PCL Diol Research Articles

Bio‐based Biodegradable and Biocompatible Hyperbranched Polyurethane: A Scaffold for Tissue Engineering

Hyperbranched polyurethanes are synthesized using TDI, PCL diol, butanediol, and pentaerythritol (1-5 wt%) as the B(4) reactant with and without the monoglyceride of sunflower oil. The biodegradation, physico-mechanical, and thermal properties are found to be tailored by varying the percentage weight of the branching unit. An MTT/hemolytic assay and subcutaneous implantation in Wistar rats followed by cytokine/ALP assay and histopathology studies confirm a better biocompatibility of HBPU with MG than without MG. HBPU supports the proliferation of dermatocytes with no toxic effect in major organs, in addition the in vitro degraded products are non-toxic. Cell adherence and proliferation endorse the bio-based HBPU as a prospective scaffold material in the niche of tissue engineering.

Catalyst-free synthesis of high elongation degradable polyurethanes containing varying ratios of isosorbide and polycaprolactone: physical properties and biocompatibility

Biocompatible and biodegradable polyurethanes were prepared with fixed aliphatic diisocyanate level and varying ratios of isosorbide, and PCL diol via a simple one-shot polymerization without a catalyst. The successful synthesis of the polyurethanes was confirmed by gel permeation chromatography, (1)H-nuclear magnetic resonance and Fourier transform-infrared spectroscopies and the thermal properties were determined by differential scanning calorimetry and showed glass transition temperatures of around 30-35 °C. The degradation tests were performed at 37 °C in phosphate buffer solution (approx. pH 7.3) and showed a mass loss of around 5 % after 12 weeks, except for the polymer with the highest isosorbide content which showed an initial rapid mass loss. The in vitro cytocompatibility test results following culture of osteoblasts on the polymer surface showed that relative cell number on all of the polyurethane films after 5 days of cultured on polymer films was lower compared to the proliferation rate on the optimized tissue culture plastic. These polymers offer significant promise due to the simplicity of the synthesis and the controlled degradation.

Physical characterization and rheological behavior of polyurethane/poly(ϵ‐caprolactone) blends, prepared by solution blending using dimethylacetamide

AbstractBlending effects of thermoplastic polyurethane based on polycaprolactone diol, PU (PCL diol), and poly (ϵ‐caprolactone) (PCL) on the rheological properties and morphological behavior of the solvent‐cast blends were investigated by parallel plate rheometer. The amount of PCL was varied from 20 to 50% by weight. Fourier transform infrared (FTIR) results showed existence of hydrogen bonding in PU/PCL blends. From FTIR, we also found the increase of PCL composition tends to reduction of intermolecular hydrogen bonding and enhancing of microphase separation in blends. Differential scanning calorimetry (DSC) indicated that these blend systems are partially miscible. Based on rheological characterization, decrease can be seen in the moduli, zero shear viscosity and plateau modulus of blends, as compared with net PU. Using Cole‐Cole plots and composition dependencies of η0 and the other viscoelastic functions expressed variation of morphology of blends due to increase of PCL content. Frequency sweep tests on PU/PCL (80/20) at five temperatures showed validity of time‐temperature superposition in this blend. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Thermoresponsive Semicrystalline Poly(ε-caprolactone) Networks: Exploiting Cross-linking with Cinnamoyl Moieties to Design Polymers with Tunable Shape Memory

