Fabrication of Hydroxy-Terminated Polybutadiene with Piezoelectric Property by Functionalized Branch Chain Modification.

Hydroxyl-terminated polybutadiene (HTPB)-based piezoelectric polymer (m-HTPB) is prepared for the first time by functionalized branch chain modification strategy. In the presence of HTPB with >98.8% cis-1,4 content, the C=C bond partly breaks down, and functionalized acetylferrocene groups are introduced to the cis-1,4 polybutadiene branch chain, retaining the high cis-1,4 content of HTPB. The whole process is conducted under mild conditions, without complicated manipulations. The microstructure and molecular weight of m-HTPB are characterized by Fourier-transform infrared (FTIR) spectra, 1H or 13C nuclear magnetic resonance spectrum (NMR), and gel permeation chromatography (GPC). The thermal properties of HTPB and m-HTPB are determined by differential scanning calorimetry (DSC). Electrochemical investigations reveal that m-HTPB exhibits higher conductance compared with HTPB. The m-HTPB flexible piezoelectric polymer is further used for in situ and real-time pressure monitoring. This simple and effective strategy provides a promising polymeric material for flexible piezoelectric sensors.

Anisotropic Reaction Properties for Different HMX/HTPB Composites: A Theoretical Study of Shock Decomposition.

Plastic-bonded explosives (PBXs) consisting of explosive grains and a polymer binder are commonly synthesized to improve mechanical properties and reduce sensitivity, but their intrinsic chemical behaviors while subjected to stress are not sufficiently understood yet. Here, we construct three composites of ß-HMX bonded with the HTPB binder to investigate the reaction characteristics under shock loading using the quantum-based molecular dynamics method. Six typical interactions between HMX and HTPB molecules are detected when the system is subjected to pressure. Although the initial electron structure is modified by the impurity states from HTPB, the metallization process for HMX does not significantly change. The shock decompositions of HMX/HTPB along the (100) and (010) surface are initiated by molecular ring dissociation and hydrogen transfer. The initial oxidations of C and H within HTPB possess advantages. As for the (001) surface, the dissociation is started with alkyl dehydrogenation oxidation, and a stronger hydrogen transfer from HTPB to HMX is detected during the following process. Furthermore, considerable fragment aggregation is observed, which mainly derives from the formation of new C-C and C-N bonds under high pressure. The effect of cluster evolution on the progression of the following reaction is further studied by analyzing the bonded structure and displacement rate.

Thermal decomposition mechanism of HMX/HTPB hybrid explosives studied by reactive molecular dynamics.

CONTEXT: The thermal decomposition process of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine/hydroxyl-terminated polybutadiene (HMX/HTPB) hybrid explosives and pure HMX explosives at different temperatures (2000 ~ 3500 K) was investigated using the reactive molecular dynamics method. This study aimed to analyze the effect of binders on the thermal decomposition of HMX at the atomic scale and reveal the thermal decomposition mechanism of HMX/HTPB. The results showed that the thermal decomposition process of the HMX molecule in the HMX/HTPB hybrid system involves a continuous denitration followed by the disintegration of the main ring. The HTPB chain will experience dehydrogenation, dehydroxylation, and chain fragmentation. Including HTPB in the hybrid system significantly increased the presence of H and OH radicals. These radicals then interacted with HMX and its decomposition products and produced more of the final products H2O and H2 in the HMX/HTPB hybrid system compared to pure HMX. Additionally, it was observed that the HTPB chain fragments attached to the HMX decomposition products prevented the formation of N2 and CO2. Furthermore, the activation energies (Ea) of the initial and intermediate decomposition stages of the HMX/HTPB hybrid system were 98.45 kJ mol-1 and 90.69 kJ mol-1, respectively. The results showed that the activation energies of the HMX/HTPB hybrid system are lower than the pure HMX system in these two stages. Consequently, HTPB will enhance HMX's thermal decomposition and decreased the system's insensitivity to heat stimuli. METHODS: The molecular dynamics simulation of the HMX/HTPB hybrid system was performed using the ReaxFF module in the LAMMPS software, and the ReaxFF/lg force field was used to describe the interatomic interactions as well as the chemical reactions.

Preparation and Performance Study of HTPB-g-(PNIPAM/PEG) Thermoresponsive Polymer Brush.

