A review of small-angle scattering models for random segmented poly(ether-urethane) copolymers

Small-angle X-ray scattering data from several experimental and commercial poly(ether urethane) formulations was used to test various scattering models based on different morphologies. The best fits were generally found with ‘globular’ scattering models based on a distorted one-dimensional lattice or the Percus-Yevick model of liquid structure. Whilst this is not conclusive proof of the morphologies exhibited by the materials studied, these scattering models are roughly consistent with many AFM and TEM studies, which indicated discrete globular or elongated cylindrical microdomains. Moreover, reasons why meandering elongated or finite lamellar microdomains may behave more like globular scattering bodies are discussed. Hence, these models are proposed as a basis for interpreting scattering data from polyurethanes.Other models were unable to fit the observed scattering data adequately. A model based on the weak segregation of copolymers was rejected on the basis of deviations from the observed scattering behaviour in the Porod region. A model based on stacks of ideal (infinite, parallel, flat) lamellae was ruled out, since it was unable to reproduce the observed peak width. The Teubner-Strey model, based on microemulsion structure, was found to be incapable of fitting the data at low q, particularly for strained samples. However, this model appeared to be more successful at reproducing the scattering observed at elevated temperatures. One possible inference is that the morphologies became more akin to microemulsions during heating.     

Annealed segmented polyether ester—poly (vinyl chloride) blends

Hytrel, PVC and blends of these polymers containing, respectively, 75% and 45% by wt of Hytrel were annealed and the dynamic mechanical and sonic velocity behaviour of these annealed samples were compared with the unannealed materials. The annealed Hytrel showed evidence of enhanced segregation of the hard and soft segments, while for PVC there was a shift of the glass transition to a higher temperature. Annealing of the 75% by wt Hytrel blend resulted in increased phase separation of the constituent materials and a very broad tan δ—temperature dispersion. It was also concluded that the 45% by wt Hytrel blend again showed phase separation on annealing, but to a lesser extent.     

Synthesis and characterization of poly(propylene glycol) polytrioxamide and poly(urea oxamide) segmented copolymers

This report describes the synthesis and characterization of unprecedented poly(propylene glycol) (PPG) polytrioxamide and poly(urea oxamide) (UOx) segmented copolymers containing monodisperse hard segments. Synthesis of the segmented copolymers relied on an efficient two‐step end‐capping sequence, which resulted in novel difunctional oxamic hydrazide‐terminated polyether oligomers. Polymerization with oxalyl chloride or 4,4′‐methylenebis(cyclohexyl isocyanate) provided the desired segmented copolymers displaying thermoplastic elastomeric behavior. Variable‐temperature Fourier transform infrared and ¹H NMR spectroscopies confirmed the presence of hard segment structures and revealed ordered hydrogen bonding interactions with thermal dissociation profiles similar to those of polyurea and polyoxamide copolymer analogs. Dynamic mechanical analysis of PPG‐UOx exhibited a longer, rubbery plateau with increased moduli compared to PPG polyurea, and tensile analysis revealed a dramatic increase in copolymer toughness due to enhanced hydrogen bonding. A new step‐growth polymerization strategy is described that is capable of producing tunable hydrogen bonding segmented copolymer architectures. © 2013 Society of Chemical Industry     

Electrospinning of linear and highly branched segmented poly(urethane urea)s

Electrospun fibrous mats were formed from linear and highly branched poly(urethane urea)s. The highly branched poly(urethane urea)s were synthesized using an A₂+B₃ methodology, where the A₂ species is an oligomeric soft segment. Since the molecular weight of the A₂ oligomer is above the entanglement molecular weight, the highly branched polymers formed electrospun fibers unlike typical hyperbranched polymers that do not entangle. Stress-strain experiments revealed superior elongation for the electrospun fibrous mats. In particular, the highly branched fiber mats did not fail at 1300% elongation, making the electrospun mats promising for potential applications where enhanced tear strength resistance is required.     

Incorporation of salicylates into poly(l-lactide)

Summary Recent studies have indicated that complications like swelling and inflammation of the surrounding tissue may occur in the late stage of thein vivo degradation of semi-crystalline PLLA bone fixation devices. Incorporation of an anti-inflammatory drug, like a salicylate, in the poly(L-lactide) chain might be a route to prevent these complications. In this study, it has been shown that it is possible to copolymerize L-lactide with di- and trisalicylide and to use salicylic acid as an initiator for the L-lactide polymerization or the L-lactide/-caprolactone copolymerization. Furthermore, PLLA was blended with poly(salicylic acid) and Zn(salicylate)2 was synthesized and turned out to be a catalyst for the ring opening polymerization of L-lactide. The binary poly(L-lactide)/o-acetyl salicylic acid system has an eutectic composition for 52 % w/w of poly(L-lactide) in the mixture. Its eutectic melting temperature is 119 °C.     

