Linear Polyurethanes Research Articles

Modification of Poly(3-Hydroxybutyrate) with a Linear Polyurethane Modifier and Organic Nanofiller-Preparation and Structure-Property Relationship.

The growing demand for products made of polymeric materials, including the commonly used polypropylene (PP), is accompanied by the problem of storing and disposing of non-biodegradable waste, increasing greenhouse gas emissions, climate change and the creation of toxic products that constitute a health hazard of all living organisms. Moreover, most of the synthetic polymers used are made from petrochemical feedstocks from non-renewable resources. The use of petrochemical raw materials also causes degradation of the natural environment. A potential solution to these problems is the use of biopolymers. Biopolymers include biodegradable or biosynthesizable polymers, i.e., obtained from renewable sources or produced synthetically but from raw materials of natural origin. One of them is the poly(3-hydroxybutyrate) (P3HB) biopolymer, whose properties are comparable to PP. Unfortunately, it is necessary to modify its properties to improve its processing and operational properties. In the work, hybrid polymer nanobiocomposites based on P3HB, with the addition of chain, uncross-linked polyurethane (PU) and layered aluminosilicate modified with organic salts (Cloisite®30B) were produced by extrusion process. The introduction of PU and Cloisite®30B to the polymer matrix (P3HB) influenced the processing parameters beneficially and resulted in a decrease in the extrusion temperature of more than 10 °C. The influence of the simultaneous addition of a constant amount of PU (10 m/m%) and the different amounts of nanoadditives (1, 2 and 3 m/m%) on the compatibility, morphology and static mechanical properties of the resulted nanobiocomposites were examined. The component interactions by Fourier transformation infrared spectroscopy (FTIR) analysis, nano- and microscale structure studies using small-angle X-ray scattering (SAXS) and morphology by scanning electron microscopy (SEM) were carried out, and the hardness and tensile strength of the obtained polymer nanobiocomposites were determined. FTIR analysis identified the compatibility of the polyester matrix, PU, and organomodified montmorillonite, the greatest being 3 m/m% Cloisite30B content. The addition of PU to the polyester elasticizes the material and decreases the material's strength and ductility. The presence of nanoclay enhanced the mechanical properties of nanobiocomposites. The resulting nanobiocomposites can be used in the production of short-life materials applied in gardening or agriculture.

Shape memory, reprocessable and photothermal networks of polyurethane with silyl ether bonds and croconaine segments

Organic dyes were integrated into networks of polyurethane (PU) in the form of croconaine segments, in order to bestow photothermal properties on the materials. In addition, the PU networks were crosslinked with polysilsesquioxane (PSSQ) so that the materials can be reprocessed (or self-healing) via the metathesis of silyl ether bonds under catalysis. Toward this end, we synthesized a novel diol bearing croconaine moiety, which was used as one of chain extenders and a series of linear PU telechelics with dihydroxyl termini were synthesized. The α,ω-dihydroxyl PU telechelics were then allowed to react with 3-isocyanatopropyltriethoxysilane to gain α,ω-ditriethoxysilane PU telechelics. Through sol-gel process, α,ω-ditriethoxysilane PU telechelics readily underwent crosslinking with PSSQ as the crosslinkages. The crosslinking of PU was in marked contrast to traditional crosslinking of PU with multifunctional ols (or amines) as the crosslinkers. Owing to the crosslinking, shape memory properties were bestowed on the organic-inorganic PU networks. Thanks to the metathesis of silyl ether bonds under catalysis, the organic-inorganic PU networks were reprocessable (or recyclable). Benefiting from the built-in of dye segments, the PU networks significantly displayed excellent photothermal conversion properties. By leveraging the photothermal properties, the shape shifting of the PU networks can be triggered via the irradiation under infrared laser and in a non-contact fashion. In addition, the PU networks were capable of displaying the light-triggered self-healing properties. Thanks to these excellent properties, we demonstrated a successful application of the PU networks a soft robot.

