Synthesis and characterization of block poly(ester‐ether‐urethane)s from bacterial poly(3‐hydroxybutyrate) oligomers

Telechelic hydroxylated poly(3‐hydroxybutyrate) (PHB‐diol) oligomers have been successfully synthesized in 90–95% yield from high molar mass PHB by tin‐catalyzed alcoholysis with different diols (mainly 1,4‐butanediol) in diglyme. The PHB‐diol oligomers structure was studied by nuclear magnetic resonance, Fourier transformed infrared spectroscopy MALDI‐ToF MS, and size exclusion chromatography, whereas their crystalline structures, thermal properties and thermal stability were analyzed by wide angle X‐ray scattering, DSC, and thermogravimetric analyses. The kinetic of the alcoholysis was studied and the influence of (i) the catalyst amount, (ii) the diol amount, (iii) the reaction temperature, and (iv) the diol chain length on the molar mass was discussed. The influence of the PHB‐diol molar mass on the thermal stability, the thermal properties and optical properties was investigated. Then, tin‐catalyzed poly(ester‐ether‐urethane)s (PEEU) of M_n = 15,000–20,000 g/mol were synthesized in 1,2‐dichloroethane from PHB‐diol oligomers (P_ester) with modified 4,4'‐MDI and different polyether‐diols (P_ether) (PEG‐2000, PEG‐4000, and PPG‐PEG‐PPG). The influence of the PHB‐diol chain length, the P_ether/P_ester ratio, the polyether segment nature and the PEG chain length on the thermal properties and crystalline structures of PEEUs was particularly discussed. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 1949–1961     

New segmented poly(ester‐urethane)s from renewable resources

The physical and mechanical properties of aliphatic homopolyesters from monomers obtainable from renewable resources, namely, 1,3‐propanediol and succinic acid, were improved by their combination with aromatic urethane segments capable of establishing strong intermolecular hydrogen bonds. Segmented poly(ester‐urethane)s were synthesized from dihydroxy‐terminated oligo(propylene succinate)s chain‐extended with 4,4′‐diisophenylmethane diisocyanate. The newly synthesized materials were exhaustively characterized by ¹H NMR spectroscopy, size exclusion chromatography, differential scanning calorimetry, dynamic mechanical analysis, and with respect to their main static mechanical properties, an Instron apparatus was used. The average repeat number of the hard segments, evaluated by NMR, ranged from 4 to 9, whereas that of the flexible segments was about 14. The degree of crystallinity, glass‐transition temperature, melting point, tensile strength, elongation, and Young's modulus were influenced by the ratio between hard and soft segments of the segmented copolymer in a predictable way. The results demonstrated that poly(ester‐urethane)s from 1,3‐propanediol and succinic acid are promising thermoplastics. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 630–639, 2001     

Synthesis of trans‐4‐hydroxy‐L‐proline‐based telechelic prepolymers and poly(ester‐urethane)

The synthesis of hydroxyproline‐based telechelic prepolymers by the condensation polymerization of trans‐4‐hydroxy‐N‐benzyloxycarbonyl‐L ‐proline methyl ester was investigated. All the polymerizations were carried out in the melt with stannous octoate as the catalyst and with different diols. The products were characterized by differential scanning calorimetry, proton nuclear magnetic resonance, infrared spectrophotometry, and inherent viscosity (η_inh). According to the analytic results, the η_inh value of the prepolymers depended on the kind and amount of diols that were added. With an increase in the 1,6‐hexanediol feed from 2 to 10 mol %, there was a decrease in η_inh from 0.78 to 0.41 along with a decrease in the glass‐transition temperature (T_g ) from 63 to 42 °C. When 2 mol % of different kinds of diols were used, η_inh ranged from 0.78 to 0.21, and T_g varied from 70 to 43 °C. These new prepolymers could be linked to poly(ester‐urethane) by the chain extender 1,6‐hexamethylene diisocyanate. The poly(ester‐urethane) was amorphous, and the T_g was 76 °C. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2449–2455, 2000     

Synthesis and Thermal Properties of Biodegradable Poly(ester‐urethane)s Based on Chemo‐Synthetic Poly[(R,S)‐3‐hydroxybutyrate]

