Investigation of the deformation of homogeneous poly(ethylene‐co‐1‐octene) by wide‐ and small‐angle X‐ray scattering using synchrotron radiation

The deformation behavior of homogeneous ethylene‐1‐octene copolymers was investigated as a function of the crystallinity and the crystal size and perfection, respectively, by wide‐ and small‐angle X‐ray scattering using synchrotron radiation. The crystallinity and the crystal size and perfection, respectively, are controlled by the copolymer composition and the condition of melt crystallization. The deformation includes rotation of crystals, followed by plastic deformation and complete melting of the initial crystal population, and final formation of microfibrils. The process of rotation, plastic deformation, and melting of crystals of the initial structure is completed at lower strain if the size and perfection of the crystals, respectively, decrease, that is, if crystals thermally melt at lower temperature. The kinetics of the fibrillation of the initial structure seems independent of the crystal symmetry, that is, rotation and melting of pseudohexagonal and orthorhombic polyethylene crystals (as evident in low‐crystalline specimens) are similar. The structure of the microfibrils, before and after stress release, is almost independent of the condition of prior melt crystallization, which supports the notion of complete melting of the initial crystal population. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1919–1930, 2002     

Morphology and Linear Viscoelasticity of Poly[ethylene‐co‐(1‐octene)]/Layered Silicate Nanocomposites

Poly[ethylene‐co‐(1‐octene)] nanocomposites with different microstructures were prepared with two kinds of organoclay by melt intercalation. X‐ray diffraction and transmission electron microscopy were used to characterize the morphology of the composites. Linear storage moduli of the composites in the melt state were found to increase greatly with increasing the extent of dispersion of silicate layers and showed an obvious sensitivity to the morphologies of the composites.     

Influence of deformation on irreversible and reversible crystallization of poly(ethylene‐co‐1‐octene)

The effect of uniaxial deformation and subsequent relaxation at ambient temperature on irreversible and reversible crystallization of homogeneous poly(ethylene‐co‐1‐octene) with 38 mol % 1‐octene melt‐crystallized at 10 K min was explored by calorimetry, X‐ray scattering, and Fourier transform infrared spectroscopy. At 298 K, the enthalpy‐based crystallinity of annealed specimens increased irreversibly by stress‐induced crystallization from initially 15% to a maximum of, at least, 19% when a permanent set of more than 200% was attained. The crystallinity increased by formation of crystals of pseudohexagonal structure at the expense of the amorphous polymer, and as a result of destruction of orthorhombic crystals. The stress‐induced increase of crystallinity was accompanied by an increase in the apparent specific heat capacity from 2.44 to about 2.59 J g^?1 K^?1, which corresponds to an increase of the total reversibility of crystallization from, at least, 0.10 to 0.17% K^?1. The specific reversibility calculated for 100% crystallinity increased from 0.67 to 0.89% K^?1 and points to a changed local equilibrium at the interface between the crystal and amorphous phases. The deformation resulted in typical changes of the phase structure and crystal morphology that involve orientation and destruction of crystals as well as the formation of fibrils. The effect of the decrease of the entropy of the strained melt on the reversibility of crystallization and melting is discussed. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1223–1235, 2002     

Morphology of poly(butylene terephthalate)–poly(ethylene terephthalate‐co‐isophthalate‐co‐sebacate) segmented copolyesters

Segmented copolyesters, namely, poly(butylene terephthalate)–poly(ethylene terephthalate‐co‐isophthalate‐co‐sebacate) (PBT‐PETIS), were synthesized with the melting transesterification processing in vacuo condition involving bulk polyester produced on a large scale (PBT) and ternary amorphous random copolyester (PETIS). Investigations on the morphology of segmented copolyesters were undertaken. The two‐phase morphology model was confirmed by transmission electron microscopy and dynamic mechanical thermal analysis. One of the phases was composed of crystallizable PBT, and the other was a homogeneous mixture of PETIS and noncrystallizable PBT. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2257–2263, 2003     

Polypropylene and poly(ethylene‐co‐1‐octene) effective synthesis with diamine‐bis(phenolate) complexes: Effect of complex structure on catalyst activity and product microstructure

