Hard Segment Composition Research Articles

Self-Healable, Transparent, Biodegradable, and Shape Memorable Polyurethanes Derived from Carbon Dioxide-Based Diols.

A series of CO2-based thermoplastic polyurethanes (TPUs) were prepared using CO2-based poly(polycarbonate) diol (PPCDL), 4,4'-methylenebis (cyclohexyl isocyanate) (HMDI), and polypropylene glycol (PPG and 1,4-butanediol (BDO) as the raw materials. The mechanical, thermal, optical, and barrier properties shape memory behaviors, while biocompatibility and degradation behaviors of the CO2-based TPUs are also systematically investigated. All the synthesized TPUs are highly transparent amorphous polymers, with one glass transition temperature at ~15-45 °C varying with hard segment content and soft segment composition. When PPG is incorporated into the soft segments, the resultant TPUs exhibit excellent self-healing and shape memory performances with the average shape fixity ratio and shape recovery ratio as high as 98.9% and 88.3%, respectively. Furthermore, the CO2-based TPUs also show superior water vapor permeability resistance, good biocompatibility, and good biodegradation properties, demonstrating their pretty competitive potential in the polyurethane industry applications.

Abundant Hydrogen Bonds Formed in a Urea-Based Gel Polymer Electrolyte Improve Interfacial Stability in Lithium Metal Batteries.

As an emerging and potential replacement system for liquid electrolytes, polymer electrolytes (PEs) exhibit unique capacity in suppressing metal dendrite formation and leakage risks. However, the most used polymer matrix, including polyether, polyester, and polysiloxane, still cannot meet the practical demands for metal electrode compatibility and long lifespan. In this study, gel polymer electrolytes consisting of a polyurea network with abundant hydrogen bonds and deep eutectic electrolyte (DEE) are designed and prepared in-situ. The hydrogen bonding between polyurea chains and polyurea-DEE provides good interfacial stability between PEs and lithium metal. As a result, the assembled Li/LiFePO4 cells based on this electrolyte deliver a long cycle life with 90 % retention after 500 cycles and 76.5 % retention after 1000 cycles at 1 C. In addition, the flexible design characteristics of polyurea structure permit easy operation for performance optimization by modulating the composition of hard and soft segments, and enhanced ionic conductivity and self-healing efficiency are obtained. This study provides a novel method for preparing advanced polymer electrolytes for lithium metal batteries.

New urethane multiblock-copolymers obtained using naphthalene diisocyanate

Multiblock-copolymers were synthesized on the base oligoethers, oligoesters, naphthalene diisocyanate, and butanediol. The thermal, thermomechanical, and physico-mechanical properties of obtained copolymers with a variable composition of soft and hard segments were investigated. The relationship between the structure and properties of a new type of multiblock-copolymers was established. New materials can find application in various conditions of mechanical loading.

Molecular Structures and Mechanisms of Waterborne Biodegradable Polyurethane Nanoparticles

Biodegradable hydrogels have become promising materials for many biological applications in the past years. Recently, novel waterborne biodegradable polyurethane (WDPU) nanoparticles have been synthesized by a green water-based process, and serve as fundamental building blocks to form materials with great biocompatibility, biodegradability, and mechanical properties. However, the molecular structures and mechanisms of the WDPU nanoparticles and the relationship between the chemical compositions of the polymer segments and the material properties of the biodegradable hydrogels at macro-scale are still not well understood. In this study, we explore the fundamental mechanisms of WDPU nanoparticles through a full atomistic simulation approach to understand how the chemical compositions at the molecular level affect the molecular structures and material properties of WDPU nanoparticles. Specifically, we compare two WDPUs, i.e. PCL75LL25 and PCL75DL25, of the same hard segment composition and very similar soft segment composition [75% poly(e-caprolatone) and 25% polylactide], except the lactide in the former is L-form and in the latter is D,L-form. Our results show that the material properties of the biodegradable hydrogel can be designed by tuning the chemical compositions of the polymer segments. We find that the PCL75DL25 and PCL75LL25 have distinct molecular structures and physical crosslinks within the nanoparticles. The molecular structure of WDPU with PDLLA as soft segments is more extended, leading to more physical crosslinks between PCL segments. This study provide fundamental insights into the molecular structures and mechanisms of WDPU nanoparticles and help enabling the design of material properties of biocompatible hydrogel.

