Thermal Stabilities and the Thermal Degradation Kinetics of Poly(ε-Caprolactone)

The thermal degradation behavior of poly(ε-caprolactone) (PCL) in nitrogen atmosphere was investigated by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) techniques and Fourier Transform Infrared (FTIR) spectroscopy. TGA/DTG/DSC curves display only one main degradation step. TGA/FTIR results indicate PCL decomposes into CO₂ and hexanoic acid before 500°C. The activation energies were estimated by iterative isoconversional procedure. Friedman plot indicates a change in degradation mechanism. The differential method and integral method were used to confirm the exact kinetic mechanism. The best models are Dn (n = 1, 2, 3, and 4) when 0.08≤a≤0.2 and R2 when 0.25≤a≤0.8.     

Electrospun Poly(ε-Caprolactone)/Silk Fibroin Coaxial Core-Sheath Nanofibers Applied to Scaffolds and Drug Carriers

Developing biologically mimetic nanofibers (NFs) is crucial for their applications as scaffolds in tissue engineering and drug carriers. Herein, we present a strategy to facilely fabricate core-sheath NFs using coaxial electrospinning technique. Poly(ε-caprolactone) (PCL) and silk fibroin (SF) were employed as component materials to construct PCL/SF NFs with PCL cores uniformly encapsulated by SF sheaths. Scanning electron microscopy and transmission electron microscopy demonstrate a uniform core-sheath structure of the coaxial NFs. The engineered core-sheath structure confers the composite NFs with greatly improved properties including surface hydrophilicity and mechanical properties. In vitro cell culture validates that the core-sheath NFs are favorable to the cultured rat pheochromocytoma cells (PC 12) attachment. To further demonstrate the advantage of the coupled structural integrity, the PCL/SF core-sheath NFs were compared with the NFs produced from PCL and SF blend. Results showed that the PCL/SF NFs possessed a tensile strength of ~6.93 ± 0.52 MPa and an elongation at break of ~294.31 ± 24.17%, whereas the blend NFs possessed ~5.55 ± 0.50 MPa and ~88.05 ± 13.98%, respectively. Dexamethasone-phosphate sodium (DEX) was employed as a model drug, whereby the in vitro release study indicates that the NFs exhibit an ideal releasing profile, capable of releasing DEX continuously over a period of 450 h. The constructed PCL/SF core-sheath NFs are promising candidates for biomedical applications. POLYM. ENG. SCI., 60:802–809, 2020. © 2020 Society of Plastics Engineers     

A Novel Docetaxel-Loaded Poly (ε-Caprolactone)/Pluronic F68 Nanoparticle Overcoming Multidrug Resistance for Breast Cancer Treatment

Multidrug resistance (MDR) in tumor cells is a significant obstacle to the success of chemotherapy in many cancers. The purpose of this research is to test the possibility of docetaxel-loaded poly (ε-caprolactone)/Pluronic F68 (PCL/Pluronic F68) nanoparticles to overcome MDR in docetaxel-resistance human breast cancer cell line. Docetaxel-loaded nanoparticles were prepared by modified solvent displacement method using commercial PCL and self-synthesized PCL/Pluronic F68, respectively. PCL/Pluronic F68 nanoparticles were found to be of spherical shape with a rough and porous surface. The nanoparticles had an average size of around 200 nm with a narrow size distribution. The in vitro drug release profile of both nanoparticle formulations showed a biphasic release pattern. There was an increased level of uptake of PCL/Pluronic F68 nanoparticles in docetaxel-resistance human breast cancer cell line, MCF-7 TAX30, when compared with PCL nanoparticles. The cytotoxicity of PCL nanoparticles was higher than commercial Taxotere^® in the MCF-7 TAX30 cell culture, but the differences were not significant (p > 0.05). However, the PCL/Pluronic F68 nanoparticles achieved significantly higher level of cytotoxicity than both of PCL nanoparticles and Taxotere^® (p < 0.05), indicating docetaxel-loaded PCL/Pluronic F68 nanoparticles could overcome multidrug resistance in human breast cancer cells and therefore have considerable potential for treatment of breast cancer.     