The overall goal of this study was to synthesize semicrystalline poly(ε-caprolactone) (PCL) copolymer networks with stimuli-responsive shape memory behavior. Herein, we investigate the influence of a cinnamoyl moiety to design shape memory polymer networks with tunable transition temperatures. The effect of various copolymer architectures (random or ABA triblock), the molecular weight of the crystalline domains, PCL diol, (M(w) 1250 or 2000 g mol(-1)) and its composition in the triblock (50 or 80 mol %) were also investigated. The polymer microstructures were confirmed by NMR, DSC, WAXS and UV-vis spectroscopic techniques. The thermal and mechanical properties and the cross-linking density of the networks were characterized by DSC, tensile testing and solvent swelling, respectively. Detailed thermomechanical investigations conducted using DMA showed that shape memory behavior was obtained only in the ABA triblock copolymers. The best shape memory fixity, R(f) of ~99% and shape recovery, R(r) of ~99% was obtained when PCL diol with M(w) 2000 g mol(-1) was incorporated in the triblock copolymer at a concentration of 50 mol %. The series of triblock copolymers with PCL at 50 mol % also showed mechanical properties with tunable shape memory transition temperatures, ranging from 54 °C to close to body temperature. Our work establishes a general design concept for inducing a shape memory effect into any semicrystalline polyester network. More specifically, it can be applied to systems which have the highest transition temperature closest to the application temperature. An advantage of our novel copolymers is their ability to be cross-linked with UV radiation without any initiator or chemical cross-linker. Possible applications are envisioned in the area of endovascular treatment of ischemic stroke and cerebrovascular aneurysms, and for femoral stents.

A biocompatible composite based on poly(ε‐caprolactone fumarate) and hydroxyapatite

AbstractFabrication of biodegradable composites applicable as hard tissue substitutes consisting of poly(ε‐caprolactone fumarate) (PCLF), methacrylic acid (MAA), and hydroxyapatite (HA) was investigated. PCLF macromers were synthesized by reaction of PCL diol with fumaryl chloride in the presence of propylene oxide and characterized by gel permeation chromatography, FTIR, and 1H NMR spectroscopy. Composites were fabricated by incorporating HA as inorganic filler in PCLF matrix which followed by thermal curing of the composition using benzoyl peroxide and MAA as a free radical initiator and reactive diluent, respectively. Uniform distribution of the fine ceramic phase in the polymer matrix was elucidated by scanning electron microscopy. The effects of the initial macromer molecular weight and the filler volume fraction on mechanical properties and cytotoxicity of the composites were also examined. Significant enhancement in the mechanical properties was observed upon increasing HA content and/or initial PCLF molecular weight. The biocompatibility of the specimens was also improved with increasing ceramic phase. Copyright © 2010 John Wiley & Sons, Ltd.

Parabolic dependence of material properties and cell behavior on the composition of polymer networks via simultaneously controlling crosslinking density and crystallinity

A systematic investigation was performed on regulating materials properties and cell behavior using hybrid networks composed of amorphous poly(propylene fumarate) (PPF) and three poly(ɛ-caprolactone) diacrylates (PCLDAs) with variance in crystallinity and melting temperature. Through controlling both crosslinking density and crystallinity in the photo-crosslinked PPF/PCLDA blends, mechanical properties could be tuned efficiently in a wide range. For PCLDA synthesized from a low-molecular weight PCL diol precursor with a low crystallinity and a low melting point, crosslinks could completely suppress crystalline domains over the composition range in the PPF/PCLDA networks. Consequently, tensile, shear, torsional, and compression moduli all increased with the composition of PPF or the crosslinking density continuously for amorphous PPF/PCLDA networks. For PCLDAs synthesized using two PCL diols with higher molecular weights, crystallinity remained for the PCLDA compositions between ∼80% and 100%. Minimum moduli and tensile stress at break were found at the lowest required composition of PPF for suppressing crystallinity. Surface physicochemical properties and morphology of the crosslinked blend disks have been characterized and their capabilities of adsorbing proteins from cell culture medium have been determined. Using both mouse MC3T3-E1 cells and rat Schwann cell precursor line (SpL201) cells, cell responses to these polymer networks such as cell adhesion, spreading, and proliferation were found to be dramatically distinct on different polymer networks and demonstrated non-monotonic or parabolic dependence on the network composition, coincident with the composition dependence of the mechanical properties.