A series of group 4 metal complexes bearing amine‐bis(phenolate) ligands with the amino side‐arm donor: (μ‐O)[Me₂N(CH₂)₂N(CH₂‐2‐O‐3,5‐tBu₂‐C₆H₂)₂ZrCl]₂ ( 1a ), R₂N(CH₂)₂N(CH₂‐2‐O‐3‐R¹‐5‐R²‐C₆H₂)₂TiCl₂ (R = Me, R¹, R² = tBu ( 2a ), R = iPr, R¹, R² = tBu ( 2b ), R = iPr, R¹ = tBu, R² = OMe ( 2c )), and Me₂N(CH₂)₂N(CH₂‐2‐O‐3,5‐tBu₂‐C₆H₂)(CH₂‐2‐O‐C₆H₄)TiCl₂ ( 2d ) are used in ethylene and propylene homopolymerization, and ethylene/1‐octene copolymerization. All complexes, upon their activation with Al(iBu)₃/Ph₃CB(C₆F₅)₄, exhibit reasonable catalytic activity for ethylene homo‐ and copolymerization giving linear polyethylene with high to ultra‐high molecular weight (600·× 10³–3600·× 10³ g/mol). The activity of 1a /Al(iBu)₃/Ph₃CB(C₆F₅)₄ shows a positive comonomer effect, leading to over 400% increase of the polymer yield, while the addition of 1‐octene causes a slight reduction of the activity of the complexes 2a‐2d . The complexes with the NMe₂ donor group ( 2a , 2d , 1a ) display a high ability to incorporate a comonomer (up to 9–22 mol%), and the use of a bulkier donor group, N(iPr)₂ ( 2b , 2c ), results in a lower 1‐octene incorporation. All the produced copolymers reveal a broad chemical composition distribution. In addition, the investigated complexes polymerized propylene with the moderate ( 1a , 2a ) to low ( 2b‐2d ) activity, giving polymers with different microstructures, from purely atactic to isotactically enriched (mmmm = 28%). © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2467–2476     

Nanocomposites of poly(ethylene terephthalate‐co‐ethylene naphthalate) with organoclay

Poly(ethylene terephthalate‐co‐ethylene naphthalate) (PETN)/organoclay was synthesized with the solution intercalation method. Hexadecylamine was used as an organophilic alkylamine in organoclay. Our aim was to clarify the intercalation of PETN chains to hexadecylamine–montmorillonite (C₁₆–MMT) and to improve both the thermal stability and tensile property. We found that the addition of only a small amount of organoclay was enough to improve the thermal stabilities and mechanical properties of PETN/C₁₆–MMT hybrid films. Maximum enhancement in both the ultimate tensile strength and initial modulus for the hybrids was observed in blends containing 4 wt % C₁₆–MMT. Below a 4 wt % clay loading, the clay particles could be highly dispersed in the polymer matrix without a large agglomeration of particles. However, an agglomerated structure did form in the polymer matrix at a 6 wt % clay content. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2581–2588, 2001     

Preparation of poly(methyl acrylate‐co‐itaconic anhydride)/SiO2 hybrid materials via the sol–gel process—The effect of the coupling agent,inorganic content,and nature of the catalyst

Transparent poly(methyl acrylate‐co‐itaconic anhydride)/SiO₂ hybrid materials were prepared from methyl acrylate‐itaconic anhydride copolymer and tetraethoxysilane (TEOS) with the coupling agent (3‐aminopropyl)triethoxysilane (APTES) via a sol–gel process. The covalent bonds between the organic and inorganic phases were introduced by the in situ aminolysis of the itaconic anhydride units with APTES forming a copolymer bearing a triethoxysilyl group. These groups subsequently were hydrolyzed with TEOS and allowed to form a network. These reactions were monitored by Fourier transform infrared analysis. The amount of APTES had a dramatic influence on the gel time and sol fraction. The effect of APTES, the inorganic content, and the nature of the catalyst on the thermal properties and morphology of the hybrid materials were studied by differential scanning calorimetry, thermogravimetric analysis, scanning electron microscopy, and atomic force microscopy. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 321–328, 2000     

Structural and mechanical behavior of polypropylene/ maleated styrene‐(ethylene‐co‐butylene)‐styrene/sisal fiber composites prepared by injection molding

