Biobased hyperbranched shape‐memory polyurethanes: Effect of different vegetable oils

Hyperbranched polyurethanes were synthesized from poly(ε‐caprolactone) diol as a macroglycol, butanediol as a chain extender, a monoglyceride of a vegetable oil (Mesua ferrea, castor, and sunflower oils separately) as a biobased chain extender, triethanolamine as a multifunctional moiety, and toluene diisocyanate by a prepolymerization technique with the A₂ + B₃ approach. The structure of the synthesized hyperbranched polyurethanes was characterized by ¹H‐NMR and X‐ray diffraction studies. M. ferrea L. seed‐oil‐based polyurethane showed the highest thermal stability, whereas the castor‐oil‐based one showed the lowest. However, the castor‐oil‐based polyurethane exhibited the highest tensile strength compared to the other vegetable‐oil‐based polyurethanes. All of the vegetable‐oil‐based polyurethanes showed good shape fixity, although the castor‐oil‐based polyurethane showed the highest shape recovery. Thus, the characteristics of the vegetable oil had a prominent role in the control of the ultimate properties, including the shape‐memory behaviors, of the hyperbranched polyurethanes. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39579.     

Crosslinked polyurethanes with shape memory properties

A series of shape memory polyurethanes (SMPUs) was prepared from polycaprolactone diol (PCL) 4000, 1,4‐butanediol (BDO), dimethylol propionic acid (DMPA), triethylamine, and 4, 4′‐diphenylmethane diisocyanate (MDI), to which excess MDI or glycerin were added to obtain crosslinked shape memory polyurethanes. Their mechanical, thermomechanical, thermal and shape memory properties were investigated by using differential scanning calorimetry (DSC), Fourier‐transform (FT‐IR) spectroscopy, dynamic mechanical analysis (DMA) and tensile testing. The results showed that crosslinked SMPUs have better thermal and thermomechanical properties than those prepared from linear polyurethanes and display good shape memory effects. Copyright © 2005 Society of Chemical Industry     

Bio-based elastomeric hyperbranched polyurethanes for shape memory application

The bio-based shape memory hyperbranched polyurethanes (HBPUs) have attracted tremendous attention both from academic and industrial researchers due to their strong potential in biomedical and other advanced applications. In the present investigation HBPUs have been synthesized from poly(??-caprolactone)diol as a macroglycol, butanediol as a chain extender, triethanolamine as a branch generating moiety, monoglyceride of Mesua ferrea L. seed oil as a bio-based chain extender, at different percentages and toluene diisocyanate by a two step one pot A₂?+?B₃ approach. The structure of the synthesized hyperbranched polyurethane was characterized by FTIR, ^IH NMR, XRD and SEM studies. ¹H NMR study indicates the formation of highly branched structure with degree of branching 0.93 for polyurethane with 5?wt% monoglyceride. TGA results indicated the increment of thermal stability from 185 to 240?°C with the increase of monoglyceride content from (0?C15) wt% for the HBPUs. The shape memory effect of the hyperbranched polyurethane increased with the increase of monoglyceride in the polymer. However, mechanical properties like tensile strength and elongation at break decreased from 19.31 to 11.48?MPa and 835 to 497%, respectively, with the increase in amount of bio-based component. Excellent impact strength and very good chemical resistance were also observed for the hyperbranched polymers. The studied bio-based HBPUs exhibit excellent shape fixity (95?C99)% as well as shape recovery 100%. Thus, the studied HBPUs have the potential to be used as advanced shape memory materials.     

