Factors influencing the small‐scale melt spinning of poly(ε‐caprolactone) monofilament fibres

Some of the main factors affecting the small‐scale melt spinning of poly(ε‐caprolactone), PCL, monofilament fibres have been studied. These factors included spinning temperature, extrusion rate, take‐up rate and draw ratio. The underlying influence of the polymer's own characteristic properties, in particular its chemical structure, transition temperatures (T_g, T_m) and crystallizability, were also interpreted within the context of the melt spinning process. Physically, the as‐spun fibres obtained were uniform in diameter and smooth in surface appearance. They were also semi‐crystalline (>50%) in morphology. Mechanically, however, they were still very weak and highly extensible. Subsequent off‐line cold‐drawing at room temperature introduced the required degree of molecular orientation to reinforce the fibres, yielding tensile strengths of approaching 300 MPa. PCL fibres of precisely controlled physical dimensions and matrix morphology are attracting increasing interest for use in biomedical applications. This paper describes how this control can be achieved through the processing operation. Copyright © 2003 Society of Chemical Industry     

Electrospun poly(L‐lactide)/poly(ε‐caprolactone) blend fibers and their cellular response to adipose‐derived stem cells

Polymer blending is one of the most effective methods for providing new, desirable biocomposites for tissue‐engineering applications. In this study, electrospun poly(L ‐lactide)/poly(ε‐caprolactone) (PLLA/PCL) blend fibrous membranes with defect‐free morphology and uniform diameter were optimally prepared by a 1 : 1 ratio of PLLA/PCL blend under a solution concentration of 10 wt %, an applied voltage of 20 kV, and a tip‐to‐collector distance of 15 cm. The fibrous membranes also showed a porous structure and high ductility. Because of the rapid solidification of polymer solution during electrospinning, the crystallinity of electrospun PLLA/PCL blend fibers was much lower than that of the PLLA/PCL blend cast film. To obtain an initial understanding of biocompatibility, adipose‐derived stem cells (ADSCs) were used as seed cells to assess the cellular response, including morphology, proliferation, viability, attachment, and multilineage differentiation on the PLLA/PCL blend fibrous scaffold. Because of the good biocompatibility and nontoxic effect on ADSCs, the PLLA/PCL blend electrospun fibrous membrane provided a high‐performance scaffold for feasible application in tissue engineering using ADSCs. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Part 7. Effects of poly(L‐lactide‐co‐ϵ‐caprolactone) on morphology,structure, crystallization,and physical properties of blends of poly(L‐lactide) and poly(ϵ‐caprolactone)

Blended films of poly(L ‐lactide) [ie poly(L ‐lactic acid)] (PLLA) and poly(?‐caprolactone) (PCL) without or mixed with 10 wt% poly(L ‐lactide‐co‐?‐caprolactone) (PLLA‐CL) were prepared by solution‐casting. The effects of PLLA‐CL on the morphology, phase structure, crystallization, and mechanical properties of films have been investigated using polarization optical microscopy, scanning electron microscopy, differential scanning calorimetry and tensile testing. Addition of PLLA‐CL decreased number densities of spherulites in PLLA and PCL films, and improved the observability of spherulites and the smoothness of cross‐section of the PLLA/PCL blend film. The melting temperatures (T_m) of PLLA and PCL in the films remained unchanged upon addition of PLLA‐CL, while the crystallinities of PLLA and PCL increased at PLLA contents [X_PLLA = weight of PLLA/(weight of PLLA and PCL)] of 0.4–0.7 and at most of the X_PLLA values, respectively. The addition of PLLA‐CL improved the tensile strength and the Young modulus of the films at X_PLLA of 0.5–0.8 and of 0–0.1 and 0.5–0.8, respectively, and the elongation at break of the films at all the X_PLLA values. These findings strongly suggest that PLLA‐CL was miscible with PLLA and PCL, and that the dissolved PLLA‐CL in PLLA‐rich and PCL‐rich phases increased the compatibility between these two phases. © 2003 Society of Chemical Industry     