Incorporation of different crystallizable amide blocks in segmented poly(ester amide)s

High molecular weight segmented poly(ester amide)s were prepared by melt polycondensation of dimethyl adipate, 1,4-butanediol and a symmetrical bisamide-diol based on ε-caprolactone and 1,2-diaminoethane or 1,4-diaminobutane. FT-IR and WAXD analysis revealed that segmented poly(ester amide)s based on the 1,4-diaminobutane (PEA(4)) give an α-type crystalline phase whereas polymers based on the 1,2-diaminoethane (PEA(2)) give a mixture of α- and γ-type crystalline phases with the latter being similar to γ-crystals present in odd-even nylons. PEA(2) and PEA(4) polymers with a hard segment content of 25 or 50 mol% have a micro-phase separated structure with an amide-rich hard phase and an ester-rich flexible soft phase. All polymers have a glass transition temperature below room temperature and melt transitions are present at 62-70 °C (T_m,1) and at 75-130 °C (T_m,2) with the latter being highest at higher hard segment content. The two melt transitions are ascribed to melting of crystals comprising single ester amide sequences and two or more ester amide sequences, respectively. These polymers have an elastic modulus in the range of 159-359 MPa, a stress at break in the range of 15-25 MPa combined with a high strain at break (590-810%). The thermal and mechanical properties are not influenced by the different crystalline structures of the polymers, only by the amount of crystallizable hard segment present.     

Synthesis,characterization, and pervaporation properties of segmented poly(urethane‐urea)s

Poly(urethane‐urea)s (PUUs) from 2,4‐tolylene diisocyanate (2,4‐TDI), poly(oxytetramethylene)diols (PTMO) or poly(butylene adipate)diol (PBA), and various diamines were synthesized and characterized by Fourier transform infrared spectroscopy, gel permeation chromatography, differential scanning calorimetry, and density measurements. Transport properties of the dense PUU‐based membranes were investigated in the pervaporation of benzene–cyclohexane mixtures. It was shown that the pervaporation characteristics of the prepared membranes depend on the structure and length of the PUU segments. The PBA‐based PUUs exhibit good pervaporation performance along with a very good durability in separation of the azeotropic benzene–cyclohexane mixture. They are characterized by the flux value of 25.5 (kg μm m⁻² h⁻¹) and the separation factor of 5.8 at 25°C, which is a reasonable compromise between the both transport parameters. The PTMO‐based PUUs display high permeation flux and low selectivity in separation of the benzene‐rich mixtures. At the feed composition of 5% benzene in cyclohexane, their selectivity and flux are in the range of 3.2 to 11.7 and 0.4 to 40.3, respectively, depending on the length of the hard and soft segments. The chemical constitution of the hard segments resulting from the chain extender used does not affect the selectivity of the PUU membranes. It enables, however, the permeability of the membranes to be tailored. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1615–1625, 1999     

聚硅氧烷/聚醚聚氨酯弹性体的合成与表征

以聚二甲基硅氧烷(PDM S)与聚丁醚(PTM G)为混合软段与4,4'-二苯甲基二异氰酸酯(M D I)、1,4-丁二醇(1,4-BD)制备出一系列的聚氨酯共聚物。用FT IR、DM A、TGA以及AFM分别对共聚物的结构、热性质以及表面形态进行了表征。结果表明,共聚物含有复杂的微相分离结构,而且与纯聚氨酯相比,含硅氧烷的聚氨酯比纯聚氨酯具有更好的热稳定性。     

Incorporation of polyfluorenes into poly(lactic acid) films for sensor and optoelectronics applications

