PCL Diol Research Articles

Shape memory performance of green in situ polymerized nanocomposites based on polyurethane/graphene nanoplatelets: Synthesis, properties, and cell behavior

Nowadays, developing biocompatible shape memory polymers is among major expanding topics in medical applications. In this study, novel biocompatible polyurethane/graphene nanoplatelet (PU/GNp) nanocomposites were synthesized from poly(ε–caprolactone)diol (PCL diol)/Castor oil and Hexamethylene diisocyanate (HDI) through in situ polymerization. Three different %wt. of GNp were incorporated into the polyol mixtures to monitor the effect of nano fillers on the shape memory behavior of PUs. The chemical structure of nanocomposites was studied by Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopies. X‐ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), transmission electron microscopy (TEM), and differential scanning calorimetry (DSC) were used to evaluate the nanocomposites properties. GNp incorporation affected the bulk morphology as well as thermal properties and crystallinity. Dynamic mechanical thermal analysis (DMTA) revealed the higher elastic modulus values for nanocomposites compared to the pure PU. The biocompatibility of PU/GNp nanocomposites was investigated via MTT assay. Finally, based on shape memory studies, the higher crystallinity, and improved elastic modulus of the nanocomposites resulted in their excellent shape fixity (about 91‐96%) and shape recovery (95‐99%) behaviors. According to the results, the prepared PU/GNp nanocomposites can be considered as potential choices for applicable shape memory devices for biomedical applications. POLYM. COMPOS., 39:4020–4033, 2018. © 2017 Society of Plastics Engineers

Characterization of model compounds and poly(amide-urea) urethanes based on amino acids by FTIR, NMR and other analytical techniques

The synthesis of novel polyurethanes is a subject of increasing interest, especially those that involve biologically active molecules. Generally, the reports on the synthesis of segmented polyurethanes using modified amino acids as chain extenders assume that the reaction occurs due to functionalities (OH and NH2) of the last compounds. However, few works really prove the reaction takes place with unmodified amino acids. In this work, spectroscopic techniques such as 1H, 13C, and 1H-1H COSY NMR and FTIR were used to chemical characterization of poly(urea-amide) urethanes synthesized from polycaprolactone diol (PCL diol 530), 4,4′-methylene-bis(cyclohexyl isocyanate) (H12MDI), and amino acids such as l-arginine, glycine or l-aspartic acid as chain extenders. In addition, model compounds (without PCL diol) were analyzed to confirm reaction of amino acids via urea and amide formation. Additionally, the polymers exhibited different physicochemical and mechanical properties depending on the chain extender used. These results suggest that unmodified amino acids can be used as chain extenders in the synthesis of poly(amide-urea) urethanes for biomedical applications.

A novel shape memory poly(ε-caprolactone) network via UV-triggered thiol-ene reaction

A facile method to prepare shape memory polymers crosslinked by SiO2 is described. A series of biodegradable shape memory networks were obtained through thiol-ene reaction triggered by UV irradiation between surface-thiol-modified SiO2 nanoparticles and end-acrylate poly (e-caprolactone) (PCL). The highly selective thiol-ene reaction ensured a uniform distribution of PCL chains between crosslinkers, contributing well-defined network architecture with enhanced mechanical and shape-memory properties. Thiol-functionalized silica nanoparticle was characterized by using FTIR and XPS analysis, and 1H NMR spectra was used to confirm the successful modification of terminal hydroxyl group of PCL diol. Surface-modified silica particles were found well dispersible in acrylate-capped PCL supported by SEM. Thermal and crystalline behaviors of the obtained polymers were analyzed by DSC and XRD, and DMA measurement proved good mechanical property. The shape memory behavior and tensile strength was somewhat tunable by the length of PCL. Acceptably, sample SiO2-SMP2k presented 99% recovery ratio and 97% shape fixity, and its relatively high tensile strength showed an attractive potential for biomedical application. Finally, a possible molecular mechanism accounting for the shape memory property was illustrated. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017, 55, 692–701

Full-atomistic simulations of poly(ϵ-caprolactone) diol models with CVFF and CGenFF