Synthesis of aniline‐terminated polyethers and resulting polyurethane/polyurea elastomers

ABSTRACTFunctionalization of polyols with aromatic amines offers a potential route to modify properties of polyurethanes, polyamides, and epoxies. Additionally, aniline termination of polyether backbones provides the opportunity to speed up reactions with isocyanates relative to hydroxyl functionalization and slow down epoxy reactions compared to reactions with primary and secondary amines. In this article, the synthesis, characterization, and physical properties of aniline‐terminated polyols with varying molecular weight, monomer type, and functionality is described. Numerous analytical techniques are employed to track the chemical modification kinetics and the resulting aniline functionalized polyol properties. In addition, synthesis and properties of poly(urethane‐urea) elastomers from several of the modified polyols are presented. The effect of hard segment composition and process temperature on tensile properties, dynamic mechanical properties, phase morphology, and chemical resistance is explored. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 1730–1742

Effect of the soft and hard segment composition on the properties of waterborne polyurethane-based solid polymer electrolyte for lithium ion batteries

A series of waterborne polyurethane (WPU) with various hard segment and soft segment content were synthesized by hexamethylene diisocyanate (HDI), polyethylene glycol (PEG), dimethylol propionic acid (DMPA), and diethylene glycol (DEG). An increase in hard segment content decreased the crystallinity and thermal stability of WPU. Solid polymer electrolytes (SPEs) were prepared by complexing the as-prepared WPU with LiTFSI. The ionic conductivity increased first with the increasing of the hard segment content and then decreased. The compatibility of WPU-based SPEs with lithium electrode was influenced by the hard segment content. The electrochemical stability windows for all the SPEs have reached around 5.0 V (vs. Li+/Li) at 60 °C. A maximum ion conductivity of 5.14 × 10−5 S cm−1 at 25 °C was found for WPU12-20%Li and 1.29 × 10−3 S cm−1 at 60 °C for WPU12-25%Li. All-solid-state LiFePO4/SPE/Li battery based on WPU12-20%Li electrolyte delivered discharge specific capacities of 159 and 162 mAh g−1 under 60 and 80 °C at 0.1 C, respectively. Tuning the appropriate hard and soft segment composition of WPU may ultimately lead to the successful use of WPU-based SPEs for all-solid-state lithium ion batteries.

Stereocomplex formation of poly(l-lactide)-poly(ε-caprolactone) multiblock copolymers with Poly(d-lactide)

Stereocomplex formation is known to increase the melting temperature of poly(l-lactide) (PLLA). In this study, we investigate the stereocomplex formation of poly(l-lactide)-poly(ε-caprolactone) multiblock copolymers (PLLA-PCL MBCs) with poly(d-lactide) (PDLA). The stereocomplexed PLLA-PCL MBCs were readily synthesized by adding PDLA into PLLA-PCL MBCs solutions. X-ray diffraction and differential scanning calorimetry measurements indicate the preferential formation of stereocomplexes. Tensile moduli of PLLA-PCL MBCs increased after stereocomplex formation; however, they conserved their large elongation at break values even when the composition of hard segments (PLLA and PDLA) in the sample increased. The combination of high Young's modulus (>400 MPa) and large elongation (>400%) is high level reported for biodegradable thermoplastic elastomers. Dynamic mechanical analysis measurements suggest improved thermal-deformation stability in the stereocomplexes. Stereocomplex formation of PLLA-PCL random multiblock copolymers synthesized by the copolymerization of PLLA and PCL oligomers with PDLA also effectively increased the melting temperature and the Young's modulus. This simple strategy of adding PDLA into PLLA-segmented copolymers may be a useful method for the synthesis of any other stereocomplexed PLLA-segmented block copolymer.