Films of neat and plasticized biodegradable poly(lactic acid) (PLA) matrices containing anionic conjugated polyelectrolytes, poly[9,9‐bis(4‐phenoxybutylsulfonate)]fluorene‐2,7‐diyl‐alt‐arylenes, with 1,4‐phenylene and 4,4″‐p‐terphenylene, respectively, as arylene groups or a neutral poly(9,9‐dialkylfluorene) for comparison were prepared by solution casting. These films were characterized using differential scanning calorimetry, thermogravimetry, scanning electron microscopy and fluorescence spectroscopy. In addition, the effects of plasticizer on the thermal properties and the oxygen permeability of the PLA films were measured through the oxygen transmission rate. Results show that it is possible to obtain thin, optically transparent and luminescent films with potential in oxygen sensing, exhibiting good thermal and photochemical stability. At high polyelectrolyte content, evidence is found for phase separation and aggregate formation and it is no longer possible to obtain completely homogeneous films. The possibility of incorporating the cationic metal complex tris(2,2′‐bipyridyl)ruthenium(II) into plasticized PLA films containing conjugated polyelectrolytes for dual‐wavelength ratiometric luminescence sensing is also discussed. Copyright © 2012 Society of Chemical Industry     

Siloxane‐based segmented poly(urethane‐urea) elastomer: Synthesis and characterization

A series of segmented poly(urethane‐urea) block copolymers were synthesized with varying proportions of polydimethylsiloxane diols in combination with polytetramethylene ether glycol (PTMG) using 4,4'‐methylenediphenyl diisocyanate followed by chain extension with a (50:50 mol %) mixture of 4,4'‐methylene‐bis(3‐chloro‐2,6‐diethylaniline) (M‐CDEA) and 1,4‐butanediol (BD). The molecular structures of polydimethylsiloxane urethane‐ureas were characterized by ATR‐FTIR and ¹H‐NMR spectroscopic techniques. Distribution of siloxane domain and its influence on surface roughness were investigated by scanning electron microscopy (SEM) and atomic forced microscopy (AFM), respectively. The mechanical and thermal properties of the elastomers were studied by thermogravimetric analysis, dynamical mechanical thermal analysis, and tensile measurement. The results showed that by incorporation of polydimethylsiloxane diol and M‐CDEA chain extender in polyurethane formulation, some improvements in thermal stability, fire resistance and surface hydrophilicity were achieved. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1743–1751, 2013     

Incorporation of azobenzene chromophore into poly(amide‐imide)

Poly(amide‐imide)s (PAI) bearing azobenzene chromophore groups were prepared by allowing a hydroxyl‐containing azobenzene dye (Disperse Red 1) to react with and reactive‐terminated PAI with weight–average molecular weights ranging from ～ 1.2 to 2.0 × 10⁴ g/mol. Such PAI were prepared by the condensation of trimellitic anhydride (TMA) and 4,4′‐methylene diphenyl diisocyanate (MDI). The final polymers presented a deep red color, with an absorption maxima in N,N‐dimethylformamide (DMF) solution at 490 nm, close to the azobenzene reactant used (Disperse Red 1) and molecular weights slightly higher than the pristine polymer, showing that the azo chromophore incorporation reaction does not lead to side reactions. The azofunctionalized polymer presented a high T_g value (170°C) that could be increased by a thermal curing process to 240°C. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 841–847, 2007     

Relationship between segment structures and elastic properties of segmented poly(urethane‐urea) elastic fibers

Studies on segmented poly(urethane‐urea) (SPUU) elastic fibers having various segment structures were done in terms of elastic recovery and stress‐strain relationship (S‐S). Three kinds of segment structures were used: 1) the same composition having different sequences of segment units, 2) the same length of soft segments having different molecular weights of polyol, and 3) different segment structures having almost the same stress at 350% elongation. The SPUU elastic fibers having higher sequence numbers of both soft and hard segment units, that is, greater block structures, show better elastic recovery properties, especially delayed elastic recovery. The SPUU elastic fibers showing better elastic recovery take an optimum value for the number‐average molecular weight (M_n) of soft segments jointed with urethane bonds. Here the optimum M_n depends on the molecular weight of polytetramethyleneglycol (PTMG) as a starting material. The hysteresis loss in S‐S for the pre‐elongation decreases with an increase of M_n of PTMG. The SPUU elastic fibers having greater block structures show lower stress with lower 2C₁ and 2C₁ + 2C₂ of Mooney‐Rivilin plot constants for elastic fibers having the same composition. This indicates a lower density of crosslinks for finite deformation. An increase of the urea bonds or the molar ratio of urea bond to urethane bond raises the stress. It is found that the polymerization process, as well as composition, is important for design structures of SPUU elastic fibers.     

