Thermosensitive Polyurethane Research Articles

Thermosensitive Polyurethane-Based Hydrogels as Potential Vehicles for Meloxicam Delivery.

Meloxicam (MX) is a nonsteroidal anti-inflammatory drug (NSAID) used mainly to reduce pain, inflammation, and fever. In the present study, thermosensitive polyurethane (PU)-based hydrogels with various excipients (PEG, PVP, HPC, and essential oil) were prepared and loaded with MX. Rheological investigations were carried out on the PU-based formulations in various shear regimes, and their viscoelastic characteristics were determined. The average size of the PU micelles was 35.8 nm at 37 °C and slightly increased at 37 nm in the presence of MX. The zeta potential values of the hydrogels were between -10 mV and -11.5 mV. At pH = 6 and temperature of 37 °C, the formulated PU-based hydrogels loaded with MX could deliver significant amounts of the active substance, between 60% and 80% over 24-48 h and more than 90% within 2 weeks. It was found that anomalous transport phenomena dominated MX's release mechanism from the PU-based networks. The results are encouraging for further studies aiming to design alternative carriers to commercial dosage forms of nonsteroidal anti-inflammatory drugs.

Impacting Neonatal Patient Care: Reducing Needle Sticks, with an Extended Dwell Catheter

Highlights Abstract Background: The use and efficacy of extended dwell peripheral intravenous catheters (EPIVs) has been extensively described at scientific conferences and in recent literature. The ramifications of repeated needle sticks include damage to vessels and ultimately the need for more invasive and costly access devices, which clearly support the need for reliable forms of vascular access. Methods: This quality improvement project spanned 4 years, 2017 through 2020, and included 128 patients who required a peripherally inserted catheter as their primary or secondary access site for a prescribed therapy. The EPIV utilized was a 4-cm, 22-gauge catheter made of thermosensitive polyurethane inserted using the Seldinger technique. Results: Over the course of 4 years, 128 patients received an EPIV for 2 or more days, totaling 849 days of therapy. Total insertion attempts were 174 or an average of 1.4 per patient. An estimated number of short PIVs needed for 849 days would have been 404 with 1011 attempts. Resultant savings with EPIV are estimated to be $30,686. Conclusions: Reducing the number of patient peripheral intravenous attempts while extending the dwell time results in less patient trauma, reliable longer-term access, reduced infection risk, reduced supply usage, and savings in terms of nursing time. The ultimate result for preterm newborns is more efficient delivery of care with less cost.

A versatile and low-toxicity material for photothermal therapy in deeper tissues.

The limited depth of the near infrared (NIR) response is one of the major flaws of the present photothermal therapy (PTT). In this article, thermosensitive polyurethane urea (TPUU) was synthesized by polymerization. Subsequent experiments showed that, compared with classical photosensitizers, TPUU has higher photothermal effects and lower cytotoxicity. These valuable properties could make the present PTT research provide more therapeutic options among different tissues and organs. As a practical example, TPUU was applied to regulate the intestinal flora through external NIR irradiation, which implied its promising expanded applications in deeper tissues.

Synthesis and characterization of PLGA-PEG-PLGA based thermosensitive polyurethane micelles for potential drug delivery

Polyurethane nanomicelle is a promising functional drug delivery system. In this work, the polyurethane (P3-PU) was synthesized from PLGA1200-PEG1450-PLGA1200 (P3, a thermosensitive and biodegradable triblock copolymer) and L-lysine ester diisocyanate (LDI). Then, reactive benzaldehyde was further imported to terminate P3-PU to obtain benzaldehyde modified polyurethane (P3-PUDA). The micelles, temperature-sensitive P3-PU nanomicelle and P3-PUDA nanomicelle, were systematically investigated, including the size, stability, temperature sensitivity, drug loading and release behavior, cytotoxic on human hepatocytes (L02), and inhibitory effect on human hepatocellular carcinoma cells (HepG2). The results show the thermosensitive behavior of the micelles can be adjusted by the terminal group. The polyurethane micelles with a uniform size between 20 nm and 30 nm showed excellent stability and good biocompatibility to L02 cells. Besides, in vitro experiments showed that Dox-loaded P3-PUDA micelles exhibited faster and higher release rate at 37 °C and better inhibitory effect on HepG2 than the Dox-loaded P3-PU micelles. Moreover, the achieved benzaldehyde modified polyurethanes also provides various possibilities to adjust further to enlarge its applications. Therefore, the polyurethane micelles will have great potential in the field of drug carriers.