Kinetic investigation and regularities during the synthesis of Poly(ε-caprolactam-co-ε-caprolactone) and Poly(ε-caprolactam-co-δ-valerolactone) biodegradable copolymers

Summary Large diversity of tailor-made poly[(ε-caprolactam)-co-(ε-caprolactone)] P[(CLA)-co-(CLO)] and poly[(ε-caprolactam)-co-(δ-valerolactone)] P[(CLA)-co-(VLO)] copolymers have been obtained via activated anionic polymerization of ε-caprolactam (CLA) with sodium caprolactam (NaCL) as a basic initiator. In the present study several poly(ε-caprolactones) (PCLOs) and poly(δ-valerolactone) polyols were employed as effective bifunctional polymeric activators (PACs) and suitable comonomers of CLA. The obtained poly(esteramides) PEAS were isolated and their structure was confirmed by the ¹H NMR and FTIR spectroscopy. The influence of the molecular weight and type of the PACs, the CLA/PAC ratio and polymerization conditions on the conversion, intrinsic viscosity and polymerization kinetic was explored. The results demonstrated that the use of the PACs reduces the polymerization time to several minutes and polymerization process proceeds without induction period at low energy of activation and high yield of copolymers. Evaluation of the PACs activity and the activation energy confirmed that the PACs are highly active compounds efficient to CLA features modification.     

Preparation of Electrospun Electroactive Nanofibers of Four Arm Star-Shaped Poly(ε-Caprolactone)-b-Poly(2-Hydroxyethyl Methacrylate) and Its Blends with Polyaniline

A combination of ring-opening polymerization and atom-transfer radical polymerization was used to synthesize a four-arm star-shaped poly(ε-caprolactone)-b-poly(2-hydroxyethyl methacrylate). The structure of obtained copolymer was determined by Fourier transform infrared, ¹H and ¹³C NMR spectroscopies. The uniform electroactive nanofibers consisting blend of four-arm star-shaped poly(ε-caprolactone)-b-poly(2-hydroxyethyl methacrylate) copolymer and polyaniline were produced using electrospinning technique. The electroactivity of prepared nanofibers was investigated using cyclic voltammetry measurement. The morphologies of electrospun nanofibers produced from four-arm star-shaped poly(ε-caprolactone)-b-poly(2-hydroxyethyl methacrylate) and their blends with polyaniline were investigated by the scanning electron microscopy. The presence of polyaniline resulted in significant decrease of sticking fibers.     

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

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

Poly(ε-caprolactone)-based additives: Plasticization efficacy and migration resistance

A family of poly(caprolactone) (PCL)-based oligomeric additives was evaluated as plasticizers for poly(vinyl chloride) (PVC). We found that the entire family of additives, which consist of a PCL core, diester linker, and alkyl chain cap, were effective plasticizers that improve migration resistance. The elongation at break and tensile strength of the blends made with the PCL-based additives were comparable to blends prepared with diisononyl phthalate (DINP), a plasticizer typically used industrially, and diheptyl succinate (DHPS), an alternative biodegradable plasticizer. Increasing concentration was found to decrease glass transition temperature (T_g) and increase elongation at break, confirming their role as functional plasticizers. We found that all of the PCL-based plasticizers exhibited significantly reduced leaching into hexanes compared to DINP and DHPS. The PCL-based plasticizers with shorter carbon chain lengths reduced leaching more than those with longer carbon chain lengths.     

Study on the Crystallization,Miscibility, Morphology,Properties of Poly(lactic acid)/Poly(ε-caprolactone) Blends

A series of blends of poly(lactic acid) (PLA) and poly(ε-caprolactone) (PCL) with different mass ratio were prepared by means of the melt blending method to study their crystallization, miscibility, morphology, and thermal and mechanical properties. The result of DSC tests showed that the melting temperatures of PLA and PCL shifted toward each other, and that the largest shift appeared at the PLA₇₀PCL₃₀ blend. This result reveals that the PLA₇₀PCL₃₀ blend gives the strongest interaction intensity among the blends. Combined the result of dynamic mechanical analysis and SEM morphologies, it was found that PLA and PCL form a partial miscible blend, in which an amount of amorphous PCL (amorphous PLA) is dissolved in the PLA-rich phase (PCL-rich phase), leading to a depression of the T_g. value. The polarized optical micrographs showed that PCL can serve as a nucleating agent to promote PLA crystallization in the PLA/PCL blend. Moreover, the PLA₇₀PCL₃₀ blend gave the largest growth rate of PLA spherulite. Finally, the mechanical property of PLA/PCL blends indicated that PLA can easily be tuned from rigid to ductile by the addition of PCL.     