A series of telechelic oligo[(R,S)‐3‐hydroxybutyrate]‐diols (PHB‐diols) was synthesized from ethyl (R,S)‐3‐hydroxybutyrate (ethyl (HB)) and four different aliphatic diols, namely, 1,4‐butanediol, 1,6‐hexanediol, 1,8‐octanediol and 1,10‐decanediol by transesterification and condensation in bulk. The structures of the synthesized oligomers were confirmed by ¹H NMR spectroscopy and MALDI‐TOF mass spectroscopy. The use of 1,4‐butanediol results in an oligoester with hydroxyl functionality of approximately 2. In the case of the higher aliphatic diols, the number average functionalities were found to be lower than 2. These differences were ascribed to side reactions which occur during polymerization, yielding unreactive end groups. Other novel families of biodegradable poly(ester‐urethane)s were synthesized either from PHB‐diol alone, or PHB‐diol mixed with poly(ε‐caprolactone)‐diol (PCL‐diol), poly(butylene adipate)‐diol (PBA‐diol) or poly(diethylene glycol adipate)‐diol (PDEGA‐diol). In each case, 1,6‐hexamethylene diisocyanate was used as a nontoxic connecting agent. The homopolymers prepared from PCL‐diol, PBA‐diol and PDEGA‐diol were also synthesized for the sake of comparison. All the prepared copolymers possess high molecular weight with glass transition temperature (T_g) values varying from –54 to –23°C. Some of the prepared copoly(ester‐urethane)s are partially crystalline with melting temperatures (T_m's) varying from 37 to 56°C.     

Segmented block copolymers of poly(ethylene glycol) and poly(ethylene terephthalate)

A new series of segmented copolymers were synthesized from poly(ethylene terephthalate) (PET) oligomers and poly(ethylene glycol) (PEG) by a two‐step solution polymerization reaction. PET oligomers were obtained by glycolysis depolymerization. Structural features were defined by infrared and nuclear magnetic resonance (NMR) spectroscopy. The copolymer composition was calculated via ¹H NMR spectroscopy. The content of soft PEG segments was higher than that of hard PET segments. A single glass‐transition temperature was detected for all the synthesized segmented copolymers. This observation was found to be independent of the initial PET‐to‐PEG molar ratio. The molar masses of the copolymers were determined by gel permeation chromatography (GPC). © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4448–4457, 2004     

Side chain liquid crystal poly(fumarate)s bearing tolane‐based mesogens

Cyanotolane or fluorotolane mesogens were for the first time introduced into the fumarate monomer under basic conditions. All fumarate monomers undergo radical polymerization in benzene in the presence of dimethyl 2,2′‐azobis(isobutyrate) as an initiator at 60 °C, affording the corresponding poly(fumarate)s with a molecular weight (M_n) of ～ 10⁴ and an exceptionally narrow polydispersity. The phase behaviors of the fumarate monomers and the correspoding poly(fumarate)s were comprehensively investigated by differential scanning calorimetry (DSC), polarized optical microscopy (POM), and X‐ray diffraction (XRD) analysis. For the fumarate monomers, fluorotolane derivatives were prone to form higher‐order liquid crystal phases such as a smectic phase, while cyanotolane derivatives tended to show a wide mesophase temperature range, depending on the alkyl chain spacer length. Very surprisingly, these features dramatically weakened when they were polymerized. The mesophase temperature ranges became narrow and completely disappeared for the poly(fumarate)s with a shorter alkyl chain spacer. A nematic phase representing lower‐order arrangements became a predominant liquid crystal phase for the poly(fumarate) carrying cyanotolane mesogens. Only the poly(fumarate) carrying fluorotolane mesogens with a longer alkyl chain spacer displayed the characteristic XRD patterns of the smectic B phase. The transient photocurrent measurements of the fumarate monomer with cyanotolane mesogens displayed a hole mobility of the order of 10^?4–10^?5 cm² V^?1 s^?1 at room temperature. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5101–5114, 2008     

Kinetic studies on the thermal polymerization of N‐chloroacetyl‐11‐aminoundecanoate potassium salt

A potassium salt of N‐chloroacetyl‐11‐aminoundecanoate was thermally polymerized to obtain the corresponding poly(glycolic acid‐alt‐11‐aminoundecanoic acid). A kinetic study was then performed that was based on isothermal and nonisothermal polymerizations performed in a differential scanning calorimeter. The complete kinetic triplet was determined (the activation energy, pre‐exponential factor, and integral function of the degree of conversion). A kinetic analysis was performed with an integral isoconversional procedure (free model), and the kinetic model was determined both with the Coats–Redfern method (the obtained isoconversional value being accepted as the effective activation energy) and through the compensation effect. The polymerization followed a three‐dimensional growth‐of‐nuclei (Avrami) kinetic mechanism. Isothermal polymerization was simulated with nonisothermal data. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1166–1176, 2005     

