Fabrication of highly porous poly (ε-caprolactone) microfibers via electrospinning

Highly porous Poly (ε-caprolactone; PCL) microfibers were successfully fabricated by collecting the fibers into a water bath during electrospinning. The morphology of the fibers collected with and without the water bath was investigated. We observed that altering the pH of the water bath affected both the fiber diameter and the size of pores on the fibers. Acidic or basic condition was found to be more favorable than neutral conditions for the formation of well-porous fibers. The morphology and pore size of the microfibers were characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The average diameter of the fibers and the pore size on the surface of the microfibers were found to be 12–14.5 and 0.3–0.7 μm, respectively. The crystallinity and thermal properties of the PCL mats were investigated by DSC. This highly porous nature of the microfibers makes PCL less crystalline and increases the surface to volume ratio of the mat. Therefore, the PCL mat obtained by water bath electrospinning may be more effective for tissue scaffolds and drug delivery than the mat obtained without water bath.     

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).     

Electrospun biocompatible poly (ε-caprolactonediol)-based polyurethane core/shell nanofibrous scaffold for controlled release of temozolomide

The electrospun biocompatible poly (ε-caprolactonediol)-based polyurethane (PCL-Diol-b-PU) core/shell nanofibrous scaffolds were prepared via the coaxial electrospinning process. Temozolomide (TMZ) as an anticancer drug was loaded into the core of fibers to control the release of TMZ for the treatment of glioblastoma. The properties of nanofibers were characterized using XRD, FTIR, SEM, and TEM analysis. The sustained delivery of TMZ without initial burst release was achieved from all prepared core–shell nanofibrous samples over 30 days. The cytotoxicity results revealed that the TMZ-loaded PCL-Diol-b-PU core–shell nanofibers could be used as a drug delivery implant to deliver TMZ against glioblastoma tumors.     

Multilayer biopolymer/poly(ε-caprolactone)/polycation nanoparticles

Combining two or more materials for carrier construction is one of the topical approaches to avoid/diminish deficiencies and to increase functionality in delivery systems for bioactive compounds. In this context, here, multilayered nanoparticles comprising both natural (atelocollagen—AteCol; hyaluronic acid derivative—HA) and synthetic [poly(ε-caprolactone)—PCL; polyethylenimine—PEI; poly(l-lysine)—PLL] polymers were prepared and characterized. The combination of a modified double-emulsion method with polymer modification reactions allowed improvement of the polymer particle’s functionality. Fourier transform infrared spectroscopy (FTIR), UV–Vis spectroscopy, fluorescence spectroscopy, dynamic light scattering, transmission/scanning electron microscopy and fluorescence microscopy investigations confirmed the obtention of the envisaged nanomaterials with the expected composition and structure. The double-layered biopolymer/PCL-based nanoparticles formed in a first synthesis step could be successfully coated with PEI and PLL. The gel electrophoresis assay attested the DNA packing ability of the formed nano-vehicles involving surface grafting of the former biopolymer/PCL-based nanoparticles in the case of both cationic polymers, for N/P ratios of 10 (PEI coating) and 3.5 (PLL coating), respectively. According to the FTIR registration, the protein’s native form was preserved. Considering the advantage of biocompatibility and high versatility (controlled size, tuned chemistry and biodegradation rate) some of the resulted nanomaterials may appear as potential candidates for biomedical uses (i.e., drug/gene delivery and tissue engineering).     

Enhanced therapeutic efficacy of clotrimazole by delivery through poly(ethylene oxide)-block-poly(ε-caprolactone) copolymer-based micelles

Amphiphilic block copolymers have been the subject of great scientific interests due to their applications in various fields including nano drug delivery. Three amphiphilic block copolymers based on poly(ε-caprolactone) as a hydrophobic segment and methoxy poly(ethylene oxide) ( as a hydrophilic part were synthesized by the ring-opening polymerization of ε-caprolactone using MeO-PEO_5K as macroinitiator by varying initial feed ratios. The synthesized polymers were further explored for their drug delivery potential using clotrimazole as model hydrophobic drug. Drug-loaded micelles were characterized for shape, size, drug encapsulation efficiency, in vitro release, and thermal stability using atomic force microscope, zetasizer, UV–visible spectrophotometry, FTIR, differential scanning calorimetry, and thermogravimetric analysis. Clotrimazole loaded in micelles were also investigated for its antifungal activity through an in vitro assay and scanning electron microscopy. The antifungal activity of drug increased significantly by delivering through polymeric micelles. Current study provides insight into different factors that can be maneuvered to achieve a variety of desired properties of micelles for improved therapeutic efficacy of drugs like clotrimazole. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47769.     

