Synthesis and characterization of copolyesters based on tartaric acid derivatives

A series of aliphatic copolyesters based on naturally occurring l-tartaric acid amenable to facile post-polymer modification have been synthesized and characterized. The hydroxyl groups of the tartaric acid were protected and copolyesters were synthesized by taking different feed molar ratio of dimethyl 2,3-O-isopropylidene tartarate and dimethyl succinate with 1,6-hexanediol. Then, a series of copolyesters were synthesized by taking equal feed molar ratio of dimethyl 2,3-O-isopropylidene tartrate and dimethyl succinate or dimethyl adipate with different alkane diols. The acetal protecting groups were then selectively hydrolyzed to prepare a new series of copolyesters with pendant hydroxyl groups along the copolymer chain. The number average molecular weights (M _n) of the copolymers were found to vary in the range of 3.7–8.4 × 10³ g mol⁻¹. The hydroxy copolyesters show higher glass transition (T _g) and melting (T _m) temperatures as compared to isopropylidene copolyesters and the T _g varies from −8.0 to −48.2 °C depending on the feed ratio of the comonomers. The hydrolytic degradation studies of copolyesters revealed that hydroxyl copolyesters degrade faster than isopropylidene copolyesters.     

Bio-based poly(ethylene terephthalate) copolyesters made from cyclic monomers derived from tartaric acid

Two cyclic acetal compounds, 2,3-O-methylene L-threitol and dimethyl 2,3-O-methylene L-threarate, both coming from naturally-occurring tartaric acid, were used as comonomers to replace ethylene glycol and dimethyl terephthalate respectively, in the preparation of PET-based copolyesters by polycondensation in the melt. Synthesis results, structure and thermal properties of the two afforded copolyester series were evaluated and compared regarding composition and type of comonomer used in each case. All the copolyesters had a random microstructure and molecular weights in the 25,000–35,000 g·mol⁻¹ range. Their thermal properties varied logically with composition along each series but they significantly changed according to which acetal comonomer was used. PET copolyesters made from acetalized L-threitol displayed thermal stability and T_g comparable to PET, whereas these two properties were depressed in the copolyesters containing threarate units. Both types of copolyesters were able to crystallize for contents in tartaric acid derived units up to around 30% by adopting the crystal structure of PET. Crystallization rates and melting temperatures decreased with copolymerization in the two series but this effect was more noticeable in copolyesters made from threitol.     

Preparation and hydrolytic degradation of sulfonated poly(ethylene terephthalate) copolymers

A series of poly(ethylene terephthalate-co-ethylene 5-sodiosulfoisophthalate) copolyesters containing from 1 up to 50 mol% of sulfonated units was prepared by melt polycondensation from ethylene glycol and mixtures of dimethyl terephthalate and dimethyl 5-sodiosulfoisophthalate. The resulting copolymers had a random microstructure and contained oligo(ethylene glycol) units in amounts increasing with the content in sulfonated isophthalate units. Copolyesters with more than 20 mol% of 5-sodiosulfoisophthalic units were amorphous and easily soluble in water. The hydrodegradability of the copolyesters was very high as compared to poly(ethylene terephthalate), and increased with the content in sulfonated units. It was demonstrated that the susceptibility to acidic hydrolysis of these copolymers is mainly due to the presence of the sodium sulfonate groups, the influence of the oligo(ethylene glycol) units in this regard being noticeable but limited.     

Synthesis, characterization, and properties of poly(ethylene terephthalate)/poly(1,4-butylene succinate) block copolymers

Reactive blending at 290 °C of a series of mixtures of poly(ethylene terephthalate) (PET) and poly(1,4-butylene succinate) (PBS) led to the formation of block PET/PBS copolyesters. The block lengths of the resulting copolymers decreased with the severity of the treatment. Copolyesters with PET/PBS molar compositions of 90/10, 80/20, 70/30, and 50/50 were prepared by this method and their composition and microstructure were characterized by ¹H and ¹³C NMR, respectively. The T_g, T_m, and crystallinity of the copolymers decreased as the content in PBS and the degree of randomness increased. The elastic modulus and tensile strength of the copolymers decreased with the content of PBS, whereas, on the contrary, the elongation at break increased. The PET/PBS copolymers exhibited a pronounced hydrolytic degradability, which increased with the content in 1,4-butylene succinic units. Hydrolysis mainly occurred on the aliphatic ester groups.     

