Polycaprolactone-based Polyurethane Research Articles

Thermal responsive polyurethane/brominated isobutylene isoprene rubber co-continuous IPNs elastomer: From tunable shape memory behavior to high damping properties

Shape memory polymers may have the highest potential as materials for aerospace engineering because of their low density, adjustable stiffness, and controlled deformation; however, large shock effects are inevitable during the deformation process of space deployment structures. To overcome the impact of shock vibrations on such complex integrated structures, an innovative interpenetrating polymer network (IPN) preparation scheme through phase distribution adjustment is proposed. In this work, thermally responsive shape memory IPNs consisting of polycaprolactone-based polyurethane (PUPCL) and brominated isobutylene isoprene rubber (BIIR) were reported for the first time. The BIIR/PUPCL (5:5) IPNs exhibited high shape fixity and recovery rates (94.4 % and 89.6 %, respectively) and repeatable shape memory behavior. Furthermore, the IPNs presented a favorable loss factor (tan δ) of 0.60 and exhibited effective damping temperature range (tan δ > 0.3) covering 83.6 K (−43.4 °C to 40.2 °C), resulting in impressive damping properties. Finally, the working process of the hinge was simulated by constructing a layer-by-layer panel with smooth deployment 30 s after heating. In addition, a gripper-shaped module based on bending deformation was successfully fabricated, exhibiting particular energy-loss properties and acting as a shock absorber. This study provides a novel design for the preparation of multifunctional polymers with potential applications in hinges and booms for aerospace engineering and intelligent protective devices.

Fabrication of Polycaprolactone-Based Polyurethanes with Enhanced Thermal Stability.

The benefit of being acquainted with thermal properties, especially the thermal stability of polyurethanes (PU), and simplified methods for their improvement is manifold. Considering this, the effect of embedding different amounts of unmodified and surface-modified TiO2 nanoparticles (NPs) within PU, based on polycaprolactone (PCL) and Boltorn® aliphatic hyperbranched polyester, on PU properties was investigated. Results obtained via scanning electron microscopy, swelling measurements, mechanical tests and thermogravimetric analysis revealed that TiO2 NPs can be primarily applied to improve the thermal performance of PU. Through surface modification of TiO2 NPs with an amphiphilic gallic acid ester containing a C12 long alkyl chain (lauryl gallate), the impact on thermal stability of PU was greater due to the better dispersion of modified TiO2 NPs in the PU matrix compared to the unmodified ones. Also, the distinct shape of DTG peaks of the composite prepared using modified TiO2 NPs indicates that applied nano-filler is mostly embedded in soft segments of PU, leading to the delay in thermal degradation of PCL, simultaneously improving the overall thermal stability of PU. In order to further explore the thermal degradation process of the prepared composites and prove the dominant role of incorporated TiO2 NPs in the course of thermal stability of PU, various iso-conversional model-free methods were applied. The evaluated apparent activation energy of the thermal degradation reaction at different conversions clearly confirmed the positive impact of TiO2 NPs on the thermal stability and aging resistance of PU.

Constructing a special interface structure of starch/PBAT composites with a novel “many-to-many” strategy

It is a challenge to achieve a high reaction ratio of compatibilizers for improving the compatibility of the composites due to high melt viscosity and short residence time during melt processing. Inspired by the fact that xanthium seeds in the nature are easy to combine with animal fur efficiently, a new “many-to-many" melting chemical reaction strategy was proposed to greatly improve the reaction ratio of compatibilizers. In this work, a polycaprolactone-based polyurethane prepolymer (PCLPU) was used to prepare compatible starch/poly(butyleneadipate-co-terephthalate) (PBAT) composites. Polyurethane nanoparticles containing a lot of –NCO groups were prepared and then reacted with tapioca starch with a lot of –OH groups in an intensive mixer to obtain starch/PBAT composite material with a special interface structure. Compared with the biocomposites without PCLPU, the PCLPU-modified biocomposites exhibited compatible morphology and excellent mechanical properties, and the reaction ratio of the PCLPU was as high as 99.2 %. The special polyurethane prepolymer interface formed in the composite interacted with the hydrophilic starch granules through urethane linkages and with hydrophobic PBAT through physical PBAT-PBAT linkages. Therefore, the novel strategy used to achieve a special interface structure for improving the mechanical properties of a composite was a simple, efficient, and environmentally friendly method.