Triple‐shape memory properties of polyurethane/polylactide–polytetramethylene ether blends

A facile method to prepare triple‐shape memory polymers was developed by blending polyurethane and polylactide–polytetramethylene with well‐separated glass transition temperatures. The thermal properties of the blends were characterized using modulated differential scanning calorimetry and differential scanning calorimetry. Field emission scanning electron microscopy, Fourier transform infrared spectroscopy and wide‐angle X‐ray diffraction were used to characterize the microstructures and crystal structures of the blends. The mechanical properties were also evaluated. The versatile triple‐shape memory effect and quantitative shape memory response were evaluated by consecutive thermal mechanical experiments based on a two‐step programming process and subsequent progressive thermal recovery. The results show that the blends have phase‐separated microstructures resulting in an ability to fix two temporary shapes independently and can recover to their original shapes sequentially. The blends have excellent triple‐shape memory properties and may have some applications in multi‐shape coatings, adhesives, films and temperature sensing or actuating elements. © 2015 Society of Chemical Industry     

Composite polymer electrolytes based on the low crosslinked copolymer of linear and hyperbranched polyurethanes

Low crosslinked copolymer of linear and hyperbranched polyurethane (CHPU) was prepared, and the ionic conductivities and thermal properties of the composite polymer electrolytes composed of CHPU and LiClO₄ were investigated. The FTIR and Raman spectra analysis indicated that the polyurethane copolymer could dissolve more lithium salt than the corresponding polymer electrolytes of the non crosslinked hyperbranched polyurethane, and showed higher conductivities. At salt concentration EO/Li = 4, the electrolyte CHPU30‐LiClO₄ reached its maximum conductivity, 1.51 × 10^?5 S cm^?1 at 25°C. DSC measurement was also used for the analysis of the thermal properties of polymer electrolytes. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3607–3613, 2007     

Thermoresponsive crosslinked isocyanate‐free polyurethanes by Diels‐Alder polymerization

This new study is a continuation of our previous work on thermocleavable nonisocyanate polyurethanes (NIPUs), but it is focused on crosslinked networks. Two systems are studied: the first system involves a dicyclocarbonate adduct with a PPO‐bicyclocarbonate and a triamine as crosslinker. The second system involves a tetracyclocarbonate DA adduct as crosslinker with the same PPO‐bicyclocarbonate and a difunctional amine. Firstly, Diels‐Alder adducts are synthesized and characterized. Then they are copolymerized to yield two types of cleavable polymer networks. The thermal behavior of synthesized polymers is fully characterized. Finally, by SEC, it was demonstrated that the obtained NIPU polymer chains are sliced up by rDA reaction. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44408.     

Recyclable bio‐based crosslinked polyurethanes with self‐healing ability

We report the synthesis of a linear bio‐based polyurethane (bio‐PU) containing furan ring by using renewable polylactide copolymer diol and 2,5‐furandimethanol as a soft segment and chain extender, respectively, in which the reversible crosslinked covalent bonds between hard segments were incorporated via Diels–Alder (D‐A) reaction between the furan ring of the chain extender and bismaleimide (BM) crosslinker. By simply controlling the amount of BM, mechanical properties of the obtained crosslinked bio‐PUs (CBPUs) were varied widely. In particular, the CBPU100 sample shows the highest tensile strength of 10.8 MPa, Young's modulus of 193 MPa, and an elongation of 155%. The differential scanning calorimetry experiments verify the recycle property of the CBPUs by the D‐A/retro‐D‐A reaction at the proper temperature. The thermal recyclability and remolding ability of these materials are demonstrated by two kinds of polymer processing methods, i.e., solution casting and hot‐compression molding. The recycled CBPUs display almost identical elongation and slightly decreased tensile strength compared to the as‐synthesized samples. Furthermore, the CBPUs also exhibit excellent self‐healing ability. Therefore, the resulting CBPUs possess tunable mechanical properties, good thermal recyclability, re‐mending, and self‐healing ability, which makes the bio‐based materials more eco‐friendly. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46272.     