Synthesis and properties of copolyesters of p,p′‐bibenzoic acid,dimer acid,and alkylene glycol

Copolyesters of p,p′‐bibenzoic acid, dimer acid, and an alkylene glycol are prepared by melt polycondensation of of dimethyl p,p′‐bibenzoate, dimer acid, and an alkylene glycol. The copolyesters are characterized by the inherent viscosity, FTIR, proton NMR, DSC, polarized microscopy, and X‐ray diffraction. The polymer composition and sequence distribution of the copolyesters can be seen from the NMR spectra. The copolyesters exhibit a degree of randomness of about 1, indicating that they are random copolymers. The glass‐transition temperature (T_g) and the melting point (T_m) of the copolyesters are found from the DSC heating curves. When the content of the flexible dimer acid unit increases, the T_g of the copolyesters decreases significantly. The copolymerization effect decreases the crystallinity and the T_m of the copolyesters. It can be seen from the DSC, polarized microscopy, and X‐ray diffraction data that some copolyesters derived from 1,6‐hexanediol and 1,5‐pentanediol exhibit a monotropic smectic phase. As the molar content of the dimer acid unit increases, the isotropic–mectic transition temperature and the smectic order decreases significantly. The liquid crystallinity is completely destroyed at certain molar contents of the dimer acid unit. The smectic order of the copolyesters derived from 1,6‐hexanediol is significantly higher than that of the copolyesters derived from 1,5‐pentanediol, and it is described as an odd–even effect. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 750–758, 2003     

Synthesis and characterization of polyesters based on tartaric acid derivatives

A series of aliphatic polyesters based on tartaric acid and its derivatives were synthesized starting from naturally occurring L-tartaric acid. The hydroxyl groups of the tartaric acid derivatives were first protected and the polyesters were synthesized by bulk and solution polycondensation methods. Two classes of polyesters were synthesized and characterized, the first by polycondensation of dimethyl 2,3-O-isopropylidene-l-tartrate with various alkanediols, and the second by reaction of 2,3-O-isopropylidene-l-threitol with various diacid chlorides. Acid catalyzed deprotection of isopropylidene groups gave well-defined polyesters having pendant hydroxyl functional groups regularly distributed along the polymer chain. The number average molecular weights (M_n) of the polymers were found to vary in the range of 2.3-15.7 × 10³ g mol⁻¹. Differential scanning calorimetry (DSC) analysis showed the glass transition temperatures (T_g) of the polyesters varied from −36.1 °C to 17.9 °C on varying the chain length.     

Synthesis of hydrophobic W18O49 nanorods for constructing UV/NIR-shielding and self-cleaning film

Nanomaterials with ultraviolet/near-infrared (UV/NIR) shielding property have great potential for developing energy-saving windows. In this work, we report low-cost W₁₈O₄₉ nanorods as UV/NIR shielding material. W₁₈O₄₉ nanorods with the length of ~20 or ~60 nm were prepared by simple solvothermal method, and they exhibited strong size-dependent absorption in the UV/NIR region. By mixing W₁₈O₄₉ nanorods with polydimethylsiloxane (PDMS), W₁₈O₄₉@PDMS films were constructed and they could shield 55.58% of UV and 75.89% of NIR light while transmit 58.03% of visible light. A sealed box with W₁₈O₄₉@PDMS-coated glass as the window exhibited a minimal temperature elevation (△T = 9.2 °C) compared to those coated with pure glass (△T = 18.2 °C) or ITO glass (△T = 12.1 °C), under the irradiation of solar light (0.6 W cm⁻²). Additionally, the films had a contact angle of 122 ± 2°, showing self-cleaning ability. Therefore, W₁₈O₄₉@PDMS films can act as cost-efficient UV/NIR-shielding and self-cleaning film.     