Digital light 3D printing of artificial bone with star-shaped polycaprolactone-based polyurethane acrylate

Advanced medical materials and manufacturing technologies are highly in demand in artificial bones. Herein, a four-arm star-shaped polycaprolactone polyurethane acrylate (FPCLA) was designed and synthesized. The photosensitive character of FPCLA contributed to the rapid prototyping and personalized customization under digital light processing (DLP) 3D printing technology. The FPCLA was prepared by introducing unsaturated double bonds into polycaprolactone tetraethyl alcohol (PCLT). We characterized the physico-chemical properties of the material through FTIR, H-NMR, GPC, DSC and SEM. Cell behaviors on material were observed in vitro. In addition, we employed a DLP 3D printer to evaluate the feasibility of FPCLA to fabricate artificial bone model. The photocuring star polycaprolactone was confirmed in detail by detection method. SEM analyses demonstrated that FPCLA has good tenacity. The material can be used to fabricated artificial bone with a diameter of 3.02 mm at its narrowest by DLP 3D printing technology. The cell survival rates of CCK-8 and Live/Dead fluorescence staining experiments were both above 90%, which indicated safety and feasibility of such new-generation artificial bone made of synthetic polymers.

Self-Healing and Degradable Polycaprolactone-Based Polyurethane Elastomer for Flexible Stretchable Strain Sensors

Self-Healing and Degradable Polycaprolactone-Based Polyurethane Elastomer for Flexible Stretchable Strain Sensors

Dual-crosslinked starch−poly(ester urethane)−oligochitosan films with high starch content: Application as biodegradable food packaging

This work offered a dual-crosslinking strategy to prepare starch−poly(ester urethane)−oligochitosan (SPEO) composites with high starch content (> 46 wt%). The crosslinking agent polycaprolactone-based polyurethane prepolymer (PPUP) with terminal −NCO groups and pendant −CHO groups was first synthesized. Then, the starch was modified by PPUP to form a crosslinked structure linked by urethane bonds. Oligochitosan (OCS) was subsequently introduced to produce another crosslinked structure linked by imine bonds, and the films were fabricated by compression molding. The chemical structures and physical performance of SPEO were characterized. Crystallinity, micromorphology and thermal analysis demonstrated that the dual-crosslinking structures enhanced the composite compatibility, which improved their mechanical properties. The surface hydrophilicity, water absorption, and in vitro degradation rate increased slowly with increasing OCS content, while a high crosslinking density provide a good barrier to water vapor permeation and therefore decreased the water vapor permeability (< 128 g/(m2∙24 h)). Due to the residual −NH2 groups of OCS, the composite film of SPEO-6 exhibited certain bacteriostatic activity against E. coli and S. aureus. Furthermore, the cytotoxicity of the composite films was assayed by the MTT method, and relative growth rates were much higher than 75% after incubation for 72 h, indicating high cytocompatibility and non-toxicity to food. The dual-crosslinked high-starch-content composites possessing high security, superior mechanical properties, good biodegradability, low water vapor permeability, and certain bacteriostatic capacity hold great potential to substitute petroleum-derived plastics for fresh-keeping food packaging applications.

Treatment of Insertional Achilles Tendinosis With Polyurethane Urea-Based Matrix Augmentation.

Surgical treatment for insertional Achilles tendinosis (IAT) sometimes requires tendon repair augmentation. The purpose of this study is to evaluate the efficacy of polycaprolactone-based polyurethane urea (PUUR) matrix augmentation in the treatment of IAT. A retrospective review was performed in surgically treated IAT. Repairs were augmented with a PUUR matrix. Factors evaluated included date of full weightbearing, patient satisfaction, Visual Analog Scale (VAS) pain score, strength, and ankle motion. The Wilcoxon signed-rank test was used to compare baseline and final follow-up VAS scores. A total of 18 cases were included in the study. The mean patient age was 54.61 ± 8.25 (40-75) years with a mean follow-up of 163.61 ± 57.81 (92-314) days. Patient satisfaction was obtained on 15 of 18 patients, with 14 patients satisfied with their outcome. Mean VAS for pain significantly decreased from 6.19 ± 1.97 (2.5-9) to 0.83 ± 1.54 (0-5) postoperatively, which was statistically significant (P < .01). Achilles tendon augmentation with the PUUR matrix is a viable option in the treatment of IAT. Its use in this condition has minimal morbidity and can be an alternative to other forms of augmentation. Level IV: Retrospective case series.

