Polyurethane Block Copolymers Research Articles

Molecular design and hygrothermal resistance of high‐toughness polysiloxane–polyurethane block copolymer composite adhesives

AbstractWith the development of new energy sources, the demand for aluminum composite films for power batteries is expanding; at the same time, higher requirements have been put forward for aluminum composite films and adhesives. Polyurethane, as the binder of aluminum composite films, strongly affects the performance of aluminum composite films when exposed to moisture and high temperature and can lead to delamination. This thesis prepares a polyurethane and silicone block copolymer composite adhesive by adjusting the ratio of hard and soft polyurethane segments to obtain polyurethane (PU) with excellent flexibility. On the basis of block copolymerization with bis‐amino‐terminated organosiloxane (ATPS), obtained excellent flexibility, high peel strength, moisture resistance, and heat resistance from a polysiloxane‐based polyurethane composite adhesive (PUSR). The properties are also tested using tensile tests and peel strength tests. The test results show that by adjusting the ATPS content, the flexibility and hydrophobicity of the PUSR composite adhesive further improved, with a tensile strength of 36 MPa, an elongation at break of 757%, and bonding performance of 11 N/15 mm. Additionally, the damp heat resistance of 6 N/15 mm, exceeding the international standard of 3 N/15 mm, in the power battery soft package aluminum–plastic film has potential application prospects.

In vitro evaluation of blood plasma coagulation responses to four medical-grade polyurethane polymers.

Segmented polyurethane (PU) block copolymers are widely used in implantable cardiovascular medical devices due to their good biocompatibility and excellent mechanical properties. More specifically, PU Biospan MS/0.4 was used in ventricular assist devices over the past decades. However, this product is being discontinued and it has become necessary to find an alternative PU biomaterial for application in cardiovascular devices. One important criterion for assessing cardiac biomaterials is blood compatibility. In this study, we characterized the surface properties of four medical-grade PU biomaterials: Biospan MS/0.4, BioSpan S, BioSpan 2F, and CarboSil 20 80A, including surface chemistry, topography, microphase separation structure and wettability, and then measured the blood plasma coagulation responses using bovine and human blood plasma. Results showed that BioSpan 2F contains high amounts of fluorine and has the lowest surface free energy while the other materials have surfaces with silicone present. An in vitro coagulation assay shows that these materials demonstrated improved blood coagulation responses compared to the polystyrene control and there were no significant differences in coagulation time among all PU biomaterials. The chromogenic assay showed all PU materials led to low FXII contact activation, and there were no significant differences in FXII contact activation, consistent with plasma coagulation responses.

A Novel NQO1 Enzyme-Responsive Polyurethane Nanocarrier for Redox-Triggered Intracellular Drug Release.