Synthesis and Physico-Chemical Characterization of Halogenated Partly Aromatic Cardo Copolyesters

Copolyesters of 1,1′-bis(3-methyl-5-chloro-4-hydroxy phenyl) cyclohexane (0.0025 mol), ethylene glycol/propylene glycol/1, 4-butanediol/1,6-hexanediol (0.0025 mol) and terephthaloyl chloride (0.005 mol) have been synthesized by interfacial polycondensation technique by using water-chloroform (4:1 v/v) as an interphase, sodium hydroxide (0.125 mol) as an acid acceptor and cetyl trimethyl ammonium bromide (50 mg) as an emulsifier. The reaction time and temperature were 3 h and 0°C, respectively. The yield of copolymers was 85–87%. Copolyesters are soluble in common solvents and possess moderate molecular weights. The structures of copolyesters are supported by FT-IR and ¹HNMR spectral data. Copolyesters are characterized for their viscosity in chloroform and 1,2-dichloroethane at 30, 35 and 40°C, densities by floatation method (1.139–1.2775 g cm^?3). It is observed that both [η] and density of copolyesters decreased with increase in alkyl chain length. Copolyesters possess excellent hydrolytic stability against water and 10% each of acids, alkalis and salt at room temperature. The observed wt. % change is ±3.15% in the selected environments. A 30 μm thick C1MPT film has 17.8 MPa tensile strength, 50.1 kV mm^?1 electric strength and 2.2 × 10¹² ohm cm volume resistivity. Copolyesters possess high T_g (148–172°C) and are thermally stable up to about 411–426°C and followed single step degradation kinetics involving 70–75% weight loss with 20–24% residual weight above 650°C. Copolyesters followed 1.19–1.94 order degradation kinetics. Activation energy and frequency factors are increased with alkyl chain length.     

Composition,thermal properties,and biodegradability of a new biodegradable aliphatic/aromatic copolyester

A series of new aliphatic/aromatic copolyesters [poly(hexylene terephthalate‐co‐hexylene adipate) (PHTA)] were synthesized on the bases of 1,6‐hexanediol, adipic acid, and dimethyl terephthalate and characterized by gel permeation chromatography, ¹H‐NMR, wide‐angle X‐ray diffraction (WAXD), differential scanning calorimetry (DSC), and compost testing. ¹H‐NMR results show that the compositions of the copolyesters were in accordance with the feed molar ratios. The WAXD patterns indicated that the crystal structures of the PHTA copolyesters were determined by the dominant crystal units, and the copolyesters became less crystallizable, even amorphous, with increasing comonomer content. The DSC curves showed that the glass‐transition temperatures (T_g′s) of the PHTA copolyesters decreased linearly, and both the melting temperature (T_m) and heat of fusion decreased first and then increased with increasing hexylene adipate unit content. Under compost conditions, PHTA copolyesters with less than 60 mol % aromatic units were biodegradable. Particularly, compared with the copolyester poly(butylene terephthalate‐co‐butylene adipate), the PHTA copolyester with the same aliphatic/aromatic composition possessed a lower T_g and T_m and better biodegradability. Additionally, the biodegradability of the copolyesters could be predicted by the number‐average sequence length of aromatic units, T_g, and the temperature difference between T_m and the temperature at which biodegradation took place. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Biodegradable polymers based on renewable resources. III. copolyesters composed of 1,4:3,6‐dianhydro‐D‐glucitol, 1,1‐bis(5‐carboxy‐2‐furyl)ethane and aliphatic dicarboxylic acid units