Supramolecular Polycaprolactone-Based Polyurethanes with Thermally Activated Shape-Memory Behavior.

In this work, using supramolecular polyurethanes theories, two polycaprolactone-based polyurethanes with 2-ureido-4-[1H]-pyrimidinone (UPy) motifs capable of forming quadruple hydrogen bonds were synthetized and characterized, focusing our attention on their capability to show thermally activated shape-memory response. In particular, 1H NMR analyses confirmed the chemical structure of the supramolecular polyurethanes, while DSC showed their totally amorphous morphology. DMTA in tensile mode was used to study their thermally activated shape-memory properties. In our case, the UPy units are the switching domains while the network formed by the segregated hard segments is the permanent domain obtained materials with excellent shape-memory response at both 100 and 85 °C. These materials are promising for multi-responsive materials where bio-based and potentially recyclable polymers with excellent shape-memory properties are needed.

Hyperelastic, shape-memorable, and ultra-cell-adhesive degradable polycaprolactone-polyurethane copolymer for tissue regeneration.

Novel polycaprolactone‐based polyurethane (PCL‐PU) copolymers with hyperelasticity, shape‐memory, and ultra‐cell‐adhesion properties are reported as clinically applicable tissue‐regenerative biomaterials. New isosorbide derivatives (propoxylated or ethoxylated ones) were developed to improve mechanical properties by enhanced reactivity in copolymer synthesis compared to the original isosorbide. Optimized PCL‐PU with propoxylated isosorbide exhibited notable mechanical performance (50 MPa tensile strength and 1150% elongation with hyperelasticity under cyclic load). The shape‐memory effect was also revealed in different forms (film, thread, and 3D scaffold) with 40%–80% recovery in tension or compression mode after plastic deformation. The ultra‐cell‐adhesive property was proven in various cell types which were reasoned to involve the heat shock protein‐mediated integrin (α5 and αV) activation, as analyzed by RNA sequencing and inhibition tests. After the tissue regenerative potential (muscle and bone) was confirmed by the myogenic and osteogenic responses in vitro, biodegradability, compatible in vivo tissue response, and healing capacity were investigated with in vivo shape‐memorable behavior. The currently exploited PCL‐PU, with its multifunctional (hyperelastic, shape‐memorable, ultra‐cell‐adhesive, and degradable) nature and biocompatibility, is considered a potential tissue‐regenerative biomaterial, especially for minimally invasive surgery that requires small incisions to approach large defects with excellent regeneration capacity.

Surgical Treatment Outcomes of Achilles Tendon Rupture and Tendinosis Augmented with Synthetic Graft

Category:Hindfoot; Sports; TraumaIntroduction/Purpose:Surgical treatments for Achilles tendon ruptures (ATR) or insertional Achilles tendinitis (IAT) traditionally have prolonged postoperative recoveries. Patients are typically kept non-weight bearing or protected weight bearing on the operative extremity for weeks after surgery to protect the repairs. The purpose of this study is to show that augmentation of typical Achilles tendon repairs with a synthetic scaffold is safe, allows for early weight bearing while preserving functional outcome and has a high patient satisfaction.Methods:A retrospective chart review was performed on all patients surgically treated for ATR or IAT from 2018 - 2020. The surgeries were performed by two fellowship trained Foot and Ankle Orthopaedic surgeons. All repairs were augmented with a synthetic scaffold made of polycaprolactone-based polyurethane urea (PUUR). Achilles tendon ruptures were direct end-to-end repairs and IAT repairs were performed with double row biocomposite anchors in the calcaneus after a calcaneus exostectomy. Exclusion criteria included flexor hallucis longus transfer, non-insertional achilles tendinosis, patients undergoing additional surgical procedures, and ATR or IAT repairs not treated with PUUR. Patients were evaluated as a cohort as well as acute ruptures, chronic ruptures (defined as more than 6 weeks old), and IAT subgroups. Primary outcomes were date of weight bearing and patient satisfaction. Secondary outcomes were final strength and ankle dorsiflexion. The Wilcoxon signed-rank test (WSR) was used to compare baseline and final follow-up NRS scores.Results:A total of 33 patients met the inclusion criteria with 12 ATR (9 acute and 3 chronic) and 21 IAT. Mean follow-up length was 150 days (43 - 314). Mean weight bearing began on postoperative day (POD) 7.33 (6-13) for acute ruptures, 14.33 (6-19) for chronic ruptures, and 9.9 (5-42) for IAT. Patient satisfaction, based on a binary yes/no response at final followup, was obtained on 27 of 33 patients with 92.6% positive indicating satisfaction with surgical outcome. Final strength averaged 5/5 for 83.9% and 4/5 for 16.1% of all patients. Final active dorsiflexion of at least 10 degrees was obtained in 93.5%. Mean numerical rating scale (NRS) for pain significantly decreased from 5.2 to 0.6 for all patients (WSR p<0.001). No patients had loss of fixation or had a re-rupture. Complications included one patient with sural neuritis and another with minor wound breakdown that did not require surgical intervention.Conclusion:Augmentation of Achilles tendon ruptures and insertional Achilles tendonitis with PUUR graft is safe, allows for early weight-bearing, has a high patient satisfaction and has acceptable functional outcomes in regards to strength and motion.