Photocurable Shape‐Memory Copolymers of ε‐Caprolactone and L‐Lactide

AbstractBiodegradable and photocurable block copolymers of ε‐caprolactone and L‐lactide were synthesized by polycondensation of PLLA diol ($\overline {M} _{{\rm n}} $ = 10 000 g · mol−1), PCL diol ($\overline {M} _{{\rm n}} $ = 10 000 g · mol−1), and a chain extender bearing a coumarin group. The effect of copolymer composition on the thermal and mechanical properties of the photocured copolymers was studied by means of DSC and cyclic tensile tests. An increase in Young's modulus and a decrease in the tensile strain with increasing PLLA content was observed for the block copolymers. Block copolymers with high PCL content showed good to excellent shape‐memory properties. Random copolymers exhibited Rf and Rr values above 90% at 45 °C for an extremely large tensile strain of 1 000%.magnified image

Reinforcing Poly(ε-caprolactone) Nanofibers with Cellulose Nanocrystals

We studied the use of cellulose nanocrystals (CNXs) obtained after acid hydrolysis of ramie cellulose fibers to reinforce poly(epsilon-caprolactone) (PCL) nanofibers. Chemical grafting with low-molecular-weight PCL diol onto the CNXs was carried out in an attempt to improve the interfacial adhesion with the fiber matrix. Grafting was confirmed via infrared spectroscopy and thermogravimetric analyses. The polymer matrix consisted of electrospun nanofibers that were collected as nonwoven webs. The morphology as well as thermal and mechanical properties of filled and unfilled nanofibers were elucidated by scanning electron microscopy, differential scanning calorimetry, and dynamic mechanical analysis, respectively. The addition of CNXs into PCL produced minimal changes in the thermal behavior of the electrospun fibers. However, a significant improvement in the mechanical properties of the nanofibers after reinforcement with unmodified CNXs was confirmed. Fiber webs from PCL reinforced with 2.5% unmodified CNXs showed ca. 1.5-fold increase in Young's modulus and the ultimate strength compared to PCL webs. Compared to the case of grafted nanocrystals, the unmodified ones imparted better morphological homogeneity to the nanofibrillar structure. The grafted nanocrystals had a negative effect on the morphology of nonwoven webs in which individual nanofibers became annealed during the electrospinning process and, therefore, could not be compared to neat PCL nonwoven webs. A rationalization for the different effects of grafted and unmodified CNXs in reinforcing PCL nanofibers is provided.

Deposition of Biodegradable Polycaprolactone Coatings Using an In‐line Atmospheric Pressure Plasma System

AbstractPolycaprolactone (PCL) is a biodegradable and bioresorbable polymer with applications ranging from use in packaging to medical sutures. In this study, the use of an atmospheric pressure plasma to deposit plasma polymerised PCL (P‐PCL) coatings from a PCL diol precursor is evaluated. Fourier transform infrared spectroscopy demonstrated the retention of PCL functional groups in the deposited coating. Changes in coating surface energy were monitored with time after deposition using the contact angle technique. The rate of degradation of 500 nm thick P‐PCL coatings was assessed after immersion in a phosphate‐buffered saline (PBS) solution at 37 °C. It was observed that slower rates of P‐PCL coating degradation were obtained for coatings deposited at higher applied powers and lower precursor flow rates.

The roles of matrix polymer crystallinity and hydroxyapatite nanoparticles in modulating material properties of photo-crosslinked composites and bone marrow stromal cell responses

Two poly(ɛ-caprolactone fumarate)s (PCLFs) with distinct physical properties have been employed to prepare nanocomposites with hydroxyapatite (HA) nanoparticles via photo-crosslinking. The two PCLFs are PCLF530 and PCLF2000, named after their precursor PCL diol with molecular weight of 530 and 2000 g mol −1, respectively. Crosslinked PCLF530 is amorphous while crosslinked PCLF2000 is semi-crystalline with a melting temperature ( T m) of ∼40 °C and a crystallinity of 40%. Consequently, the rheological and mechanical properties of crosslinked PCLF2000 are significantly greater than those of crosslinked PCLF530. Structural characterizations and physical properties of both series of crosslinked PCLF/HA nanocomposites with HA compositions of 0%, 5%, 10%, 20%, and 30% have been investigated. By adding HA nanoparticles, crosslinked PCLF530/HA nanocomposites demonstrate enhanced rheological and mechanical properties while the enhancement in compressive modulus is less prominent in crosslinked PCLF2000/HA nanocomposites. In vitro cell attachment and proliferation have been performed using rat bone marrow stromal cells (BMSCs) and correlated with the material properties. Cell attachment and proliferation on crosslinked PCLF530/HA nanocomposite disks have been enhanced strongly with increasing the HA composition. However, surface morphology and surface chemistry such as composition, hydrophilicity, and the capability of adsorbing protein cannot be used to interpret the cell responses on different samples. Instead, the role of surface stiffness in regulating cell responses can be supported by the correlation between the change in compressive modulus and BMSC proliferation on these two series of crosslinked PCLFs and PCLF/HA nanocomposites.