Impact of organoclays on the phase morphology and the compatibilization efficiency of immiscible poly(ethylene terephthalate)/poly(ε-caprolactone) blends

Adding nanofillers Cloisite 30B (C30B) and Cloisite 15A (C15A) to poly(ethylene terephthalate) (PET)/poly(ε-caprolactone) (PCL) (70/30, wt/wt) blends via melt blending can improve their phase morphology and change their interface properties. The effects of the different selective localization of clay on the structure and the morphologies are studied and evaluated by theoretical and experimental methods. It is found that C30B is selectively localized in PET and at the PET-PCL interface, whereas C15A is mainly localized at the interface. Moreover, the changes in the rheological behavior of the blends are attributed to the formation of clay network-like structures. X-ray diffraction, scanning electron microscope, and transmission electron micrograph observations also evidenced an exfoliated and/or intercalated structure of C30B, and intercalated structure of C15A in the blend, together with significant morphology changes of the initially immiscible blend. The relative permeability to PET/PCL of the nanocomposites decreased with the increasing of nanoclays content. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48812.     

Facile preparation of poly(ε-caprolactone)/Fe3O4@graphene oxide superparamagnetic nanocomposites

The main goal in this work was to prepare and characterize a kind of novel superparamagnetic poly(ε-caprolactone)/Fe₃O₄@graphene oxide (PCL/Fe₃O₄@GO) nanocomposites via facile in situ polymerization. Fabrication procedure included two steps: (1) GO nanosheets were decorated with Fe₃O₄ nanoparticles by an inverse co-precipitation method, which resulted in the production of the magnetite/GO hybrid nanoparticles (Fe₃O₄@GO); (2) incorporation of Fe₃O₄@GO into PCL matrix through in situ polymerization afforded the magnetic nanocomposites (PCL/Fe₃O₄@GO). The microstructure, morphology, crystallization properties, thermal stability and magnetization properties of nanocomposites were investigated with various techniques in detail. Results of wide-angle X-ray diffraction showed that the incorporation of the Fe₃O₄@GO nanoparticles did not affect the crystal structure of PCL. Images of field emission scanning electron microscope and transmission electron microscopy showed Fe₃O₄@GO nanoparticles evenly spread over PCL/Fe₃O₄@GO nanocomposites. Differential scanning calorimeter and polar optical microscopy showed that the crystallization temperature increased and the spherulites size decreased by the presence of Fe₃O₄@GO nanoparticles in the nanocomposites due to the heterogeneous nucleation effect. Thermogravimetric analysis indicated that the addition of Fe₃O₄@GO nanoparticles reduced the thermal stability of PCL in the nanocomposites. The superparamagnetic behavior of the PCL/Fe₃O₄@GO nanocomposites was testified by the superconducting quantum interference device magnetometer analysis. The obtained superparamagnetic nanocomposites present potential applications in tissue engineering and targeted drug delivery.     

Preparation of polylactide/poly(ε-caprolactone) microspheres enclosing acetamiprid and evaluation of release behavior

Reduction of the amount of pesticides applied to agricultural land is essential for environmental conservation. It can be accomplished by immobilization of the pesticides in polymer supports, which prevents their volatilization, degradation and leaching losses, and provides controlled release of the chemicals. In the present study, acetamiprid, a novel pesticide, was encapsulated in PLA-based microspheres using the solvent evaporation method via oil-in-oil (O/O) emulsion. Silicon oil and an acetonitrile solution with dissolved synthetic polymer(s) and acetamiprid were used as an outer and inner oil phases, respectively. The entrapment efficiency of the pesticide in the case of PLA microspheres decreased with increasing the concentration of the pesticide in the inner oil phase. The amount of acetamiprid released from the microspheres was less than 18 %. On the other hand, incorporation of poly(-caprolactone) (PCL) into the PLA microspheres resulted in increased amount of releasable pesticide (approximately 89 %). These results indicate that the PCL/PLA microsphere is a promising immobilization support of the acetamiprid for practical application.     