The design of nano-drug delivery vehicles responsive to tumor microenvironment stimuli has become a crucial aspect in developing cancer therapy in recent years. Among them, the enzyme-responsive nano-drug delivery system is particularly effective, as it utilizes tumor-specific and highly expressed enzymes as precise targets, leading to increased drug release at the target sites, reduced nonspecific release, and improved efficacy while minimizing toxic side effects on normal tissues. NAD(P)H:quinone oxidoreductase 1 (NQO1) is an important reductase associated with cancer and is overexpressed in some cancer cells, particularly in lung and breast cancer. Thus, the design of nanocarriers with high selectivity and responsiveness to NQO1 is of great significance for tumor diagnosis and treatment. It has been reported that under physiological conditions, NQO1 can specifically reduce the trimethyl-locked benzoquinone structure through a two-electron reduction, resulting in rapid lactonization via an enzymatic reaction. Based on this, a novel reduction-sensitive polyurethane (PEG-PTU-PEG) block copolymer was designed and synthesized by copolymerizing diisocyanate, a reduction-sensitive monomer (TMBQ), and poly(ethylene glycol). The successful synthesis of monomers and polymers was verified by nuclear magnetic resonance (1H NMR) and gel permeation chromatography (GPC). Then, the PEG-PTU-PEG micelles were successfully prepared by self-assembly, and their reductive dissociation behavior in the presence of Na2S2O4 was verified by dynamic light scattering (DLS), 1H NMR, and GPC. Next, the model drug doxorubicin (DOX) was encapsulated into the hydrophobic core of this polyurethane micelles by microemulsion method. It was observed that the drug-loaded micelles could also achieve a redox response and rapidly release the encapsulated substances. In vitro cell experiments demonstrated that PEG-PTU-PEG micelles had good biocompatibility and a low hemolysis rate (<5%). Furthermore, in the presence of an NQO1 enzyme inhibitor (dicoumarol), lower drug release from micelles was observed in A549 and 4T1 cells by both fluorescence microscopy and flow cytometry assays, but not in NIH-3T3 control cells. Predictably, DOX-loaded micelles also showed lower cytotoxicity in 4T1 cells in the presence of NQO1 enzyme inhibitors. These results indicate that drug-loaded polyurethane micelles could accomplish specific drug release in the reducing environment in the presence of NQO1 enzymes. Therefore, this study provides a new option for the construction of polyurethane nanocarriers for precise targeting and reductive release, which could benefit the intracellular drug-specific release and precision therapy of tumors.

PEO-PU block copolymer membrane for air dehumidification

Membrane separation was an efficient process for air dehumidification. In this study, an environmentally friendly and low-cost polyethylene oxide (PEO)-polyurethane (PU) block copolymer (Permax232) membrane was prepared successfully using water as solvent. An aqueous polycarbondiimide (PCD) crosslinking agent was added into the membrane to improve its water stability property. The physicochemical properties and the crosslinking mechanism of the membrane were investigated using various analytical methods. Compared with the Permax232 membrane, the cross-linked Permax232 membrane exhibited improved water stability and mechanical properties. The surface roughness of the cross-linked membrane increased, and the intensity of the crystalline peak decreased. The crosslink density increased with the PCD content based on the water swelling method. The modified Flory-Huggins model showed excellent agreement between the crosslink density and water vapor sorption. When the appropriate amount of PCD was added, the Permax232 membrane exhibited a high water vapor permeability of 1.45 × 105 Barrer and a water vapor/N2 selectivity of 8.2 × 104. In addition, the water vapor permeability of the cross-linked Permax232 membrane did not change significantly with increasing temperature at the same humidity.

Sequence-Controlled Polyurethane Block Copolymer Displays Differentiated Immunoglobulin-G Adsorption That Influences Human Monocyte Adhesion and Activity.

The ability to specify an adsorbed protein layer through the polymer chemistry design of immunomodulatory biomaterials is important when considering a desired immune response, such as reducing pro-inflammatory activity. Limited work has been undertaken to elucidate the role of monomer sequence in this process, when copolymeric systems are involved. In this study, we demonstrate the advantage of an alternating radical copolymerization strategy as opposed to a random statistical copolymerization to order monomers in the synthesis of degradable polar-hydrophobic-ionic polyurethanes (D-PHI), biomaterials originally designed to reduce inflammatory monocyte activation. A monomer system consisting of a vinyl-terminated polyurethane cross-linker, maleic acid (MA), and ethyl vinyl ether (EVE), not only generated a diverse chemical environment of polar, hydrophobic, and ionic functional groups, but also formed a charge transfer complex (CTC) reactive to alternating polymerizations. Conversion of MA and EVE occurred in a constant proportion regardless of monomer availability, a phenomenon not observed in conventional D-PHI formulations. For feeds with unequal molar quantities of MA and EVE, the final conversion was limited and proportional to the limiting reagent, leading to an overall higher polyurethane cross-linker content. The presence of a reactive CTC was also found to limit the monomer conversion. Compared to a D-PHI with random monomer arrangement using methacrylic acid (MAA) and methyl methacrylate (MMA), a reduction in Fab region exposure from adsorbed immunoglobulin G and a reduction in average adherent monocyte activity were found in the sequence-controlled version. These results represent the first example of using an alternating copolymerization approach to generate regularly defined polymer chemistries in radical chain-growth biomaterials for achieving immunomodulation, and highlight the importance of considering sequence control as a design strategy for future immunomodulatory biomaterial development.