In recent years, a great deal of work has been devoted to the development of thermoresponsive polymers that can be made into new types of smart materials. In this paper, a branched polymer, HTPB-g-(PNIPAM/PEG), with polyolefin chain segments as the backbone and having polyethylene glycol (PEG) and poly(N-isopropylacrylamide) (PNIPAM) as side chains was synthesized by ATRP and click reactions using N3-HTPB-Br as the macroinitiator. This initiator was designed and synthesized using hydroxyl-terminated polybutadiene (HTPB) as the substrate. The temperature-responsive behavior of the branched polymer was investigated. The lower critical solution temperature (LCST) of the branched polymer was determined by ultraviolet and visible spectrophotometry (UV-vis) and was found to be 35.2 °C. The relationship between the diameter size of micelles and temperature was determined by dynamic light scattering (DLS). It was found that the diameter size changed at 36 °C, which was nearly consistent with the result obtained by UV-vis. The results of the study indicate that HTPB-g-(PNIPAM/PEG) is a temperature-responsive polymer. At room temperature, the polymer can self-assemble into composite micelles, with the main chain as the core and the branched chain as the shell. When the temperature was increased beyond LCST, the polyolefin main chain along with the PNIPAM branched chain assembled to form the nucleus, and the PEG branched chain constituted the shell.

Study on Mechanical Properties and Failure Mechanisms of Highly Filled Hydroxy-Terminated Polybutadiene Propellant under Different Tensile Loading Conditions.

To study the mechanical properties of highly filled hydroxy-terminated polybutadiene (HTPB) propellant with 90 wt% solid fillers, the stress-strain curves of the propellant under different temperatures (-50 to 70 °C) and strain rates (0.000476 to 0.119048 s-1) were obtained by uniaxial tensile test. Moreover, to obtain the glass transition temperature and understand the effect of low temperatures on the mechanical properties of the propellant, DMA experiments were carried out. On this basis, the mechanical response laws of the propellant were analyzed, and the master curves of mechanical properties were established. Furthermore, the fracture features of the propellant under typical loading conditions were obtained by SEM, and the corresponding failure mechanisms were analyzed. The results show that the maximum strength decreases with increasing temperature, while the maximum elongation increases with increasing temperature at the same strain rate. The maximum tensile strength increases with increasing strain rate, while the maximum elongation decreases with increasing strain rate at the same temperature. The maximum tensile strength is lowest with a value of 0.35 MPa when the temperature is 343.15 K and the strain rate is 0.000476 s-1, at which time the maximum elongation reaches the highest with a value of 44%. In terms of failure mechanisms, the propellant shows no particle fracture, and the failure modes of the propellant are mainly matrix tearing and dewetting.

In Situ Monitoring of Curing Reaction in Solid Composite Propellant with Fiber-Optic Sensors.

Curing activity in the preparation of solid composite propellants determines the performance of solid rocket motors in operation. Limited by the lack of effective monitoring tools, the complete curing behavior and thermal-induced curing kinetics are rarely disclosed. It is still a challenge to monitor in situ and in real-time the physical and chemical cross-linking reaction during the curing of propellant. Herein, we demonstrate a promising approach based on optical fiber capable of being implanted inside the propellant to monitor the internal stress evolution during the curing process, by taking hydroxyl-terminated polybutadiene propellant as an example. Attributed to the strain and temperature sensitivity of a pair of optical fiber gratings, the thermal-assisted physico-chemical cross-linking states of curing process have been demonstrated in detail. By tracking the stress-induced wavelength shifts of fiber gratings and calculating the curing mechanism function, the complete curing roadmap, including the viscous flow stage, gel stage, hardening stage can be clearly revealed, and the curing completion times are obtained as 154, 81, and 40 h, at the curing temperatures of 60, 70, and 80 °C, respectively. The apparent activation energy of this curing system obtained by calculation is 73.88 kJ/mol. This flexible fiber-based sensor provides an effective tool for unraveling the cure kinetic mechanism, and paves a universal pathway to guide the preparation and applications of versatile composite materials for solid rocket motors.

Solid Rocket Propellant Photo-Polymerization with an In-House LED-UV Prototype.

