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).     

Effect of crosslinking monomers on the performance of electron beam-induced biodegradable Bionolle–rubber blends

To find out the better crosslinking monomer for vulcanization of natural rubber under electron beam (EB) radiation, the dry rubber was masticated with different polyfunctional monomers like TMPTA, NVP, and ethylene glycol diacrylate of different numbers of CH₂ CH₂ O group, such as 1G, 3G, 7G, and 10 G. The masticated films were irradiated with different doses under EB at 10 kGy/pass. The highest tensile strength (25 MPa) of the rubber was observed in the presence of TMPTA (3phr) at 150 kGy dose. The gel content of the rubber increased with an increase of dose. Bionolle was mixed with the masticated rubber containing 3 phr TMPTA at different proportions; films of these blends along with Bionolle were irradiated under EB with different doses. The concentration of rubber in Bionolle and radiation dose were optimized. The elastomer with 5% masticated showed the highest tensile strength (62 MPa). The gel content of the blends was found to increase with an increase of radiation dose as well as rubber concentration in Bionolle. The elastomers or blends were found to possess good thermal properties. The elastomers exhibited a much lower loss of tensile strength due to the thermal aging compared with pure Bionolle. The elastomers sustained their original shape for 300 min at 180°C, whereas Bionolle sustained its shape for only 3 min at 120°C under the same load (50 g). Among all the elastomers, 5% rubber containing elastomer was found to be better in all respects. It was observed from scanning electron microscopy and differential scanning calorimetry studies that 5% rubber is well mixed with Bionolle. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 799–807, 2001     

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.     

Single-component poly(ε-caprolactone) composites

Non-covalently bonded crystalline inclusion compounds (ICs) have been formed by threading host cyclic starches, α-cyclodextrins (α-CDs), onto guest poly(ε-caprolactone) (PCL) chains and by co-crystallization of guest PCL and host urea (U). PCLs were coalesced from both ICs by appropriate removal of the α-CD and U hosts. When added at low concentrations, PCL coalesced from its α-CD–IC served as an effective self-nucleating agent for the bulk crystallization of as-received PCL from the melt. Film sandwiches consisting of two layers of as-received (asr) (control), and one layer each of asr and self-nucleated (nuc) (composite) PCLs were produced by melt pressing. A composite sandwich consisting of a film of neat PCL coalesced from its U–IC (c-PCL) and a film of asr-PCL was also melt pressed. DSC showed that both composite films maintain their characteristic structures and properties even after melt-pressing them together. Both single component film sandwiches exhibited strong interfaces and better mechanical properties than the asr-PCL/asr-PCL control composite sandwiches. These results are similar to those previously obtained on similarly prepared nylon-6 (N-6) sandwich composites made with asr- and nuc-N-6 films with the same levels of crystallinity. However, while the elongation at break was greatly reduced in the asr-N-6/nuc-N-6 composite, asr-/asr-, asr-/c-, and asr-/nuc-, PCL/PCL-composites all showed similarly large elongations at break. The above room temperature and well below room temperature glass-transition temperatures of N-6 and PCL are likely the cause of their widely different elongations at break.     

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     

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.     

Stability of nanocomposites of poly(ε-caprolactone) with tungsten trioxide

Nanocomposites of poly(ε-caprolactone) (PCL) and tungsten trioxide (WO₃) were prepared by solvent casting using 5 and 10% of WO₃ nanoparticles. The nanocomposites were characterized using several analytical techniques such as XRD, SEM, thermal analysis (TGA and DSC), spectroscopic methods (FTIR and UV/Vis) to gather information on the modifications introduced by WO₃. Photodegradation of PCL/WO₃ nanocomposites was studied exposing the samples to a Xenon lamp, which simulates the UV spectrum of the sun. The results obtained showed that due to the incorporation of WO₃ nanoparticles, the nanocomposites exhibit higher thermal stability together with higher photodegradation efficiency.     