Structural modifications of segmented poly(hydroxyether-siloxane) copolymers

Summary Hydroxyether linked copolymers were synthesized from ,-bis(aminopropyl)polydimethyl diphenylsiloxane oligomers and diglydicylether of bisphenol-A (DGEBA). The siloxane oligomers were synthesized by the bulk coequilibration of the various weight percents cyclic dimethylsiloxane tetramer (D₄) with cyclic diphenylsiloxane tetramer (D₄) using a basic catalyst. The molecular weight and functionality was controlled by the incorporation of 1,3-bis(aminopropyl)-tetramethyldisiloxane end blocker. The copolymers containing low diphenylsiloxane compositions have two T_g's suggesting a microphase separation. Networks containing higher diphenylsiloxane compositions show a single phase morphology. The mechanical behavior of these copolymers is influenced by the composition changes.     

Macromolecular assemblies of segmented poly(ester urethane)s and poly(ether urethane)s

Polyurethanes containing different soft and hard segments were investigated by fluorescence and scanning electron microscopy. The polarity dependence of the vibrational structure of the pyrene emission spectrum indicated the formation of aggregates at concentrations, which are significantly below the critical concentrations, which define the separation of dilute‐semidilute domains. Unlike the samples with 4,4′‐methylene diphenylene diisocyanate, the samples with 2,4‐tolylene diisocyanate in hard segments give the fluorescence spectra in which the pyrene excimer appears. The supermolecular structures associated with the form of spherulites or of spherical micelles were detected by scanning electron microscopy. The results were compared with previous reports concerning viscometric data. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

A comparative study of the structure-property behavior of highly branched segmented poly(urethane urea) copolymers and their linear analogs

The solid-state structure-property behavior of highly branched segmented poly(urethane urea) (PUU) copolymers and their linear analog was investigated. A limited study of their solution rheological behavior was also undertaken. The linear PUUs were synthesized by the two-step prepolymer method, whereas the oligomeric A₂+B₃ methodology was utilized to synthesize the highly branched materials. The soft segments (SS) were either poly(tetramethylene oxide) (PTMO) or poly(propylene oxide) (PPO). All copolymers utilized in this study, with one exception, contained 28 wt% hard segment (HS) content. DMA, SAXS, and AFM studies indicated that the linear as well as the highly branched PUUs were microphase separated. The SS T_g of the highly branched PUUs was nearly identical to that of their respective linear analogs. However, the linear copolymers exhibited broader and less temperature sensitive rubbery plateaus, both attributed to one or both of two reasons. The first is better hydrogen bonding organization of the HS phase as well as greater HS lengths than in the highly branched analogs. The second parameter is that of a potentially higher chain entanglement for the linear systems relative to the branched analogs. Tapping-mode AFM phase images confirmed the microphase morphology indicated by SAXS and DMA. Ambient temperature strain-induced crystallization was observed in the PUU based on PTMO 2040 g/mol at a uniaxial strain of ca. 400%, irrespective of the chain architecture. Stress-strain, stress relaxation, and mechanical hysteresis of the highly branched copolymers were in general slightly poorer than that of their linear analogs. Ambient temperature solution viscosity of the highly branched materials in dimethyl formamide was substantially lower that that of the linear samples of nearly equal molecular weight.     

Synthesis and physicochemical characterization of a well-defined poly(butadiene 1,3)-block-poly(dimethylsiloxane) copolymer

For the first time, order-order and order-disorder transitions were detected and characterized in a model diblock copolymer of poly(butadiene-1,3) and poly(dimethylsiloxane) (PB-b-PDMS). This model PB-b-PDMS copolymer was synthesized by the sequential anionic polymerization (high vacuum techniques) of butadiene 1,3 (B) and hexamethylciclotrisiloxane (D₃), and subsequently characterized by nuclear magnetic resonance (¹H and ¹³C NMR), size exclusion chromatography (SEC), Fourier Transform infrared spectroscopy (FTIR), Small-Angle X-ray scattering (SAXS) and rheology. SAXS combined with rheological experiments shows that the order-order and order-disorder transitions are thermoreversible. This fact indicates that the copolymer has sufficient mobility at the timescale and at the temperatures of interest to reach their equilibrium morphologies.     