Safety Profile of Synthetic Elastic Degradable Matrix for Soft Tissue Reconstruction in Foot & Ankle Surgery.

Augmentation of soft tissue repairs has been helpful in protecting surgically repaired tissues as they heal. FlexBand (Artelon, Marietta, Georgia) is a synthetic, degradable, polycaprolactone-based polyurethane urea (PUUR) matrix that has been investigated and used for soft tissue repair in a variety of settings. The purpose of this study was to evaluate the safety profile of a PUUR matrix in a large cohort of patients undergoing soft tissue repairs about the foot and ankle. A retrospective chart review of consecutive patients who underwent surgery using FlexBand to augment a soft tissue repair was performed to evaluate for major and minor complications related to the PUUR matrix. Results. A total of 105 patients with an average >6 months follow-up were included. The most common procedures were spring ligament repair, Achilles tendon repair, and Brostrom. There were 12 complications. Four major complications occurred with only 1 requiring PUUR matrix removal. Patients with wound complications had a higher body mass index (BMI) and rate of smoking. Complication rates involving PUUR matrix in soft tissue foot and ankle reconstruction procedures are low and comparable with historical complication rates. The PUUR matrix is safe for use in a variety of soft tissue procedures about the foot and ankle.Level of Evidence: Level 4, Retrospective case-series.

The design of polycaprolactone-polyurethane/chitosan composite for bone tissue engineering

In this work, polycaprolactone-based polyurethane urea (PCLUU)/chitosan (CS) composites were fabricated and studied in terms of growth, adhesion, and differentiation of human bone marrow mesenchymal stem cells (hBMSCs) to osteoblasts. The prepared scaffolds were characterized using FT-IR, SEM, 1H NMR, XRD, compression test, water contact angle test, TGA, and in vitro degradation assays. The enhancement of compressive strength (15.82 MPa) and thermal stability occurred due to the stronger interactions between the polymer chains of PCLUU and the CS molecules. The SEM micrographs indicated homogenous and dense morphologies for the prepared scaffold. The in vitro cytocompatibility tests confirmed the non-toxic and biocompatible nature of the prepared scaffolds. The composites promoted the formation of calcium levels and the alkaline phosphatase activity of hBMSCs. The RT-PCR analysis revealed the upregulation of Runt-related transcription factor 2 (Runx2) and osteocalcin (OCN) genes in the hBMSCs cultured on the prepared scaffold in both the growth and osteogenic medium. Alizarin red staining indicated the enhancement of extracellular calcium deposition of the hBMSCs cultured on the fabricated scaffold. Collectively, the prepared scaffold indicated extraordinary properties as a beneficial implantable scaffold in bone tissue engineering and regeneration.

Study on Cyclic Compressive and Dynamic Mechanical Properties of Porous Polyurethane Composites Prepared with Hollow Silica Microspheres.