Hybrid composites consisting of isotactic poly(propylene) (PP), sisal fiber (SF), and maleic anhydride grafted styrene‐(ethylene‐co‐butylene)‐styrene copolymer (MA‐SEBS) were prepared by melt compounding, followed by injection molding. The melt‐compounding torque behavior, thermal properties, morphology, crystal structure, and mechanical behavior of the PP/MA‐SEBS/SF composites were systematically investigated. The torque test, thermogravimetric analysis, differential scanning calorimetric, and scanning electron microscopic results all indicated that MA‐SEBS was an effective compatibilizer for the PP/SF composites, and there was a synergism between MA‐SEBS and PP/SF in the thermal stability of the PP/MA‐SEBS/SF composites. Wide‐angle X‐ray diffraction analysis indicated that the α form and β form of the PP crystals coexisted in the PP/MA‐SEBS/SF composites. With the incorporation of MA‐SEBS, the relative amount of β‐form PP crystals decreased significantly. Mechanical tests showed that the tensile strength and impact toughness of the PP/SF composites were generally improved by the incorporation of MA‐SEBS. The instrumented drop‐weight dart‐impact test was also used to examine the impact‐fracture behavior of these composites. The results revealed that the maximum impact force (F_max), impact‐fracture energy (E_T), total impact duration (t_r), crack‐initiation time (t_init), and crack‐propagation time (t_prop) of the composites all tended to increase with an increasing MA‐SEBS content. From these results, the incorporation of MA‐SEBS into PP/SF composites can retard both the crack initiation and propagation phases of the impact‐fracture process. These prolonged the crack initiation and propagation time and increased the energy consumption during impact fracture, thereby leading to toughening of PP/MA‐SEBS/SF composites. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1214–1222, 2002     

Synthesis of high‐molecular‐weight aliphatic–aromatic copolyesters from poly(ethylene‐co‐1,6‐hexene terephthalate) and poly(L‐lactic acid) by chain extension

A series of aliphatic–aromatic multiblock copolyesters consisting of poly(ethylene‐co‐1,6‐hexene terephthalate) (PEHT) and poly(L ‐lactic acid) (PLLA) were synthesized successfully by chain‐extension reaction of dihydroxyl terminated PEHT‐OH prepolymer and dihydroxyl terminated PLLA‐OH prepolymer using toluene‐2,4‐diisoyanate as a chain extender. PEHT‐OH prepolymers were prepared by two step reactions using dimethyl terephthalate, ethylene glycol, and 1,6‐hexanediol as raw materials. PLLA‐OH prepolymers were prepared by direct polycondensation of L ‐lactic acid in the presence of 1,4‐butanediol. The chemical structures, the molecular weights and the thermal properties of PEHT‐OH, PLLA‐OH prepolymers, and PEHT‐PLLA copolymers were characterized by FTIR, ¹H NMR, GPC, TG, and DSC. This synthetic method has been proved to be very efficient for the synthesis of high‐molecular‐weight copolyesters (say, higher than M_w = 3 × 10⁵ g/mol). Only one glass transition temperature was found in the DSC curves of PEHT‐PLLA copolymers, indicating that the PLLA and PEHT segments had good miscibility. TG curves showed that all the copolyesters had good thermal stabilities. The resulting novel aromatic–aliphatic copolyesters are expected to find a potential application in the area of biodegradable polymer materials. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5898–5907, 2009     

Toughening of a propylene‐b‐(ethylene‐co‐propylene) copolymer by a plastomer

Several blends, covering the entire range of compositions, of a metallocenic ethylene‐1‐octene copolymer (CEO) with a multiphasic block copolymer, propylene‐b‐(ethylene‐co‐propylene) (CPE) [composed of semicrystalline isotactic polypropylene (iPP) and amorphous ethylene‐co‐propylene segments], have been prepared and analyzed by differential scanning calorimetry, X‐ray diffraction, optical microscopy, stress‐strain and microhardness measurements, and dynamic mechanical thermal analysis. The results show that for high CEO contents, the crystallization of the iPP component is inhibited and slowed down in such a way that it crystallizes at much lower temperatures, simultaneously with the crystallization of the CEO crystals. The mechanical results suggest very clearly the toughening effect of CEO as its content increases in the blends, although it is accompanied by a decrease in stiffness. The analysis of the viscoelastic relaxations displays, first, the glass transition of the amorphous blocks of CPE appearing at around 223 K, which is responsible for the initial toughening of the plain CPE copolymer in relation to iPP homopolymer. Moreover, the additional toughening due to the addition of CEO in the blends is explained by the presence of the β relaxation of CEO that appears at about 223 K. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1869–1880, 2002     