Thermal energy regulated and thermochromic composite film with temperature-sensitive “breathable” stomata

Intelligent breathable membranes with multiple functions attach wide attentions of people which provide protection and comfort to meet the pressing demand for future protective clothing. We proposed a novel thermal energy regulated and thermochromic composite film with temperature-sensitive “breathable” stomata consisted of thermochromic nanofibrous membrane (TC-NFM) and thermo-sensitive polyurethane (PU) film. Thermochromic nanoencapsulated phase change materials (TC-NPCMs) were introduced as functional fillers into polyvinyl alcohol/water-soluble polyurethane (PVA/WPU) solution for electrospinning process. And methylated melamine–formaldehyde (MMF) was innovatively used to modify the water resistance of TC-NFM. By adjusting the molecular weight of the soft segment, the thermo-sensitive PU film was successfully prepared. Consequently, the prepared TC-NFM exhibited high enthalpy of 44.3 J g−1 and kept superior energy storage and release property even after 100th cyclic experiments. The water vapor permeability of thermo-sensitive PU film was triggered near the comfortable temperature of the human body. The results presented here might facilitate improvements in the field of thermal regulation clothing, intelligent clothing, wearable temperature sensor and reversible thermochromic coating materials.

Hybrid Injectable Sol-Gel Systems Based on Thermo-Sensitive Polyurethane Hydrogels Carrying pH-Sensitive Mesoporous Silica Nanoparticles for the Controlled and Triggered Release of Therapeutic Agents.

Injectable therapeutic formulations locally releasing their cargo with tunable kinetics in response to external biochemical/physical cues are gaining interest in the scientific community, with the aim to overcome the cons of traditional administration routes. In this work, we proposed an alternative solution to this challenging goal by combining thermo-sensitive hydrogels based on custom-made amphiphilic poly(ether urethane)s (PEUs) and mesoporous silica nanoparticles coated with a self-immolative polymer sensitive to acid pH (MSN-CS-SIP). By exploiting PEU chemical versatility, Boc-protected amino groups were introduced as PEU building block (PEU-Boc), which were then subjected to a deprotection reaction to expose pendant primary amines along the polymer backbone (PEU-NH2, 3E18 -NH2/gPEU–NH2) with the aim to accelerate system response to external acid pH environment. Then, thermo-sensitive hydrogels were designed (15% w/v) showing fast gelation in physiological conditions (approximately 5 min), while no significant changes in gelation temperature and kinetics were induced by the Boc-deprotection. Conversely, free amines in PEU-NH2 effectively enhanced and accelerated acid pH transfer (pH 5) through hydrogel thickness (PEU-Boc and PEU-NH2 gels covered approximately 42 and 52% of the pH delta between their initial pH and the pH of the surrounding buffer within 30 min incubation, respectively). MSN-CS-SIP carrying a fluorescent cargo as model drug (MSN-CS-SIP-Ru) were then encapsulated within the hydrogels with no significant effects on their thermo-sensitivity. Injectability and in situ gelation at 37°C were demonstrated ex vivo through sub-cutaneous injection in rodents. Moreover, MSN-CS-SIP-Ru-loaded gels turned out to be detectable through the skin by IVIS imaging. Cargo acid pH-triggered delivery from PEU-Boc and PEU-NH2 gels was finally demonstrated through drug release tests in neutral and acid pH environments (in acid pH environment approximately 2-fold higher cargo release). Additionally, acid-triggered payload release from PEU-NH2 gels was significantly higher compared to PEU-Boc systems at 3 and 4 days incubation. The herein designed hybrid injectable formulations could thus represent a significant step forward in the development of multi-stimuli sensitive drug carriers. Indeed, being able to adapt their behavior in response to biochemical cues from the surrounding physio-pathological environment, these formulations can effectively trigger the release of their payload according to therapeutic needs.