Composite solid propellants have used cast molding production technology for many decades, with intrinsic limitations on production flexibility, promptness, and grain geometry, as well as environmental implications on toxicity and global carbon footprint. This traditional method involves the use of toxic chemicals, has a long processing time, requires high temperature, and the products have limited geometries. To overcome those issues, different photo-curable resins have been evaluated as possible matrices. In fact, the UV-curing process is fast and has low energy consumption. The photocuring reaction parameters of six different pristine formulations were evaluated by Fourier transform infrared spectroscopy analysis. After finding the optimal curing parameters, different composites were prepared by adding 75 or 80 wt% ammonium sulfate particles used as an inert replacement for the oxidant. The thermomechanical properties and thermal resistance of the UV-cured composites were characterized via dynamic thermal-mechanical and thermogravimetric analysis. Subsequently, the mechanical properties of the inert propellants were investigated by tensile tests. The most promising resin systems for the production of solid rocket propellants were then 3D printed by an in-house developed illumination system and the obtained object micro-structure was evaluated by X-ray computed tomography.

Effect of Mechanical Heterogeneity on the Structural Integrity of HTPB Propellant Grain.

To investigate the structural effects of the mechanical heterogeneity of Hydroxyl-terminated polybutadiene (HTPB) propellant grain under ignition pressurization, a gradient finite element method was proposed to evaluate its structural integrity. The heterogeneous mechanical properties of the propellant grain were constructed and assessed. The results demonstrate that the mechanical properties of the propellant grain are spatially variable when taking into account the effect of the load. The range of variation in the mechanical properties is related to the size of the load and its effect on the mechanical properties of the propellant. Two key parameters that affect the mechanical response of the grain are the non-uniform distribution of the modulus and the damage strain threshold. An increase in the propellant modulus leads to an increase in the stress response and a decrease in the strain response of the propellant grain under ignition pressurization. Meanwhile, an increase in the damage strain threshold improves the propellant's modulus in the linear elastic stage in a disguised form. This also leads to an increase in the stress response and a decrease in the strain response when the strain response exceeds the damage strain threshold. The safety factor, based on the equivalent strain failure criterion of the grain, directly depends on both the strain response of the propellant grain and the maximum elongation of the propellant. Furthermore, the change in the safety factor of two propellant grains is primarily affected by the maximum elongation of the propellant.

Comparative Study on Thermal Response Mechanism of Two Binders during Slow Cook-Off.

The HTPE (hydroxyl-terminated polyether) propellant had a lower ignition temperature (150 °C vs. 240 °C) than the HTPB (hydroxy-terminated polybutadiene) propellant in the slow cook-off test. The reactions of the two propellants were combustion and explosion, respectively. A series of experiments including the changes of colors and the intensity of infrared characteristic peaks were designed to characterize the differences in the thermal response mechanisms of the HTPB and HTPE binder systems. As a solid phase filler to accidental ignition, the weight loss and microscopic morphology of AP (30~230 °C) were observed by TG and SEM. The defects of the propellant caused by the cook-off were quantitatively analyzed by the box counting method. Above 120 °C, the HTPE propellant began to melt and disperse in the holes, filling the cracks, which generated during the decomposition of AP at a low temperature. Melting products were called the "high-temperature self-repair body". A series of analyses proved that the different thermal responses of the two binders were the main cause of the slow cook-off results, which were likewise verified in the propellant mechanical properties and gel fraction test. From the microscopic point of view, the mechanism of HTPE's slow cook-off performance superior to HTPB was revealed in this article.

One-Pot Preparation of HTPB/nNi and Its Catalyst for AP.

The liquid phase reduction method is a common method used for preparing nano-nickel powder (nNi). However, the nNi surface is easily oxidized to form nickel oxide film, which affects its performance. In this work, nNi was prepared using anhydrous ethanol as a solvent and hydrazine hydrate as a reducing agent. Furthermore, HTPB/nNi composites were prepared using hydroxyl-terminated polybutadiene (HTPB) as a coating agent. The structure and morphology of the samples are characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The catalytic behavior of HTPB/nNi on the thermal decomposition of ammonium perchlorate (AP) is studied by differential scanning calorimetry (DSC) and thermogravimetric analyzer (TG). The results show that HTPB/nNi has little effect on the low temperature thermal decomposition of AP, but the peak of high temperature thermal decomposition advances from 456 °C to 332 °C.

Numerical Conversion Method for the Dynamic Storage Modulus and Relaxation Modulus of Hydroxy-Terminated Polybutadiene (HTPB) Propellants.