The effect of electron beam irradiation on dynamic shear rheological behavior of a poly (propylene‐co‐ethylene) heterophasic copolymer

In this study the effect of electron beam irradiation on rheological properties of a poly (propylene‐co‐ethylene) heterophasic copolymer is evaluated. Using dynamic viscoelastic measurement in the linear viscoelastic range of deformation, it is observed that the complex viscosity and dynamic modulus of polypropylenes were decreased by increasing the irradiation dose. Polypropylene heterophasic copolymers consist of ethylene propylene rubber phase dispersed in polypropylene homopolymer matrix. The high energy electron beams simultaneously affect both isotactic polypropylene (iPP) matrix and ethylene propylene dispersed phase. The molecular chains of polypropylene homopolymer phase breakdown to smaller species, those are prone to degradation and branching as well. Increase in the melt flow rate behavior and shifting the cross‐over point to higher frequencies and increase in melt strength are due to this phenomenon. At the same time, the ethylene propylene phase of the polypropylene copolymer cross‐links due to irradiation, and a significant effect on the rheological behavior of samples are observed. The mathematical modeling of complex viscosity behavior revealed the conformity of experimental data with modified Carreau equation. Copyright © 2010 John Wiley & Sons, Ltd.     

Silica aerogel–poly(ethylene‐co‐vinyl acetate) composite for transparent heat retention films

Poly(ethylene‐co‐vinyl acetate) (EVA) plastic films are widely used for solar coverings including photovoltaic modules and commercial greenhouse films, but are poor at controlling heat flow. In this work, silica aerogel (SA) nanogels were examined for preparing transparent heat retention EVA films that block far infrared spectra radiation to maintain heat, without compromising the optical performance of the films. SA nanogels were melt‐mixed using a mini twin‐screw extruder with EVA pellets to form SA/EVA composite, which were pressed into thin films with controlled thickness. The composite films were characterized in terms of optical properties using a variety of analytical methods including FTIR, UV–Vis spectroscopy, electron, confocal, and atomic force microscopy. Both thermicity and thermal conductivity of commercial and experimental SA/EVA films were measured. The results demonstrated that the SA/EVA films gave improved infrared retention compared to commercial thermal plastic films without compromising visible light transmission, showing the potential for this approach in next generation heat retention films. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 927–935     

Effect of PEO‐PPO‐PEO copolymer on the mechanical and thermal properties and morphological behavior of biodegradable poly (L‐lactic acid) (PLLA) and poly (butylene succinate‐co‐L‐lactate) (PBSL) blends

A blend of two biodegradable and semi‐crystalline polymers, poly (L‐lactic acid) (PLLA; 70 wt%) and poly (butylene succinate‐co‐L‐lactate) (PBSL; 30 wt%), was prepared in the presence of various polyethylene oxide‐polypropylene oxide‐polyethylene oxide (PEO‐PPO‐PEO) triblock copolymer contents (0.5, 1, 2 wt%). Mechanical, thermal properties, and Fourier transform infrared (FTIR) analysis of the blends were investigated. It was found that the addition of copolymer to PLLA/PBSL improved the fracture toughness of the blends as shown by mode I fracture energies. It was supported by morphological analysis where the brittle deformation behavior of PLLA changed to ductile deformation with the presence of elongated fibril structure in the blend with copolymer system. The glass transition temperature (T_g), melting temperature (T_m) of PLLA, and PBSL shift‐closed together indicated that some compatibility exists in the blends. In short, PEO‐PPO‐PEO could be used as compatibilizer to improve the toughness and compatibility of the PLLA/PBSL blends. Copyright © 2010 John Wiley & Sons, Ltd.     