Influence of aqueous dispersions in place of organic solvents during the synthesis of shape memory polyurethanes on their structure and properties

In this work, the effect of synthesizing shape memory polyurethanes in aqueous dispersions instead of in organic solvents on the structure and properties of the obtained polymers was investigated. Shape memory polyurethanes based on polycaprolactone diol and isophorone diisocyanate were synthesized by two routes: (1) aqueous dispersion (PU/SM_WATER) and (2) dissolution in THF (PU/SM_THF). The samples were analyzed by infrared spectroscopy (FTIR), X‐ray diffraction (XRD), static light scattering (SLS), atomic force microscopy (AFM), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and mechanical tests. The aqueous dispersion method led to the production of polyurethanes with a higher degree of phase separation and a higher degree of crystallinity. The morphology of the obtained polyurethanes demonstrated that PU/SM_WATER displays a structure with better defined phase separated domains. The polyurethanes exhibited similar average molar masses, soft segment glass transitions (T_gs) and mechanical properties. The lower degrees of phase separation and crystallinity of the PU/SM_THF led to lower values for the shape memory properties (shape recovery ratio (R_r)). The observed changes in the structure of the polyurethanes due to the replacement of organic solvent by an aqueous dispersion during their syntheses confirmed the preparation of shape memory polyurethanes with enhanced shape memory properties. POLYM. ENG. SCI., 57:432–440, 2017. © 2016 Society of Plastics Engineers     

Bio-based hyperbranched polyurethanes for surface coating applications

High performance vegetable oil based hyperbranched polymers are not only interesting but also very useful with respect to current scenario of advanced coating materials. So in the present study hyperbranched polyurethanes have been synthesized from the monoglyceride of Mesua ferrea L. seed oil, poly(?-caprolactone)diol, 2,4-toluene diisocyanate and glycerol without using any catalyst by a two-step one pot A₂ + B₃ approach. The linear analog (neglecting little possible branching due to different components of monoglyceride) of the hyperbranched polyurethane has also been prepared by the same method without using glycerol, just to compare with hyperbranched polymer. The formation of polymers was confirmed by FTIR, ¹H NMR, UV and SEM studies and measurements of hydroxyl value, solubility and viscosity. TGA results indicated the high thermal stability of hyperbranched and linear polymers (210–220 °C). The properties like tensile strength, impact strength, hardness, adhesion, flexibility, gloss, elongation at break and chemical resistance were influenced by the hard segment content of the polymers. The hyperbranched polyurethane with 30% hard segment content showed the optimum properties. The values of hydrodynamic diameter of hyperbranched polymers compared to the linear analog support the hyperbranched formation. Thus it confirms the formation of mechanically strong and thermally stable hyperbranched polyurethane coating materials from a vegetable oil.     

Effect of microphase‐separation promoters on the shape‐memory behavior of polyurethane

A series of segmented polyurethanes (PUs) with novel thermosensitive shape‐memory behavior were synthesized via the in situ addition of a small amount of 1‐octadecanol (ODO) to a PU system. For comparison, liquid paraffin (LP) modified PUs were also synthesized. The effects of a small amount of ODO or LP on the PU suprastructure and the thermosensitive shape‐memory properties were studied with X‐ray diffraction, differential scanning calorimetry, dynamic mechanical analysis, and shape‐memory studies. The results indicated that the in situ addition of a small amount of ODO (e.g., 0.3 wt %) remarkably promoted microphase separation, facilitating the ordered packing of soft segments and the formation of perfect hard‐segment domains and thus significantly improving the shape‐memory properties. In contrast, LP had less significant influence on the shape‐memory behavior because of the macrophase separation of these nonpolar alkyl chains from the PU system. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:5224–5231, 2006     

Synthesis,characterization, and antibacterial activity of metal‐containing polyurethanes

Metal salts of mono(hydroxyethoxyethyl)phthalate [M(HEEP)₂] (M = Ca²⁺, Cd²⁺, and Pb²⁺) were synthesized by the reaction of diethylene glycol, phthalic anhydride, and metal acetates. A series of metal‐containing polyurethanes (PUs) were synthesized by the reaction of hexamethylene diisocyanate or tolylene 2,4‐diisocyanate with Ca²⁺, Cd²⁺, and Pb²⁺ salts of mono(hydroxyethoxyethyl)phthalate using di‐n‐butyltin dilaurate as a catalyst. The PUs were well characterized by FTIR, ¹H, and ¹³C NMR, solid‐state ¹³C‐CP‐MAS NMR, viscosity, solubility, elemental, and X‐ray diffraction studies. Thermal properties of the polymers were also studied by using thermogravimetric analysis and differential scanning calorimetry. The antibacterial activities of these polyurethanes have also been investigated by using the agar diffusion method. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 288–295, 2004     