Study of the effect of crystallization conditions on the structure of polyurethane block copolymer based on poly-ε-caprolactone diol and isophoron diisocyanate

In the paper a study of isothermal crystallization kinetics of polyurethane on the basis of poly-ε-caprolactone diol, isopforon diisocyanate and 1, 4-butanediol is presented. The process of isothermal crystallization in the temperatures range from -15 to 30ºC was studied by DSC method. Analysis of total melting enthalpy and degree of crystallinity of the polyurethane allows to obtain material with one or two melting points of polyester block at desired temperature. These results will help in design of new thermoplastic elastomers with one- or two-stage shape memory effect.

Flexible poly(styrene‐ethylene‐butadiene‐styrene) hybrid nanofibers for bioengineering and water filtration applications

AbstractAmong the thermoplastic elastomers that play important roles in the polymer industry due to their superior properties, styrene‐based species and polyurethane block copolymers are of great interest. Poly(styrene‐ethylene‐butadiene‐styrene) (SEBS) as a triblock copolymer seems to have the potential to meet many demands in different applications due to various industrial requirements where durability, biocompatibility, breaking elongation, and interfacial adhesion are important. In this study, the SEBS triblock copolymer was functionalized with natural (Satureja hortensis, SH) and synthetic (nanopowder, TiO2) agents to obtain composite nanofibers by electrospinning and electrospraying methods for use in biomedical and water filtration applications. The results were compared with thermoplastic polyurethane (TPU) composite nanofibers, which are commonly used in these fields. Here, functionalized SEBS nanofibers exhibited antibacterial effect while at the same time improving cell viability. In addition, because of successful water filtration by using the SEBS composite nanofibers, the material may have a good potential to be used comparably to TPU for the application.

Multiscale synchrotron scattering studies of the temperature-dependent changes in the structure and deformation response of a thermoplastic polyurethane elastomer

The distinct molecular architecture and thermomechanical properties of polyurethane block copolymers make them suitable for applications ranging from textile fibers to temperature sensors. In the present study, differential scanning calorimetry (DSC) analysis and macroscopic stress relaxation measurements are used to identify the key internal processes occurring in the temperature ranges between −10 °C and 0 °C and between 60 °C and 70 °C. The underlying physical phenomena are elucidated by the small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS) study of synchrotron beams, allowing the exploration of the structure-property relationships as a function of temperature. In situ multiscale deformation analysis under uniaxial cyclic thermomechanical loading reveals a significant anomaly in the strain evolution at the nanoscale (assessed via SAXS) in the range between −10 °C and 0 °C owing to the ‘melting’ of the soft matrix. Furthermore, WAXS measurement of crystal strain within the hard regions reveals significant compressive residual strains arising from unloading at ∼60 °C, which are associated with the dynamic shape memory effect in polyurethane at these temperatures.

Designing formulation variables of extrusion-based manufacturing of carbon black conductive polymer composites for piezoresistive sensing