Various copolyesters were synthesized by bulk polycondensation of the respective combinations of 1,4;3,6‐dianhydro‐D ‐glucitol (1) as the diol component and 1,1‐bis[5‐(methoxycarbonyl)‐2‐furyl]ethane (3b) and seven dimethyl dialkanoates with methylene chain lengths of 4, 5, 6, 7, 8, 10, and 12 (4a–4g) as the dicarboxylic acid components. Most of the copolyesters were amorphous, while a copolyester composed of 1, 3b, and dodecanedioic acid (4g) (3b:4g = 25:75) units as well as homopolyesters derived from 1 and azelaic acid (4d), sebacic acid (4e), and dodecandioic acid (4g), respectively, were partially crystalline. All these homo‐ and copolyesters were soluble in chloroform, dichloromethane, pyridine, trifluoroacetic acid, and m‐cresol. The number‐average molecular weights of these polyesters were estimated to be in the range of 10,000–20,000 by SEC using chloroform as an eluent and standard polystyrene as a reference. The biodegradability of these copolyesters was assessed by enzymatic degradation using four different enzymes in a phosphate buffer solution at 37°C and by soil burial degradation tests in composted soil at 27°C. In general, biodegradability of the copolyesters decreased with increase in the difuran dicarboxylate 3b content. Copolyesters containing sebasic acid 4e units showed higher biodegradability. Soil burial degradation in the soil that was treated with antibiotics, together with electron microscopic observation, indicated that actinomycetes are mainly responsible for the degradation of the copolyesters containing 3b units in the present soil burial test. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 3342–3350, 1999     

Preparation and catalytic activity of K4Zr5O12 for the oxidation of soot from vehicle engine emissions

Pure phase K₄Zr₅O₁₂ is synthesized via solid state method in the present work. Various K/Zr ratios and temperatures are applied, and the synthesis process is investigated in detail by means of X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy. Its catalytic activity for soot oxidation is studied by temperature programmed oxidation with different types of soot/catalyst contacts. It is revealed that K₄Zr₅O₁₂ is very active in the presence of 2–10% O₂ for both tight and loose contacts (T_p(tight) = 335 °C, T_p(ethanol) = 355 °C and T_p(shaking) = 370 °C). Thermal stability study shows that K₄Zr₅O₁₂ is highly stable up to at least 900 °C.     

Solution combustion synthesis of iron-deficient Sc2-xFexO3 (x = 0.17-0.47) nanocrystals with bixbyite structure: The effect of spatial constraints

In this paper, nanopowders based on iron-deficient Sc_2-xFe_xO₃ (x = 0.17–0.47) nanocrystals with bixbyite structure and crystallite size of 3.7–38.9 nm were successfully synthesized via solution combustion. Variable glycine-to-nitrate (G/N) ratio was the main controlling factor. A wide range of experimental and computational methods were used to analyze the impact of spatial constraints on the resulting solid-state products. It was found that solution combustion mode greatly influenced on the temperature and gaseous products in the reaction zone. Volume (G/N = 0.4–0.8, T_max = 1179–1511 °C), self-propagating (G/N = 1.0–1.4, T_max = 614–957 °C) or smoldering (G/N = 0.2, T_max = 443 °C) combustion modes were acquired during the synthesis depending on G/N ratio. It was shown that the formation of impurity phases of am-Fe₂O₃ (T_max < 850 °C), c-Fe₃O₄ (900 °C < T_max < 1500 °C) or c-FeO (T_max > 1500 °C) was possible, depending on the combustion temperature. Besides, the combustion mode affected the porous and surfacial structure of resulting mesoporous nanopowders – specific surface area and total pore volume varied in ranges of 1.7–82.8 m²/g and 0.0088–0.1538 cm³/g, consequently. Chemical composition and unit cell parameters of Sc_2-xFe_xO₃ showed the positive deviation from Vegard's law. The average sizes of the interpore thickness (h) depending on G/N ratio were found from values of specific surface area and pycnometric density of nanopowders, which made it possible to establish the presence of spatial constraints for the crystals' growth of Sc_2-xFe_xO₃ at h values below 10 nm. Analysis of aspect (h/D) ratio allowed to determine synthetic parameters which led to mono- or polycrystalline structure of interpore space in resulting Sc_2-xFe_xO₃-based nanopowders. The results and patterns established in this paper allowed to synthesize a new type of foam-like functional materials based on rare-earth ferrites.     