Crosslinking of polyurethane with boronic ester bonds: An impact of B–N coordination

In this contribution, we reported a new approach to crosslink linear polyurethane (PU) with dynamic boronic ester bonds. First, a linear PU was synthesized, which carries a plethora of 1,3-diol structural units. Second, two structurally similar diboronic acids were designed and synthesized, which contained amino and amido groups, respectively. Thereafter, the crosslinking between the linear PU and the diboronic acids was carried out via the generation of boronic ester bonds. Thanks to the crosslinking, the PU networks significantly displayed improved thermomechanical properties, contingent on types of crosslinkers. More importantly, the excellent reprocessing and shape memory properties were imparted to the PU networks, which were implemented by dynamic boronic ester bonds between 1,3-diol moieties of the linear PU and boronic acids of the crosslinkers. The dynamic exchange of boronic ester bonds is responsible for the reprocessing properties. For the shape memory properties, the PU networks featured the reprogramming behavior of original shapes via the dynamic exchange of boronic ester bonds. More importantly, the shape memory properties were also dependent on types of diphenylboronic acids, which was reflected with the difference in dynamicity of boronic ester bonds. For the PU networks with amino-containing crosslinker, the boronic ester bonds featured the B–N coordination. As a result, the boronic ester bonds had the increased dynamicity, which significantly affected the reprocessing properties.

A biodegradable shape memory polyurethane film as a postoperative anti-adhesion barrier for minimally invasive surgery

Postoperative adhesions commonly form in various tissues, resulting in serious implications and an increased risk of secondary surgery. The application of anti-adhesion films as physical barriers has proven effective in reducing adhesion incidence and severity. However, existing anti-adhesion films require manual deployment during minimally invasive surgery, posing inconvenience and possibility of further injury. To address these limitations, we have developed an intelligent anti-adhesion film based on shape memory polyurethane. In this work, a linear shape memory polyurethane (ISO2-PU), incorporating hexamethylene isocyanate and isosorbitol as hard segments and poly(D, L-lactic acid) macrodiol as soft segments, was fabricated into an anti-adhesion film. The favorable shape memory effect of the ISO2-PU film ensures its convenient delivery and automatic unfolding, as revealed by a simulation experiment for endoscopic surgical implantation. Furthermore, the glass transition temperature (Tg) close to body temperature endows the ISO2-PU film with good mechanical compliance, thus ensuring a reliable fit with the wounded tissue to avoid undesired folding. Finally, in vivo experiments using a rat cecal abdominal wall injury model demonstrated that the combination of reliable fit, appropriate degradation rate, and good cytocompatibility promises the ISO2-PU film with high anti-adhesion efficacy. This work validates the concept of shape memory anti-adhesion barrier and expands future directions for advanced anti-adhesion biomaterials. Statement of significancePostoperative adhesions are a common complication that occurs widely after various surgeries. This work developed an intelligent anti-adhesion film based on a linear shape memory polyurethane (ISO2-PU). This film is featured with remarkable shape memory effect and mechanical compliance at body temperature, appropriate degradability, and good cytocompatibility. These merits ensure convenient delivery and smart unfolding of ISO2-PU film during minimally invasive surgery and favorable postoperative anti-adhesion efficacy. The results validate the concept of shape memory anti-adhesion barrier and paves a way for designing next-generation anti-adhesion biomaterials.

Polymer Bionanocomposites Based on a P3BH/Polyurethane Matrix with Organomodified Montmorillonite-Mechanical and Thermal Properties, Biodegradability, and Cytotoxicity.