Highly sensitive conductive polymer composites for piezoresistive sensing are developed by a design of the formulation variables of extrusion-based manufacturing (filler type/amount, polymer amount) and annealing (a), considering thermoplastic polyurethane (TPU) and/or olefin block copolymer (OBC) as polymer matrix and carbon black (CB) as conductive filler. With ternary composites - based on a CB type with stronger filler-matrix interactions and an appropriate OBC/TPU blend mass ratio (40/60 with CB amount of 5–10 m%; 50/50 with CB amount of 10 m%), the challenging region of both high sensitivity and static strain (maximal gauge factors (GFmax) > 50 and εmax > 100%) can be realized: GFmax > 104 and εmax = 20–240%. OBC binary composites with a high CB2 amount (e.g. 15 m%) are however needed for ultrahigh static strains (εmax > 600%). Well-designed ternary composites (e.g. OBC40-CB/TPU60-7-a and OBC30-CB/TPU70-7-a) possess a large dynamic resistance change, negligible hysteresis and high stability and display strain sensor application potential. Highly CB2 loaded binary (≥12 m%) and ternary composites (10 m%) exhibit a more obvious strain-dependent dynamic hysteretic behavior, as they switch from a dual peak to single peak pattern toward the sensing strain limit, which is interesting for self-diagnose.

Facile and Low-Cost Route for Sensitive Stretchable Sensors by Controlling Kinetic and Thermodynamic Conductive Network Regulating Strategies.

Highly sensitive conductive polymer composites (CPCs) are designed employing a facile and low-cost extrusion manufacturing process for both low- and high-strain sensing in the field of, for example, structural health/damage monitoring and human body movement tracking. Focus is on the morphology control for extrusion-processed carbon black (CB)-filled CPCs, utilizing binary and ternary composites based on thermoplastic polyurethane (TPU) and olefin block copolymer (OBC). The relevance of the correct CB amount, kinetic control through a variation of the compounding sequence, and thermodynamic control induced by annealing is highlighted, considering a wide range of experimental (e.g., static and dynamic resistance/scanning electron microscopy/rheological measurements) and theoretical analyses. High CB mass fractions (20 m %) are needed for OBC (or TPU)-CB binary composites but only lead to an intermediate sensitivity as their conductive network is fully packed and therefore difficult to be truly destructed. Annealing is needed to enable a monotonic increase of the relative resistance with respect to strain. With ternary composites, a much higher sensitivity with a clearer monotonic increase results, provided that a low CB mass fraction (10-16 m %) is used and annealing is applied. In particular, with CB first dispersed in OBC and annealing, a less compact, hence, brittle conductive network (10-12 m % CB) is obtained, allowing high-performance sensing.

Biomimetic n-HA/GCO-PU composite scaffold with hierarchical structure for bone regeneration

Event Abstract Back to Event Biomimetic n-HA/GCO-PU composite scaffold with hierarchical structure for bone regeneration Yubao Li1, Limei Li1*, Yi Zuo1*, Qin Zou1 and Jidong Li1* 1 Analytical & Testing Center, Research Center for Nano Biomaterials, China Introduction: Matching structure to function is a challenge to synthetic biomaterials[1],[2]. The skeletal hierarchical structure from microscale to nanoscale formed by the cooperation of organic molecules and inorganic crystals, has not been fully investigated and utilized. Combination of nano-hydroxyapatite (n-HA) crystals and polyurethane (PU) block copolymer will give us a chance to establish a biomimetic hierarchical structure and realize biological function. This study has explored the effect of nano- to micro- structure on the mechanical and biological properties of the composite scaffold. Materials and Methods: The n-HA/PU composite scaffolds with 40 wt% n-HA crystals were made by in situ polymerization and simultaneous foaming[3]. Both pristine castor oil (CO) and glyceride of castor oil (GCO) were separately used to prepare PU scaffolds (named n-HA/CO-PU, n-HA/GCO-PU). The physico-chemical properties were analyzed by FTIR, XRD, XPS, NMR, DMA, SEM, TEM, mechanical test and micro-CT analysis. The cell behavior and bone regeneration capacity were also evaluated via in vitro culture and in vivo implantation. Results and Discussion: The composite scaffolds have been structured in three levels: the PU hard/soft block structure in molecular level, the n-HA crystals dispersed in PU matrix in nano-level (Fig. 1), and the porous scaffold structure in micro-level [Fig. 2]. The three level hierarchical structures may be similar to the segmented collagen, the mineral in organic matrix and the cancellous structure of natural bone, making up the material basis of high performance scaffold for bone regeneration[4]. The results showed that the modification of PU soft segment by GCO could largely increase the scaffold compressive strength by 48% and elastic modulus by 96%. The n-HA crystals with fine dispersity not only improved the interface bonding with PU matrix, but also provided good bioactivityfor bonding with bone tissue. The hierarchical structure and good mechanical quality of the n-HA/GCO-PU composite scaffold were found to be appropriate for growth of cells and regeneration of bony tissue [Fig. 2], presenting good prospect for bone repair and regeneration. Conclusion: We found that the use of glyceride of castor oil for soft segment, and the incorporation of n-HA crystals are crucial for the mechanical improvement of PU-based composite scaffolds; the scaffold composition, porous structure and mechanical quality are favorable for cell proliferation and new boneregeneration. Combination of the two factors afford better mechanical improvement, suggesting the important role of the tightly bonding interface between n-HA crystals and PU matrix. The nano- to micro- hierarchical structure, improved mechanical properties of the nano composite scaffold can be a biomimetic approach to natural bone tissue, presenting strong vitality in bone regeneration and reconstruction. The authors appreciate financial support from China NSFC fund (No. 31370971), Sichuan and Chengdu project (No. 2012FZ0125, 12DXYB145JH-005).

