suggested that this is due to hydrolytic chain scission of amorphous PCL. Inclusion of 5 wt-% PVP/I increased this process in films containing 100 : 0 and 80 : 20 high/low molecular weight PCL (but not 60 : 40), but the extent of this was small. This study highlighted significant aging properties of PCL in a moist atmosphere. Consequently, it is recommended that suitable packaging materials should be employed to control the exposure of PCL films to water during storage.     

Fabrication of fibrous poly (ɛ-caprolactone) nano-fibers containing cerium doped-bioglasses nanoparticles encapsulated collagen

Novel nanosized designed ceramic powders, cerium (Ce) doped bioglass (BG) with various doped Ce content, were synthesized by sol–gel method in order to be employed in the development of PCL fibrous scaffold for bone tissue engineering applications. Characterization techniques such as X-ray diffraction analysis, transmission electron microscopy, Fourier transform infrared spectroscopy, and energy-dispersive X-ray spectroscopy were employed to evaluate the developed Ce doped BG powders. The results confirmed successful doping of Ce inside BG structure. 0, 1, 3, and 10 wt% Ce doped 58S BG were successfully encapsulated in the collagen microspheres by water-in-oil emulsion method and the average particle size and hydrodynamic diameter of microspheres were determined using scanning electron microscopy and dynamic light scattering analysis, respectively. Next, 0, 1, 3, and 10 wt% Ce doped 58S BG encapsulated collagen microspheres were loaded inside the Poly(ɛ-caprolactone) fibrous scaffold and their in vitro bioactivity and biocompatibility properties were evaluated. The results of soaking samples in the simulated body fluid showed that all Ce doped 58S BG encapsulated collagen microspheres loaded PCL fibrous scaffold have acceptable bioactivity and apatite formation ability over time. The biocompatibility evaluation of developed scaffolds showed high viability and proliferation of MG63 cells cultured on the surface of 3% Ce doped 58S BG encapsulated collagen microsphere loaded in the PCL fibrous scaffold and its high potential ability for bone tissue engineering applications. These results potentially open new aspects for scaffolds aimed at the regeneration of bone defects.     

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     

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     

Miscibility of poly(styrene-co-vinyl phenol) with poly(ɛ-caprolactone)

Summary Poly(styrene-co-vinyl phenol) (STVPh)/poly(-caprolactone)(PCL) blends showed enhanced miscibility over polystyrene/PCL blend, and showed single glass transition temperature when the contents of vinyl phenol (VPh) in copolymer were higher than 10 wt % (maximum content of VPh in STVPh used in this study was 20 wt%). STVPh 4, STVPh 7, STVPh 10 (4, 7, 10 were VPh wt%)/PCL blends showed cloud points on heating for miscible blend system, and this phase separation was reversible on cooling. From melting point depression of PCL, interaction parameter, B. for miscible STVPh 12/PCL blend system was evaluated.     

Kinetics of nucleation and crystallization in poly(?-caprolactone) (PCL)

The recently developed differential fast scanning calorimetry (DFSC) is used for a new look at the crystal growth of poly(?-caprolactone) (PCL) from 185 K, below the glass transition temperature, to 330 K, close to the equilibrium melting temperature. The DFSC allows temperature control of the sample and determination of its heat capacity using heating rates from 50 to 50,000 K/s. The crystal nucleation and crystallization halftimes were determined simultaneously. The obtained halftimes cover a range from 3 × 10⁻² s (nucleation at 215 K) to 3 × 10⁹ s (crystallization at 185 K). After attempting to analyze the experiments with the classical nucleation and growth model, developed for systems consisting of small molecules, a new methodology is described which addresses the specific problems of crystallization of flexible linear macromolecules. The key problems which are attempted to be resolved concern the differences between the structures of the various entities identified and their specific role in the mechanism of growth. The structures range from configurations having practically unmeasurable latent heats of ordering (nuclei) to being clearly-recognizable, ordered species with rather sharp disordering endotherms in the temperature range from the glass transition to equilibrium melting for increasingly perfect and larger crystals. The mechanisms and kinetics of growth involve also a detailed understanding of the interaction with the surrounding rigid-amorphous fraction (RAF) in dependence of crystal size and perfection.     

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.     