Effect of the γ‐form crystal on the thermal fractionation of poly(propylene‐co‐ethylene)

The effect of the γ‐form crystal on the thermal fractionation of a commercial poly(propylene‐co‐ethylene) (PPE) has been studied by differential scanning calorimetry (DSC) and wide‐angle X‐ray diffraction (WAXD) techniques. Two thermal fractionation techniques, stepwise isothermal crystallization (SIC) and successive self‐nucleation and annealing (SSA), have been used to characterize the molecular heterogeneity of the PPE. The results indicate that the SSA technique possesses a stronger fractionation ability than that of the SIC technique. The heating scan of the SSA fractionated sample exhibits 12 endothermic peaks, whereas the scan of the SIC fractionated sample only shows eight melting peaks. The WAXD observations of the fractionated PPE samples prove that the content of the γ‐form crystals formed during the thermal treatment of the SIC technique is much higher than that of the SSA treatment. The former is 57.4%, whereas the later is 12.6%. The effect of theγ‐form crystals on thermal fractionation ability is discussed. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4320–4325, 2004     

Porous Biodegradable Scaffold: Predetermined Porosity by Dissolution of Poly(ester‐anhydride) Fibers from Polyester Matrix

A novel selective leaching method for the porogenization of the biodegradable scaffolds was developed. Continuous, predetermined pore structure was prepared by dissolving fast eroding poly(ε‐caprolactone)‐based poly(ester‐anhydride) fibers from the photo‐crosslinked poly(ε‐caprolactone) matrix. The porogen fibers dissolved in the phosphate buffer (pH 7.4, 37 °C) within a week, resulting in the porosity that replicated exactly the single fiber dimensions and the overall arrangement of the fibers. The amount of the porosity, estimated with micro‐CT, corresponded with the initial amount of the fibers. The potential to include bioactive agents in the porogen fibers was demonstrated with the bioactive glass.

     

Biodegradable fibers of poly(3‐hydroxybutyrate) produced by high‐speed melt spinning and spin drawing

The effects of high‐speed melt spinning and spin drawing on the structure and resulting properties of bacterial generated poly(3‐hydroxybutyrate) (PHB) fibers were investigated. The fibers were characterized by their degree of crystallinity by differential scanning calorimetry (DSC) and wide‐angle X‐ray scattering (WAXS), their orientation by WAXS, and the textile physical properties. The WAXS studies revealed that the fibers spun at high speeds and high draw ratios possessed orthorhombic (α modification) and hexagonal (β modification) crystals, the latter as a result of stress‐induced crystallization. The fiber structures formed during these processes were fibril‐like as the atomic force microscopy images demonstrated. The maximum physical break stress, the modulus, and the elongation at break observed in the fibril‐like spin drawn fibers were about 330 MPa, 7.7 GPa, and 37%, respectively. The fibers obtained by a low draw ratio of 4.0 had spherulitic structures and poor textile physical properties. The PHB pellets were analyzed by their degradation during the processes of drying and spinning and by their thermal and rheological properties. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2841–2850, 2000     

Catalysts and temperature driven melt polycondensation reaction for helical poly(ester‐urethane)s based on natural L‐amino acids

Catalyst and temperature driven melt polycondensation reaction was developed for natural L‐amino acid monomers to produce new classes of poly(ester‐urethane)s. Wide ranges of catalysts from alkali, alkali earth metal, transition metal and lanthanides were developed for the condensation of amino acid monomers with diols to yield poly(ester‐urethane)s. A‐B Diblock and A‐B‐A triblock species were obtained by carefully choosing mono‐ or diols in model reactions. More than two dozens of transition metal and lanthanide catalysts were identified for the polycondensation to yield high molecular weight poly(ester‐urethane)s. Theoretical studies revealed that the carbonyl carbon in ester possessed low electron density compared to the carbonyl carbon in urethane which driven the thermo‐selective polymerization process. Optical purity of the L‐amino acid residues in the melt polycondensation process was investigated using D‐ and L‐isomers and the resultant products were analyzed by chiral‐HPLC and CD spectroscopy. CD analysis revealed that the amino acid based polymers were self‐assembled as β‐sheet and polyproline type II secondary structures. Electron and atomic force microscopic analysis confirmed the formation of helical nano‐fibrous morphology in poly(ester‐urethane)s. The newly developed melt polycondensation process is very efficient and optimized for wide range of catalysts to produce diverse polymer structures from natural L‐amino acids. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1065–1077     