Polymers with shape memory effect from renewable resources: crosslinking of polyesters based on isosorbide,itaconic acid and succinic acid

Polycondensation of isosorbide with itaconic acid and succinic acid was performed in the presence of sulfuric acid as a catalyst in toluene around 140 °C under microwave irradiation. Molar ratios of itaconic acid were varied to investigate the influence of itaconic acid on molecular weights and glass transition temperatures. For polyesters of isosorbide, itaconic acid and succinic acid T_g values were found from 57 °C to 65 °C. The molecular weights obtained varied from 1200 Da for poly(isosorbide itaconate) UPE100 up to 3500 Da for poly(isosorbide succinate) UPE0. The copolyesters obtained were crosslinked radically with dimethyl itaconate giving a round shaped material with slightly raised T_g values up to 74 °C. Furthermore, with dimethyl itaconate crosslinked copolyesters showed a one‐way shape memory effect upon heating after deformation at the glass transition temperature. © 2013 Society of Chemical Industry     

Thermal properties of poly(tetramethyl-p-silphenylene siloxane) and (tetramethyl-p-silphenylene siloxane-dimethyl siloxane) copolymers

Some physical properties of poly(tetramethyl-p-silphenylene siloxane) homopolymer and random block copolymers of tetramethyl-p-silphenylene siloxane-dimethyl siloxane have been determined and correlated with polymer structure. Differential scanning calorimetry (d.s.c.), differential thermal analysis (d.t.a.), density gradient column measurements and optical hot stage melting point determination and diluent techniques were used. The thermodynamic melting temperature of the homopolymer was estimated to be 160°C and its heat of fusion, ΔH_u, found to be 54.4 J/g (13 cal/g or 2710 cal/mol of monomer repeat units). Its limiting glass transition temperature, T_g, was ?20°C. T_g of the copolymer was found to vary almost monotonically with increasing dimethyl siloxane (DMS) content ranging from ?20° (0% DMS) to just above ?123°C, for pure DMS polymer. The copolymer melting temperature was found to increase as the fraction of the crystalline (hard) TMPS constituent was increased. Based upon copolymer theory and extrapolated melting point data, it was estimated that the block size of soft DMS component in the copolymer most probably consists of twelve monomer units distributed amongst TMPS sequences of varying length.     

The unique behavior of the catalytic system Pd(OAc)2/N-heterocyclic carbene on the telomerization of isoprene with methanol

The catalytic system Pd(OAc)₂/1,3-bis(2,4,6-trimethylphenyl)imidazolium chloride (IMes · HCl) promotes the telomerization of isoprene with methanol resulting in methoxy-dimers with a head-to-head coupling of the isoprene units at unprecedented activity and selectivity. Employing 1,3-bis(2,6-di-i-propylphenyl)-4,5-dihydroimidazolium tetrafluoroborate (SIPr · HBF₄) instead of IMes · HCl, new sesquiterpenes are obtained by the trimerization of isoprene.     

Synthesis and characterization of poly(ethylene‐co‐trimethylene terephthalate)s

Taking advantage of a melt polycondensation process, a series of copolyesters composed of pure terephthalate acid (PTA), ethylene glycol (EG), and 1,3‐propanediol (1,3‐PDO) were synthesized. The component, molecular weight, molecular weight distribution, and thermal properties of the copolymers were characterized. The results show that the contents of trimethylene terephthalate (TT) units in the resulting copolyesters are higher than PDO compositions in original diol. Oligomer content in the copolyesters varies with the compositions and attains a minimum value when the TT ingredient is 49.52 mol %. The glass transition temperature (T_g) of the copolyesters varies from 78.5°C for PET (polyethylene terephthalate) to 43.5°C for PTT (polytrimethylene terephthalate) and decreases monotonically with the components. The copolyesters are amorphous copolymers when TT content is in the range of 32.4–40.8 mol %, as calculated from the melting enthalpy (ΔH_m) measured via differential scanning calorimetry. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1511–1521 2006     

Evolution of yttria-stabilized zirconia (100) surface morphology with temperature

The evolution with temperature of the morphology of yttria-stabilized zirconia (100) stepped surfaces has been studied by AFM in a non-contact dynamic mode in air. The characteristics of the surface structure as the average step heights and terrace widths are determined as a function of the annealing temperature. Step formation begins around 0.43 T_M (1000 °C). Step coalescence is observed above 0.50 T_M (1200 °C) and leads to a stable stepped structure at 0.60 T_M (1500 °C). The processes responsible for the structural evolution observed on the sample surfaces are discussed and a comparison with results obtained on Al₂O₃ (0001) single crystal surfaces under similar experimental conditions is presented.     