Synthesis and Drug-Release Behavior of Porous Biodegradable Amphiphilic Co-polymeric Hydrogels

A series of amphiphilic random block co-polymers were synthesized by the condensation of hydrophobic polycaprolactone diol (PCL diol) with hydrophilic dicarboxy poly(ethylene glycol) (PEG-diacid), obtained by reacting poly(ethylene glycol) (PEG) with succinic anhydride. The PEG/PCL random block co-polymers were then acrylated with acryloyl chloride to form PEG/PCL diacrylates (PCEdA), and then characterized by FT-IR, 1H-NMR and GPC. The porous biodegradable gels were prepared through photo-polymerization of the PCEdA dissolved in DMSO at low temperature. Thermal behavior, swelling ratio and morphological characteristics as well as biodegradability of the presented gels were investigated. Results showed that the swelling ratio of the gel in deionized water increased with an increase of the PEG chain length in the copolymeric gel. DSC thermograms indicated that the melting point of the PCEdA was lower than that of PCL and PEG blocks, but a new crystalline peak of the co-polymeric gel appeared with increasing of the segmental length of the PEG. Thermal stability of PCE gel was higher than that of PCE diol. The pore size of the gel was influenced by the concentration of PCEdA. The drug-release behavior of PCE gels was also investigated.

Effect of the hard segment chemistry and structure on the thermal and mechanical properties of novel biomedical segmented poly(esterurethanes)

Two series of biomedical segmented polyurethanes (SPU) based on poly(epsilon-caprolactone) diol (PCL diol), 1,6-hexamethylene diisocyanate (HDI) or L: -lysine methyl ester diisocyanate (LDI) and three novel chain extenders, were synthesized and characterized. Chain extenders containing urea groups or an aromatic amino-acid derivative were incorporated in the SPU formulation to strengthen the hard segment interactions through either bidentate hydrogen bonding or pi-stacking interactions, respectively. By varying the composition of the hard segment (diisocyanate and chain extender), its structure was varied to investigate the structure-property relationships. The different chemical composition and symmetry of hard segment modulated the phase separation of soft and hard domains, as demonstrated by the thermal behavior. Hard segment association was more enhanced by using a combination of symmetric diisocyanate and urea-diol chain extenders. The hard segment cohesion had an important effect on the observed mechanical behavior. Polyurethanes synthesized using HDI (Series H) were stronger than those obtained using LDI (Series L). The latter SPU exhibited no tendency to undergo cold-drawing and the lowest ultimate properties. Incorporation of the aromatic chain extender produced opposite effects, resulting in polyurethanes with the highest elongation and tearing energy (Series H) and the lowest strain at break (Series L). Since the synthesized biodegradable SPU possess a range of thermal and mechanical properties, these materials may hold potential for use in soft tissue engineering scaffold applications.

Segmented poly(esterurethane urea)s from novel urea–diol chain extenders: Synthesis, characterization and in vitro biological properties

This work describes the preparation, physicochemical characterization, mechanical properties and in vitro biological properties of two bioresorbable aliphatic segmented poly(esterurethane urea)s (SPEUU) based on poly( ε-caprolactone) diol (PCL diol), 1,6-hexamethylene diisocyanate and two novel urea–diol chain extenders. To strengthen the interactions through hydrogen bonding in the hard segments of SPEUU, novel chain extenders containing urea groups were synthesized and used in the SPEUU formulation. The different chemical structures of the chain extenders modulated the phase separation of soft and hard segments, as demonstrated by the thermal behavior. The hard segment association was enhanced using a diurea–diol chain extender. The biological interactions between the obtained materials and blood were studied by in vitro methods. Research on the protein adsorption, platelet adhesion and thrombus formation is presented. Studies of protein adsorption onto polymeric surfaces showed that SPEUU adsorbed more albumin than fibrinogen. Studies on platelet adhesion and thrombus formation of SPEUU-coated coverslips indicated the antithrombogenic behavior of these surfaces. The synthesized SPEUU revealed no signs of cytotoxicity to Chinese hamster ovary cells, showing satisfactory cytocompatibility.