Synthesis of poly[(2‐oxo‐1,3‐dioxolane‐4‐yl) methyl methacrylate‐co‐ethyl acrylate] by incorporation of carbon dioxide into epoxide polymer and the miscibility behavior of its blends with poly(methyl methacrylate) or poly(vinyl chloride)

This study was related to the investigation of the chemical fixation of carbon dioxide to a copolymer bearing epoxide and the application of the cyclic carbonate group containing copolymer‐to‐polymer blends. In the synthesis of poly[(2‐oxo‐1,3‐dioxolane‐4‐yl) methyl methacrylate‐co‐ethyl acrylate] [poly(DOMA‐co‐EA)] from poly(glycidyl methacrylate‐co‐ethyl acrylate) [poly(GMA‐co‐EA)] and CO₂, quaternary ammonium salts showed good catalytic activity. The films of poly(DOMA‐co‐EA) with poly(methyl methacrylate) (PMMA) or poly(vinyl chloride) (PVC) blends were cast from N,N′‐dimethylformamide solution. The miscibility of the blends of poly(DOMA‐co‐EA) with PMMA or PVC have been investigated both by DSC and visual inspection of the blends. The optical clarity test and DSC analysis showed that poly(DOMA‐co‐EA) containing blends were miscible over the whole composition range. The miscibility behaviors were discussed in terms of Fourier transform infrared spectra and interaction parameters based on the binary interaction model. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1472–1480, 2001     

Biodegradable electrospun mat: Novel block copolymer of poly (p‐dioxanone‐co‐L‐lactide)‐block‐poly(ethylene glycol)

Ultrafine fibers of a laboratory‐synthesized new biodegradable poly(p‐dioxanone‐co‐L ‐lactide)‐block‐poly(ethylene glycol) copolymer were electrospun from solution and collected as a nonwoven mat. The structure and morphology of the electrospun membrane were investigated by scanning electron microscopy, differential scanning calorimetry (DSC), wide‐angle X‐ray diffraction (WAXD), and a mercury porosimeter. Solutions of the copolymer, ranging in the lactide fraction from 60 to 80 mol % in copolymer composition, were readily electrospun at room temperature from solutions up to 20 wt % in methylene chloride. We demonstrate the ability to control the fiber diameter of the copolymer as a function of solution concentration with dimethylformamide as a cosolvent. DSC and WAXD results showed the relatively poor crystallinity of the electrospun copolymer fiber. Electrospun copolymer membrane was applied for the hydrolytic degradation in phosphate buffer solution (pH = 7.5) at 37 °C. Preliminary results of the hydrolytic degradation demonstrated the degradation rate of the electrospun membrane was slower than that of the corresponding copolymers of cast film. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1955–1964, 2003     

Synthesis of double hydrophilic poly(ethylene oxide)‐b‐poly(2‐hydroxyethyl acrylate) by single‐electron transfer–living radical polymerization

In this study, the polymerization of (2‐hydroxyethyl) acrylate (HEA), in polar media, using Cu(0)‐mediated radical polymerization also called single‐electron transfer–living radical polymerization (SET‐LRP) is reported. The kinetics aspects of both the homopolymerization and the copolymerization from a poly(ethylene oxide) (PEO) macroinitiator were analyzed by ¹H NMR. The effects of both the ligand and the solvent were studied. The polymerization was shown to reach very high monomer conversions and to proceed in a well‐controlled fashion in the presence of tris[2‐(dimethylamino)ethyl]amine Me6‐TREN and N, N,N′, N″, N″‐pentamethyldiethylenetriamine (PMDETA) in dimethylsulfoxide (DMSO). SET‐LRP of HEA was also led in water, and it was shown to be faster than in DMSO. In pure water, Me₆‐TREN allowed a better control over the molar masses and polydispersity indices than PMDETA and TREN. Double hydrophilic PEO‐b‐PHEA block copolymers, exhibiting various PHEA block lengths up to 100 HEA units, were synthesized, in the same manner, from a bromide‐terminated PEO macroinitiator. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Energy‐damping behaviors of poly(methyl acrylate‐co‐divinylbenzene) microspheres coated with a porous nickel–phosphorus layer