The thermal,mechanical and viscoelastic properties of poly(butylene succinate-<Emphasis Type="Italic">co</Emphasis>-terephthalate) (PBST) copolyesters with high content of BT units

Poly(butylene succinate-co-terephthalate) (PBST) copolyesters, with rigid butylene terephthalate (BT) units varying from 50 to 70 mol%, were synthesized via direct esterification route. The chemical structure and comonomer composition were characterized by ¹H NMR. The weight-average molecular weights (M _w ) of the prepared products measured by GPC spanned a range of 1.39 × 10⁵–1.93 × 10⁵ with corresponding M _w /M _n value of 2.23–2.42. Based on the WAXD analysis, PBST copolyesters were identified to have the same crystal structure as that of poly(butylene terephthalate) (PBT). The researches on the thermal properties showed that the melting temperature and decomposed temperature of PBST copolyesters increased with the increasing content of rigid BT units through DSC and TGA measurement. Furthermore, the tensile test results presented that the copolyester with higher content of BT units had higher initial modulus, higher breaking strength but lower elongation at break. Additionally, the viscoelastic properties of the prepared PBST films were analyzed by DMA measurement. It was found that both storage modulus (E′) and loss modulus (E″) corresponding to the peak tended to heighten with the increase of BT units, indicating the copolyester with higher BT units content had the more prominent viscoelasticity. The peak of loss factor (tan δ) curve shifted to higher temperature as the content of rigid BT units increased due to the increasing of the glass transition temperature (T _g).     

Study of sintering behavior of PAN–PZT using dilatometry and co-relation with piezoelectric properties

The sintering behavior of Pb(Al_0.5Nb_0.5)O₃–Pb(Zr_0.52Ti_0.48)O₃ (PAN–PZT) ceramics was investigated. The sintering process of PAN–PZT was divided into four stages based on the amount of in-situ linear shrinkage: (Stage 1) initial stage at sintering temperature RT≤T_s≤ to 770 °C, (Stage 2) perovskite formation stage at 770≤T_s≤990 °C, (Stage 3) densification stage at 990≤T_s≤1265 °C and (Stage 4) Pb-loss stage at T_s>1265 °C. During stage 1, heating of PAN–PZT compact did not cause structural changes except the thermal expansion. During stage 2, the PZT-perovskite structure was formed by rearrangement of crystals. During stage 3, the specimen was rapidly densified with two peaks of strain rate. During stage 4, Pb was volatilized and this loss resulted in sudden increase of shrinkage. On analyzing the sintering stages, the optimized sintering conditions were considered as 1250 °C just before of Pb-loss stage. The effects of T_s on the crystal structure, microstructure and the piezoelectric performance were analyzed and documented.     

Effects of Sn on the microstructure and dielectric properties in BaTiO3-based ceramics

Ba_0.985Bi_0.01TiO₃–BaTi_1?xSn_xO₃ powders were synthesized by a two-step soft chemical method. Ceramics with core–shell structure could be easily obtained by using these uniformly distributed powders. The ceramics not only satisfied the requirement of EIA-X8R specification, but also were near to that of EIA-X9R specification. Microstructural evaluation conducted by X-ray diffraction and scanning electron microscopy confirmed the hierarchical structure of the ceramic grains. The shape of the ε–T curves near the dielectric peak became broad when x increased from 0.001 to 0.02. The permittivity of Ba_0.985Bi_0.01TiO₃–BaTi_0.98Sn_0.02O₃ ceramic was ～23,000, ΔC/C_20 °C was ?15%, 14.4% and ?15% at ?55 °C, 120 °C and 170 °C, respectively, and the dielectric loss was 0.5. The results showed that the content of Sn had a strong impact on the diffusion and the dielectric properties of the ceramics.