Thermomechanical and Shape Memory Performances of Thermo-sensitive Polyurethane Fibers

This study is the first step to investigate usability of shape memory polyurethane (SMPU) fibers for smart garment applications. SMPU fibers were spun by wet spinning process and chemical/mechanical characterization was carried out. SMPU solutions were prepared with two different concentrations (20 % and 25 %) and three different coagulation bath concentrations (0 %, 1 % and 3 %) were used for determining optimum spinning parameters. For investigating influences of spinning process on crystal structure, mechanical, thermal and shape memory performances of fibers, X-ray diffraction (XRD), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), scanning electron microscopy (SEM) and mechanical tests were conducted. DSC and DMA analysis results show that shape memory polyurethane fibers have a glass transition temperature about 35-40 oC which is suitable for body temperature. Moreover, SMPU fibers showed good tensile performance with an average tenacity of 1.38 cN/dtex and elongation at break of 350 %. Thermo mechanical test results showed that, all shape memory fibers have good shape memory effect with recovery and fixity ratios up to 91 % and 71 % respectively.

Water vapor permeability of thermosensitive polyurethane films obtained from isophorone diisocyanate and polyester or polyether polyol

A series of thermosensitive films for firefighting applications were synthesized by two-step polymerization from two types of polyol and isophorone diisocyanate and by the formation of aqueous polyurethane dispersions. This study was conducted to clarify the influence of different parameters such as the type of polyol, the chain length of polyol, and the hard segment content on the chemical, thermal, mechanical and diffusion properties of the final films using ATR infrared spectroscopy, differential scanning calorimetry, thermogravimetric analyses, water vapor permeability, swelling behavior, contact angle measurement, and dynamic mechanical analyses. It was noticed that the humidity transfer was influenced by the soft segment crystallization. Indeed, it enhanced the chain mobility in bulk materials leading to an increase in water vapor permeability rather than in swelling. In contrast, low crystallization induced surface state modification resulting in higher swelling capacity.

Synthesis and Characterization of Temperature-Sensitive TSPU/PNIPAAm Semi-IPN Polymer

Thermo-sensitive polyurethane (TSPU) was synthesized from poly(ε-caprolactone) and 4,4’-methylenebis (phenyl isocyanate) by a two-step process with 1,4-butanediol as the chain extender. Following that, a novel temperature-sensitive material was created by the strategy of IPN from TSPU and PNIPAAm in the method of in situ polymerization. The chemical structure and thermo properties of the semi-IPN were characterized with FT-IR and DSC. The results prove that intensive inter-molecular interactions exist between TSPU and PNIPAAm chains, which have significant influence on the phase transition behaviors of the material. According to these results, the transition temperature of the semi-IPN can be adjusted in the range of 30~40 °C by controlling the composition of TSPU and the semi-IPNs.

Membrane formation temperature-dependent gas transport through thermo-sensitive polyurethane containing in situ-generated TiO2 nanoparticles