Effect of chain‐extender modification on the structure and properties of thermoplastic poly(ether ester) elastomers

ABSTRACTThe effect of the modulation of a bulky chain extender (CE), 4,8‐bis(hydroxymethyl)tricyclo[5.2.1.0(2,6)]decane (TCDO) or hydroquinone bis(hydroxyethyl)ether (HBHEE), on the properties of poly(ether ester) elastomers was investigated. The incorporation of various amounts of TCDO or HBHEE greatly changed the hard‐segment (HS) structure and microphase separation behavior; this resulted in a variation of the physical properties, especially for samples with high HS compositions. TCDO and HBHEE were used as minor CEs together with 1,4‐butanediol as the major CE for the synthesis of poly(ether ester) elastomers based on the transesterification of dimethyl 2,6‐naphthalene dicarboxylate with poly(tetramethylene ether glycol). On the basis of the amount of the minor CE incorporated, samples ranging from an elastomer to thermoplastic. The prepared samples were characterized by various spectroscopic, thermal, and mechanical analyses. The poly(ether ester) elastomers formed honeycomb‐structured porous films and microfibers (0.3–1.3 μm in diameter) through the application of a breath figures technique and electrospinning, respectively. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 42888.

Thermoplastic polyurethanes with isosorbide chain extender

ABSTRACTIsosorbide, a renewable diol derived from starch, was used alone or in combination with butane diol (BD) as the chain extender in two series of thermoplastic polyurethanes (TPU) with 50 and 70% polytetramethylene ether glycol (PTMEG) soft segment concentration (SSC), respectively. In the synthesized TPUs, the hard segment composition was systematically varied in both series following BD/isosorbide molar ratios of 100 : 0; 75 : 25; 50 : 50; 25 : 75, and 0 : 100 to examine in detail the effect of chain extenders on properties of segmented polyurethane elastomers with different morphologies. We found that polyurethanes with 50% SSC were hard elastomers with Shore D hardness of around 50, which is consistent with assumed co‐continuous morphology. Polymers with 70% SSC displayed lower Shore A hardness of 74–79 (Shore D around 25) as a result of globular hard domains dispersed in the soft matrix. Insertion of isosorbide increased rigidity, melting point and glass transition temperature of hard segments and tensile strength of elastomers with 50% SSC. These effects were weaker or non‐existent in 70% SSC series due to the short hard segments and low content of isosorbide. We also found that the thermal stability was lowered by increasing isosorbide content in both series. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42830.

The role of the soft phase in the hardening effect and the rate dependence of the ultimate physico-mechanical properties of urethane-containing segmented elastomers

Segmented urethane elastomers (SUE) with polytetramethylene oxide soft segments, toluene diisocyanate (TDI)/methylene-bis-o-chloroaniline (MOCA) hard segments, TDI/ MOCA + TDI/butanediol (BD) and TDI/MOCA + isophorone diisocyanate/MOCA mixed segments were investigated. A microphase separation in SUE was adjusted by the variation in the composition of the hard segments or preparation conditions. It was shown that non-linear relationships of SUE’s thermo-mechanical, thermal and mechanical properties on the composition of hard segments, including an extremal one, were typical. Basic dependence types of SUE strength on the stretching rates (direct, reciprocal, extremal) were determined at various stages of the elastomer structure evolution. A significant increase in the SUE strength was found at a low degree of microphase separation. A strong effect of interaction in the soft phase on the physicochemical properties of block copolymers was shown. An improvement of the miscibility between hard and soft phases and a loose structure of the hard phase promote a stabilisation of the strength value in a wide range of the stretching rates. The effect of the strength increase equals to 30–50 %.