Preparation of PVDF/PVP core–shell nanofibers mats via homogeneous electrospinning

The polyvinylpyrrolidone (PVP)/poly(vinylidene fluoride) (PVDF) core–shell nanofiber mats with superhydrophobic surface have been prepared via electrospinning its homogeneous blending solutions, and the formation of the core–shell structure was achieved by the thermal induced phase separation assisted with the low surface tension of PVDF. The electrospinnability of the blending solutions was also investigated by varying the blending ratio of the PVP and PVDF, and it enhanced with the increase of PVP content. SEM and TEM results showed that the fibers size was varied in the range of 100 nm–600 nm with smooth surface and core–shell structure. The composition of the shell layer was determined by the XPS analysis, and further confirmed by water contact angle (WCA) testing. As the fraction of PVDF exceeding PVP in the electrospinning solutions, the nanofiber mats showed superhydrophobic property with the WCA above 120°. It indicated that the PVDF was concentrated in the shell layer of the fibers. X-Ray diffraction (XRD) and attenuated total reflection infrared spectroscopy (ATR-IR) analysis indicated that the PVDF was aggregated with the β-phase crystallite as dominant crystallite. The nanofiber mats with the gas breathability and watertightness ability due to the porous structure and superhydrophobic would be potential applied in wound healing.     

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.     

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.     

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 of core–shell hybrid nanoparticles by mineralization on poly(ε-caprolactone)-b-poly(methacrylic acid) copolymer micelles

Polymer micelles containing calcium phosphate (CaP) minerals on the shell domain were developed by nanotemplate-driven mineralization. The polymer micelle nanotemplate was prepared by self-assembly of a poly(ε-caprolactone)-b-poly(methacrylic acid) (PCL-b-PMAA) copolymer. PMAA formed the anionic outer shell, and PCL constructed the hydrophobic inner core. Subsequent addition of calcium and phosphate ions to micellar solutions induced CaP mineral deposition within the PMAA shell domain. Transmission electron microscopy (TEM) showed the well-defined nanostructure consisting of the CaP nanoshell and the PCL inner core. Energy-dispersive X-ray spectroscopy (EDS) confirmed CaP deposition on polymer micelles. Dynamic light scattering (DLS) study showed CaP mineralization greatly enhanced the micellar stability.     

Phase behavior of LiClO4-doped poly(ε-caprolactone)-b-poly(ethylene oxide) hybrids in the presence of competitive interactions

The phase behavior of a series of LiClO₄-doped poly(ε-caprolactone)-b-poly(ethylene oxide) (PCL-b-PEO) was studied as a function of PEO volume fraction (f_PEO), doping ratio (r) and temperature (T). It is found that the morphology of the hybrids changes from disordered structure (DIS) to hexagonally packed cylindrical (HEX) structure and then to lamellar (LAM) structure as the volume fraction of the PEO/salt phase (f_PEO/salt) increases at f_PEO/salt < 0.5. Order–order transitions are observed upon heating some hybrids. An approximate phase diagram of the PCL-b-PEO/LiClO₄ hybrids with f_PEO/salt < 0.5 was constructed in terms of f_PEO/salt and the segregation strength (χ_effN). As compared with the phase diagram of the weakly segregated diblock copolymers, the phase diagram of the hybrids has two features: the boundaries of the LAM and HEX structures shifts to lower f_PEO/salt and body-centered cubic spherical (BCC) structure is not observed for the samples studied. This can be attributed to the weaker ability of the salt inducing microphase separation at low f_PEO and the conformational change of the PEO block induced by the salt. Some unexpected phase behaviors were observed for the hybrids with f_PEO/salt > 0.5, including the hexagonally perforated layers (HPL) to LAM transition upon heating the same hybrid and HEX to gyroid (GYR) transition with the increase of doping ratio at the same temperature. These unexpected phase behaviors are qualitatively interpreted based on the competitive association of the PCL block with Li⁺ ions at elevated temperatures and higher doping ratios, which leads to re-distribution of the Li⁺ ions in different phases and the inconsistency between the calculated f_PEO/salt and the real volume fraction of the PEO/salt phase.     