Synthesis of shape memory polyurethane/clay nanocomposites and analysis of shape memory,thermal, and mechanical properties

In this study, shape memory polyurethane/clay nanocomposites were synthesized by using two‐step in situ polymerization. The effects of nanoparticle content on mechanical, thermal, and shape memory properties were studied. Soft and hard segments of polyurethanes were based on polycaprolactone (PCL) diol and 4,4′‐diphenylmethane diisocyanate/1,4‐butanediol molar ratio with 70/30, respectively. The differential scanning calorimetry, tensile test, dynamic mechanical thermal analysis, parallel plate rheometer, and X‐ray diffraction were used to evaluate the properties of the nanocomposites. To evaluate shape memory properties, a tensile device equipped with a thermal chamber was used. Glass transition temperature of soft segments has been increased by nanoclay loading. Addition of nanoclay to polyurethane matrix caused to disrupt ordering in hard domains, decrease in elongation and tensile strength. The results show that crystallinity of soft segments and dispersion of nanoparticles affect on the mechanical properties and shape memory behavior of nanocomposites, distinctly. Nanocomposite containing 1 wt% shows the best shape memory properties. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Renewable resource modified polyol derived aliphatic hyperbranched polyurethane as a biodegradable and UV‐resistant smart material

Renewable resource tailored tough, elastomeric, biodegradable, smart aliphatic hyperbranched polyurethanes were synthesized using castor oil modified polyol containing fatty amide triol, glycerol, diethanolamine and monoglyceride of sunflower oil via an A_x + B_y (x , y ≥ 2) approach. To the best of our knowledge, this is the first report of the synthesis of solely aliphatic hyperbranched polyurethanes by employing renewable resources. The synthesized polyurethanes were characterized by Fourier transform infrared, NMR and XRD techniques. The hyperbranched polyurethanes exhibited good mechanical properties, especially elongation at break (668%), toughness (32.16 MJ m^?3) and impact resistance (19.02 kJ m^?1); also high thermal stability (above 300 °C) and good chemical resistance. Also, the hyperbranched polyurethanes were found to show adequate biodegradability and significant UV light resistance. Moreover, they demonstrated excellent multi‐stimuli‐driven shape recovery ability (up to 97%) under direct sunlight (10⁵ lux), thermal energy (50 °C) and microwave irradiation (450 W). The performance of the hyperbranched polyurethanes was compared with renewable resource based and synthetic linear polyurethane to judge the superiority of the hyperbranched architecture. Therefore, these new aliphatic macromolecules hold significant promise as smart materials for advanced applications. © 2017 Society of Chemical Industry     

Influence of fluorocarbon chains on the crystallization behaviors of aliphatic polyurethanes

The aliphatic polyurethanes were synthesized from either hexamethylene diisocyanate (HDI) and 2,2,3,3‐tetrafluoror‐1,4‐butanediol or HDI and 1,4‐butandiol. The crystallization behaviors of the aliphatic polyurethanes were characterized using differential scanning calorimetry, wide‐angle X‐ray diffraction, and polarized optical microscopy. The effects of fluorocarbon chains on the solubility behavior, microstructure, thermal transition property, crystal morphology, and crystallization behaviors were investigated. The fluorinated polyurethane exhibited a lower viscosity, higher solubility in organic solvents, smaller fraction of ordered hydrogen‐bonded carbonyls, and lower transition temperatures than the corresponding fluorine‐free polyurethane. The wide‐angle X‐ray diffraction measurements reflected change of crystal structure with the (CF₂)₂ moieties in place of (CH₂)₂ moieties. Polarized optical microscopy also revealed that the polyurethanes exhibited a variety of spherulitic texture. The isothermal crystallization process of the polyurethanes was described by the Avrami analysis. The result showed that the Avrami exponent (n) was around 2.5, which suggested the growth of crystal might be spherulite growth corresponding to homogeneous (thermal) nucleation and diffusion control. The crystallization activation energy was estimated to be ?130.9 kJ/mol for the fluorinated polyurethane and ?276.9 kJ/mol for the fluorine‐free polyurethane from Arrhenius form. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Morphology–properties relationship in high‐renewable content polyurethanes