Poly(ϵ-caprolactone) (PCL) diol, with good biodegradation and biocompatibility, is one of the widely used soft segments (SSs) in composing bio-polyester-urethanes (Bio-PUs), which show great potential in both biomedical and tissue engineering applications. Properties of Bio-PUs are tunable by combining SS monomers with different molecular weights, structures, modifications, and ratio of components. Although numbers of research have reported many Bio-PUs properties, few studies have been done at the molecular scale. In this study, we use molecular dynamic (MD) simulation to construct atomistic models for two commonly used PCL diol SSs with different molecular weights 1247.58 Da and 1932.42 Da. We compare the simulation results by using two widely used classical force fields for organic molecules: Consistent Valence Force Field (CVFF) and CHARMM General Force Field (CGenFF), and discuss the validity and accuracy. Melt density, volume, polymer conformations, transition temperature, and mechanical properties of PCL diols are calculated and compared with experiments. Our results show that both force fields provide accurate predictions on the properties of PCL diol system at the molecular scale and could help the design of future Bio-PUs.

Study on physicochemical properties of poly(ester-urethane) derived from biodegradable poly(ε-caprolactone) and poly(butylene succinate) as soft segments

Novel biodegradable polyester-based polyurethanes were developed based on poly(e-caprolactone) diol (PCL diol) and poly(butylene succinate) diol (PBS diol) as the biodegradable soft segments (SS), and diisocyanate and 1,4-butanediol (BDO) as the hard segment (HS). The PBS diol ( $$ \overline{{M_{\text{n}} }} $$ = 2000 g/mol) was successfully synthesized by melt condensation. The PBS diol and polyurethane sheets were characterized for chemical structure using NMR and FTIR techniques. The effect of hard segments and diisocyanate type on thermo-mechanical properties and hydrolytic degradation were examined by means of tensile testing, TGA, DSC and DMTA. The stress–strain curves of PURs reached the high 715 % elongation at break, 32.5 MPa tensile strength, and 123.8 MPa Young’s modulus. Increased hard segment content increased the tensile properties, thermal resistance and T g, but the hydrolytic degradation rate decreased. The IPDI-based polyurethane gave lower tensile properties, T g and hydrolytic degradation rate, but higher thermal stability than the TDI-based polyurethane.

Synthesis of water-based cationic polyurethane for antibacterial and gene delivery applications

Cationic polymers are often used as antimicrobial materials and transfection reagents. Water-based process could reduce environmental pollution and prevent the risk of solvent residue in the final product. In this study, waterborne biodegradable cationic polyurethane (WCPU) was synthesized by reacting polycaprolactone (PCL diol), isophorone diisocyanate (IPDI), and N-methyldiethanolamine (N-MDEA) under 75°C. An aqueous dispersion of WCPU nanoparticles (NPs) could be acquired by vigorous stirring under acidic condition. The particles in the dispersion had an average size of ⿼80nm and a zeta potential of ⿼60mV. When cast into films, the contact angle of the film was ⿼67° and the zeta potential was ⿼16mV. WCPU NPs demonstrated excellent antibacterial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) (100% inhibition with a contact time of 3h). Meanwhile, the antibacterial ratio of WCPU films to E. coli and S. aureus reached 100% after 24h of contact. Moreover, WCPU NPs could be used as a transfection reagent without significant toxicity for concentrations less than 1000μg/mL and showed the ability to condensate plasmid DNA. The transfection efficiency for HEK293T cells and hBMSCs was ⿼60% and ⿼30% at 48h, respectively, after the transfection. Therefore, the WCPU synthesized in this study has potential antibacterial and gene delivery applications.