As a typical viscoelastic material, solid propellants have a large difference in mechanical properties under static and dynamic loading. This variability is manifested in the difference in values of the relaxation modulus and dynamic modulus, which serve as the entry point for studying the dynamic and static mechanical properties of propellants. The relaxation modulus and dynamic modulus have a clear integral relationship in theory, but their consistency in engineering practice has never been verified. In this paper, by introducing the "catch-up factor λ" and "waiting factor γ", a method for the inter-conversion of the dynamic storage modulus and relaxation modulus of HTPB propellant is established, and the consistency between them is verified. The results show that the time region of the calculated conversion values of the relaxation modulus obtained by this method covers 10−8−104 s, spanning twelve orders of magnitude. Compared to that of the relaxation modulus (10−4−104 s, spanning eight orders of magnitude), an expansion of four orders of magnitude is achieved. This enhances the expression ability of the relaxation modulus on the mechanical properties of the propellant. Furthermore, when the conversion method is applied to the dynamic−static modulus conversion of the other two HTPB propellants, the results show that the correlation coefficient between the calculated and measured conversion values is R2 > 0.933. This proves the applicability of this method to the dynamic−static modulus conversion of other types of HTPB propellants. It was also found that λ and γ have the same universal optimal value for different HTPB propellants. As a bridge for static and dynamic modulus conversion, this method greatly expands the expression ability of the relaxation modulus and dynamic storage modulus on the mechanical properties of the HTPB propellant, which is of great significance in the research into the mechanical properties of the propellant.

Enhanced oxygen barrier properties of poly(lactic acid) via oxygen scavenging strategy combining with uniaxial stretching.

Poly(lactic acid) (PLA) films with significantly enhanced mechanical and oxygen barrier properties were obtained via oxygen scavenging strategy combining with uniaxial stretching. In this study, PLA was melt blended with 3 phr of hydroxy-terminated polybutadiene (HTPB) and different contents of acetyl(tributyl citrate) (ATBC) and cobalt neodecanoate. It was then followed by compression molding and uniaxial stretching. After uniaxial stretching, the crystallinity of all films was significantly improved, which contributed to the enhancement in the oxygen barrier performance of composite materials. The morphological analysis carried out using scanning electron microscopy (SEM) revealed that ATBC could obviously promote the dispersion of HTPB in PLA. Overall, the blend films showed a decrease in the oxygen permeability coefficient as compared with the neat PLA film, which reached a similar level to oriented PET film. The optical and mechanical properties of the blend films with ATBC also improved considerably. This work provides a method to prepare high-crystalline polymers with superior gas-barrier properties having great potential for use in high-barrier applications, such as polymers for oxygen-sensitive food packaging.

Microbial degradation and community structure analysis of hydroxyl-terminated polybutadiene (HTPB).

Hydroxyl-terminated polybutadiene (HTPB) is a curing adhesive that is commonly used in the production of ammunition, and it emerged during the time of war. After entering the peaceful era, several countries around the globe have focused on the destruction of expired ammunition using safe and economical methods in terms of consumption of energy. Microorganisms exhibit a highly efficient and environment friendly degradation capability for variety of refractory substances. Therefore, in this study we screened five strains of microorganisms from five environmental soil samples for their ability to degrade HTPB. These microorganisms were identified as Microbacterium trichothecenolyticum, Microbacterium esteraromaticum, Arthrobacter pascens, Pseudonocardia carboxydivorans and Ochrobactrum anthropic based on 16S rRNA gene similarity index. We observed the uncorroded and corroded HTPB sample through scanning electron microscopy and observed the formation of lot of holes and gullies in HTPB after corrosion. An 18S rRNA gene clone library was constructed for HTPB-degrading fungi. Based on the results of library evaluation, it was found that the structure of the HTPB-degrading fungi community was relatively simple. A total of 54 positive clones were obtained. These clones represented some uncultured microorganisms that were closely related to Scytalidium lignicola, Pseudokahliella and Gonostomum strenuum. This study will help in the implementation of environment friendly degradation strategies for HTPB degradation.

The Functional Differences between the GroEL Chaperonin of Escherichia coli and the HtpB Chaperonin of Legionella pneumophila Can Be Mapped to Specific Amino Acid Residues.