ハードセグメントとソフトセグメントから成る分子力学モデルを用いたポリウレタンの形状変化機能に関する動的粘弾性シミュレーション

The present study attempted to model dynamic viscoelastic properties of polyurethane block copolymers to understand the effect of molecular properties on shape change functions of the materials. For this purpose, we proposed dynamic viscoelastic simulations to obtain stress response in frequency domain against oscillating strain history, using molecular mechanics models consisting of hard and soft segments. The simulations employed coarse-grained bead-spring model based on the force fields given by bond-stretch potential for covalent bonding and Lennard-Jones potential for intermolecular interaction. The rigidity and aggregability of hard segments (HS) were represented by varying the molecular mechanics parameters for these force fields. The proposed simulation could reproduce a clear glass transition from glassy state to rubbery state in frequency domain. The rigidity of HS increased the stiffness at glassy state and tanδ as an indicator of energy dissipation as well, which led to the sharpening of glass transition range. The aggregability of HS increased the stiffness at rubbery state and it also shifted glass transition point to a higher frequency and broadened glass transition range by changing the mobility of soft segments (SS). Finally, a spherically aggregated HS domain was found to degrade shape change functions from the viewpoint of storage modulus. We concluded that the shape change functions of the materials were closely related to energy storage ability of HS and mobility of SS, and that the aggregability of HS yielded by hydrogen bonding in polyurethanes plays an important role in shape change functions.

Hot press transferring of graphene nanoplatelets on polyurethane block copolymers film for electroactive shape memory devices

ABSTRACTWe report a transferring method of graphene nanoplatelets (GNPs) on polyurethane (PU) block copolymers film. We polymerized PU block copolymer films, and then, a GNP layer, deposited on glossy paper by drop casting, was transferred by hot press from the glossy surface to the synthetized PU substrate. Nanoindentation test showed that GNP coated PU substrate exhibits improved mechanical properties with respect to the neat PU film. When an electric bias was applied to the GNP coating, the heat generated by Joule effect was transferred to the PU substrate showing an electroactive shape recovery effect. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014, 52, 1100–1106

Surface plasma modification and tropoelastin coating of a polyurethane co-polymer for enhanced cell attachment and reduced thrombogenicity