Poly(vinyl pyrrolidone‐co‐vinyl acetate)‐graft‐poly(ε‐caprolactone) as a compatibilizer for cellulose acetate/poly(ε‐caprolactone) blends

Poly(vinyl pyrrolidone‐co‐vinyl acetate)‐graft‐poly(ε‐caprolactone) (PVPVAc‐g‐PCL) was synthesized by radical copolymerization of N‐vinyl‐2‐pyrrolidone (VP)/vinyl acetate (VAc) comonomer and PCL macromonomer containing a reactive 2‐hydroxyethyl methacrylate terminal. The graft copolymer was designed in order to improve the interfacial adhesiveness of an immiscible blend system composed of cellulose acetate/poly(ε‐caprolactone) (CA/PCL). Adequate selections of preparation conditions led to successful acquisition of a series of graft copolymer samples with different values of molecular weight ( ), number of grafts (n), and segmental molecular weight of PVPVAc between adjacent grafts (M_n (between grafts)). Differential scanning calorimetry measurements gave a still immiscible indication for all of the ternary blends of CA/PCL/PVPVAc‐g‐PCL (72 : 18 : 10 in weight) that were prepared by using any of the copolymer samples as a compatibilizer. However, the incorporation enabled the CA/PCL (4 : 1) blend to be easily melt‐molded to give a visually homogeneous film sheet. This compatibilizing effect was found to be drastically enhanced when PVPVAc‐g‐PCLs of higher and M_n (between grafts) and lower n were employed. Scanning electron microscopy revealed that a uniform dispersion of the respective ingredients in the ternary blends was attainable with an assurance of the mixing scale of several hundreds of nanometers. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Enzymatic degradation of blends of poly(ε‐caprolactone) and poly(styrene‐co‐acrylonitrile) by Pseudomonas lipase

In polymer blends, the composition and microcrystalline structure of the blend near surfaces can be markedly different from the bulk properties. In this study, the enzymatic degradation of poly(ε‐caprolactone) (PCL) and its blends with poly(styrene‐co‐acrylonitrile) (SAN) was conducted in a phosphate buffer solution containing Pseudomonas lipase, and the degradation behavior was correlated with the surface properties and crystalline microstructure of the blends. The enzymatic degradation preferentially took place at the amorphous part of PCL film. The melt‐quenched PCL film with low crystallinity and small lamellar thickness showed a higher degradation rate compared with isothermally crystallized (at 36, 40, and 44°C) PCL films. Also, there was a vast difference in the enzymatic degradation behavior of pure PCL and PCL/SAN blends. The pure PCL showed 100% weight loss in a very short time (i.e., 72 h), whereas the PCL/SAN blend containing just 1% SAN showed ～50% weight loss and the degradation ceased, and the blend containing 40% SAN showed almost no weight loss. These results suggest that as degradation proceeds, the nondegradable SAN content increases at the surface of PCL/SAN films and prevents the lipase from attacking the biodegradable PCL chains. This phenomenon was observed even for a very high PCL content in the blend samples. In the blend with low PCL content, the inaccessibility of the amorphous interphase with high SAN content prevented the attack of lipase on the lamellae of PCL. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 868–879, 2002     

Synthesis and characterization of fullerene grafted poly(ε‐caprolactone)

The fullerene grafted poly(ε‐caprolactone) (PCL) was successfully synthesized with a graft efficiency of 80%. The fullerene moieties grafted onto the PCL chain aggregate into 1–2 μm particles so that a physical pseudo‐network is formed. Because of the existence of the network structure, the fullerene grafted PCL film can retain its shape at much higher temperatures than that of pure PCL film, as observed in dynamic mechanical tests. It shows a hydrophobic gelling behavior in chloroform solution. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Toward environment‐friendly composites of poly(ε‐caprolactone) reinforced with stereocomplex‐type poly(l‐lactide)/poly(d‐lactide)