Group I chaperonins are a highly conserved family of essential proteins that self-assemble into molecular nanoboxes that mediate the folding of cytoplasmic proteins in bacteria and organelles. GroEL, the chaperonin of Escherichia coli, is the archetype of the family. Protein folding-independent functions have been described for numerous chaperonins, including HtpB, the chaperonin of the bacterial pathogen Legionella pneumophila. Several protein folding-independent functions attributed to HtpB are not shared by GroEL, suggesting that differences in the amino acid (aa) sequence between these two proteins could correlate with functional differences. GroEL and HtpB differ in 137 scattered aa positions. Using the Evolutionary Trace (ET) bioinformatics method, site-directed mutagenesis, and a functional reporter test based upon a yeast-two-hybrid interaction with the eukaryotic protein ECM29, it was determined that out of those 137 aa, ten (M68, M212, S236, K298, N507 and the cluster AEHKD in positions 471-475) were involved in the interaction of HtpB with ECM29. GroEL was completely unable to interact with ECM29, but when GroEL was modified at those 10 aa positions, to display the HtpB aa, it acquired a weak ability to interact with ECM29. This constitutes proof of concept that the unique functional abilities of HtpB can be mapped to specific aa positions.

Preparation and Characterization of Al/HTPB Composite for High Energetic Materials.

Nanosized Al (nAl) powders offer increased reactivity than the conventional micron-sized counterpart, thanks to their reduced size and increased specific surface area. While desirable from the combustion viewpoint, this high reactivity comes at the cost of difficult handling and implementation of the nanosized powders in preparations. The coating with hydroxyl-terminated polybutadiene (HTPB) is proposed to improve powder handling and ease of use of nAl and to limit its sensitivity to aging. The nAl/HTPB composite can be an intermediate product for the subsequent manufacturing of mixed high-energy materials while maintaining the qualities and advantages of nAl. In this work, experimental studies of the high-energy mixture nAl/HTPB are carried out. The investigated materials include two composites: nAl (90 wt.%) + HTPB (10 wt.%) and nAl (80 wt.%) + HTPB (20 wt.%). Thermogravimetric analysis (TGA) is performed from 30 to 1000 °C at slow heating rate (10 °C/min) in inert (Ar) and oxidizing (air) environment. The combustion characteristics of propellant formulations loaded with conventional and HTPB-coated nAl are analyzed and discussed. Results show the increased burning rate performance of nAl/HTPB-loaded propellants over the counterpart loaded with micron-sized Al.

Influence of Thermally-Accelerated Aging on the Dynamic Mechanical Properties of HTPB Coating and Crosslinking Density-Modified Model for the Payne Effect.

Hydroxyl terminated polybutadiene (HTPB) coating is widely used in a solid rocket motor, but an aging phenomenon exists during long-term storage, which causes irreversible damage to the performance of this HTPB coating. In order to study the effect of aging on the dynamic mechanical properties of the HTPB coating, the thermally-accelerated aging test was carried out. The variation of maximum elongation and crosslinking density with aging time was obtained, and a good linear relationship between maximum elongation and crosslinking density was found by correlation analysis. The changing regularity of dynamic mechanical properties with aging time was analyzed. It was found that with the increase of aging time, Tg of HTPB coating increased, Tα, tan ß and tan α decreased, and the functional relationships between the loss factor parameters and crosslinking density were constructed. The storage modulus and loss modulus of HTPB coating increased with the increase of aging time, and decreased with the increase of pre-strain. The aging enhanced the Payne effect of HTPB coating, while the pre-strain had a weakening effect. In view of the Payne effect of HTPB coating, the crosslinking density was introduced into Kraus model as aging evaluation parameter, and the crosslinking density modified models with and without pre-strain were established. The proposed models can effectively solve the problem that the Kraus model has a poor fitting effect under the condition of small strain (generally less than 1%) and on the loss modulus, which have improved the correlations between the fitting results and the test results.

[Determination of hydroxy terminated polybutadiene in the blends by liquid critical condition chromatography].