Polymers currently utilized for dermal and vascular applications possess sub-optimal biocompatibility which reduces their efficacy. Improving the cell-binding and blood-contacting properties of these polymers would substantially improve their clinical utility. Tropoelastin is a highly extensible extracellular matrix protein with beneficial cell interactive and low thrombogenic properties. We transferred these benefits to the polyurethane block copolymer Elast-Eon E2A through a specific combination of surface plasma modifications and coating with human tropoelastin. The cell-binding activity of bound tropoelastin was modulated by ion implantation of the underlying polymer, and correlated with surface hydrophobicity, carbon and oxygen content. This combined treatment enhanced human dermal fibroblast (HDF) and human umbilical vein endothelial cell (HUVEC) attachment, cytoskeletal assembly and viability, combined with elevated PECAM-1 staining of HUVEC cell junctions. The thrombogenicity of the polymer was ameliorated by tropoelastin coating. We propose that a combination of metered plasma treatment and tropoelastin coating of Elast-Eon can serve to improve the biological performance of implantable devices such as vascular conduits.

Control of Hyperbranched Structure of Polycaprolactone/Poly(ethylene glycol) Polyurethane Block Copolymers by Glycerol and Their Hydrogels for Potential Cell Delivery

A series of biodegradable amphiphilic polyurethane block copolymers with hyperbranched structure were synthesized by copolymerizing poly(ε-caprolactone) (PCL) and poly(ethylene glycol) (PEG) together with glycerol. The copolymers were characterized, and their composition and branch length were varied with the feeding ratio between PCL, PEG, and glycerol used. Hydrogels were formed from these copolymers by swelling of water at low polymer concentrations. The hydrogels were thixotropic, and their dynamic viscoelastic properties were dependent on the copolymer composition, branch length, and polymer concentration. Hydrolytic degradation of the hydrogels was evaluated by mass loss and changes in molecular structures. The porous morphology of the hydrogels provided good permeability for gas and nutrition. Together with the tunable rheological properties, the hydrogels were found to be suitable for 3D living cell encapsulation and delivery. The morphology of the solid copolymers was semicrystalline, while the hydrogels were totally amorphous without crystallinity, providing a mild aqueous environment for living cells. When the encapsulated cells were recovered from the hydrogels followed by subculture, they showed good cell viability and proliferation ability. The results indicate that the hyperbranched copolymers hydrogels developed in this work may be promising candidates for potential injectable cell delivery application.

Disulfide Cross‐Linked Polyurethane Micelles as a Reduction‐Triggered Drug Delivery System for Cancer Therapy

Nanoscale carriers that stably load drugs in blood circulation and release the payloads in desirable sites in response to a specific trigger are of great interest for smart drug delivery systems. For this purpose, a novel type of disulfide core cross-linked micelles, which are facilely fabricated by cross-linking of poly(ethylene glycol)/polyurethane block copolymers containing cyclic disulfide moieties via a thiol-disulfide exchange reaction, are developed. A broad-spectrum anti-cancer drug, doxorubicin (DOX), is loaded into the micelles as a model drug. The drug release from the core cross-linked polyurethane micelles (CCL-PUMs) loaded with DOX is suppressed in normal phosphate buffer saline (PBS), whereas it is markedly accelerated with addition of an intracellular reducing agent, glutathione (GSH). Notably, although DOX-loaded CCL-PUMs display lower cytotoxicity in vitro compared to either free DOX or DOX-loaded uncross-linked polyurethane micelles, the drug-loaded CCL-PUMs show the highest anti-tumor efficacy with reduced toxicity in vivo. Since enhanced anti-tumor efficacy and reduced toxic side effects are key aspects of efficient cancer therapy, the novel reduction-responsive CCL-PUMs may hold great potential as a bio-triggered drug delivery system for cancer therapy.