In this work, stereocomplex‐poly(l ‐ and d ‐lactide) (sc‐PLA) was incorporated into poly(ε‐caprolactone) (PCL) to fabricate a novel biodegradable polymer composite. PCL/sc‐PLA composites were prepared by solution casting at sc‐PLA loadings of 5–30 wt %. Differential scanning calorimetry (DSC) and wide‐angle X‐ray diffraction (WAXD) demonstrated the formation of the stereocomplex in the blends. DSC and WAXD curves also indicated that the addition of sc‐PLA did not alter the crystal structure of PCL. Rheology and mechanical properties of neat PCL and the PCL/sc‐PLA composites were investigated in detail. Rheological measurements indicated that the composites exhibited evident solid‐like response in the low frequency region as the sc‐PLA loadings reached up to 20 wt %. Moreover, the long‐range motion of PCL chains was highly restrained. Dynamic mechanical analysis showed that the storage modulus (E′) of PCL in the composites was improved and the glass transition temperature values were hardly changed after the addition of sc‐PLA. Tensile tests showed that the Young's modulus, and yield strength of the composites were enhanced by the addition of sc‐PLA while the tensile strength and elongation at break were reduced. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40208.     

Properties and degradation behavior of surface functionalized MWCNT/poly(L‐lactide‐co‐ε‐caprolactone) biodegradable nanocomposites

In this research, poly(L ‐lactide‐co‐ε‐caprolactone) (PLACL) reinforced with well‐dispersed multiwalled carbon nanotubes (MWCNTs) nanocomposites were prepared by oxidization and functionalization of the MWCNT surfaces using oligomeric L ‐lactide (LA) and ε‐caprolactone (CL). It is found that the surface functionalization can effectively improve the dispersion and adhesion of MWCNTs in PLACL. The surface functionalization will have a significant effect on the physical, thermomechanical, and degradation properties of MWCNT/PLACL composites. The tensile modulus, yield stress, tensile strength, and elongation at break of composite increased 49%, 60%, 70%, and 94%, respectively, when the concentration of functionalized MWCNTs in composite is 2 wt %. The in vitro degradation rate of nanocomposites in phosphate buffer solution increased about 100%. The glass transition temperature (T_g) of composites was decreased when the concentration of functionalized MWCNTs is 0.5 wt %. With further increasing the concentration of functionalized MWCNTs, the T_g was increased. The degradation kinetics of nanocomposites can be engineered and functionalized by varying the contents of pristine or functionalized MWCNTs. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Enhanced crystallization of poly(L‐lactide‐co‐ε‐caprolactone) during storage at room temperature

Copolymer of L ‐lactide and ε‐caprolactone [P(LLA‐CL)] (50/50) was synthesized using stannous octoate and was stored at room temperature. The change in physical properties occurring during this storage at room temperature was investigated by differential scanning calorimetry (DSC), X‐ray diffractometry, polarizing optical microscopy, tensile and bending tests, and light absorbance measurements. It was concluded that the increase in mechanical properties and light absorbance during storage can be ascribed to gradual selective crystallization of the L ‐lactide sequence in P(LLA‐CL) at room temperature. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 947–953, 2000     

Melt rheology of poly(ϵ‐caprolactone)/poly(styrene‐co‐acrylonitrile) blends

Dynamic viscoelastic properties for miscible blends of poly(?‐caprolactone) (PCL) and poly(styrene‐co‐acrylonitrile) (SAN) were measured. It was found that the time–temperature superposition principle is applicable over the entire temperature range studied for the blends. The temperature dependency of the shift factors a_T can be expressed by the Williams–Landel–Ferry equation: log a_T = ?8.86(T ? T_s)/(101.6 + T ? T_s). The compositional dependency of T_s represents the Gordon–Taylor equation. The zero‐shear viscosities are found to increase concavely upward with an increase in weight fraction of SAN at constant temperature, but concavely downward at constant free volume fraction. It is concluded that the relaxation behavior of the PCL/SAN blends is similar to that of a blend consisting of homologous polymers. It is emphasized that the viscoelastic functions of the miscible blends should be compared in the iso‐free volume state. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2037–2041, 2001     