In the present work, hybrid nanobiocomposites based on poly(3-hydroxybutyrate), P3HB, with the use of aromatic linear polyurethane as modifier and organic nanoclay, Cloisite 30B, as a nanofiller were produced. The aromatic linear polyurethane (PU) was synthesized in a reaction of diphenylmethane 4,4'-diisocyanate and polyethylene glycol with a molecular mass of 1000 g/mole. The obtained nanobiocomposites were characterized by the small-angle X-ray scattering technique, scanning electron microscopy, Fourier infrared spectroscopy, thermogravimetry, and differential scanning calorimetry, and moreover, their selected mechanical properties, biodegradability, and cytotoxicity were tested. The effect of the organomodified montmorillonite presence in the biocomposites on their properties was investigated and compared to those of the native P3HB and the P3HB-PU composition. The obtained hybrid nanobiocomposites have an exfoliated structure. The presence and content of Cloisite 30B influence the P3HB-PU composition's properties, and 2 wt.% Cloisite 30B leads to the best improvement in the aforementioned properties. The obtained results indicate that the thermal stability and mechanical properties of P3HB were improved, particularly in terms of increasing the degradation temperature, reducing hardness, and increasing impact strength, which were also confirmed by the morphological analysis of these bionanocomposites. However, the presence of organomodified montmorillonite in the obtained polymer biocomposites decreased their biodegradability slightly. The produced hybrid polymer nanobiocomposites have tailored mechanical and thermal properties and processing conditions for their expected application in the production of biodegradable, short-lived products for agriculture. Moreover, in vitro studies on human skin fibroblasts and keratinocytes showed their satisfactory biocompatibility and low cytotoxicity, which make them safe when in contact with the human body, for instance, in biomedical applications.

Linear polyurethanes with excellent comprehensive properties from poly(ethylene carbonate) diol

The synthesis of polyurethanes (PUs) from the reaction of low molecular weight poly(ethylene carbonate) diol (PECD) is rarely investigated. This work reports a novel PU with excellent mechanical properties from the solution polymerization of 4,4′-diphenylmethane diisocyanate (MDI) with PECD that was derived from the copolymerization of carbon dioxide (CO2) and ethylene oxide (EO). The tensile strength, the elongation at break and 300 % constant tensile strength of the PECD-PU were up to 66 ± 2 MPa, 880 % ± 50 % and 13 MPa, respectively, higher than the control PUs from the reaction of MDI with commercial polyethers or polyesters. The PECD-PU with high CO2 carbonate content exhibited good solvent resistance and chemical stability. Of importance, the mechanical properties and chemical resistance of PECD-PU were significantly enhanced with the increasing content of CO2, i.e., the carbonate unit in PECD. This work provides comprehensive properties of PECD-derived PUs, indicating that PECD is a competitive precursor for the preparation of PU and has broad application prospects.

Strategic design of degradable polyurethanes: Site-specific depolymerization, film-forming behavior, and reprocessability

This paper reports on the rational design of linear sustainable polyurethanes with on-demand depolymerization capabilities and film-forming properties. In this molecular approach, self-immolative urethane motifs are engineered to not only induce rapid degradation in response to an external stimulus via sequential elimination but also provide sufficient inter-chain interactions to yield nanofibers or free-standing films. Amalgamation with various isocyanate or polyol components results in a range of degradable polyurethanes, while doping with europium complexes or carbon black leads to the formation of free-standing hybrid films with photoluminescent or conductive properties, respectively. These films can be reversibly cast using a facile dissolution process, and the predetermined depolymerization products can then be used to generate upcycled materials such as polyurea or polyacrylate films. We believe that our conceptual design for sustainable polyurethanes can be advanced further when combined with conventional engineering techniques to meet industrial and environmental requirements and create desirable materials for contemporary applications.

Biopolymer Compositions Based on Poly(3-hydroxybutyrate) and Linear Polyurethanes with Aromatic Rings-Preparation and Properties Evaluation.