Interfacial characteristics of poly(ε-caprolactone)-grafted-halloysites nanotubes bionanocomposites

Dielectric and thermal characterization of nanohybrid films based on poly(ε-caprolactone) biopolymer were investigated. Nano-composites samples with distinct loadings of halloysite nanotubes (HNT) were prepared by in situ Ring Opening Polymerisation of ε-caprolactone. The effect of the incorporated HNT on the molecular relaxation process and interfacial polarization of PCL was studied via broadband dielectric spectroscopy (BDS) on a frequency domain starting from 1E-1 to 1E6 Hz and at temperatures ranging from −70°C to 50°C. The BDS measurements revealed four significant dielectric processes α-primary relaxation attributed to glass transition, β-secondary relaxation and two interfacial polarizations due to the semi-crystalline character of PCL and the added HNT fillers. According to our results, the weight ratio of HNT ranging between 3% and 5% is recommended for achieving the highest performing nanocomposite that can be used in several applications.     

Two-way reversible shape memory behaviour of crosslinked poly(ε-caprolactone)

Polymers capable of reversible “two-way” shape memory behaviour are of great interest for applications where reversible actuation is demanded, and semicrystalline crosslinked systems have been indicated as an interesting solution towards this end. In this work we have explored the two-way shape memory response of semicrystalline poly(ε-caprolactone)-based polymer networks, prepared with various macromolecular architectures starting from linear, three- and four-arm star poly(ε-caprolactone) functionalized with methacrylate end-groups. All the materials have revealed two-way shape memory capabilities. The effect arises from an elongation process that takes place when the material is cooled under an applied load below the crystallization temperature, and that is completely reversed when heated again above melting temperature, in a manner that strongly depends on the applied load and on the material crosslink density. Two-dimensional XRD analysis, carried out on elongated specimens, shows that the elongation on cooling is accompanied by a change in the crystallinity orientation along the direction of stretch.     

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.     

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.     

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.     

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     

Hydrolysis behaviour of crosslinked poly(ester anhydride) networks prepared from functionalised poly(ε-caprolactone) precursors

Biodegradable poly(ester anhydride) networks based on functionalised poly(ε-caprolactone) precursors with different hydrophobicities, molecular weights and architectures were synthesised. Networks that were prepared from the star-shaped precursors clearly showed higher gel contents and crosslinking densities than the networks that were prepared from the linear precursors. Functionalising with different alkenylsuccinic anhydrides and/or varying the molecular weight of the precursor, the thermal properties, surface hydrophobicity and erosion of the crosslinked networks were widely tailored. The dissolution behaviour of the networks changed dramatically as the molecular weight of the precursor increased from 2000 to 4000 g/mol or the alkenyl chain of the alkenylsuccinic anhydride increased from 8 to 18 carbons. The networks that were prepared from the lower molecular weight precursors, without an alkenyl chain or with an 8 carbon alkenyl chain, lost their mass in a few days, whereas the networks that were prepared from higher molecular weight precursors or contained a hydrophobic 18 carbon alkenyl chain did not show any mass loss over a period of 8 weeks.     

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.     

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.     

Functionalization of agglomerating nanodiamonds with biodegradable poly(ε-caprolactone) through surface-initiated polymerization

Nanodiamond (ND) has been widely used in various applications because of its unique and outstanding properties. However, serious aggregation of ND limits its further applications. Two approaches, namely, hexamethylene diisocyanate (HDI) modification and acyl chloride modification, were developed to graft biodegradable poly(ε-caprolactone) (PCL) from ND surface through ring-opening polymerization of ε-caprolactone (CL) initiated by tin(II) 2-ethylhexanoate. Both FTIR and Raman results reveal that the PCL chains are covalently bonded to the NDs, and the proportion by weight of PCL gains 21.47% and 24.21%, respectively, as determined by thermogravimetric analysis. The functionalized NDs with long biopolymer chains can be easily and stably dispersed in various solvents. Dynamic light scattering analysis, TEM images, dispersion stability test and CDD images demonstrate that the dispersion and hydrophobicity of NDs have been significantly improved after modification with PCL. The NDs modified by PCL provide a new method to functionalize and deaggregate ND particles, and thus a new prospect of multipurpose applications both in biomedical systems and in other fields.     

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.