Thermal properties and crystallization behaviour of blends of poly(ε‐caprolactone) with chitin and chitosan

Blend films of poly(ε‐caprolactone) (PCL) with chitin and chitosan were prepared as completely biodegradable polyester/polysaccharide composites. Differential scanning calorimetry and Fourier‐transform infrared (FTIR) spectroscopy revealed that the crystallization of PCL, which had been suppressed by blending with chitin and chitosan, progressed with the elapse of time after film preparation. The suppression of crystallization of PCL by blending with polysaccharides was also observed by solid‐state ¹³C NMR spectroscopy. Furthermore, FTIR spectra indicated that the extent of hydrogen bonding between PCL and polysaccharides, which suppressed the crystallization of PCL, decreased with elapse of time after film preparation. Wide‐angle X‐ray diffraction indicated that the polysaccharides affected the crystallization of PCL and slightly deformed its crystalline lattice. Copyright © 2003 Society of Chemical Industry     

Synthesis of poly(vinyl alcohol)‐graft‐poly(ε‐caprolactone) and poly(vinyl alcohol)‐graft‐poly(lactide) in melt with magnesium hydride as catalyst

Grafting of poly(ε‐caprolactone) (PCL) and poly(lactide) (PLA) chains on poly(vinyl alcohol) backbone (PVA degree of hydrolysis 99%) was investigated using MgH₂ environmental catalyst and melt‐grown ring‐opening polymerization (ROP) of ε‐caprolactone (CL) and L ‐lactide (LA), that avoiding undesirable toxic catalyst and solvent. The ability of MgH₂ as catalyst as well as yield of reaction were discussed according to various PVA/CL/MgH₂ and PVA/LA/MgH₂ ratio. PVA‐g‐PCL and PVA‐g‐PLA were characterized by ¹H‐ and ¹³C‐NMR, DSC, SEC, IR. For graft copolymers easily soluble in tetrahydrofuran (THF) or chloroform, wettability and surface energy of cast film varied in relation with the length and number of hydrophobic chains. Aqueous solution of micelle‐like particles was realized by dissolution in THF then addition of water. Critical micelle concentration (CMC) decreased with hydrophobic chains. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Miscibility of block copolymers of poly(ε‐caprolactone) and poly(ethylene glycol) with poly(3‐hydroxybutyrate) as well as the compatibilizing effect of these copolymers in blends of poly(ε‐caprolactone) and poly(3‐hydroxybutyrate)

Atactic poly(3‐hydroxybutyrate) (a‐PHB) and block copolymers of poly(ethylene glycol) (PEG) with poly(ε‐caprolactone) (PCL‐b‐PEG) were synthesized through anionic polymerization and coordination polymerization, respectively. As demonstrated by differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA) measurements, both chemosynthesized a‐PHB and biosynthesized isotactic PHB (i‐PHB) are miscible with the PEG segment phase of PCL‐b‐PEGs. However, there is no evidence showing miscibility between both PHBs and the PCL segment phase of the copolymer even though PCL has been block‐copolymerized with PEG. Based on these results, PCL‐b‐PEG was added, as a compatibilizer, to both the PCL/a‐PHB blends and the PCL i‐PHB blends. The blend films were obtained through the evaporation of chloroform solutions of mixed components. Excitingly, the improvement in mechanical properties of PCL/PHB blends was achieved as anticipated initially upon the addition of PCL‐b‐PEG. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2600–2608, 2001     

Poly(ethyl glycol) assisting water sorption enhancement of poly(ε‐caprolactone) blend for drug delivery