Thermo-mechanical behavior of electrospun thermoplastic polyurethane nanofibers

Analysis of the thermo-mechanical behavior of electrospun thermoplastic polyurethane (TPU) block co-polymer nanofibers (glass transition temperature∼−50°C) is presented. Upon heating, nanofibers began to massively contract, at ∼70°C, whereas TPU cast films started to expand. Radial wide-angle X-ray scattering (WAXS) profiles of the nanofibers and the films showed no diffraction peaks related to crystals, whereas their amorphous halo had an asymmetric shape, which can be approximated by two components, associated with hard and soft segments. During heating, noticeable changes in the contribution of these components were only observed in nanofibers. These changes, which were accompanied with an endothermic DSC peak, coinciding with the start of the nanofibers contraction, can be attributed to relaxation of an oriented stretched amorphous phase created during electrospinning. Such structure relaxation becomes possible when a portion of the hard segment clusters, forming an effective physical network, is destroyed upon heating.

Manufacturing and characteristics analysis of PU/MWNT film for electrosatic dissipation

This study surveys the characteristics of the nanocomposite film for PU/MWNT. For this purpose, several kinds of PU/MWNT nanocomposite films were prepared with four kinds of MWNT, MWNT contents and two kinds of dispersion times and ESD (Electrostatic Dissipation) films composed with polyurethane (PU) block copolymer and selected multi-walled carbon nanotube (MWNT) were also prepared by disperse processing with various MWNT contents and dispersion times, and their mechanical and chemical properties were investigated with electrical conductivity. The tensile properties and chemical properties of PU/MWNT nanocomposite films were measured using UV-visible spectrometer and discussed with the manufacturing conditions of nanocomposite film. Furthermore, the PU/MWNT films were made by dispersing with five kinds of CNT content and six kinds of dispersion time under the DMF (dimethylformamide) solution, and the mechanical properties of the PU/MWNT films were analyzed by Instron and discussed with various dispersion conditions.

Synthesis and characterization of hydroxypropyl terminated polydimethylsiloxane-polyurethane copolymers

Polyurethane (PU) block copolymers were synthesized using prepared hydroxypropyl terminated polydimethylsiloxane (HTPDMS MW 990) and polyether diols (N-210) as soft segment with 4,4′-diphenylmethane diisocyanate (MDI) and 1,4-butanediol. This low molecular weight polydimethylsiloxanes (PDMS) containing hydroxypropyl end-groups displayed better compatibility with PU than common PDMS. In this article, we illustrate its synthesis routes and confirmed the proposed molecular structures using NMR and infrared radiation (IR). We varied the contents of HTPDMS and N-210 in soft segments (HTPDMS—N-210: 0 : 100, 20 : 80, 40 : 60, 60 : 40, 80 : 20, and 100 : 0) to synthesize a series of PDMS-PU copolymer. IR spectroscopy showed the assignment characteristic groups of each peak in copolymers and confirmed that the desired HTPDMS-PU copolymers have been prepared. The different thermal, dynamic mechanical and surface properties of the copolymers were compared by thermogravimetry, DMA, contact angle and solvent resistance. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

PH and reduction dual responsive polyurethane triblock copolymers for efficient intracellular drug delivery

A series of pH/reduction dual responsive poly(ethylene glycol)/polyurethane triblock copolymers containing tertiary amines and disulfide bonds are reported. The polyurethane block copolymers self-assembled into stable micelles in aqueous medium at pH 7.4, which responded rapidly to both a narrow pH change within the physiologically relevant pH range and a reduction environment mimicking the intracellular space. The in vitro drug release from doxorubicin (DOX)-loaded polyurethane micelles was significantly accelerated by reducing the pH or by addition of an intracellular reducing agent, glutathione (GSH). Confocal laser scanning microscopy (CLSM) and flow cytometry measurements revealed that the intracellular drug release from the DOX-loaded nanoparticles was increased in the HeLa cells with enhanced intracellular GSH level. In addition, even though the polyurethane block copolymers exhibited good cytocompatibility, the DOX-loaded polyurethane micelles displayed efficient growth inhibition of HeLa and HepG2 cells, which showed a dependence on the intracellular GSH concentration. Owing to their unique responsiveness to dual biological stimuli, the biocompatible and bioreducible polyurethane block copolymers have the potential to serve as a versatile platform for intracellular drug delivery.