Gas foaming of segmented poly(ester amide) films

Biodegradable segmented poly(ester amide)s, based on dimethyl adipate, 1,4-butanediol and N,N′-1,2-ethanediyl-bis[6-hydroxy-hexanamide], with two distinct melting transitions were gas foamed using carbon dioxide (CO₂). Polymer films were saturated with CO₂ at 50 bar for 6 h after which the pressure was released. The samples were immersed in octane at the desired temperature after which foaming started immediately. Just above the lower melt transition the polymers retain adequate mechanical properties and dimensional stability, while the chain mobility increased sufficiently to nucleate and expand gas cells during the foaming process. In this way semi-crystalline poly(ester amide)s can be gas foamed below the flow temperature.Two poly(ester amide)s with 25 mol% (PEA2,5-25) and 50 mol% (PEA2,5-50) of bisamide segment content were foamed at 70 and 105 °C, respectively. The storage modulus (G′) of both pure polymers at the onset foaming temperature is 50-60 MPa. Closed-cell foams were obtained with a maximum porosity of ∼90%. The average pore size of PEA2,5-25 ranges from 77 to 99 μm. In contrast, the average pore size of PEA2,5-50 is in between 2 and 4 μm and can be increased to 100 μm by lowering the CO₂ saturation pressure to 20 bar. The porosity of PEA2,5-50 foams using this saturation pressure decreased to 70%.     

Synthesis and properties of well-defined poly (dimethylsiloxane)-b-poly(2-hydroxyethyl methacrylate) copolymers

Block copolymers containing dimethyl siloxane and 2-hydroxyethyl methacrylate sequences were synthesized by group transfer polymerization (GTP) of 2-trimethylsilyloxyethyl methacrylate (TMS-HEMA) using silyl ketene acetal terminated poly(dimethylsiloxane) (PDMS) as macroinitiator, followed by hydrolysis of TMS-HEMA to HEMA. The block copolymers were obtained with controlled molecular weight and narrow molecular weight distribution. Trimethylsilyl groups in the P(TMS-HEMA) block could be selectively hydrolyzed without cleaving Si-O bond in PDMS block. The block copolymers formed micelles in methanol, the effective diameters (R_h) of which were in the range of 78 – 110 nm with narrow distribution by dynamic light scattering (DLS). The TEM image showed micelles with a spherical shape. Received: 10 May 2001/Revised version: 23 August 2001/Accepted: 24 August 2001     

Synthesis of well-defined functional macromolecular chimeras based on poly(ethylene oxide) or poly(N-vinyl pyrrolidone)

By using either NH₂-functionalized linear/4-arm star poly(ethylene oxide) or NH₂-TEMPO initiator, the following novel polymer/polypeptide hybrids (macromolecular chimeras) of poly(ethylene oxide), PEO and poly(N-vinyl pyrrolidone), PNVP, were synthesized: PEO-b-(PBLG or PBLL), PEO-b-PBLL-b-PBLG, 4-arm star copolymer (PEO-b-PBLG)₄, PNVP-b-PBLG-b-PBLL, where PBLG is poly(γ-benzyl-l-glutamate) and PBLL, poly(tert-butyloxycarbonyl-l-lysine). The amino-groups are used for the ring opening polymerization (ROP) of α-amino acid carboxyanhydrides (NCAs), while TEMPO was employed for the polymerization of NVP. Molecular characterization revealed the high molecular weight and compositional homogeneity of the macromolecular chimeras prepared. The success of the synthesis was based on the recently developed living ROP of NCAs and controlled/living TEMPO polymerization, using high vacuum techniques.     

Thermal stability and decomposition behaviors of segmented copolymer poly(urethane-urea-amide)

Polyurethane (PU) has become one of the most important segmented copolymers, due to it can be tailored to suit a wide range of application requirements by changing their structures and compositions. Amide, urethane and urea, which are capable of forming intermolecular hydrogen bonding to enhance the microphase separated morphology, are now used to consist segmented copolymers (poly(urethane-urea-amide) PUUA). In order to understand the usage temperature of the material and the protective measures which can be used, we wanted study the thermal stability and degradation process of PUUA. For study the stability of molecule structure, the thermal degradation behaviors of PUUA were extensively investigated with the thermogravimetric analysis (TG) under pure nitrogen and air, firstly. And the degradation activation energy of PUUA was further determined by the Flynn-Wall-Ozawa method. To find the order of thermal stability of bonds, thermogravimeter coupled with FTIR spectrophotometer (TG/FTIR) was used to research their gaseous products and their releasing intensity under nitrogen. In addition, the thermal decomposition behaviors of PUUA under air were also simulated by TG/FTIR. All results demonstrated that the bond of polyurethane decomposed firstly, both under air and nitrogen. And the protection of the bond of polyurethane was beneficial to prolong the service life of PUUA materials.