Synthesis of intracellular reduction-sensitive amphiphilic polyethyleneimine and poly(ε-caprolactone) graft copolymer for on-demand release of doxorubicin and p53 plasmid DNA

This study aims to present a new intelligent polymeric nano-system used for combining chemotherapy with non-viral gene therapy against human cancers. An amphiphilic copolymer synthesized through the conjugation of low molecular weight polyethyleneimine (LMw-PEI) and poly(ε-caprolactone) (PCL) via a bio-cleavable disulfide linkage was successfully employed for the simultaneous delivery of drug and gene molecules into target cells. Compared to the conventional PCL copolymerization pathway, this paper represents a straightforward and efficient reaction pathway including the activation of PCL-diol hydroxyl end groups, cystamine attachment and LMw-PEI conjugation which are successfully performed at mild conditions as confirmed by FTIR and 1H NMR. Thermal, morphological characteristics as well as biocompatibility of the copolymer were investigated. The copolymer showed great tendency to form positively charged nanoparticles (∼163.1nm, +35.3mV) with hydrophobic core and hydrophilic shell compartments implicating its potential for encapsulation of anti-cancer drug and plasmid DNA, respectively. The gel retardation assay confirmed that the nanoparticles could successfully inhibit the migration of pDNA at ∼5 nanoparticle/pDNAw/w. The in vitro cytotoxicity tests and LDH assay revealed that the cationic amphiphilic copolymer was essentially non-toxic in different carcinoma cell lines in contrast to branched PEI 25K. Moreover, the presence of redox sensitive disulfide linkages provided smart nanoparticles with on-demand release behavior in response to reducing agents such as cytoplasmic glutathione (GSH). Importantly, confocal microscopy images revealed that in contrast to free Dox, the nanoparticles were capable of faster internalizing into the cells and accumulating in the perinuclear region or even in the nucleus. Finally, the co-delivery of Dox and p53-pDNA using the copolymer displayed greater cytotoxic effect compared with the Dox-loaded nanoparticle counterpart as revealed by cell viability and Caspase 3 expression assay. These results suggest the copolymer as a promising candidate for the development of smart delivery systems. Statement of SignificanceWe employed cystamine dihydrochloride as a disulfide linkage for the conjugation of PCL diol and low molecular weight PEI segments through a straightforward and efficient reaction pathway at mild conditions. The new copolymer was essentially non-toxic in different carcinoma cell lines and showed great tendency to form positively charged nanoparticles. Therefore, it can be utilized as a promising platform for simultaneous drug and gene delivery to aggressive cancers. The results of drug and gene co-delivery experiments confirmed the pivotal role of disulfide linkage on the controlled release of both drug and gene molecules in response to glutathione concentration gradient between extracellular and intracellular microenvironments. In addition, the co-delivery of doxorubicin and p53 plasmid DNA using the new copolymer displayed greater cytotoxic effect compared with single agent (i.e. Dox) loaded counterpart, which indicated the significance of rapid dissociation of therapeutic agents from the carrier for synergistic cytotoxic effects on cancer cells.

Surface‐functionalized polyurethane nanoparticles for targeted cancer therapy

AbstractPolymer nanoparticles (nps) have gained growing interest as carriers for anticancer drugs as they can target tumour tissues by both passive and active pathways. While the passive targeting mechanisms mainly rely on the small size of the carriers, active targeting requires surface modifications of the polymer core in order to introduce specific functionalities to actively recognize cancer cells. The present work proposes an innovative method for the preparation of surface‐functionalized nps based on the use of biodegradable polyester‐ and polyester/ether‐urethanes (PURs) embedding amino functionalities. Two polyurethanes were prepared, one based on just poly(ϵ‐caprolactone) diol (PCL‐PUR) and the other based on both PCL diol and poly(ethylene glycol) (PEG) (70/30 ratio, PCL‐PEG‐PUR). Nanoparticles of small size ranging between 150 and 200 nm and negative ζ potential (ranging from −18 mV to −27 mV) were obtained. Functional groups were exposed post nps preparation as confirmed by X‐ray photoelectron spectroscopy, ninhydrin assay and 1H NMR, which evidenced a 24% tert‐butyloxycarbonyl cleavage for PCL‐PUR‐NH2 nps and 29% for PCL‐PEG‐PUR‐NH2 nps. The monoclonal antibody Herceptin (HER), which targets HER‐2 receptors, was coupled through ethyl(dimethylaminopropyl) carbodiimide/N‐hydroxysuccinimide (EDC/NHS) mediated chemistry. The optimal HER:NH2 ratio was determined to be 1:16 for the PEG‐containing PUR and 1:8 for PCL‐PUR. HER‐nps maintained the intrinsic cytotoxicity of the antibody, as shown by the ca 50% decrease of HER‐2‐expressing HeLa cell viability. The results indicate that our protocol for surface functionalization of PUR nps, based on surface exposure of previously inserted functional groups followed by covalent coupling of biomolecules, is suitable for the preparation of nps for active recognition of target cells. © 2016 Society of Chemical Industry