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 characterization of a novel amphiphilic poly (ethylene glycol)–poly (ε-caprolactone) graft copolymers

A series of amphiphilic graft copolymers PEO-g-PCL with different poly (ε-caprolactone) (PCL) molecular weight were successfully synthesized by a combination of anionic ring-opening polymerization (AROP) and coordination-insertion ring-opening polymerization. The linear PEO was produced by AROP of ethylene oxide (EO) and ethoxyethyl glycidyl ether initiated by 2-(2-methoxyethoxy) ethoxide potassium, and the hydroxyl groups on the backbone were deprotected after hydrolysis. The ring-opening polymerization of CL was initiated using the linear poly (ethylene oxide) (PEO) with hydroxyl group on repeated monomer as macroinitiator and Sn(Oct)₂ as catalyst, then amphiphilic graft copolymers PEO-g-PCL were obtained. By changing the ratio of monomer and macroinitiator, a series of PEO-g-PCL with well-defined structure, molecular weight control, and narrow molecular weight distribution were prepared. The expected intermediates and final products were confirmed by ¹H NMR and GPC analyzes. In addition, these amphiphilic graft copolymers could form spherical aggregates in aqueous solution by self-assemble, which were characterized by transmission electron microscopy, and the critical micelle concentration values of graft copolymers PEO-g-PCL were also examined in this article.     

Porous and self-strengthened poly(ε-caprolactone)/calcium sulfate hemihydrate composite fibers for bone regeneration

Porous polycaprolactone (PCL)/calcium sulfate hemihydrate (CSH) composite fibers with different compositions were fabricated via electrospinning by using chloroform/dimethyl sulfoxide (volume ratio = 8:2) as the co-solvent. It was found that the incorporation of fine CSH powders greatly improved the morphology of the PCL fibers and generated continuous, bead-free PCL/CSH composite fibers with the pore diameter varying from 0.2 to 1.1 μm when 20% CSH was added. As compared with the PCL fibers, the PCL/CSH composite fibers also exhibited enhanced thermal stability and hydrophilicity. The tensile strength and elastic modulus of the PCL/CSH fibrous membranes first increased and then decreased with the increase of the CSH content, while their ductility exhibited a sustained decrease. Moreover, after immersion in water, the PCL-20%CSH composite fibers presented a much higher tensile strength than the pristine ones probably due to the self-setting of the CSH powders through the porous structure. In addition, the PCL-20%CSH composite fibers displayed a strong ability to form bone-like apatite after immersion in simulated body fluid for 3 days, which suggests their potential applications in bone tissue regeneration as a novel type of substitute.     

High-efficiency synthesis of dendrimer-like poly(ethylene oxide) via “arm-first” approach

In this study, a dendrimer-like polymer based on poly(ethylene oxide) (PEO) was synthesized through a combination of anionic ring-opening polymerization (AROP) and click reaction via arm-first method. Firstly, the polymeric arm, a linear PEO with one alkynyl group and two bromo groups, was synthesized by AROP of ethylene oxide followed by functionalization with propargyl bromide and esterified with 2-bromopropionic bromide. Second, a star PEO carrying three azide groups was synthesized though AROP of ethylene oxide used 1,1,1-tris(hydrosymethyl) ethane as initiator followed esterificated with 2-bromopropionic acid and azidation. By azide–alkyne click reactions between the azide-terminated PEO star polymer and linear PEO with functionalization alkynyl group, a three generation dendrimer-like PEO, G3-PEO-24Br, was successfully synthesized. The resulting polymers were observed to have precisely controlled molecular weights and compositions with narrow molecular weight distributions.     

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     

Preparation and the controlled release effect study of graphene oxide-modified poly(ε-caprolactone)

Functionalized graphene oxide-modified poly(ε-caprolactone) composites ((graphene oxide)GO/PCL) were successfully synthesized by Steglich esterification for drug applications of controlled release. Lomefloxacin (LMF) was selected as a model drug to investigate its controlled release properties. The controlled release effect of the LMF-contained pills of the GO/PCL and polylactic acid blend was evaluated. In contrast to the pure PCL, GO/PCL could effectively adjust the time of drug release and release the drug at a constant rate, achieving the controlled release requirements. Furthermore, different additive amounts of graphene oxide have different effects on adjusting the time of controlled release, while the best result obtained under the ratio is 4% GO/PCL as carrier of drug. Thus, high-quality drug carrier materials are obtained which are more suitable for clinical use. Exploring the optimum addition of graphene oxide is very significant for the development of GO/PCL carrier material.