Development and Assessment of Electrospun Poly(ε-caprolactone)–Poly(vinylalcohol) Blend Nanofibers for Pest Control in Stored Products

l-Carvone is a constituent of essential oil consisting of monoterpene ketone that possesses various medicinal properties. In this context, the present study focuses on the fabrication and assessment of electrospun poly(ε-caprolactone)–poly(vinylalcohol blend nanofibers imbibed with l-Carvone (5%, w/v) that served as a suitable polymeric carrier to preserve the antimicrobial and antioxidant activities of l-Carvone for a longer period of time. The fumigant potential of l-Carvone and C-PP fibers were assessed toward saw-toothed beetle, a major pest found in stored products. The prepared fragrant C-PP fibers displayed a promising potential formulation for the control of stored product pest such as saw-toothed beetle.     

One-Pot Synthesis of Poly(linoleic acid)-g-Poly(styrene)-g-Poly(ε-caprolactone) Graft Copolymers

One-pot synthesis of graft copolymers by ring-opening polymerization and free radical polymerization using polymeric linoleic acid peroxide (PLina) is reported. Graft copolymers having structures of poly(linoleic acid)-g-polystyrene-g-poly(ε-caprolactone) were synthesized from PLina, possessing peroxide groups on the main chain by the combination of free radical polymerization of styrene and ring-opening polymerization of ε-caprolactone in one-step. Principal parameters, such as monomer concentration, initiator concentration, and polymerization time, which effect the one-pot polymerization reactions were evaluated. The obtained graft copolymers were characterized by ¹H-NMR and DOSY-NMR spectroscopy, gel permeation chromatography, thermal gravimetric analysis and differential scanning calorimetry techniques.     

Poly(ε-caprolactone) diol functionalized with a cinnamoyl group and its UV-triggered in-plane alignment

Stimuli-sensitive biomaterials can present variable and tailored functions under specific external stimuli, thus showing potential for application in various biosciences. Significant efforts have focused on the utilization of light as a stimulus in biomedical applications because of its unique advantages, especially the precise control over its position, movement, and non-contact irradiation. This article highlights the preparation of a photo-reactive oligomer composed of biodegradable moieties and its UV-triggered in-plane molecular orientation, implicating its surface as a potential molecular alignment layer. We focus especially on the alignment of nematic liquid crystalline (LC) molecules on the biodegradable layer with molecular orientation, because they are promising candidates for sensing and interfacial applications.     

Adhesion at Poly(Butylacrylate)–Poly(Dimethylsiloxane) Interfaces

We present an investigation of the adhesion modulation mechanisms of silica-like nanoparticles (MQ resins) incorporated in polydimethylsiloxane (PDMS) elastomers and acrylic adhesives. The Johnson-Kendall-Roberts (JKR) test has been used to gain information on the both zero velocity and the velocity dependence of the adhesive strength, avoiding as much as possible contributions to the adhesive strength of bulk dissipation in the adhesive (which is not the case with peel tests). As the incorporation of the MQ resins into the elastomers deeply affects their own mechanical properties, the loading and unloading curves of small poly(butylacrylate) (PBA) lenses on either PDMS elastomers, adsorbed PDMS and pure MQ resin layers are compared in a systematic manner. The PBA chains are observed to have a neat affinity for the MQ resin nanoparticles. When MQ resins are present at the interface, they tend to prevent facture propagation, thus producing a larger deformation of the PBA lens. The modulation of adhesion is then dominated by the corresponding dissipation inside the acrylic adhesive.     