A method based on liquid critical condition chromatography (LCCC) was established for the quantification of hydroxy-terminated polybutadiene (HTPB) in polymer blends. The critical conditions for HTPB were investigated using a C18 column as the stationary phase, and tetrahydrofuran (THF)-acetonitrile (ACN) or THF-water as the mobile phase. Irrespective of the relative molecular mass, HTPB was eluted under the critical conditions of THF-ACN (70.7:29.3, v/v) or THF-water (92:8, v/v). Under the optimal conditions, the HTPB exhibited satisfactory linearity in the range of 46.7-216.4 mg/L, with a correlation coefficient (r) of 0.997. The limit of detection reached 4.2 mg/L. The recoveries of HTPB from the prepared mixtures of HTPB and mineral oil ranged from 89.2% to 101.1%, with a relative standard derivation of less than 0.66% (n=6). This method was successfully applied to the quantitative analysis of HTPB in a commercial polyurethane adhesive, and 26.6% of HTPB was detected in the product. This LCCC method is simple, convenient, highly selective, and reliable for quality control and failure studies of formulated products.

The rapid H2 release from AlH3 dehydrogenation forming porous layer in AlH3/hydroxyl-terminated polybutadiene (HTPB) fuels during combustion.

Although the motivation of AlH3 enhancing combustion were recognized in many research, the promotion mechanism have been rarely explored. Herein, a previously unreported porous layer mechanism when combustion were determined in HTPB/AlH3 fuels by SEM, thermo-analysis and a new simplified calculation method, owing to rapidly released gas phase H2 from AlH3 dehydrogenation exposing in melting layer. 5/10% 40-80 µm and 10% 80-200 µm AlH3-HTPB formulas show the regression rate increase by, 25.7%, 29.0% and 43.0% at Gox = 350 kg/m2·s, while by 57.2%, 42.0% and 44.2% enhancement at Gox = 150 kg/m2·s. The low AlH3 content (≤ 10%) promotes the regression rate obviously, while excess AlH3 content (≥ 20%) promotes slightly as a result of comprehensive factors combined by energy release, a certain porous layer mechanism, aggregated Al2O3 attached on the burning surface and the blocking effect of the gaseous released H2. A new model predicting the overlapping process of AlH3 dehydrogenation and Al oxidation in air atmosphere was developed by superimposing AlH3 dehydrogenation simulation and corresponding separated Al oxidation simulation. A 1.5th Avrami-Erofeev (A-E) simulation was proposed for Al passivation weight gain between 420 and 520 K with an activation energy of 124.92 kJ/mol and the pre-exponential of 10^12.35.

Review of novel energetic polymers and binders - high energy propellant ingredients for the new space race.

Current solid rocket propellant formulations still employ traditional ingredients utilized since the 1960s, such as hydroxyl terminated polybutadiene (HTPB). Recent advances in energetic polymer see many binders capable of providing higher specific impulse and burn rates over HTPB. As shown by calculations, even slight increases in specific impulse can drastically increase the maximum payload of a launch system. Therefore, replacing HTPB with energetic binders could provide heavy space missions the needed extra boost. Energetic binders could also be paired with chlorine-free energetic oxidizers to synergistically provide a specific impulse exceedingly higher than the current formulation while reducing pollution. A comprehensive evaluation of the synthesis, mechanical properties, and performance of various trending and overlooked energetic polymers is described. Several outstanding candidates show promising properties to replace HTPB.

Facile preparation of pH-responsive polyurethane nanocarrier for oral delivery.

This study reports a novel one pot synthesis of pH-responsive nanocarrier for oral delivery of hydrophobic drug under gastrointestinal tract. Triblock copolymer MPEG-HTPB-MPEG was synthesized coupling of MPEG and HTPB using hexamethylene diisocyanate(HDI) and pH-responsive carboxylic acid group was attached to polybuthadiene backbone by thiol-ene click reaction in a facile and convenient procedure. The MPEG-HTPB (g-COOH)-MPEG block copolymers were self-organized into micelle assemblies in the water. The size and shape of the micelle assemblies were confirmed by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The nanocarriers have high drug loading ability for poorly water-soluble drug. The pH-responsive profile was demonstrated by pH-dependent swelling and in vitro drug release. <10.0% IBU was released under artificial gastric fluid after 2h, whereas an immediate release was observed under artificial intestinal fluid. The XTT assay indicated that the micelle obtained from PEG-HTPB (g-COOH)-PEG triblock copolymer are safe in a wide range of concentrations. The results show that pH-responsive PEG-HTPB (g-COOH)-PEG triblock copolymers are promising nanocarriers for the oral administration of hydrophobic drugs.