Dielectric properties of self‐catalytic interpenetrating polymer network based on modified bismaleimide and cyanate ester resins

Bismaleimide (BMI) resins with good thermal stability, fire resistance, low water absorption, and good retention of mechanical properties at elevated temperatures, especially in hot/wet environments, have attracted more attention in the electronic and aerospace industries. However, their relatively high dielectric constant limits their application in the aforementioned fields. In this work, a new promising approach is presented that consists of the formation of a self‐catalytic thermoset/thermoset interpenetrating polymer network. Interpenetrating polymer networks (IPNs) based on modified BMI resin (BMI/DBA) and cyanate ester (b10) were synthesized via prepolymerization followed by thermal curing. The self‐catalytic curing mechanism of BMI/DBA‐CE IPN resin systems was examined by differential scanning calorimetry. The dielectric properties of the cured BMI/DBA‐CE IPN resin systems were evaluated by a dielectric analyzer and shown in dielectric properties‐temperature‐log frequency three‐dimensional plots. The effect of temperature and frequency on the dielectric constant of the cured BMI/DBA‐CE IPN resin systems is discussed. The composition effect on the dielectric constant of the cured IPN resin systems was analyzed on the basis of Maxwell's equation and rule of mixture. The obtained BMI/DBA‐CE IPN resin systems have the combined advantages of low dielectric constant and loss, high‐temperature resistance, and good processability, which have many applications in the microelectronic and aerospace industries. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1123–1134, 2003     

Poly[(R)‐3‐hydroxybutyrate)]/poly(styrene) blends compatibilized with the relevant block copolymer

A novel triblock copolymer PS–PHB–PS based on the microbial polyester Poly[(R)‐3‐hydroxybutyrate)] (PHB) and poly(styrene) (PS) was prepared to be used as compatibilizer for the corresponding PHB/PS blends. It was prepared in a three‐step procedure consisting of (i) transesterification reaction between ethylene glycol and a high‐molecular‐weight PHB, (ii) synthesis of bromo‐terminated PHB macroinitiator, and (iii) atom transfer radical polymerization polymerization of styrene initiated by the PHB‐based macroinitiator. Fourier transform infrared, gel permeation chromatography, ¹H‐, and ¹³C‐NMR spectroscopies were used to determine the molecular structure and/or end‐group functionalities at each step of the procedure. Although thermogravimetric analysis showed that the block copolymer underwent a stepwise thermal degradation and had better thermal stability than their respective homopolymers, differential scanning calorimetry displayed that the PHB block in the copolymer could not crystallize, and thus generating a total amorphous structure. Atomic force microscopy images indicated that the block copolymer was phase segregated in a well‐defined morphological structure with nanodomain size of ～40 nm. Contact angle measurements proved that the wettability properties of the block copolymer were in between those of the PHB and PS homopolymers. Blends analyzed for their morphology and thermal properties showed good miscibility and had well‐defined morphological features. Polymer blends exhibited lower crystallinity and decreased stiffness which was proportional to the amount of compatibilizer content in the blends. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Poly(ester urethane)s with polycaprolactone soft segments: A morphological study

Two series of poly(ester urethane)s were prepared, containing polycaprolactone (PCL) as the soft segment with molecular weights of 530 and 2000. In each series, the soft‐segment/hard‐segment ratio was varied, and the morphological changes were monitored with differential scanning calorimetry, dynamic mechanical thermal analysis, wide‐angle X‐ray scattering, and scanning electron microscopy techniques. The polyurethanes with longer PCL segments retained their crystallinity, whereas those with shorter PCL segments did not. A morphological model is proposed, in which a continuous PCL‐rich matrix contains both PCL crystallites and domains of urethane hard segments. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4117–4130, 2002     