Thermo-sensitive polyurethane (TSPU) solution containing varying concentration of in situ-generated TiO2 nanoparticles was successfully prepared via an organic–inorganic hybrid technique, and the final nanocomposite membranes were formed via solution casting. Depending on the membrane formation temperature (Tmf) during casting, completely-opposite gas transport behaviors of the TSPU nanocomposite membranes were observed. When Tmf was lower than the melting point (Tm) of soft segment (PCL10000) in the TSPU, gas permeability coefficients of the nanocomposite membranes were found to increase significantly with increasing nano-TiO2 concentration. Conventional composite theory failed to explain such observation because filler particles are generally considered to create more tortuous diffusion path in the polymer for penetrants, and should thereby lead to a systematic reduction in gas permeability. This counter-intuitive phenomenon was then rationalized by postulating that rigid TSPU chain could not pack efficiently around the TiO2 nanoparticles during solvent evaporation, which resulted in polymer layer with higher free volume at the interface than the bulk polymer regions. Evidences supporting such presumption were provided by (1) density measurement that found negative deviation of actual densities of TSPU nanocomposite membranes from theoretical prediction; (2) positron annihilation lifetime spectroscopy that demonstrated increased free-volume size and concentration within TSPU upon the in situ generation of TiO2 nanoparticles. However, when Tmf was elevated above the Tm of the soft segment, flexible TSPU chain seemed able to pack around the TiO2 nanoparticles as efficiently as in the bulk polymer. In this case, gas transport behavior of the TSPU nanocomposite membranes followed the prediction of conventional composite theory.

Thermosensitive polyurethane film and finished leather with controllable water vapor permeability

AbstractThree types of water based polyurethane (PU), i.e. one ordinary elastomeric polyurethane (EPU) and two thermosensitive polyurethane (TSPU), were synthesized and applied in leather finishing. Differential scanning calorimetry, positron annihilation lifetimes (PAL), water swelling, and water vapor permeability (WVP) were measured to evaluate how the structure of the synthesized PU and the temperature influenced the WVP of the PU finished leather. In contrast to EPU, TSPU(b) with a glass transition reversible phase and TSPU(c) with a crystal transition reversible phase showed an obvious phase separation structure and a phase transition in the normal wearing temperature range. PAL study indicated that when the temperature was higher than the designed phase transition temperature, the ortho‐positronium lifetime (τ3) and the average radius (R) of free volume of TSPU showed dramatic changes, whereas τ3 and R of EPU remained unchanged. The water swelling and WVP of TSPU finished leather were found to depend on the structure of the polymer and the temperature, and they gave different responses to temperature variation. When the temperature was higher than the designed phase transition temperature, a significant WVP increase from 3800 g/(m2 24 h) to 7830 g/(m2 24 h) for TSPU(b) finished leather and from 4100 g/(m2 24 h) to 9450 g/(m2 24 h) for TSPU(c) finished leather were observed. Whereas EPU finished leather showed low WVP, and increased slightly as temperature increased. Phase transition accompanying a significant change in WVP can be used to develop “smart leather” with controllable water vapor permeability. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Thermo-sensitive polyurethane membrane with controllable water vapor permeation for food packaging

The size and shape of free volume (FV) holes available in membrane materials control the rate of gas diffusion and its permeability. Based on this principle, a segmented, thermo-sensitive polyurethane (TSPU) membrane with functional gate, i.e., the ability to sense and respond to external thermo-stimuli, was synthesized. This smart membrane exhibited close-open characteristics to the size of the FV hole and water vapor permeation and thus can be used as smart food packaging materials. Differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), positron annihilation lifetimes (PAL) and water vapor permeability (WVP) were used to evaluate how the morphological structure of TSPU and the temperature influence the FV holes size. In DSC and DMA studies, TSPU with a crystalline transition reversible phase showed an obvious phase-separated structure and a phase transition temperature at 53 °C (defined as the switch temperature and used as a functional gate). Moreover, the switch temperature (T s ) and the thermal-sensitivity of TSPU remained available after two or three thermal cyclic processes. The PAL study indicated that the FV hole size of TSPU is closely related to theT s . When the temperature varied cyclically fromT s -10 °C toT s +10 °C, the average radius (R) of the FV holes of the TSPU membrane also shifted cyclically from 0.23 to 0.467 nm, exhibiting an “open-close” feature. As a result, the WVP of the TSPU membrane also shifted cyclically from 4.30 to 8.58 kg/m2d, which produced an “increase-decrease” response to the thermo-stimuli. This phase transition accompanying significant changes in the FV hole size and WVP can be used to develop “smart materials” with functional gates and controllable water vapor permeation, which support the possible applications of TSPU for food packaging.