Rheological study of segmented polyurethane and polycaprolactone blends

The dynamic rheological properties of segmented polyurethane based on polycaprolactone diol (PU-PCL diol) and poly (ɛ-caprolactone) (PCL) blends were experimentally examined and theoretically analyzed using Palierne model. PU–PCL diol was melt blended with PCL in three different ratios of 20, 30, and 40%. Initial modeling attempts failed to fit the experimental data of these blends, as the model overpredicted their rheological data. This failure is believed to be due to partial dissolution of PCL in PU. According to our obtained results from differential scanning calorimetry and dynamic thermal mechanical analysis, pure PU–PCL diol is diluted by its homopolymer. By calculating the complex modulus of this diluted matrix using a simple mixing rule and its incorporation into the model, good fitting of the Palierne equation to the experimental data was obtained.

A Novel Polycaprolactone/Hydroxyapatite Scaffold for Bone Tissue Engineering

In this study, novel polycaprolactone/hydroxyapatite (PCL/HA) scaffolds were prepared to increase mechanical properties and degradation of PCL/HA ones for bone tissue engineering. PCL macromers were synthesized through the reaction of PCL diol (Mn: 530, 1250, and 2000) and PCL triol (Mn: 900) with acryloyl chloride and confirmed using nuclear magnetic resonance spectrometer (NMR) and fourier transform infrared (FTIR). The PCL/HA scaffolds were prepared by cross-linking of PCL macromer in the presence of HA by UV treatment and freeze drying methods. Mechanical property and porosity as well as degradability of the PCL/HA scaffolds were also investigated. PCL/HA scaffolds showed faster degradation and higher compressive modulus than those of PCL itself due to their low crystallinity and modification of terminal groups. The pore morphology and pore sizes of the PCL/HA scaffold were checked by scanning electron microscope (SEM). Cell cytotoxicity and proliferation of MG-63 osteoblast cultured onto the PCL/HA scaffold was assessed by lactate dehydrogenase (LDH) assay and Alamar blue assay, respectively. The novel PCL/HA scaffold appears to be suitable for bone substitutes.

Synthesis and characterization of biodegradable elastic hydrogels based on poly(ethylene glycol) and poly(ε-caprolactone) blocks

Novel biodegradable elastic hydrogels, based on hydrophilic and hydrophobic polymer blocks, were synthesized via the radical crosslinking reaction of diacrylates of poly(ethylene glycol) (PEG) and poly(e-caprolactone) (PCL). PEG and PCL diols were diacrylated with acryloyl chloride in the presence of triethylamine, with the reaction confirmed by FT-IR and1H-NMR measurements. The diacrylate polymers were used as building-blocks for the syntheses of a series of hydrogels, with different block compositions, by simply varying the feed ratios and molecular weights of the block components. The swelling ratio of the hydrogels was controlled by the balance between the hydrophilic and hydrophobic polymer blocks. Usually, the swelling ratio increases with increasing PEG content and decreasing block length within the network structure. The hydrogels exhibited negative thermo-sensitive swelling behavior due to the coexistence of hydrophilic and hydrophobic polymer components in their network structure, and such thermo-responsive swelling/deswelling behavior could be repeated using a temperature cycle, without any significant change in the swelling ratio.In vitro degradation tests showed that degradation occurred over a 3 to 8 month period. Due to their biodegradability, biocompatibility, elasticity and functionality, these hydrogels could be utilized in various biomedical applications, such as tissue engineering and drug delivery systems.