Porous polycaprolactone-based polyurethane composites containing hollow silica microspheres were synthesized by one-step bulk polymerization. The effects of incorporated hollow silica microspheres on the cyclic compressive and dynamic mechanical properties of the composites were examined. Cyclic compression testing was carried out to record the accumulated stress versus strain profiles during 100 continuous loading and unloading cycles and to study the compressive behavior and time-dependent recovery of the composites. The effects of frequency on the dynamic mechanical properties of the composites was also investigated using a dynamic mechanical analyzer. Cole-Cole and Wicket plots were drawn to check the validity of the time-temperature supposition of the composites in the temperature and frequency ranges considered. Master curves of the composites were constructed based on the time-temperature superposition principle to obtain the long-term dynamic mechanical behavior of the composites.

Synthesis, Characterization, and Electrospinning of a Functionalizable, Polycaprolactone-Based Polyurethane for Soft Tissue Engineering.

We synthesized a biodegradable, elastomeric, and functionalizable polyurethane (PU) that can be electrospun for use as a scaffold in soft tissue engineering. The PU was synthesized from polycaprolactone diol, hexamethylene diisocyanate, and dimethylolpropionic acid (DMPA) chain extender using two-step polymerization and designated as PU-DMPA. A control PU using 1,4-butanediol (1,4-BDO) as a chain extender was synthesized similarly and designated as PU-BDO. The chemical structure of the two PUs was verified by FT-IR and 1H-NMR. The PU-DMPA had a lower molecular weight than the PU-BDO (~16,700 Da vs. ~78,600 Da). The melting enthalpy of the PU-DMPA was greater than that of the PU-BDO. Both the PUs exhibited elastomeric behaviors with a comparable elongation at break ( 13.2). The PU-DMPA had a higher initial modulus (19.8 MPa vs. 8.7 MPa) and a lower linear modulus (0.7 MPa vs. 1.2 MPa) and ultimate strength (9.5 MPa vs. 13.8 MPa) than the PU-BDO. The PU-DMPA had better hydrophilicity than the PU-BDO. Both the PUs displayed no cytotoxicity, although the adhesion of human umbilical artery smooth muscle cells on the PU-DMPA surface was better. Bead free electrospun PU-DMPA membranes with a narrow fiber diameter distribution were successfully fabricated. As a demonstration of its functionalizability, gelatin was conjugated to the electrospun PU-DMPA membrane using carbodiimide chemistry. Moreover, hyaluronic acid was immobilized on the amino-functionalized PU-DMPA. In conclusion, the PU-DMPA has the potential to be used as a scaffold material for soft tissue engineering.

Hydrolytic stability and biocompatibility on smooth muscle cells of polyethylene glycol–polycaprolactone-based polyurethanes

Abstract

Highly toughened polylactide (PLA) by reactive blending with novel polycaprolactone-based polyurethane (PCLU) blends

Polylactide (PLA)/polycaprolactone-based polyurethane (PCLU) blends were prepared by reactive blending of PLA with poly (caprolactone) triol (PCL-polyols) and isophorone diisocyanate (IPDI). The interfacial compatibility was markedly improved by the reaction of the terminal hydroxyl groups of PLA and the N=C=O groups of IPDI, as confirmed by Fourier transform infrared spectroscopy. Results of tensile testing and a notched impact test suggest that the elongation at break and impact strength of PLA/PCLU blends increased to more than 20 and 5 times those of neat PLA, respectively. Moreover, the tensile strength of PLA/PCLU blends slightly decreased. Excellent interfacial adhesion enabled the dispersed polyurethane elastomeric particles to act as effective stress concentration areas. The shearing yielding of PLA matrix triggered by internal cavitation was the main mechanical toughening mechanism.

Anterior tibial tendon repair with polycaprolactone-based polyurethane urea based graft (Artelon)