Effect of clay loading on the structural and mechanical properties of organoclay/HDI-based thermoplastic polyurethane nanocomposites

AbstractThermoplastic polyurethane/organically-modified montmorillonite (TPU/OMMT) nanocomposites were synthesized by the pre-polymer polymerization method using Cloisite® 30B organoclay, 1,6-hexamethylene diisocyanate (HDI), polycaprolactone diol (PCL diol, 2000 g/mol) and 1,4-butanediol (BDO). The hard segment content of the TPU was maintained at ~25.5% while the role of clay content was investigated at 1, 3 and 5 wt.% of clay concentration. The aim of this work was to obtain a high-performance polyurethane system while reaching a general microstructure-property relationship for TPU/OMMT nanocomposites. Clay exfoliation was achieved at 1 and 3 wt.% of clay loadings while some agglomerated clay sheets were observed in samples containing 5 wt.% OMMT. Significant hydrogen bonding occurred between the urethane linkages with unreacted -CH2CH2OH groups of the OMMT particles which resulted in strong matrix-filler interactions. Consequently, the values of tensile modulus were enhanced with clay content; namely a 177% improvement was observed for samples containing 5 wt.% OMMT. On the other hand, samples exhibited more thermoplastic behavior with the increase of clay content which resulted in lower deformability and lower values of tensile strength.

Synthesis of Thermoresponsive Amphiphilic Polyurethane Gel as a New Cell Printing Material near Body Temperature.

Waterborne polyurethane (PU) based on poly(ε-caprolactone) (PCL) diol and a second oligodiol containing amphiphilic blocks was synthesized in this study. The microstructure was characterized by dynamic light scattering (DLS), small-angle X-ray scattering (SAXS), and rheological measurement of the PU dispersion. The surface hydrophilicity measurement, infrared spectroscopy, wide-angle X-ray diffraction, mechanical and thermal analyses were conducted in solid state. It was observed that the presence of a small amount of amphiphilic blocks in the soft segment resulted in significant changes in microstructure. When 90 mol % PCL diol and 10 mol % amphiphilic blocks of poly(l-lactide)-poly(ethylene oxide) (PLLA-PEO) diol were used as the soft segment, the synthesized PU had a water contact angle of ∼24° and degree of crystallinity of ∼14%. The dispersion had a low viscosity below room temperature. As the temperature was raised to body temperature (37 °C), the dispersion rapidly (∼170 s) underwent sol-gel transition with excellent gel modulus (G' ≈ 6.5 kPa) in 20 min. PU dispersions with a solid content of 25-30% could be easily mixed with cells in sol state, extruded by a 3D printer, and deposited layer by layer as a gel. Cells remained alive and proliferating in the printed hydrogel scaffold. We expect that the development of novel thermoresponsive PU system can be used as smart injectable hydrogel and applied as a new type of bio-3D printing ink.

Stability of biodegradable waterborne polyurethane films in buffered saline solutions.