Effect of the hard segment structure on properties of resorcinol derivatives-based polyurethane elastomers

Two series of polyurethane elastomers were obtained from poly(1,4-butylene adipate) diol and 1,6-diisocyanatohexane, which were then chain extended with resorcinol derivatives such as benzene-1,3-diol, 2,4-dihydroxybenzaldehyde, or 1-(2,4-dihydroxyphenyl) hexan-1-one. This article investigates the effects induced in polyurethane elastomer properties by varying the hard segment composition through changing the amount of aliphatic diisocyanate and through the influence of the chemical structure of the resorcinol derivatives’ chain extenders. The different chemical composition and the presence of different dangling chains on the chain extender structure influenced hard segment cohesion, resulting in important effects on the polyurethane elastomer properties. The incorporation of aliphatic diisocyanate alongside the aromatic chain extender leads to changes in the physical and mechanical properties of the polyurethane elastomers compared with aromatic rigid diisocyanates. These polyurethane elastomers were characterized using Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, and mechanical measurements. We synthesized resorcinol-based polyurethane elastomers with aliphatic–aromatic hard segment structures, with the resorcinol addition making it unnecessary to transform phenolic OH groups into aliphatic OH groups.

Triple Shape Memory Effect of Star-Shaped Polyurethane

In this study, we synthesized one type of star-shaped polyurethane (SPU) with star-shaped poly(ε-caprolactone) (SPCL) containing different arm numbers as soft segment and 4,4'-diphenyl methane diisocyanate (MDI) as well as chain extender 1,4-butylene glycol (BDO) as hard segment. Proton nuclear magnetic resonance (1H-NMR) confirmed the chemical structure of the material. Differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) results indicated that both the melting temperature (Tm) and transition temperature (Ttrans) of SPU decreased with the hard segment composition increase. X-ray diffraction (XRD) results demonstrated that the increase of the crystallinity of SPU following the raised arm numbers endowed a high shape fixity of six-arm star-shaped polyurethane (6S-PU) and a wide melting temperature range, which resulted in an excellent triple-shape memory effect of 6S-PU. The in vitro cytotoxicity assay evaluated with osteoblasts through Alamar blue assay demonstrates that this copolymer possessed good cytocompatibility. This material can be potentially used as a new smart material in the field of biomaterials.

Electrostrictive properties of thermoplastic polyurethane elastomer: Effects of urethane type and soft–hard segment composition

The electromechanical behavior of thermoplastic elastomer polyurethane (TPE-PU) is investigated under the effects of urethane type (ester and ether-types) and soft–hard segments at various electric field strengths and temperatures. The highest dielectric constant, electrical breakdown strength, and specific conductivity belong to the ester-type polyurethane (LPR matrix), while the lowest values are obtained from the ether-type polyurethane composing predominantly with the soft-segment (E 80A matrix). Under the electric field strength in the range between 0 and 2 kV/mm, the LPR matrix attains the storage modulus sensitivity (ΔG′/G′0) up to 2 at 2 kV/mm. For the temporal response, the polyurethanes behave with good reproductively (number of cycles >105 times) and with very good recoverability. The steady state behavior can be attained at the first actuation and at the electric field strength of 1 kV/mm. Furthermore, the storage modulus (G′) shows linearly negative responses with increasing temperature. In the deflection experiments, the deflection distance and the dielectrophoresis force increase monotonically with increasing electric field strength. All of the TPE-PU possesses very fast response times for activation (<10 s.) and deactivation (<5 s.). TPE-PU material is systematically shown here to be a potentially good actuator material with high efficiency based on the electrostrictive performance data obtained.