Fabrication and In Vitro Bioactivity of Poly (ϵ-caprolactone) Composites Filled with Silane-Modified Nano-Apatite Particles

Silane coupling agents were firstly employed to modify the surfaces of nano-apatite (n-HA) particles, and then thin films of the silanized n-HA/PCL composites were successfully developed by incorporating solvent dispersion and thermal co-blending with hot-pressing methods. In vitro studies were conducted using the 2-time simulated body fluid (2SBF). Composite specimens were soaked in 2SBF from 3 to 14. Results showed that a layer of bone-like apatite was formed within 7 days on the surfaces of all composites, after its immersion in 2SBF, demonstrating moderate in vitro bioactivity of these composites.     

Synthesis and crystallization kinetics of silsesquioxane-based hybrid star poly(ε-caprolactone)

A series of silsesquioxane-based hybrid star poly(ε-caprolactone) with different arm length (SHPCL-4, SHPCL-10, SHPCL-40) were synthesized from ring-opening polymerisation of ε-caprolactone as a monomer initiated by silsesquioxane-based hybrid polyol (SBOH). Two linear poly(ε-caprolactone)s, LPCL-25 and LPCL-35, were also prepared for comparison. The sequence of LPCL-25<LPCL-35<SHPCL-4<SHPCL-10<SHPCL-40 for total molecular weights (M_n) and the sequence of SHPCL-4<SHPCL-10<LPCL-25<LPCL-35<SHPCL-40 for average molecular weight per arm were determined by ¹H NMR and GPC measurements. The ¹H NMR data also suggested that SHPCLs possess a spheric architecture with 29.2 arms in average. The crystallization kinetics study by non-isothermal DSC showed that the starting temperature of crystallization (T_s), the ending temperature (T_e) and the peak temperature of exothermic curve (T_p) are in the order as: SHPCL-4<SHPCL-10<LPCL-25<SHPCL-40≈LPCL-35, while the crystallinity (X_c) follows the order of SHPCL-4<SHPCL-10<SHPCL-40<LPCL-25<LPCL-35. The corrected overall crystallization rate constant (K_c) calculated from Avrami equation were found to be in the order as: SHPCL-4<SHPCL-10<LPCL-35<LPCL-25≈SHPCL-40, which was further evidenced by the real time morphological observation with polarized light microscopy (POM). It is also found by the POM measurements that the inorganic core and star architecture greatly retards the nucleation of SHPCLs with short arms, while it helps the nucleation of SHPCL with longer arms.     

Preparation and characterization of poly(ɛ-caprolactone) nonwoven mats via melt electrospinning

Laser melt electrospinning is a novel technology to produce nonwoven scaffolds for tissue engineering (TE) applications. This solvent-free process is far safer than common solution electrospinning. In this paper, we demonstrated the poly(?-caprolactone) (PCL) fibers diameters could be governed from 3 to 12 μm with changing electrospinning parameters. The various diameters can meet the needs of scaffold properties such as porosity, pore size, etc. Our experiential results also showed that the fibers diameter tended to decrease as laser current increased. The degradation of PCL molecular chains often occurs in the melt electrospinning process due to mechanical scission and thermal degradation. The crystallinity of as-spun PCL fibers was approximately equal to that of the annealing fibers by X-ray diffraction (XRD) and differential scanning calorimetry (DSC). In our experiential, the collected PCL electrospun fibers often fused together to form a three-dimension network structure, which is favorable to mechanical properties.     

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).     

Synthesis and characterization of polyrotaxanes comprising α-cyclodextrins and poly(ε-caprolactone) end-capped with poly(N-isopropylacrylamide)s

Biodegradable polyrotaxane (PR)-based triblock copolymers were synthesized via the atom transfer radical polymerization (ATRP) of N-isopropylacrylamide (NIPAAm) initiated with polypseudorotaxanes (PPRs) consisting of a distal 2-bromopropiomyl bromide end-capping poly(ε-caprolactone) (Br-PCL-Br) and a varying amount of α-cyclodextrins (α-CDs) in the presence of Cu(I)Br/PMDETA at 25 °C in aqueous solution. The copolymers were featured by relatively higher yields from 46.0% to 82.8% as compared with previous reports. Their structure was characterized in detail by using ¹H NMR, ¹³C CP/MAS NMR, GPC, WXRD, DSC and TGA analyses. When a feed molar ratio of NIPAAm to Br-PCL-Br was changed from 50 to 200, the degree of polymerization of PNIPAAm blocks attached to two ends of PPRs was in a range of 158–500. About one third of the added α-CDs were still entrapped on the central PCL chain after the ATRP process. Attaching PNIPAAm rendered the copolymers soluble in aqueous solution showing the thermo-responsibility as evidenced by turbidity measurements.     