The stability of polyurethane (PU) is of critical importance for applications such as in coating industry or as biomaterials. To eliminate the environmental concerns on the synthesis of PU which involves the use of organic solvents, the aqueous-based or waterborne PU (WBPU) has been developed. WBPU, however, may be unstable in an electrolyte-rich environment. In this study, the authors reported the stability of biodegradable WBPU in the buffered saline solutions evaluated by atomic force microscopy (AFM). Various biodegradable WBPU films were prepared by spin coating on coverslip glass, with a thickness of ∼300 nm. The surface AFM images of poly(ε-caprolactone) (PCL) diol-based WBPU revealed nanoglobular structure. The same feature was observed when 20% molar of the PCL diol soft segment was replaced by polyethylene butylenes adipate diol. After hydration in buffered saline solutions for 24 h, the surface domains generally increased in sizes and became irregular in shape. On the other hand, when the soft segment was replaced by 20% poly(l-lactide) diol, a meshlike surface structure was demonstrated by AFM. When the latter WBPU was hydrated, the surface domains appeared to be disconnected. Results from the attenuated total reflectance infrared spectroscopy and x-ray photoelectron spectroscopy indicated that the surface chemistry of WBPU films was altered after hydration. These changes were probably associated with the neutralization of carboxylate by ions in the saline solutions, resulting in the rearrangements of soft and hard segments and causing instability of the WBPU.

Triphenylphosphonium‐Conjugated Poly(ε‐caprolactone)‐Based Self‐Assembled Nanostructures as Nanosized Drugs and Drug Delivery Carriers for Mitochondria‐Targeting Synergistic Anticancer Drug Delivery

For mitochondria‐targeting delivery, a coupling reaction between poly(ε‐caprolactone) diol (PCL diol) and 4‐carboxybutyltriphenylphosphonium (4‐carboxybutyl TPP) results in the synthesis of amphiphilic TPP‐PCL‐TPP (TPCL) polymers with a bola‐like structure. In aqueous environments, the TPCL polymer self‐assembled via cosolvent dispersion and film hydration, resulting in the formation of cationic nanoparticles (NPs) less than 50 nm in size with zeta‐potentials of approximately 40 mV. Interestingly, different preparation methods for TPCL NPs result in various morphologies such as nanovesicles, nanofibers, and nanosheets. In vitro cytotoxicity results with TPCL NPs indicate IC50 values of approximately 10–60 μg mL−1, suggesting their potential as anticancer nanodrugs. TPCL NPs can be loaded both with hydrophobic doxorubicin (Dox) and its hydrophilic salt form (Dox·HCl), and their drug loading contents are approximately 2–10 wt% depending on the loading method and the hydrophilicity/hydrophobicity of the drugs. Although Dox·HCl exhibits more cellular and nuclear uptake, resulting in greater antitumor effects than Dox, most drug‐loaded TPCL NPs exhibit higher mitochondrial uptake and approximately 2–7‐fold higher mitochondria‐to‐nucleus preference than free drugs, resulting in superior (approximately 7.5–18‐fold) tumor‐killing activity for most drug‐loaded TPCL NPs compared with free drugs. In conclusion, TPCL‐based nanoparticles have potential both as antitumor nanodrugs themselves and as nanocarriers for chemical therapeutics.

Water Sensitive Coatings Deposited by Aerosol Assisted Atmospheric Plasma Process: Tailoring the Hydrolysis Rate by the Precursor Chemistry

Biocompatible plasma polymers are expected to be used in various applications in medicine such as drug delivery with a controlled release. In this context we investigated the possibility to monitor the kinetic of hydrolytic degradation of plasma polymers by tailoring the chemistry of the precursor. A homemade precursor way synthesized by grafting acrylate function on both side of a polycaprolactone diol (PCL diol) to produce a PCL diacrylate characterized by IR, NMR, and MS to confirm its chemical structure. Acrylates constitute a promising class of precursors to improve the retention of the integrity of the precursor by working in soft plasma conditions. The plasma polymerization of the so-synthesized precursor have been highlighted by means of a multi technique analytical strategy and ensured the retention of hydrolyzable ester function of the precursor. Finally the thickness consumption during immersion in PBS were performed and found to be slower as compared to the degradation kinetic of a plasma polymerized methacrylic anhydride.