Poly(urea)urethanes based on amorphous quaternizable hard segments and a crystalline polyol derived from castor oil

A set of poly(urea)urethanes (PUU), with different contents of amorphous hard segment and castor oil-derived crystalline polyol as soft segment, was prepared combining bulk and solution polymerizations. It is shown that both the soft segment crystallinity and hard segment glassy nature control the stiffness of the materials and that phase mixing at intermediate hard segment compositions produces softer materials. Upon yielding, PUU developed large plasticity associated to the nature of soft segments. At longer strains, PUU presented strain-induced crystallization related both to soft segments alignment and crystallization, leading to strong and tough materials, especially with high hard segment content compositions. Despite the hydrophobicity of the soft segments, the PUU with 65 wt% hard segment content was dispersable in water after quaternization with acetic acid. The high amount of urea groups in this quaternized PUU makes one think of these types of polymers as promising water soluble environmentally friendly strong adhesives, coatings, or water soluble polymeric electrolites.

Thermal and surface characterization of polyurethane–urea clay nanocomposite coatings

AbstractThis paper reports synthesis and characterization of polyurethane–urea (PU‐urea) and the nanocomposites derived from the PU‐urea with silicate clays. Organophilic montmorillonite cotreated by cetyl trimethyl ammonium bromide (CTAB) was synthesized and used to prepare PU‐urea/montmorillonite nanocomposites coatings. PU‐ureas were prepared from polyethylene glycol (PEG), polypropylene glycol (PPG), trimethylol propane (TMP), and 4,4′‐diphenylmethane diisocyanate (MDI) by reacting excess diisocyanate with polyether glycols. The excess isocyanate of the prepolymers was cured with atmospheric moisture. The synthesized moisture cured PU‐urea and nanocomposites were characterized by Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), differential scanning calorimetric (DSC), and angle resolved X‐ray photoelectron spectroscopy (AR‐XPS). The thermal stability of the PU‐urea nanocomposites was higher relative to the mother PU‐urea films. DSC results showed a slight enhancement in the soft segment glass transition temperature after 3 wt % clay loading. The surface properties showed an enrichment of the soft segment toward the surface. An enhancement in the hard segment composition in the nanocomposite coatings has resulted in enhancing the phase mixing process. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2393–2401, 2006

Thermal and viscoelastic properties of polyurethane-imide/clay hybrid coatings

This paper reports the synthesis and characterization of polyurethane (PU)-imide/clay hybrid coatings based on two types of polyester (PE) polyols (PE-1 and PE-2). PE-1 was prepared from neopentyl glycol (NPG), adipic acid (AA) and isophathalic acid (IPA), whereas PE-2 contains NPG, AA, IPA and TMP (trimethylol propane) with the same hydroxyl value 280 as PE-1. Cetyl trimethyl ammonium bromide (CTAB) modified montmorillonite (K10) was used as the organoclay for the synthesis of the hybrid coatings. The organoclay particles (3 wt%) were well-dispersed into the PE matrix by ultrasonication method. Then the isocyanate terminated PU prepolymers were synthesized by the reaction of polyester polyols with hard segments such as 2,4-toluene diisocyanate (TDI) or isophorone diisocyanate (IPDI) in different NCO/OH ratios e.g., 1.6:1, 2:1 and 3:1, respectively. Finally the thermally stable imide rings were incorporated into the PU backbone by complete reaction of excess NCO content present in the PU prepolymer with pyromellitic dianhydride (PMDA). The thermogravimetric analysis (TGA) shows a higher thermal stability for the PU-imide hybrid coatings with respect to the corresponding PU-imide films. A higher NCO/OH ratio has resulted in higher thermal stability. The activation energies of degradation were calculated by the Broido and Coats–Redfern methods, respectively. The dynamic mechanical thermal analysis (DMTA) results show an enhancement in the glass transition temperature value ( T g) for the clay containing hybrid coatings. The surface analysis by angle resolved X-ray photoelectron spectroscopy (AR-XPS) showed an enrichment of the soft segment towards the surface, and an enhancement in the hard segment composition in the hybrid coatings, resulted in phase mixing.