基于PLA的形状记忆聚酯嵌段聚氨酯的相分离行为

以2,4-甲苯二异氰酸酯(TDI)为封端剂,乙二醇(EG)为扩链剂通过2步法合成了一系列具有不同聚丙交酯(PLA)分子量和不同TDI-EG链段长度的聚丙交酯嵌段聚氨酯(PLA-PU)。其中,PLA的分子量从1 500到9 500,PLA、TDI和EG的摩尔比从1:2:1至l:7:6。通过DSC和WAXD等测试技术对材料的两相分离程度进行了研究。结果发现,PLA-PU的相分离程度与样品的热历史具有密切的关系,样品中PLA的分子量和TDI-EG长度对于材料的相分离速率和相分离结构的完善程度具有较大的影响。     

Nonisothermal crystallization behavior and crystalline structure of poly(3‐hydroxybutyrate)/layered double hydroxide nanocomposites

X‐ray diffraction method and differential scanning calorimetry analysis have been used to investigate the nonisothermal crystallization of poly(3‐hydroxybutyrate) (PHB)/poly(ethylene glycol) phosphonates (PEOPAs)‐modified layered double hydroxide (PMLDH) nanocomposites. Effects of cooling rates and PMLDH contents on the nonisothermal crystallization behavior of PHB were explored. These results show that the addition of 2 wt % PMLDH into PHB caused heterogeneous nucleation increasing the crystallization rate and reducing the activation energy. By adding PMLDH into the PHB probably hinder the transport ability of the molecule chains and result in a decreasing crystallity of PHB, thus increasing the activation energy. The correlation among melting behavior, apparent crystallite size, and paracrystalline distortion of PHB/PMLDH nanocomposites has been also discussed. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 995–1002, 2007     

Synthesis and properties of cationic ionomers from poly(ester‐urethane)s based on polylactide

l ‐Lactide (l ‐LA) was polymerized in the presence of N‐methyldiethanolamine as an initiator and Sn(Oct)₂ as a catalyst to give hydroxy‐telechelic poly(l ‐lactide) (PLLA‐diol) bearing a tertiary amine group at the center of the polymer chain. Successive chain extension of the PLLA‐diol with hexamethylene diisocyanate afforded PLLA‐based poly(ester‐urethane)s (PEU) with equally spaced tertiary amine groups. Treatment of the PEU with iodomethane converted tertiary amine groups to quaternary ammonium groups to give cationic ionomers (PEU‐MeI). The thermal, mechanical, hydrophilic, and biodegradation properties of the obtained polymers were investigated. The thermal properties of the PEUs and the PEU‐MeIs were similar each other. The PEU‐MeIs exhibited higher tensile modulus than those of the starting PEUs. The contact angles of water on the PEU‐MeIs were lower than those of the PEUs with similar NMDA content indicating their higher hydrophilicity. In compost degradation tests, the PEU‐MeIs showed slower degradation than those of the PEUs. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4423–4428     

Poly(p‐phenylene sulfide) nonisothermal cold‐crystallization

The poly(p‐phenylene sulfide) (PPS) nonisothermal cold‐crystallization behavior was investigated in a wide heating rate range. The techniques employed were the usual Differential Scanning Calorimetry (DSC), and the less conventional FT‐IR spectroscopy and Energy Dispersive X‐ray Diffraction (EDXD). The low heating rates (Φ) explored by EDXD (0.1 K min^?1) and FT‐IR (0.5–10 K min^?1) are contiguous and complementary to the DSC ones (5–30 K min^?1). The crystallization temperature changes from 95 °C at Φ = 0.05 K min^?1 to 130 °C at Φ = 30 K min^?1. In such a wide temperature range the Kissinger model failed. The model is based on an Arrhenius temperature dependence of the crystallization rate and is widely employed to evaluate the activation energy of the crystallization process. The experimental results were satisfactorily fit by replacing in the Kissinger model the Arrhenius equation with the Vogel–Fulcher–Tamann function and fixing U* = 6.28 k J mol^?1, the activation energy needed for the chains movements, according to Hoffmann. The temperature at which the polymer chains are motionless (T_∞ = 42 °C) was found by fitting the experimental data. It appears to be reasonable in the light of our previously reported isothermal crystallization results, which indicated T_∞ = 48 °C. Moreover, at the lower heating rate, mostly explored by FT‐IR, a secondary stepwise crystallization process was well evidenced. In first approximation, it contributes to about 17% of the crystallinity reached by the sample. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2725–2736, 2005