Characterization of chain dimensions of poly(ε-caprolactone) diols in THF by size-exclusion chromatography coupled with multi-angle light scattering (SEC-MALS)

In this work, we studied the chain dimensions, shape, and thermodynamic characteristics of poly(e-caprolactone) diols (HO-PCL-OH) in solution. PCL diol samples of different molecular weights and architectures were synthesized using immobilized Yarrowia lipolytica lipase as catalyst. Gel permeation chromatography (GPC) with online right-angle laser-light scattering (RALLS), differential viscometer (DV), and interferometric refractometer IRS detectors offered a proper way to obtain information on thermodynamic characteristics and chain flexibility. The weight-average molecular weights of the PCL diol samples (M w ) ranged from 2,750 to 13,120 uma. The z-average radius of hydrodynamic volume (<R h 2 > z 1/2 ) vs. z-average molecular weight curve (M z ) could be satisfactorily fitted to a power-law equation. Mark–Houwink–Sakurada parameters (K = 2.74 × 10−3 dL/g and a = 0.64) were derived from the plots of [η] w against M w . The overall results clearly suggest that a flexible geometry is present in tetrahydrofuran (THF) solution of PCL at 33 °C. Unlike other PCL systems, PCL diols are more hydrophilic and expected to form associated species. They behave differently from common hydrophobic polymers and do not strictly conform to thermodynamic relationships generally used in Polymer Science. A more compact geometry is present for Mn lower than 4,000 Da. For higher molecular weights, the chain expands and become more elongated. Plots of ln [η] w against ln M w (MHS equation) and of log R hz against log M z suggest that PCL diols behave as flexible chains in a good solvent.

Synthesis, Characterization and in Vitro Evaluation of New Composite Bisphosphonate Delivery Systems

In this study, new composite bisphosphonate delivery systems were obtained from polyurethanes (PUs) and nanocrystalline hydroxyapatite (HA). The biodegradable PUs were first synthesized from poly(ε-caprolactone) diols (PCL diols), poly(ethylene adipate) diol, 1,6-hexamethylene diisocyanate, 1,4-butanediol and HA. Moreover, the PCL diols were synthesized by the ring-opening polymerization catalysed by the lipase from Candida antarctica. Next, composite drug delivery systems for clodronate were prepared. The mechanical properties of the obtained biomaterials were determined. The cytotoxicity of the synthesized polymers was tested. The preliminary results show that the obtained composites are perspective biomaterials and they can be potentially applied in the technology of implantation drug delivery systems.

Fabrication of biodegradable polyurethane microspheres by a facile and green process.

Two different compositions of water-based biodegradable polyurethane (PU) in the form of homogeneous nanoparticles (NPs) were synthesized using biodegradable polyesters as the soft segment. The first PU (PU01) was based on poly(ε-caprolactone) (PCL) diol and the second PU (PU02) was based on 40% PCL diol and 60% polyethylene butylene adipate diol. The PU NP dispersions with different solid contents were sprayed into liquid nitrogen and resuspended in water to generate elastic microspheres (50-60 µm) with different nanoporosities. In vitro degradation analysis revealed that microspheres of PU02 (i.e., PU02 MS) degraded faster than those of PU01 (PU01 MS). Methylene blue was encapsulated during microsphere formation and the release was investigated. Microspheres made from a lower content (10%) of PU02 dispersion (i.e., PU02 MS_10) showed a greater burst release of methylene blue in 6 h, whereas those made from a higher content (30%) of PU01 dispersion (i.e., PU01 MS_30) revealed a prolonged release with a significantly lower burst release. Biocompatibility evaluation using L929 fibroblasts demonstrated that cells were attached and proliferated on microspheres after 24 h. On the other hand, microspheres may further self-assemble into films and scaffolds. Surface modification of microspheres by chitosan may modify the self-assembly behavior of microspheres. Microspheres could be stacked to form scaffolds with different macroporosities. Fibroblasts were successfully seeded and grown in the microsphere-stacked scaffolds. We concluded that the biodegradable and elastic microspheres may be facilely produced from a green and sustainable process with potential applications in drug release and three-dimensional cell culture.