Study on degradation and systemic toxicity of mulitiblock poly(aliphatic/aromatic-ester) copolymers

The series of PED multiblock copolymers were synthesized. They are composed of poly(butylene terephthalate) (PBT) aromatic units (hard segments) and aliphatic sequences of dimer fatty acids (DFA) (soft segments). The composition of hard segments vary in the range from 26 to 70 wt. %. These polymers can be tailor-made, and therefore, their properties can change along with the composition, from very soft and flexible materials to semi-rigid polymers. Their susceptibility to degradation is a function of hard/soft segment composition. Degradation test (buffer saline solution, pH = 7.4, temp. 37 °C, time 5 weeks) as well as in vivo implantation test for 6 months confirm this statement. Polymers containing higher concentrations of soft segments are more susceptible to degradation than the materials with higher concentrations of hard, aromatic segments as demonstrated by GPC and ATR FT-IR. The chloroformic extracts from PED copolymers were analyzed by GC/MS to evaluate the chemical composition of potential extractables, especially from the polymers demonstrating higher susceptibility to degradation. Prepared saline extracts were subjected to the pyrogenicity tests on rabbits. The influence of the polymer composition on skin irritation was also evaluated by the intracutaneous injections of polymer extracts. Additionally, hemolysis test in contact with bulk polymers was performed. Evaluating the nature of local tissue response to PED extracts and the results of hemolysis test, we did not detect any indication of systemic toxicity over the compositional range of PED copolymers. These novel copolymers were shown to be biocompatible and are very promising materials for biomedical applications.

Viscometric Study of Poly(Ester Urethane) Solutions: 3 Influence of Chemical Structure on the Conformational Transition

This article presents a comparative study of the intrinsic viscosity of segmented poly(ester urethane)s obtained from aromatic diisocyanates with poly(ethylene glycol)adipate and thiodiglycol or diethylene glycol as chain extenders, using a multistep polyaddition process. The data allow the determination of changes in the conformation of the polyurethanes in N,N-dimethyl formamide at 20-45 °C, which are discussed in relation to the behavior of the poly(ethylene glycol)adipate in the same solvent and as a function of the soft and hard segment composition.

Influence of Hard Segments to Specific Refractive Index Increments of Segmented Poly(Ester Urethane)s

The segmented poly(ester urethane)s were obtained from 4,4′-methylene diphenylene diisocyanate and 2,4-tolylene dissocyanate with thiodiglycol, diethylene glycol, or 4,4′-dihidroxydiethoxydiphenyl sulfone as chain extender, and poly(ethylene glycol)adipate using a multistep polyaddition process. Specific refractive index increments of these segmented copolymers in N,N-dimethyl-formamide have been determined by the Lorenz–Lorentz and Gladstone–Dale equations and the corresponding group contributions to the molar refraction and to the molar volume. The results are compared with the experimental values. Also, for studied samples we can observe the contribution of composition of hard segments to the refractive index and specific refractive index increment.

The effect of hard and soft segment composition and molecular architecture on the morphology and mechanical properties of polystyrene–polyisobutylene thermoplastic elastomeric block copolymers

This paper reports the effects of hard (polystyrene, PS) and soft (polyisobutylene, PIB) segment composition and the molecular architecture (linear versus star, PS and PIB block length) on the morphology and mechanical properties of polystyrene/polyisobutylene (SIBS) block copolymers synthesized by living carbocationic polymerization. Atomic force microscopy, dynamic mechanical thermal analysis and tensile testing verified the phase-separated nature of the block copolymers, which behaved as thermoplastic elastomers (TPEs). The morphology of these TPEs is similar to polydiene-based TPEs, and is defined by the soft/hard segment composition. Interestingly, topology (linear vs star) did not have a major influence on morphology. Tensile testing showed that for both linear and three-arm star block copolymers, the modulus and tensile strength increased while elongation at break decreased with higher PS content. However, three-arm star block copolymers showed larger moduli than their linear homologues with similar PS content and PIB arm length, indicating the influence of molecular architecture on mechanical properties. These results might serve as a foundation for macromolecular engineering design for optimizing properties.