Hybrid microspheres of poly(methyl acrylate‐co‐divinylbenzene) (PMADVB) with a thin and porous nickel–phosphorus (Ni–P) alloy layer were prepared via suspension polymerization and electroless nickel plating. The characterization of pristine and nickel‐coated microspheres was carried out with a differential scanning calorimeter and a scanning electron spectroscope equipped with an energy‐dispersive system. The glass‐transition range of Ni–P‐coated PMADVB was broadened and extended in the higher temperature direction. This effect allowed the PMADVB network to embrace more diversified energy states of the segment motion, this being a desired feature for damping sound waves. The low‐frequency (100–1000‐Hz) sound absorption behavior of the microspheres was tested with a sound attenuation kit. Besides the testing of their low‐frequency damping performance, an investigation into the ultrasonic‐wave (～35 kHz) absorption feature of the microspheres was conducted through chemical means; that is, the attenuation to the ultrasonic wave with respect to the unprotective situation was assessed through the chemisorption extent of copper ions on a biomass adsorbent. The Ni–P deposition layer was found to augment the damping capacity of the polymer network. The alloy layer was determined to cause an expansion of the glass‐transition range of PMADVB and its wave‐scattering capability because this layer was made up of submicrometer metallic grains. In this work, the particulars of the metal–polymer interactions were associated with a core–shell structure. The metal outer layer was thought to create a spherical temperature field inside the PMADVB network, and concerted motions of the polymer segments resulted. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2710–2723, 2004     

Cu(0)/2,6‐bis(imino)pyridines catalyzed single‐electron transfer‐living radical polymerization of methyl methacrylate initiated with poly(vinylidene fluoride‐co‐chlorotrifluoroethylene)

A series of 2,6‐bis(imino)pyridines, as common ligands for late transition metal catalyst in ethylene coordination polymerization, were successfully employed in single‐electron transfer‐living radical polymerization (SET‐LRP) of methyl methacrylate (MMA) by using poly(vinylidene fluoride‐co‐chlorotrifluoroethylene) (P(VDF‐co‐CTFE)) as macroinitiator with low concentration of copper catalyst under relative mild‐reaction conditions. Well‐controlled polymerization features were observed under varied reaction conditions including reaction temperature, catalyst concentration, as well as monomer amount in feed. The typical side reactions including the chain‐transfer reaction and dehydrochlorination reaction happened on P(VDF‐co‐CTFE) in atom‐transfer radical polymerization process were avoided in current system. The relationship between the catalytic activity and the chemical structure of 2,6‐bis(imino)pyridine ligands was investigated by comparing both the electrochemical properties of Cu(II)/2,6‐bis(imino)pyridine and the kinetic results of SET‐LRP of MMA catalyzed with different ligands. The substitute groups onto N‐binding sites with proper steric bulk and electron donating are desirable for both high‐propagation reaction rate and C? Cl bonds activation capability on P(VDF‐co‐CTFE). The catalytic activity of Cu(0)/2,6‐bis(imino)pyridines is comparable with Cu(0)/2,2′‐bipyridine under the consistent reaction conditions. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4378–4388     

Synthesis and properties of multiblock copolymers consisting of poly(L‐lactic acid) and poly(oxypropylene‐ co‐oxyethylene) prepared by direct polycondensation

A multiblock copoly(ester–ether) consisting of poly(l ‐lactic acid) (PLLA) and poly(oxypropylene‐co‐oxyethylene) (PN) was prepared and characterized. Preparation was done via the solution polycondensation of a thermal oligocondensate of l ‐lactic acid, a commercially available telechelic polyether (PN: Pluronic‐F68), and dodecanedioic acid as a carboxyl/hydroxyl adjusting agent. When stannous oxide was used as the catalyst, the molecular weight of the resultant PLLA/PN block copolymers became very high (even with a high PN content) under optimized reaction conditions. The refluxing of diphenyl ether (solvent) at reduced pressure allowed the efficient removal of the condensed water from the reaction system and the feed‐back of the intermediately formed l ‐lactide at the same time in order to successfully bring about a high degree of condensation. The copolymer films obtained by solution casting became more flexible with the increasing PN content as soft segments. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1513–1521, 1999