Hybrid Organic-Inorganic Nanocomposites Based on Poly(ϵ-Caprolactone)/Polyhedral Oligomeric Silsesquioxane: Synthesis and In Vitro Evaluations

Hybrid poly(ϵ-caprolactone) (PCL) containing nanocomposites and non-hybrid linear PCL diols were synthesized by anionic ring opening polymerization of ϵ-caprolactone on a POSS or ethylene glycol central blocks, respectively. Monolith scaffolds were then fabricated from the hybrid nanocomposites and non-hybrid linear PCL diols via non-solvent induced phase separation technique. The effects of inclusion of POSS nanocage in the polymer chain structure on specific surface area and pore size of the scaffolds was investigated by multipoint BET method. This perfect scrutiny will introduce an excellent nanoparticle pendent to the PCL chains to promote the in vitro properties of the implants potentially applicable in tissue engineering.

Synthesis, characterization and hydrolytic degradation of polyester-urethanes obtained by lipase biocatalysis

The enzymatic synthesis of α–ω-telechelic polycaprolactone diols (HOPCLOH) and block copolymers was studied. Synthesis of α–ω-telechelic PCL diols was carried out by enzymatic ring opening polymerization with Yarrowia lipolytica lipase immobilized on Lewatit VP OC K2629 and Amberlyst 15, and using ethylene glycol, diethylene glycol and polyethylene glycol as initiators. Biodegradable linear polyester-urethanes were prepared from synthesized PCL diols and hexamethylenediisocyanate (HDI). Polyester-urethanes degradation was studied using thermogravimetric analysis (TGA) and hydrolysis (alkaline, acidic and neutral). It was found that content of ether linkages influences the thermal stability and hydrolytic degradation behavior of the analyzed polyurethanes. Hydrolytic degradation proceeds faster in alkaline media, in agreement with the expected susceptibility of ester COO– bonds to degradation in the polyester urethanes.

In situ photocrosslinkable nanohybrids based on poly(ε-caprolactone fumarate)/polyhedral oligomeric silsesquioxane: synthesis and characterization

Two types of biodegradable, in situ photocrosslinkable macromers were synthesized consisting a linear copolyester i.e., PCLF based on fumaric acid (FA) and poly(e-caprolactone diol) (PCL diol), and its nanohybrid counterpart (POSS-PCLF) composed of FA, PCL diol and polyhedral oligomeric silsesquioxane (POSS). Chemical structure of the macromers was characterized by 1HNMR and FTIR spectroscopy. The synthesized macromers were photocrosslinked by visible light irradiation in the presence of camphorquinone and N,N’-dimethylaminoethyl methacrylate as a photoinitiator and accelerator, respectively. Photocrosslinking characteristics of the compositions were investigated as a function of the initial PCL diol molecular weight, presence of POSS nanoparticles or N-vinylpyrrolidone (NVP, as a reactive diluent) by tracing degree of conversion by FTIR spectroscopy, equilibrium swelling studies. Thermal and dynamical properties of the macromers and the resulting networks were studied by TGA, DSC and DMA techniques pre- and post-photocrosslinking. In contrast to the self-crosslinkability of the macromers, the crosslinking reaction was promoted more efficiently in the presence of NVP as a reactive diluent. This scrutiny showed that there is an optimum point for POSS concentration to obtain the maximum improvement in the network properties.

Preparation and Properties of Bio-based Polyurethane Containing Polycaprolactone and Natural Rubber

Novel polyurethanes were successfully synthesized by a one-shot polymerization. They contained poly(e-caprolactone) diol (PCL diol) and hydroxyl telechelic natural rubber (HTNR) as the soft segment. The effect of the NCO:OH molar ratio (0.75:1.00–2.25:1.00), chain extender and PCL:HTNR molar ratio (1:1, 0.7:0.3 and 0.3:0.7) on the thermal and mechanical properties of the resulting polyurethane were investigated. FTIR analysis showed the presence of urethane linkages and crosslinking or chain branching. The derived polyurethanes demonstrated excellent mechanical properties, which depended on their chemical composition. Their tensile behavior seemed to have typical elastomeric characteristics. Polyurethanes became amorphous and showed a phase separation between the PCL diol and HTNR segments. The phase separation between the soft and the hard segments was observed by the DMTA technique whereas DSC results showed only the glass transition temperatures of the soft segment. The longer and more flexible chain and non-polarity of HTNR was responsible of a decrease in the mechanical properties and transition temperatures.