Cytotoxicity and Compatibility of Polymeric Blend: Evaluation of the Cytotoxicity in Fibroblast Bovine Cells and Compatibility of Poly(ɛ-Caprolactone)/Poly(Methyl Methacrylate-co-Butyl Methacrylate) Blend Films

Blends between poly(?-caprolactone) and poly(methyl methacrylate-co-butyl methacrylate) were prepared by solution blending in the presence of dichloromethane as solvent. The compatibility of the blends was studied by Fourier-transform infrared spectroscopy, Raman spectroscopy, micro-Raman imaging, and thermogravimetric analysis. Cytotoxicity assays were also performed to assess the feasibility of using such materials in veterinary devices. Based on results, we conclude that poly(?-caprolactone) and poly(methyl methacrylate-co-butyl methacrylate)-form compatible blends owing to specific interactions between carbonyl groups of poly(methyl methacrylate-co-butyl methacrylate) and hydrogens present in the polymeric chain of poly(?-caprolactone). Furthermore, these materials were not toxic to bovine fibroblasts, which supports their possible use in cattle veterinary devices.     

Poly(ε-caprolactone) Diols (HOPCLOH) and Their Poly(ester-urethanes) (PEUs): The Effect of Linear Aliphatic Diols [HO–(CH2)m–OH] as Initiators

α,ω-Hydroxy telechelic poly(ε-caprolactones) were prepared by ring-opening polymerization of the ε-caprolactone catalyzed by ammonium decamolybdate in the presence of different aliphatic diols [HO–(CH₂)_m–OH, where m?=?2, 4, 6, 8, 10, 12, 14, and 16] as initiators to obtain a family of α,ω-hydroxy telechelic poly(ε-caprolactone) [HO–PCL–O–(CH₂)_m–O–PCL–OH, m?=?2, 4, 6, 8, 10, 12, 14, and 16]. The content of the alkyl group (AG) (–(CH₂)_m–) had an important effect on the crystallinity (x_i) of α,ω-hydroxy telechelic poly(ε-caprolactone), showing a proportional relationship. In poly(ester-urethanes) derived from α,ω-hydroxy telechelic poly(ε-caprolactones) and 1,6-hexamethylene diisocyanate, the AG also showed a similar effect on the x_i and eventually on the mechanical properties, increasing the values of the modulus. Therefore, AG content was a factor to induce a plastic behavior in poly(ester-urethanes). The effect of AG on the water uptake of poly(ester-urethanes) after 1 week was negligible.     

Poly(ε-caprolactone)-block-poly(N-vinyl pyrrolidone) diblock copolymers grafted from macrocyclic oligomeric silsesquioxane

Poly(ε-caprolactone)-block-poly(N-vinyl pyrrolidone) diblock copolymers grafted from macrocyclic oligomeric silsesquioxane (MOSS) (denoted MOSS[PCL-b-PVPy]₁₂) were synthesized via the sequential polymerizations involving ring-opening polymerization (ROP) of ε-caprolactone (CL) and RAFT/MADIX polymerization of N-vinyl pyrrolidone (NVP). The organic-inorganic brush-like diblock copolymers were characterized by means of nuclear magnetic resonance spectroscopy (NMR) and gel permeation chromatography (GPC). Small angle X-ray scattering (SAXS) showed that all the MOSS[PCL-b-PVPy]₁₂ was microphase-separated in the amorphous state. The microphase-separated morphologies were quite dependent on the length of PVPy blocks and the crystallization behavior of PCL subchains was significantly affected by the lengths of PVPy subchains. In aqueous solutions, the MOSS[PCL-b-PVPy]₁₂ can be self-assembled into the polymeric micelles as evidenced by dynamic light scattering (DLS) and transmission election microscopy (TEM). The critical micelle concentrations of the brush-like diblock copolymers increased with increasing the lengths of PVPy blocks. It is proposed that the stability of the micellar cores was increased with the macrocyclic molecular brush structure of the diblock copolymers and the formation of the MOSS aggregates via MOSS–MOSS interactions.     

Effect of Surface Modification of Nano-Hydroxyapatite Particles on In Vitro Biocompatibility of Poly (ϵ-Caprolactone)–Matrix Composite Biomaterials

Three silane coupling agents were employed to modify the surfaces of nano-hydroxyapatite particles. Alamar Blue activity and alkaline phosphatase assay on the surfaces of the modified n-HA/PCL composites were carefully examined. The results showed that the KH792 silane modification had positively impact in interaction between bone marrow cells, and it suggested this KH792 modified composite was basically biocompatible with bone cells of rats.     