Structure and properties of polyurethane/YAG:Tb3+ nanocomposites with luminescence properties

Elastic polyurethanes films with luminescent properties have attracted increasing attention, both as a subject of fundamental and applied research. In the present study, polyurethane nanocomposites containing 0.05 to 0.2 wt. % of nanofillers were prepared by in situ polymerization. These nanocomposites were subsequently used to investigate the influence of the nanoparticles’ content on their structure and properties. PUR was synthesized using polycaprolactone diol (PCL diol) and dicyclohexylmethane-4,4’-diisocyanate (HMDI) with addition of diols as chains extenders. The nanofiller in the form of yttrium-aluminum-garnet (YAG) containing 10 wt. % of Tb3+ was added and samples of composites were synthesized employing prepolymer fabrication route. Series of nanocomposites with exhibited high luminescence and intensity of emission. Microstructure of these composites was investigated using atomic force microscopy (AFM) in a tapping mode. The grain size analysis of nanofillers was performed with high resolution scanning electron microscopy (HRSEM) and high resolution transmission electron microscopy (HRTEM). The mechanical and optical properties of the specimens have been correlated to their microstructure.

Biodegradable molecularly imprinted polymers based on poly(ε-caprolactone)

Novel biodegradable molecularly imprinted polymers (MIPs) based on poly(e-caprolactone) (PCL) were prepared by combining two important properties required of ideal biomaterials, biodegradability (with biocompatibility) and molecular recognition properties. Acrylate or methacrylate end-capped PCL macromers were synthesized through the reaction of PCL diol or triol with acryloyl or methacryloyl chloride. The synthesis of acrylate or methacrylate end-capped macromers was confirmed using FT-IR and H NMR spectroscopic techniques. These macromers were used to prepare biodegradable crosslinked networks by photopolymerization with functional monomer (acrylic acid) and a model template (theophylline). The theophylline-imprinted polymer showed higher binding capacity for theophylline compared with non-imprinted polymer (NIP), and also showed selectivity for theophylline over caffeine (similar structure molecules). PCL-based MIP degraded 8% of the initial weight in 30 days in phosphate-buffered saline (PBS) solution (pH 7.4) and over 90% of the initial weight within 24 h in 1 N NaOH at 37°C.

Miscibility of TPU(PCL diol)/PCL Blend and Its Effect on PCL Crystallinity

AbstractPoly(ε‐caprolactone) (PCL) was melt blended with thermoplastic polyurethane based on polycaprolactone diol (TPU(PCL diol)). The amount of PCL was varied from 20% to 50% by weight. A single composition dependent glass transition temperature (from DSC) shows the miscibility of system. Also the negative value of polymer‐polymer interaction density, obtained from the analysis of the equilibrium melting point depression, confirms the blends' miscibility. Tc and Tm of the PCL component in the blend decrease significantly with an increase in the TPU content, in comparison with that of pure PCL. The position of the diffraction peak related to (110) planes of PCL in the blends using WAXS has been shifted to lower value. This means the b‐axis of orthorhombic unit cell of PCL is spread out in the blends. On the whole, increase of TPU content in the blend decreases crystallization ability of PCL compared to pure PCL.

A facile approach to biodegradable poly(ε-caprolactone)-poly(ethylene glycol)-based polyurethanes containing pendant amino groups

A novel biodegradable poly(ε-caprolactone)-poly(ethylene glycol)-based polyurethanes (PCL-PEG-PU) with pendant amino groups was synthesized by direct coupling of PEG ester of NH 2-protected-(aspartic acid) (PEG-Asp-PEG diols) and poly(ε-caprolactone) (PCL) diols with hexamethylene dissocyanate (HDI) under mild reaction conditions and by subsequent deprotection of benzyloxycarbonyl (Cbz) groups. GPC, 1H NMR, and 13C NMR studies confirmed the polymer structures and the complete deprotection. DSC and WXRD results indicated that the crystallinity of the copolymer was enhanced with increasing PCL diols in the copolymer. The content of amino group in the polymer could be adjusted by changing the molar ratio of PEG-Asp-PEG diols to PCL diols. Thus the results of this study provide a good way to prepare polyurethanes bearing hydrophilic PEG segments and reactive amino groups without complicated synthesis.