Poly(ε‐caprolactone) (PCL) has been thermally synthesized, and then fractionated to blend with poly(ethyl glycol) (PEG). Blend films of PCL and PEG have been prepared by solution casting. Fourier transform infrared spectrum and differential scanning calorimetry of the films have been carried out, and the results indicate some hydrogen bonding interaction between the two components, which is resulted from the carbonyl groups of PCL and the hydroxyl end‐groups of the low‐molecular‐weight PEG. Scanning electron microscope images of the blend films reveal porous network structures for their surfaces and for their inner parts and the porous structure becomes more pronounced with the increase of PEG in the blend film. Ibuprofen (IBU) was used as the model drug to test the drug release behavior for the PCL/PEG blend matrices. The results show that IBU could be released from the blend tablets rapidly, and the release rate increases with PEG content. Analysis of the release profiles indicates PCL erosion control release mechanism of pure PCL tablet, but drug diffusion control of the blend tablet, because PEG can absorb water to allow water feasible to diffuse into drug core and dissolve drug. Therefore, the interconnected channels in the blend matrices and the hydrophilic nature of PEG contribute to the improvement of the IBU release rate. The research indicates that drug release rate from PCL based material could be efficiently improved by addition of small amount of hydrophilic low‐molecular‐weight PEG. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Transesterification in homogeneous poly(ε‐caprolactone)–epoxy blends

Transesterification has been investigated in poly(ε‐caprolactone) (PCL)–epoxy blends. In the hot melt process, the hydroxyl on diglycidyl ether of bisphenol‐A (DGEBA) monomers is too low to give a noticeable transesterification reaction. In the postcure process, model reactions reveal that the hydroxyls from a ring‐opening reaction are able to react with the esters of PCL. In the meantime, the PCL molecular weight decrease and its distribution becomes broader. Nuclear magnetic resonance spectra reveal that fraction of the tertiary hydroxyls converts to secondary hydroxyls. In the cured DGEBA–3,3′‐dimethylmethylene‐di(cyclohexylamine)–PCL blend, a homogeneous morphology is achieved. PCL segments are grafted onto the epoxy network after postcuring and result in the lower T_g observed in the differential scanning calorimetry thermogram. A higher transesterification extent also results in broader transition peaks by dynamic mechanical analysis. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 75–82, 1999     

Effect of peroxide crosslinking on thermal and mechanical properties of poly(ε‐caprolactone)

Poly(ε‐caprolactone) (PCL), a saturated polyester, derived from ring‐opening polymerization of ε‐caprolactone, was chemically crosslinked with various amounts of benzoyl peroxide (BPO) by a two‐step method by first evenly dispersing the BPO into the PCL matrix and then crosslinking at elevated temperature. The gel fraction increased with an increase in BPO content. The modified Charlesby–Pinner equation was used to calculate the ratio of chain scission and crosslinking. The results showed that both scission and crosslinking occurred, and that crosslinking predominated over scission. The number‐average molecular weight between the crosslinks determined by the rubber elasticity theory using the hot set test showed a decrease with increasing BPO content. The melting temperature and crystallinity decreased with an increase in BPO content, and the crystallization temperature increased after crosslinking. Dynamic mechanical analysis results showed a decrease in the glass transition temperature as a result of chemical crosslinking of PCL. This was explained by the observed reduction in crystallinity and the increase in free volume due to restrictions in chain packing. Moreover, Young's modulus and elongation at break generally decreased with an increase in BPO content, but the tensile strength first increased with BPO content up to 1.0 wt%, reached a maximum, and then decreased. Copyright © 2007 Society of Chemical Industry     