New thermogelling copolymers composed of heptakis(2,6-di-O-methyl)-β-cyclodextrin, poly(propylene glycol), and poly(ethylene glycol)

A series of new thermosensitive polyurethane copolymers composed of heptakis(2,6-di-O-methyl)-β-cyclodextrin (DM-β-CD), poly(propylene glycol) (PPG), and poly(ethylene glycol) (PEG) blocks using 1,6-hexamethylene diisocyanate (HMDI) as a coupling agent were synthesized. Their chemical structures and molecular characteristics were studied using GPC analysis and 1H NMR and 13C NMR spectral analysis. We found that the copolymers had high molecular weight and the DM-β-CD, PPG, and PEG blocks were bonded by a hexamethylene dicarbamyl (HMDC) junction. DSC analysis showed that the molar motion of the PPG and PEG segments was restricted in the copolymers. Moreover, the copolymers are amphiphilic and they have very low critical micelle concentration (CMC) values ranging from 2.63–8.51 g L−1. Upon increasing temperature, the aqueous solutions of the copolymers were found to undergo a reversible clear sol–gel–turbid sol transition. The results from phase diagrams showed that the copolymers had very low critical gelation concentration (CGC) values ranging within 3–6 wt%. The copolymers synthesized in the study are easily soluble in water at room temperature, thus hydrophobic pharmaceutical agents could be entrapped into the hydrophobic cavity of CDs or loaded in the core of micelles. Then, these pharmaceutical agents are encapsulated into the gel when the copolymer forms a gel depot at around body temperature. Hence, these copolymers have potential to be used as injectable drug delivery systems.

The polyurethane membranes with temperature sensitivity for water vapor permeation

The size and shape of free-volume holes available in membrane materials control the rate of gas diffusion and its permeability. Based on this principle, two segmented thermo-sensitive polyurethane (TSPU) membranes with functional gates, i.e. the ability to sense and respond to external thermo-stimuli, were synthesized and used for water vapor controllable permeation. Differential scanning calorimetry (DSC), positron annihilation lifetimes (PAL), water swelling and water vapor permeability (WVP) were used to evaluate how the structure of the polyurethane (PU) and the temperature influence the free-volume holes size and the water vapor permeability (WVP) of the PU membranes. DSC study reveals that TSPU with a glass transition or a crystalline transition reversible phase shows an obvious phase-separated structure and a phase transition temperature (defined as switch temperature, T s). PAL study indicates that the free-volume holes size of TSPU is closely related to the T s. When the temperature is higher than the T s, the ortho-positronium ( o-Ps) lifetime ( τ 3) and the average radius ( R) of free-volume holes of TSPU membrane increase dramatically. As a result, the WVP of TSPU membrane shows a dramatic increase. Additionally, the water swelling and the WVP of TSPU membrane are found to depend on the inner structure of the polymer, and they also give different responses to temperature variation. When the temperature is higher than the T s, there is a significant increase of WVP from 3.80 kg/m 2 day to 7.63 kg/m 2 day for TSPU(a) and from 4.30 kg/m 2 day to 8.58 kg/m 2 day for TSPU(b), respectively. Phase transition accompanying significant changes in free-volume holes size and WVP can be used to develop “smart membranes” with functional gates and controllable gas permeation.

Synthesis and properties of thermosensitive polyurethane- b-poly( N-isopropyl acrylamide)

Polyurethane- b-poly( N-isopropyl acryl amide) block copolymers having 0–40% N-isopropyl acryl amide have been synthesized via AB crosslinked polymerization technique and tested for various properties. It was possible to systematically control the thermal, mechanical, dynamic mechanical properties as well as swelling–deswelling characteristics of the copolymers by controlling the block length.