Polymer biocompositions of poly(3-hydroxybutyrate) (P3HB) and linear polyurethanes (PU) with aromatic rings were produced by melt-blending at different P3HB/PU weight ratios (100/0, 95/5, 90/10, and 85/15). Polyurethanes have been prepared with 4,4'-diphenylmethane diisocyanate and polyethylene glycols with molar masses of 400 g/mol (PU400), 1000g/mol (PU1000), and 1500 g/mol (PU1500). The compatibility and morphology of the obtained polymer blends were determined by infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and differential scanning calorimetry (DSC). The effect of the polyurethane content in the biocompositions on their thermal stability and mechanical properties was investigated and compared with those of the native P3HB. It was shown that increasing the PU content in P3HB-PU compositions to 10 wt.% leads to an improvement in the mentioned properties. The obtained results demonstrated that the thermal stability and mechanical properties of P3HB were improved, particularly in terms of increasing the degradation temperature, reducing hardness, and increasing impact strength. The best thermal and mechanical properties were shown by the P3HB-PU polymer compositions containing 10 wt.% of polyurethane modifiers, especially PU1000, which was also confirmed by the morphology analysis of these biocompositions. The presence of polyurethanes in the resulting polymer biocomposites decreases their glass transition temperatures, i.e., makes the materials more flexible. The resulting polymer biocompositions have suitable mechanical properties and thermal properties within the processing conditions for the predicted application as biodegradable, short-lived products for agriculture.

Mechanically robust poly(urethane-imide) aerogels with excellent thermal insulation and sound absorption by ambient drying

Polyimide (PI) aerogels are the great candidates for sound absorption, thermal insulation and mechanical cushioning materials due to their low density, excellent mechanical properties and good thermal stability. However, the high shrinkage and hydrophilicity of PI aerogels, as well as the time-consuming and complexity of the process directly limit their wide application in many fields. Herein, a facile one-step method for the synthesis of porous monolithic poly(urethane-imide) (PUI) aerogels was successfully developed. Hydrothermal synthesis and ambient drying methods were adopted in the construction of monolithic chemically cross-linked PUI aerogels, which avoids the complex imidization process. PUI aerogels were homogeneously produced by a chemical cross-linking copolymerization reaction between polyurethane (PU) oligomers, Benzene-1,2,4,5-tetracarboxylic dianhydride (PMDA) and 1, 3, 5-tris (6-isocyanatohexyl)-1, 3, 5-triazine-2, 4, 6(1H, 3H, 5H)-trione without any catalysts. Interestingly, the introduction of linear flexible PU oligomers chain segments effectively prevented the shrinkage of the network backbone and enhanced the hydrophobicity of PUI aerogels. The obtained PUI aerogels have low density (0.196 g/cm3), low shrinkage (9.30%), high porosity (79.54%) and hydrophobicity (water contact angle of 129.2°). Under high pressure, PUI aerogel was compressed but not break and the compression Young's modulus as high as 3.638 MPa. Moreover, the thermal conductivity of PUI aerogels was only 59.92 mW/m/K at 150 °C. When the back cavity depth was 5 mm, the highest sound absorption coefficient of PUI aerogel was up to 0.7219. This work provides a new method for the development of lightweight, high-mechanical-strength polymer aerogels, and the prepared aerogels have a potential application in the field of multifunctional integrated sound absorption materials.

Dendronized polyurethanes showing improved mechanical properties and unprecedent thermoresponsiveness

Introduction of topological structures to polyurethanes (PUs) may impart them with different microphase separation, which would be beneficial to afford them novel properties and expand their applications. Herein, a series of dendronized polyurethanes (DPUs) were synthesized with polyols carrying three-fold dendritic OEGs as the soft segment and either aliphatic or aromatic isocyanates as the hard segments. Different from conventional PUs with linear polyols as the soft segments, DPUs contain soft segments with spherical pendants, which may contribute different phase separation. In addition, dendritic OEGs afford DPUs with excellent thermoresponsiveness. Films from aliphatic DPUs and those from the mixture of aromatic DPU and linear PU were prepared. These thermoresponsive DPU films show tunable regulation capacity for encapsulated guests during thermally-induced aggregation of the dendritic OEGs. Remarkably, the phase separations of DPUs were found to be closely related to the amount of dendritic OEGs, and the PU films exhibited excellent mechanical properties with suitable amount of dendritic OEGs as the soft segment. Therefore, dendronization of PUs not only can modulate their microphase separation, but also provides a unique approach to develop PUs materials with novel properties.