Category: Sports Introduction/Purpose: Ruptures of the anterior tibial tendon are rare injuries usually occurring in patients over the age of 40. Delayed diagnosis is common and reconstruction often involves the use of autograft or allografts. This paper reports on the use of a polycaprolactone-based polyurethane urea (PUUR) hyperelastic polymer (Artelon) in the repair or reconstruction of anterior tibial tendon ruptures. Methods: Artelon® is a knitted textile matrix that is manufactured from fibers of polycaprolactone-based polyurethane urea (PUUR), a hyperelastic and creep-resistant polymer. Previous studies have demonstrated that Artelon integrates without immune reaction, has mechanical properties that resemble healing tendons and ligaments, and degrades benignly through hydrolysis over a 5-6 year span. This is a retrospective examination of the first 6 cases of anterior tibial tendon reconstruction using the Artelon PUUR graft. Patient outcomes are measured with AOFAS scores. In addition, range of motion and strength of the injured side is compared to the native, uninjured side. Results: There were no complications using the Artelon graft to augment anterior tibial tendon reconstruction and repair. Patient outcomes at 6 months were significantly improved compared to preoperative. Range of motion and strength were similar to the contralateral, uninjured side. Conclusion: Artelon is a safe, effective soft tissue augmentation device that can be used in the setting of anterior tibial tendon repaair or reconstruction.

Tunable Elastomers with an Antithrombotic Component for Cardiovascular Applications.

This study reports the development of a novel family of biodegradable polyurethanes for use as tissue engineered cardiovascular scaffolds or blood-contacting medical devices. Covalent incorporation of the antiplatelet agent dipyridamole into biodegradable polycaprolactone-based polyurethanes yields biocompatible materials with improved thromboresistance and tunable mechanical strength and elasticity. Altering the ratio of the dipyridamole to the diisocyanate linking unit and the polycaprolactone macromer enables control over both the drug content and the polymer cross-link density. Covalent cross-linking in the materials achieves significant elasticity and a tunable range of elastic moduli similar to that of native cardiovascular tissues. Interestingly, the cross-link density of the polyurethanes is inversely related to the elastic modulus, an effect attributed to decreasing crystallinity in the more cross-linked polymers. In vitro characterization shows that the antiplatelet agent is homogeneously distributed in the materials and is released slowly throughout the polymer degradation process. The drug-containing polyurethanes support endothelial cell and vascular smooth muscle cell proliferation, while demonstrating reduced levels of platelet adhesion and activation, supporting their candidacy as promising substrates for cardiovascular tissue engineering.

Synthesis and Characterization of Polycaprolactone-Based Polyurethanes for the Fabrication of Elastic Guided Bone Regeneration Membrane.

The aim of this research is to synthesize polycaprolactone-based polyurethanes (PCL-based PUs) that can be further used for the fabrication of guided bone regeneration (GBR) membranes with higher tensile strength and elongation at break than collagen and PTFE membranes. The PCL-based PUs were prepared by the polymerization of polycaprolactone (PCL) diol with 1,6-hexamethylene diisocyanate (HDI) at different ratios using either polyethylene glycol (PEG) or ethylenediamine (EDA) as chain extenders. The chemical, mechanical, and thermal properties of the synthesized polymers were determined using NMR, FTIR, GPC, DSC, and tensile tester. The PCL and polyurethanes were fabricated as nanofiber membranes by electrospinning, and their mechanical properties and SEM morphology were also investigated. In vitro tests, including WST-1 assay, SEM of cells, and phalloidin cytoskeleton staining, were also performed. It was shown that electrospun membranes made of PCL and PCL-HDI-PEG (2 : 3 : 1) possessed tensile strength of 19.84 MPa and 11.72 MPa and elongation at break of 627% and 362%, respectively. These numbers are equivalent or higher than most of the commercially available collagen and PTFE membrane. As a result, these membranes may have potential for future GBR applications.

High-strain slide-ring shape-memory polycaprolactone-based polyurethane.

To enable shape-memory polymer networks to achieve recoverable high deformability with a simultaneous high shape-fixity ratio and shape-recovery ratio, novel semi-crystalline slide-ring shape-memory polycaprolactone-based polyurethane (SR-SMPCLU) with movable net-points constructed by a topologically interlocked slide-ring structure was designed and fabricated. The SR-SMPCLU not only exhibited good shape fixity, almost complete shape recovery, and a fast shape-recovery speed, it also showed an outstanding recoverable high-strain capacity with 95.83% Rr under a deformation strain of 1410% due to the pulley effect of the topological slide-ring structure. Furthermore, the SR-SMPCLU system maintained excellent shape-memory performance with increasing the training cycle numbers at 45% and even 280% deformation strain. The effects of the slide-ring cross-linker content, deformation strain, and successive shape-memory cycles on the shape-memory performance were investigated. A possible mechanism for the shape-memory effect of the SR-SMPCLU system is proposed.