Application of Poly(acetic Acid)–Based Graft Copolymer as a Compatibilizer for Poly(L-lactic Acid)/Poly(butylenesuccinate) Blend System

Poly(L-lactic acid) (PLLA) was blended with poly(butylenesuccinate) (PBS) using a single-screw extruder to modify the poor characteristics of these polymers. Furthermore, when both polymers were blended, the graft copolymer that was synthesized by partially saponified poly(vinyl alcohol) (PSPVA) and ?-caprolactone (?-CL) was used as a novel compatibilizer. The structure of the synthesized compatibilizer was determined by ¹H or ¹³C NMR. From this result, the ring-opening polymerization of the ?-CL occurred at the hydroxyl group of PSPVA. The structures of the PLLA/PBS solvent-cast blended films could be observed via an optical microscope. From the optical microscopic observation, the structures of the solvent-cast blended films with the synthesized compatibilizer were more homogeneous than those of the solvent-cast blended films without the compatibilizer. The mechanical properties of the PLLA/PBS extruded blended films were determined by a tensile test. The result showed the tensile strength of the blended films with the synthesized compatibilizer was greater than that of the blended films without the compatibilizer.     

Preparation and Properties of Biodegradable Shape Memory Polylactic Acid/Poly(ε-caprolactone) Blends under Volume Elongational Deformation

In this work, a novel eccentric rotor mixer (ERM), which can generate circulating volume elongational deformation, is employed to prepare biodegradable polylactic acid (PLA)/poly(ε-caprolactone) (PCL) thermo-responsive shape-memory blends without a compatibilizer. The results of scanning electron microscopy (SEM) show that the ERM has more efficient dispersion and compatibilization for blends than conventional Banbury mixers, which is beneficial for shape-memory performance. The results of Fourier transform infrared (FTIR) and differential scanning calorimetry (DSC) also confirm the consequences. Then, morphological and mechanical properties and shape memory behaviors of the blends are investigated in detail. Co-continuous morphology is found on EF-PLA50. The blends exhibit remarkable shape-memory performance. The bending shape fixing ratio and recovery ratio of the blends are more than 94% and are still more than 90% after five shape memory cycles. With the increase of PLA content, the shape fixing ratio of blends decreases, while the shape recovery ratio increases and the shape recovery time becomes shorter. All the blends show good mechanical properties.     

Structure and Performance of Poly(vinyl alcohol)/Poly(γ-benzyl L-glutamate) Blend Membranes

Poly(vinyl alcohol) (PVA)/poly(γ-benzyl L-glutamate) (PBLG) blend membranes with different PBLG wt contents were prepared by pervaporation. Structure and surface morphologies of PVA/PBLG blend membranes were investigated by Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). Thermal, mechanical, and chemical properties of PVA/PBLG blend membrane were studied by differential scanning calorimeter (DSC), tensile strength tests, and other physical methods. It was revealed that the introduction of PBLG homopolymer into PVA could exert an outstanding effect on the properties of PVA membrane.     

Poly(Vinylpyrrolidone)-Embedded Bismuth Ferrite—Poly(Vinylidene Fluoride-co-Hexafluoropropylene) Composites with Enhanced Dielectric Properties

The dielectric properties of poly(vinylpyrrolidone) (PVP)-modified bismuth ferrite (BFO) particles in the poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP) matrix were prepared through solution casting techniques. The composites showed enhanced dielectric constant (90) and reduced dielectric loss (<0.5) at 40?wt% of PVP-modified BFO particles. The dielectric constant of the resultant composites with PVP-modified BFO was much higher as compared to that of unmodified BFO-P(VDF-HFP) composites. The maximum remnant polarization reached (2Pr?～?1.12?µC?cm^?2) in the PVP-modified BFO-P(VDF-HFP) composites. The demonstrated approach might provide a route for using PVP-modified BFO particles to enhance the dielectric and ferroelectric performance of the composites.