Super-Flexible Water-Proof Actuators.

Humidity-responsive materials hold broad application prospects in sensing, energy production, and other fields. Particularly, humidity-sensitive, flexibility, and water resistance are pivotal factors in the development of optimized humidity-responsive materials. In this study, hydrophobic linear polyurethane and hydrophilic 4-vinylphenylboronic acid (4-VPBA) form a semi-intercross cross-linking network. This copolymer of polyurethane exhibits excellent humidity-sensitive, mechanical properties, and water resistance. Its maximum tensile strength and maximum elongation can reach 40.56MPa and 543.47%, respectively. After being immersed in water at various temperatures for 15 days, it exhibited a swelling ratio of only 3.28% in water at 5°C and 9.58% in water at 70°C. While the presence of 4-VPBA network imparts humidity-sensitive, reversible, and multidirectional bending abilities, under the stimulus of water vapor, it can bend 43° within 1.4s. The demonstrated material surpasses current bidirectional humidity actuators in actuating ability. Based on these characteristics, automatically opening waterproof umbrellas and windows, as well as bionic-arms, crawling robots, and self-propelled boats, are successfully developed.

Semi-Transparent Luminescent Solar Concentrators Based on Intramolecular Energy Transfer in Polyurethane Matrices.

Luminescent solar concentrators (LSCs) are spectral conversion devices offering interesting opportunities for the integration of photovoltaics into the built environment and portable systems. The Förster-resonance energy transfer (FRET) process can boost the optical response of LSCs by reducing energy losses typically associated to non-radiative processes occurring within the device under operation. In this work, a new class of FRET-based thin-film LSC devices is presented, in which the synthetic versatility of linear polyurethanes (PU) is exploited to control the photophysical properties and the device performance of the resulting LSCs. A series of luminescent linear PUs are synthesized in the presence of two novel bis-hydroxyl-functionalized luminophores of suitable optical properties, used as chain extenders during the step-growth polyaddition reaction for the formation of the linear macromolecular network. By synthetically tuning their composition, the obtained luminescent PUs can achieve a high energy transfer efficiency (≈90%) between the covalently linked luminophores. The corresponding LSC devices exhibit excellent photonic response, with external and internal photon efficiencies as high as ≈4% and ≈37%, respectively. Furthermore, their optimized power conversion efficiency combined with their enhanced average visible-light transmittance highlight their suitability for potential use as transparent solar energy devices.

Preparation and properties of superhydrophobic fluorinated polyurethane with room temperature self-healing performance

This study synthesized a series of linear polyurethane elastomers (FTPU) with hydrophobicity and self-healing properties by adjusting the content of Polytetrahydrofuran (PTMEG) and fluorinated polyol (F-OH) as soft chain segments, isophorone diisocyanate (IPDI) and disulfide as hard chain segments. FT-IR, XPS, OM, 3D optical surface profilometer, contact angle tester, SEM, TG, and solvent resistance test were used to characterize its structure and study its self-healing, hydrophobicity, heat resistance, solvent resistance, etc. The results showed that with the increase of F-OH addition, the repair time was shortened and the repair effect was enhanced under the synergistic effect of disulfide bonds and fluorine hydrogen bonds. When the content of F-OH is 50 wt%, the self-healing efficiency is the highest, reaching 94.7%. FTPU can complete self-healing at room temperature (23 ± 2 °C) for 10 h, and self-healing can be completed within 6 min at 100 °C. Second, the introduction of F-OH significantly increased the F content on the surface of FTPU, and the water contact angle of FTPU gradually increased from 70° to 105.5°. More importantly, when FTPU was applied to fabrics, superhydrophobic fabrics with a contact angle of up to 154° were obtained. In addition, FTPU also exhibits excellent thermal stability and solvent resistance, with the T5% of FTPU-3 reaching 331 °C. FTPU has excellent comprehensive performance and can be widely used in various fields such as medical devices, electronic skin, flexible devices, etc.