The effect of diisocyanate nature and hard segment content on the morphology and properties of high‐renewable content segmented thermoplastic polyurethanes was studied. Vegetable oil‐based polyether diol and corn sugar derived chain extender were used as renewable reactants together with an aliphatic (1,6‐hexamethylene diisocyanate, HDI) or aromatic (4,4′‐diphenylmethane diisocyanate, MDI) diisocyanate as hard segment. Segmented thermoplastic polyurethanes were synthesized by two‐step bulk polymerization. Morphology and physicochemical, thermal and mechanical properties were analyzed by Fourier‐transform infrared spectroscopy, differential scanning calorimetry, dynamic mechanical analysis, atomic force microscopy, and mechanical testing. The effect of mechanical deformation over the microstructure was also analyzed. Changes in crystallinity and hard segment hydrogen bonding after mechanical testing were evaluated by Fourier‐transform infrared spectroscopy and differential scanning calorimetry. The increase of physical crosslinking sites by aromatic diisocyanate and chain extender ratio in the polyurethane results in hard segment crystalline domains with spherulitic morphology, which enhance the stiffness and hardness whereas percentage elongation at break diminish. The flexible, linear aliphatic nature of HDI favors the arrangement of urethane groups thus creating strong hard segment interactions and hard segment crystal microdomains composed of fibrillar morphology are observed. POLYM. ENG. SCI., 54:2282–2291, 2014. © 2013 Society of Plastics Engineers     

Shape‐memory property and characterization of epoxy resin‐modified Mesua ferrea L. seed oil‐based hyperbranched polyurethane

Modification of existing polymers leads to enhancement of many desirable properties. So, a hyperbranched polyurethane (HBPU) of monoglyceride of Mesua ferrea L. seed oil, poly(ε‐caprolactone)diol (M_n = 3000 g mol^?1), 2,4‐toluene diisocyanate, and glycerol with 30% hard segment (NCO/OH = 0.96) has been modified with different amounts of bisphenol‐A based epoxy resin. The system is cured by poly(amido amine) hardener at 120°C for specified period of time. Improvement of thermostability, scratch hardness, and impact strength are observed by this modification of HBPU. The differential scanning calorimetry (DSC) results show improvement of melting temperature of the modified systems. The enhancement of tensile strength is about 2.4 times compared with that of the unmodified one. The morphology and structural changes due to variation of epoxy content was studied by scanning electron microscopy (SEM) analysis and Fourier transform infrared (FTIR) spectroscopy. The rheological properties of the epoxy‐modified HBPU show the dependence on the amount of epoxy resin. Shape memory study of the crosslinked HBPUs shows 90–98% thermoresponsive shape recovery. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Mesomorphic properties of cholesteric side‐chain liquid crystalline polysiloxanes and elastomers

A series of crosslinked liquid crystalline polymers and corresponding uncrosslinked liquid crystalline polymers were prepared by graft copolymerization. Their liquid crystalline properties were characterized by differential scanning calorimetry, polarizing optical microscopy, and X‐ray diffraction measurements. The results showed that the crosslinking obtained in the isotropic state and the introduction of nonmesogenic crosslinking units into a polymeric structure could cause additional reduction of the clearing point (T_i) of the crosslinked polymers, compared with the corresponding uncrosslinked polymers. The crosslinked polymers (P‐2–P‐4) with a low crosslinking density exhibited cholesteric phases as did the uncrosslinked polymers. In contrast, a high crosslinking density made the crosslinked polymer P‐5 lose its thermotropic liquid crystalline property. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 773–778, 2004     