Stereocomplex formation in enantiomeric diblock and triblock copolymers of poly (ɛ-caprolactone) and polylactide

Summary Enantiomeric diblock and triblock copolymers from caprolactone and lactide with various compositions were synthesized using alcohol/tin octoate as initiator system. Stereocomplexes were formed between pairs of enantiomeric block copolymers and their thermal properties examined. The melting temperatures of the crystalline PCL and PLA phases are depending on the composition of block copolymers. A raise of approximately 55°C of the temperature of PLA phase is observed in the blends as a consequence of stereocomplex formation as well in diblock as in triblock copolymers. Received: 31 July 2000/Revised version: 11 October 2000/Accepted: 26 October 2000     

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.     

Synthesis and characterization of poly(ε-caprolactone)-containing amino acid-based poly(ether ester amide)s

A new family of biodegradable amino acid-based poly(ether ester amide)s (AA-PEEAs) consisting of three building blocks [poly(ε-caprolactone) (PCL), L -phenylalanine (Phe), and aliphatic acid dichloride] were synthesized by a solution polycondensation. Using DMA as the solvent, these PCL-containing Phe-PEEA polymers were obtained with fair to very good yields with weight average molecular weight (M_w) ranging from 6.9 kg/mol to 31.0 kg/mol, depending on the original molecular weight of PCL. The chemical structures of the PCL-containing Phe-PEEA polymers were confirmed by IR and NMR spectra. These PCL-containing Phe-PEEAs had lower T_g than most of the oligoethylene glycol (OEG) based AA-PEEAs due to the more molecular flexibility of the PCL block in the backbones, but had higher T_g than non-amino acid based PEEA. The solubility of the PCL-containing Phe-PEEA polymers in a wide range of common organic solvents, such as THF and chloroform, was significantly improved when comparing with aliphatic diol based poly(ester amide)s and OEG based AA-PEEAs. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Crystal orientation of poly(?-caprolactone) blocks confined in crystallized polyethylene lamellar morphology of poly(?-caprolactone)-block-polyethylene copolymers

The crystal orientation of poly(?-caprolactone) (PCL) blocks in PCL-block-polyethylene (PE) copolymers has been investigated using two-dimensional small-angle X-ray scattering (2D-SAXS) and 2D wide-angle X-ray diffraction (2D-WAXD) as a function of crystallization temperature T_c and thickness of PCL layers d_PCL. The PCL blocks were spatially confined in the solid lamellar morphology formed by the crystallization of PE blocks (PE lamellar morphology), an alternating structure of crystallized PE lamellae and amorphous PCL layers. This confinement is expected to be intermediate between hard confinement by glassy lamellar microdomains and soft confinement by rubbery ones, because the crystallized PE lamellae consist of hard PE crystals covered with amorphous (or soft) PE blocks. The 2D-SAXS results showed uniaxial orientation of the PE lamellar morphology after applying the rotational shear to the sample. Therefore, it was possible to investigate crystal orientation of PCL blocks within the oriented PE lamellar morphology. The 2D-WAXD results revealed that the c axis of PCL crystals (i.e., stem direction of PCL chains) was parallel to the lamellar surface normal irrespective of T_c when 16.5 nm ≥ d_PCL ≥ 10.7 nm. However, it changed significantly with changing T_c when d_PCL = 8.8 nm; the c axis was perpendicular to the lamellar surface normal at 45 °C ≥ T_c ≥ 25 °C while it was almost random at 20 °C ≥ T_c ≥ 0 °C. These results suggest that the PE lamellar morphology plays a similar role to glassy lamellar microdomains regarding spatial confinement against subsequent PCL crystallization.     

Synthesis of poly(N-isopropylacrylamide)-b-poly(ɛ-caprolactone) and its inclusion compound of β-cyclodextrin

Well-defined amphiphilic poly(N-isopropylacrylamide)-b-poly(ɛ-caprolactone) (PNIPAM-b-PCL) block copolymers have been successfully prepared in two steps. PNIPAMOH is firstly prepared by using 4,4′-azobis(4-cyano-1-pentanol) as bifunctional initiator, and then PNIPAM-b-PCL copolymer is synthesized via a ring-opening polymerization of CL using PNIPAMOH as a macro-initiator in the presence of stannous octoate as a catalyst. The PNIPAM-b-PCL copolymers self-assemble to form spherical micelles of 50–130 nm in diameter, which can be modulated by the chain length of PCL block. The inclusion complexes are fabricated by treating PNIPAM-b-PCL with β-cyclodextrin and they are characterized by infrared and ¹H NMR spectroscopies, X-ray powder diffraction, thermogravimetric analysis, and differential scanning calorimetry.