Inside Cover

The cover image by Songqi Ma shows the upcycling of linear polyurethane into a dynamic covalent crosslinked network through a chain‐breaking crosslinking process on a micro twin‐screw extruder. During the chain‐breaking stage, more crosslinking sites are produced, which is beneficial for achieving high crosslinking degree during the crosslinking stage. DOI: 10.1002/pol.20230424 image

Thermoplastic polyurethane/POSS nanohybrids: Synthesis, morphology, and biological properties.

Recent studies show good osteoinductive properties of polyurethanes modified with polyhedral oligomeric silsesquioxanes (POSS). In this work, three types of POSS; propanediolisobutyl-POSS (PHI-POSS), disilanolisobutyl-POSS (DSI-POSS), and octahydroxybutyl-POSS (OCTA-POSS) were chemically incorporated into linear polyurethane based on an aliphatic isocyanate, hexamethylene diisocyanate (HDI), to obtain new nanohybrid PU-POSS materials. The full conversion of POSS was confirmed by Fourier transform infrared spectroscopy (FTIR-ATR) spectra of the model reactions with pure HDI. The materials obtained were investigated by FTIR, SEM-EDS, and DSC. The DSC studies showed the thermoplasticity of the obtained materials and apparently good recovery. 30-day immersion in SBF (simulated body fluid) revealed an increase in the rate of deposition of hydroxyapatite (HAp) for the highest POSS loadings, resulting in thick layers of hydroxyapatite (~60-40 μm), and the Ca/P ratio 1.67 (even 1.785). The structure and properties of the inorganic layer depend on the type of POSS, the number of hard segments, and those containing POSS, which can be tailored by changing the HDI/poly(tetramethylene glycol) (PTMG) ratio. Furthermore, the obtained composites revealed good biocompatibility, as confirmed by cytotoxicity tests conducted on two cell lines; normal human dermal fibroblasts (NHDF) and primary human osteoblasts (HOB). Adherent cells seeded on the tested materials showed viability even after a 48-h incubation. After this time, the population of viable, and proliferating cells exceeded 90%. Bioimaging studies have shown the fibroblast and osteoblast cells were well attached to the surface of the tested materials.

Polyurethane based thin hydrogels for sustained protein delivery

The development of materials that allow the sustained release of therapeutic proteins is the key feature for improving their pharmacokinetics, bioavailability, and dose reduction. In this context, hydrogels are attracting interest, but their design to provide a sustained release profile is still a challenge. Usually, a large mass of polymer is required to prolong the release of the therapeutic agent, involving hydrogels with high thicknesses, which limits their use in some applications. Here, the synthesis of thin thermoresponsive and functionalized hydrogels (tHGs) for sustained protein release is reported to tackle this problem. tHGs were obtained by photo-crosslinking of linear thermoresponsive polyurethanes (PU) based on polyethilenglycol and a functional diol (methyldiethanolamine) that contribute to tertiary amine functionality. These biocompatible tHGs conserved the thermosensitive property of PU, exhibiting a reversible volume change between the swollen and the collapsed state, as a function of temperature. tHGs were able to load the model protein ovalbumin homogenously in their matrix, and sustainably release it during 25 days with a tuneable profile, by changing the PU composition. Finally, this proposal, which combined a very thin delivery film with a sustained protein release, could be a good candidate for its application in ocular therapy.

Investigation of the in vitro biological activities of polyethylene glycol-based thermally stable polyurethane elastomers.