Effect of solvent exposure on the properties of hydroxy‐terminated polybutadiene‐based polyurethanes

Hydroxy‐terminated polybutadiene‐based prepolyurethanes and diamine chain extended polyurethane‐ureas were prepared and treated with various organic solvents in the moisture‐cured state in order to modify their ultimate strength. FTIR studies with solvent‐treated polyurethanes and polyurethane‐ureas confirmed that organic solvents penetrated inside the polyurethane hard segments and affected hydrogen bonding. The polar and non‐polar solvents showed different abilities to penetrate into polyurethane hard segments. Solvent treatment after moisture curing increased the tensile strength of these polyurethanes and polyurethane‐ureas with respect to control samples. The stress–strain behaviour of solvent‐treated polyurethane follows the constrained junction model. The change in hard segment crystallinity on solvent treatment has been explained by wide‐angle X‐ray diffraction study. The better orientation in polybutadiene soft segments evidenced from SEM (scanning electron microscopy) pictures is believed to be the main reason behind the improved tensile properties of solvent‐treated polyurethane samples. The effect of solvent treatment, as well as stretching, on the diffusion coefficient of hexane in polyurethanes was investigated. Copyright © 2003 Society of Chemical Industry     

Wet‐driven shape‐memory behaviors and thermal adaptability of cotton knitted fabrics containing crosslinked poly(ethylene glycol) moieties

Cotton knitted fabrics were treated with poly(ethylene glycol) (PEG) in the presence of polyhydric alcohol etherified dimethylol dihydroxy ethylene urea as the crosslinker and magnesium chloride hexahydrate as the catalyst. In wet–dry cycles, the fabrics treated with 30% PEG1500 in the presence of 15% crosslinker and 3% catalyst showed obvious wet‐driven shape‐memory behaviors in terms of a 12% shrinkage rate in the wet state and a 80% shrinkage‐recovery rate in the dry state. The results of weight gain, morphological structures, Fourier transform infrared spectra, and X‐ray diffraction pattern tests confirmed PEG deposits on the surface of the treated fabrics, demonstrated the crosslinking of cotton cellulose with PEG and crosslinker, and also explained the wet‐driven shape‐memory mechanism. The results from differential scanning calorimetry show that the treated fabrics with wet‐driven shape‐memory behaviors had a phase‐change enthalpy and heat‐storage capacity. The crosslinking of cotton cellulose with PEG had a strong influence on the mechanical performance and air permeability of the cotton knitted fabrics. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43473.     

Hyperbranched‐modified epoxy thermosets: Enhancement of thermomechanical and shape‐memory performances

In this study a complete characterization of the thermomechanical and shape‐memory properties of epoxy shape‐memory polymers modified with hyperbranched polymer and aliphatic diamine was performed. Focusing on the mechanical properties that are highly desirable for shape‐memory polymers, tensile behavior until break was analyzed at different temperatures and microhardness and impact strength were determined at room temperature. As regards shape memory performance, the materials were fully characterized at different programming temperatures to study how this influenced the recovery ratio, fixity ratio, shape‐recovery velocity, and switching temperature. Tensile testing revealed a peak in deformability and in the stored energy density at the onset of the glass transition temperature, demonstrating that this is the best programming temperature for obtaining the best shape‐memory performances. The Young's moduli revealed more rigid structures in formulations with higher hyperbranched polymer content, while microhardness showed higher values with increasing hyperbranched polymer content due to the increased crosslinking density. Impact strength was greatly improved as the aliphatic diamine content increases due to the energy dissipation capability of its flexible structure. As regards the shape‐memory properties, increasing the programming temperature has a minor effect on formulations with a lower hyperbranched polymer content and worsens these properties when the hyperbranched polymer content is increased. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44623.