Study of the biodegradable poly(ε‐caprolactone)/clay nanocomposite foams

In this article, biodegradable poly(ε‐caprolactone)/layered silicate nanocomposites were prepared and characterized. The dispersion state of modified clay in PCL matrix and its effect on thermal, rheological and mechanical properties of PCL were studied. The PCL/clay nanocomposites were then foamed using chemical foaming method. Cellular parameters such as mean cell size, cell wall thickness and cell densities of nanocomposite foams with different clay loading were collected. Effect of layered silicate on the structure and mechanical properties of PCL foams were evaluated. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effects of plasma treatment on biocompatibility of poly[(L‐lactide)‐co‐(ϵ‐caprolactone)] and poly[(L‐lactide)‐co‐glycolide] electrospun nanofibrous membranes

Poly[(l ‐lactide)‐co ‐(? ‐caprolactone)] (PLCL) and poly[(l ‐lactide)‐co ‐glycolide] (PLGA) copolymers are widely used in neural guide tissue regeneration. In this research, the surface modification of their hydrophilicity was achieved using plasma treatment. Attachment and proliferation of olfactory ensheathing cells on treated electrospun membranes increased by 26 and 32%, respectively, compared to the untreated PLCL and PLGA counterparts. Cells cultivated on both the PLCL and PLGA membranes showed high viability (>95%) and healthy morphologies with no evidence of cytotoxic effects. Cells grown on treated electrospun fibres displayed significant increases in mitochondrial activity and reductions in membrane leakage when compared to untreated samples. The results suggested that plasma treatment of the surface of the polymers enhanced both cell viability and growth without incurring any cytotoxic effects. © 2017 Society of Chemical Industry     

Biodegradable studies of poly(trimethylenecarbonate‐ε‐caprolactone)‐block‐poly(p‐dioxanone), poly(dioxanone), and poly(glycolide‐ε‐caprolactone) (Monocryl®) monofilaments

The aim of the study was to investigate the mechanical properties and biodegradability of poly(trimethylenecarbonate‐ε‐caprolactone)‐block‐poly(p‐dioxanone) [P(TMC‐ε‐CL)‐block‐PDO] in comparison with poly(p‐dioxanone) and poly(glycolide‐ε‐caprolactone) (Monocryl®) monofilaments in vivo and in vitro. P(TMC‐ε‐CL)‐block‐PDO copolymer and poly(p‐dioxanone) were prepared by using ring‐opening polymerization reaction. The monofilament fibers were obtained using conventional melt spun methods. The physicochemical and mechanical properties, such as viscosity, molecular weight, crystallinity, and knot security, were studied. Tensile strength, breaking strength retention, and surface morphology of P(TMC‐ε‐CL)‐block‐PDO, poly(p‐dioxanone), and Monocryl monofilament fibers were studied by immersion in phosphate‐buffered distilled water (pH 7.2) at 37°C and in vivo. The implantation studies of absorbable suture strands were performed in gluteal muscle of rats. The polymers, P(TMC‐ε‐CL)‐block‐PDO, poly(p‐dioxanone), and Monocryl, were semicrystalline and showed 27, 32, and 34% crystallinity, respectively. Those mechanical properties of P(TMC‐ε‐CL)‐block‐PDO were comparatively lower than other polymers. The biodegradability of poly(dioxanone) homopolymer is much slower compared with that of two copolymers. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 737–743, 2006     

Synthesis and characterization of polyurethane elastomers based on chitosan and poly(ε‐caprolactone)

Biodegradable polyurethane (PU) elastomers with potential for biomedical and industrial applications were synthesized by the reaction of poly(ε‐caprolactone) (PCL) and isophorone diisocyanate (IPDI), extended with different mass ratio of chitosan and 1,4‐butane diol (BDO). Their chemical structures were characterized using FTIR, ¹HNMR, and ¹³CNMR, and thermal properties were determined by TGA and DMTA. Incorporation of chitosan contents into the polyurethane backbone caused improvement in thermal stability and thermal degradation rate. Optimum thermal properties and degradation profile were obtained from elastomer extended with chitosan. The crystallinity and hydrophilicity of the prepared polymers were also examined by X‐ray and contact angle measurements. The results showed that hydrophilicity decreased and crystallinity increased with increasing of chitosan content in polyurethane backbone. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009