The intense urge to replace conventional polymers with ecofriendly monomers is a step towards green products. The novelty of this study is the extraction of starch from the biowaste of wheat bran (WB) and banana peel (BP) for use as a monomer in the form of chain extenders. For the synthesis of polyurethane (PU) elastomers, polyethylene glycol (PEG) bearing an average molecular weight Mn = 1000 g mol-1 was used as a macrodiol, which was reacted with isophorone diisocyanate (IPDI) to develop NCO-terminated prepolymer chains. These prepolymer chains were terminated with chain extenders. Two series of linear PU elastomers were prepared by varying the concentration of chain extenders (0.5-2.5 mol%), inducing a variation of 40 to 70 wt% in the hard segment (HS). Fourier-transform infrared (FTIR) spectroscopy confirmed the formation of urethane linkages. Thermal gravimetric analysis (TGA) showed a thermal stability of up to 250 °C. Dynamic mechanical analysis (DMA) revealed a storage modulus (E') of up to 140 MPa. Furthermore, the hemolytic activities of up to 8.97 ± 0.1% were recorded. The inhibition of biofilm formation was investigated against E. coli and S. aureus (%), which was supported by phase contrast microscopy.

Polymer Biocompositions and Nanobiocomposites Based on P3HB with Polyurethane and Montmorillonite.

Due to the growing interest in biopolymers, biosynthesizable and biodegradable polymers currently occupy a special place. Unfortunately, the properties of native biopolymers make them not good enough for use as substitutes for conventional polymers. Therefore, attempts are being made to modify their properties. In this work, in order to improve the properties of the poly(3-hydroxybutyrate) (P3HB) biopolymer, linear aliphatic polyurethane (PU) based on 1,4-butanediol (BD) and hexamethylene 1,6-diisocyanate (HDI) was used. The conducted studies on the effect of the amount of PU used (5, 10, 15 and 20 m/m%) showed an improvement in the thermal properties of the prepared polymer blends. As part of the tested mechanical properties of the new polymer blends, we noted the desired increase in the tensile strength, and the impact strength showed a decrease in hardness, in particular at the presence of 5 m/m% PU. Therefore, for further improvement, hybrid nanobiocomposites with 5 m/m% PU and organically modified montmorillonite (MMT) (Cloisite 30®B) were produced. The nanoadditive was used in a typical amount of 1-3 m/m%. It was found that the obtained nanobiocomposites containing the smallest amount of nanofillers, i.e., 1 m/m% Cloisite®30B, exhibited the best mechanical and thermal properties.

Supramolecular photoresponsive polyurethane with movable crosslinks based on photoisomerization of azobenzene

AbstractLight‐driven actuators are widely used for smart devices such as soft robots. One of the main challenges for actuators is achieving rapid responsiveness, in addition to ensuring favorable mechanical properties. Herein, we focused on photoresponsive polyurethane (CD‐Azo‐PU) based on controlling the crystallization of the hard segments in polyurethane (PU) by complexation between azobenzene (Azo) and cyclodextrins (CDs). CD‐Azo‐PU incorporated polyurethane as the main chain and a 1:2 inclusion complex between Azo and γCD as a movable crosslink point. Upon ultraviolet light (UV, λ = 365 nm) irradiation, the photoresponsiveness of CD‐Azo‐PU bent toward the light source (defined as positive), while that of the linear Azo polyurethane (Azo‐LPU) without peracetylated γ‐cyclodextrin diol (TAcγCD‐diOH) as a movable crosslinker bent in the direction opposite the light source. The bending rates were determined to be 0.25°/s for CD‐Azo‐PU and 0.083°/s for Azo‐LPU, indicating that the bending rate for CD‐Azo‐PU was faster than that for Azo‐LPU. By incorporating movable crosslinks into CD‐Azo‐PU, we successfully achieved specific photoresponsive actuation with an enhanced rate.

High Resilience and Elongation of Linear Polyurethane Acrylate Modified with Polyetheramines

High Resilience and Elongation of Linear Polyurethane Acrylate Modified with Polyetheramines